uorb: compress format definitions

Reduces flash usage by ~16KB.

- compress formats at build-time into a single string with all formats
- then at runtime iteratively decompress using
  https://github.com/atomicobject/heatshrink

.gitmodules

@@ -72,3 +72,6 @@
 	path = src/modules/zenoh/zenoh-pico
 	url = https://github.com/px4/zenoh-pico
 	branch = pr-zubf-werror-fix
+[submodule "src/lib/heatshrink/heatshrink"]
+	path = src/lib/heatshrink/heatshrink
+	url = https://github.com/PX4/heatshrink.git

Tools/astyle/files_to_check_code_style.sh

@@ -25,6 +25,7 @@ exec find boards msg src platforms test \
     -path src/lib/crypto/monocypher -prune -o \
     -path src/lib/crypto/libtomcrypt -prune -o \
     -path src/lib/crypto/libtommath -prune -o \
+    -path src/lib/heatshrink/heatshrink -prune -o \
     -path src/modules/uxrce_dds_client/Micro-XRCE-DDS-Client -prune -o \
     -path src/lib/cdrstream/cyclonedds -prune -o \
     -path src/lib/cdrstream/rosidl -prune -o \

Tools/msg/px_generate_uorb_compressed_fields.py

@@ -0,0 +1,232 @@
+#!/usr/bin/env python3
+#############################################################################
+#
+#   Copyright (C) 2023 PX4 Pro Development Team. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name PX4 nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+#############################################################################
+
+"""
+Generates cpp source + header files with compressed uorb topic fields from json files
+"""
+
+import argparse
+import json
+import struct
+from operator import itemgetter
+import sys
+import os
+
+sys.path.append(os.path.join(os.path.dirname(os.path.realpath(__file__)), '../../src/lib/heatshrink'))
+import heatshrink_encode
+
+
+def parse_json_files(json_files: [str]) -> dict:
+    """Read list of json files into a dict"""
+    definitions = {}
+    for json_file in json_files:
+        with open(json_file, encoding='utf-8') as file_handle:
+            definition = json.load(file_handle)
+            assert definition['name'] not in definitions
+            definitions[definition['name']] = definition
+            definitions[definition['name']]['completed'] = False
+
+    return definitions
+
+
+def get_ordered_list_by_dependency(name: str, definitions: dict) -> [str]:
+    """Iterate dependency graph and create an ordered list"""
+    if definitions[name]['completed']:
+        return []
+    ret = []
+    # Get nested types first (DFS)
+    for dependency in definitions[name]['dependencies']:
+        ret.extend(get_ordered_list_by_dependency(dependency, definitions))
+
+    ret.append(name)
+    definitions[name]['completed'] = True
+    return ret
+
+
+def get_field_definitions(names: [str], definitions: dict) -> (bytes, [str]):
+    """Get byte array with all definitions"""
+    ret = bytes()
+    formats_list = []
+
+    for name in names:
+        # Format as '<# orb_ids><orb_id0...><# orb_ids dependencies<orb_id_dependency0...><fields><null>'
+        assert len(definitions[name]['orb_ids']) < 255
+        assert len(definitions[name]['dependencies']) < 255
+        ret += struct.pack('<B', len(definitions[name]['orb_ids']))
+        for orb_id in definitions[name]['orb_ids']:
+            assert orb_id < (1 << 16)
+            ret += struct.pack('<H', orb_id)
+        # Dependencies
+        ret += struct.pack('<B', len(definitions[name]['dependencies']))
+        for dependent_message_name in definitions[name]['dependencies']:
+            # Get ORB ID by looking up the name in all definitions
+            dependent_orb_id_list = [definitions[k]['main_orb_id'] for k in definitions if
+                                     definitions[k]['name'] == dependent_message_name]
+            assert len(dependent_orb_id_list) == 1
+            orb_id = dependent_orb_id_list[0]
+            assert (1 << 16) > orb_id >= 0
+            ret += struct.pack('<H', orb_id)
+
+        ret += bytes(definitions[name]['fields'], 'latin1')
+        ret += b'\0'
+
+        formats_list.append(definitions[name]['fields'])
+
+    return ret, formats_list
+
+
+def write_fields_to_cpp_file(file_name: str, compressed_fields: bytes):
+    fields_str = ', '.join(str(c) for c in compressed_fields)
+    with open(file_name, 'w') as file_handle:
+        file_handle.write('''
+// Auto-generated from px4_generate_uorb_compressed_fields.py
+#include <uORB/topics/uORBMessageFieldsGenerated.hpp>
+
+namespace uORB {
+
+static const uint8_t compressed_fields[] = {
+    {FIELDS}
+};
+
+const uint8_t* orb_compressed_message_formats()
+{
+    return compressed_fields;
+}
+unsigned orb_compressed_message_formats_size()
+{
+    return sizeof(compressed_fields) / sizeof(compressed_fields[0]);
+}
+
+} // namespace uORB
+'''.replace('{FIELDS}', fields_str))
+
+
+def c_encode(s, encoding='ascii'):
+    result = ''
+    for c in s:
+        if not (32 <= ord(c) < 127) or c in ('\\', '"'):
+            result += '\\%03o' % ord(c)
+        else:
+            result += c
+    return '"' + result + '"'
+
+
+def write_fields_to_hpp_file(file_name: str, definitions: dict, window_length: int, lookahead_length: int,
+                             format_list: [str]):
+    max_tokenized_field_length, max_tokenized_field_length_msg = max(
+        ((len(definitions[k]['fields']), k) for k in definitions), key=itemgetter(0))
+    max_num_orb_ids = max(len(definitions[k]['orb_ids']) for k in definitions)
+    max_num_orb_id_dependencies = max(len(definitions[k]['dependencies']) for k in definitions)
+
+    with open(file_name, 'w') as file_handle:
+        file_handle.write('''
+// Auto-generated from px4_generate_uorb_compressed_fields.py
+#include <cstdint>
+
+namespace uORB {
+
+ /**
+  * Get compressed string of all uorb message format definitions
+  */
+const uint8_t* orb_compressed_message_formats();
+
+/**
+ * Get length of compressed message format definitions
+ */
+unsigned orb_compressed_message_formats_size();
+
+static constexpr unsigned orb_tokenized_fields_max_length = {MAX_TOKENIZED_FIELD_LENGTH}; // {MAX_TOKENIZED_FIELD_LENGTH_MSG}
+static constexpr unsigned orb_compressed_max_num_orb_ids = {MAX_NUM_ORB_IDS};
+static constexpr unsigned orb_compressed_max_num_orb_id_dependencies = {MAX_NUM_ORB_ID_DEPENDENCIES};
+
+static constexpr unsigned orb_compressed_heatshrink_window_length = {WINDOW_LENGTH};
+static constexpr unsigned orb_compressed_heatshrink_lookahead_length = {LOOKAHEAD_LENGTH};
+
+#define ORB_DECOMPRESSED_MESSAGE_FIELDS {{DECOMPRESSED_MESSAGE_FIELDS}}
+
+} // namespace uORB
+'''
+                          .replace('{MAX_TOKENIZED_FIELD_LENGTH}', str(max_tokenized_field_length))
+                          .replace('{MAX_TOKENIZED_FIELD_LENGTH_MSG}', max_tokenized_field_length_msg)
+                          .replace('{MAX_NUM_ORB_IDS}', str(max_num_orb_ids))
+                          .replace('{MAX_NUM_ORB_ID_DEPENDENCIES}', str(max_num_orb_id_dependencies))
+                          .replace('{WINDOW_LENGTH}', str(window_length))
+                          .replace('{LOOKAHEAD_LENGTH}', str(lookahead_length))
+                          .replace('{DECOMPRESSED_MESSAGE_FIELDS}', ','.join(c_encode(x) for x in format_list))
+                          )
+
+
+def main():
+    parser = argparse.ArgumentParser(description='Generate compressed uorb topic fields')
+    parser.add_argument('-f', dest='file',
+                        help="json input files",
+                        nargs="+")
+    parser.add_argument('--source-output-file', dest='output_cpp',
+                        help='cpp output file to generate')
+    parser.add_argument('--header-output-file', dest='output_hpp',
+                        help='hpp output file to generate')
+    parser.add_argument('-v', '--verbose',
+                        action='store_true',
+                        help="verbose output")
+    args = parser.parse_args()
+
+    if args.file is not None:
+        definitions = parse_json_files(args.file)
+
+        # Get array of all field definitions
+        names = []
+        for definition in definitions:
+            names.extend(get_ordered_list_by_dependency(definitions[definition]['name'], definitions))
+        names.reverse()  # Dependent definitions must be after
+        assert len(names) == len(definitions)
+        for definition in definitions:  # sanity check
+            assert definitions[definition]['completed']
+        field_definitions, format_list = get_field_definitions(names, definitions)
+
+        # Compress
+        window_size = 8  # Larger value = better compression; memory requirement (for decompression): 2 ^ window_size
+        lookahead = 4
+        compressed_field_definitions = heatshrink_encode.encode(field_definitions, window_size, lookahead)
+
+        if args.verbose:
+            print(
+                f'Field definitions: size: {len(field_definitions)}, reduction from compression: {len(field_definitions) - len(compressed_field_definitions)}')
+
+        # Write cpp & hpp file
+        write_fields_to_cpp_file(args.output_cpp, compressed_field_definitions)
+        write_fields_to_hpp_file(args.output_hpp, definitions, window_size, lookahead, format_list)
+
+
+if __name__ == "__main__":
+    main()

Tools/msg/px_generate_uorb_topic_files.py

@@ -70,9 +70,8 @@ __license__ = "BSD"
 __email__ = "thomasgubler@gmail.com"
 
 
-TEMPLATE_FILE = ['msg.h.em', 'msg.cpp.em', 'uorb_idl_header.h.em']
+TEMPLATE_FILE = ['msg.h.em', 'msg.cpp.em', 'uorb_idl_header.h.em', 'msg.json.em']
-TOPICS_LIST_TEMPLATE_FILE = ['uORBTopics.hpp.em', 'uORBTopics.cpp.em']
+TOPICS_LIST_TEMPLATE_FILE = ['uORBTopics.hpp.em', 'uORBTopics.cpp.em', None, None]
-OUTPUT_FILE_EXT = ['.h', '.cpp', '.h']
 INCL_DEFAULT = ['std_msgs:./msg/std_msgs']
 PACKAGE = 'px4'
 TOPICS_TOKEN = '# TOPICS '
@@ -105,7 +104,7 @@ def get_topics(filename):
     return result
 
 
-def generate_output_from_file(format_idx, filename, outputdir, package, templatedir, includepath):
+def generate_output_from_file(format_idx, filename, outputdir, package, templatedir, includepath, all_topics):
     """
     Converts a single .msg file to an uorb header/source file
     """
@@ -155,6 +154,7 @@ def generate_output_from_file(format_idx, filename, outputdir, package, template
         "msg_context": msg_context,
         "spec": spec,
         "topics": topics,
+        "all_topics": all_topics,
     }
 
     # Make sure output directory exists:
@@ -162,10 +162,11 @@ def generate_output_from_file(format_idx, filename, outputdir, package, template
         os.makedirs(outputdir)
 
     template_file = os.path.join(templatedir, TEMPLATE_FILE[format_idx])
+    extension = os.path.splitext(os.path.splitext(TEMPLATE_FILE[format_idx])[0])[1]
     if format_idx == 2:
-        output_file = os.path.join(outputdir, file_base_name + OUTPUT_FILE_EXT[format_idx])
+        output_file = os.path.join(outputdir, file_base_name + extension)
     else:
-        output_file = os.path.join(outputdir, full_type_name_snake + OUTPUT_FILE_EXT[format_idx])
+        output_file = os.path.join(outputdir, full_type_name_snake + extension)
 
     return generate_by_template(output_file, template_file, em_globals)
 
@@ -195,17 +196,13 @@ def generate_by_template(output_file, template_file, em_globals):
     return True
 
 
-def generate_topics_list_file_from_files(files, outputdir, template_filename, templatedir):
+def generate_topics_list_file_from_files(files, outputdir, template_filename, templatedir, all_topics):
     # generate cpp file with topics list
     filenames = []
     for filename in [os.path.basename(p) for p in files if os.path.basename(p).endswith(".msg")]:
         filenames.append(re.sub(r'(?<!^)(?=[A-Z])', '_', filename).lower())
 
-    topics = []
+    tl_globals = {"msgs": filenames, "all_topics": all_topics}
-    for msg_filename in files:
-        topics.extend(get_topics(msg_filename))
-
-    tl_globals = {"msgs": filenames, "topics": topics}
     tl_template_file = os.path.join(templatedir, template_filename)
     tl_out_file = os.path.join(outputdir, template_filename.replace(".em", ""))
 
@@ -222,8 +219,9 @@ if __name__ == "__main__":
     parser.add_argument('--headers', help='Generate header files', action='store_true')
     parser.add_argument('--sources', help='Generate source files', action='store_true')
     parser.add_argument('--uorb-idl-header', help='Generate uORB compatible idl header', action='store_true')
+    parser.add_argument('--json', help='Generate json files', action='store_true')
     parser.add_argument('-f', dest='file',
-                        help="files to convert (use only without -d)",
+                        help="files to convert",
                         nargs="+")
     parser.add_argument('-i', dest="include_paths",
                         help='Additional Include Paths', nargs="*",
@@ -247,17 +245,21 @@ if __name__ == "__main__":
     elif args.sources:
         generate_idx = 1
     elif args.uorb_idl_header:
-        for f in args.file:
+        generate_idx = 2
-            print(f)
+    elif args.json:
-            generate_output_from_file(2, f, args.outputdir, args.package, args.templatedir, INCL_DEFAULT)
+        generate_idx = 3
-        exit(0)
     else:
-        print('Error: either --headers or --sources must be specified')
+        print('Error: either --headers, --sources or --json must be specified')
         exit(-1)
     if args.file is not None:
+        all_topics = []
+        for msg_filename in args.file:
+            all_topics.extend(get_topics(msg_filename))
+        all_topics.sort()
+
         for f in args.file:
-            generate_output_from_file(generate_idx, f, args.outputdir, args.package, args.templatedir, INCL_DEFAULT)
+            generate_output_from_file(generate_idx, f, args.outputdir, args.package, args.templatedir, INCL_DEFAULT, all_topics)
 
         # Generate topics list header and source file
-        if os.path.isfile(os.path.join(args.templatedir, TOPICS_LIST_TEMPLATE_FILE[generate_idx])):
+        if TOPICS_LIST_TEMPLATE_FILE[generate_idx] is not None and os.path.isfile(os.path.join(args.templatedir, TOPICS_LIST_TEMPLATE_FILE[generate_idx])):
-            generate_topics_list_file_from_files(args.file, args.outputdir, TOPICS_LIST_TEMPLATE_FILE[generate_idx], args.templatedir)
+            generate_topics_list_file_from_files(args.file, args.outputdir, TOPICS_LIST_TEMPLATE_FILE[generate_idx], args.templatedir, all_topics)

Tools/msg/templates/uorb/msg.cpp.em

@@ -14,6 +14,7 @@
 @#  - spec (msggen.MsgSpec) Parsed specification of the .msg file
 @#  - search_path (dict) search paths for genmsg
 @#  - topics (List of String) topic names
+@#  - all_topics (List of String) all generated topic names (sorted)
 @###############################################
 /****************************************************************************
  *
@@ -59,7 +60,6 @@ uorb_struct = '%s_s'%name_snake_case
 
 sorted_fields = sorted(spec.parsed_fields(), key=sizeof_field_type, reverse=True)
 struct_size, padding_end_size = add_padding_bytes(sorted_fields, search_path)
-topic_fields = ["%s %s" % (convert_type(field.type, True), field.name) for field in sorted_fields]
 }@
 
 #include <inttypes.h>
@@ -72,12 +72,9 @@ topic_fields = ["%s %s" % (convert_type(field.type, True), field.name) for field
 #include <lib/matrix/matrix/math.hpp>
 #include <lib/mathlib/mathlib.h>
 
-@# join all msg files in one line e.g: "float[3] position;float[3] velocity;bool armed"
-@# This is used for the logger
-constexpr char __orb_@(name_snake_case)_fields[] = "@( ";".join(topic_fields) );";
-
 @[for topic in topics]@
-ORB_DEFINE(@topic, struct @uorb_struct, @(struct_size-padding_end_size), __orb_@(name_snake_case)_fields, static_cast<orb_id_size_t>(ORB_ID::@topic));
+static_assert(static_cast<orb_id_size_t>(ORB_ID::@topic) == @(all_topics.index(topic)), "ORB_ID index mismatch");
+ORB_DEFINE(@topic, struct @uorb_struct, @(struct_size-padding_end_size), static_cast<orb_id_size_t>(ORB_ID::@topic));
 @[end for]
 
 void print_message(const orb_metadata *meta, const @uorb_struct& message)

Tools/msg/templates/uorb/msg.json.em

@@ -0,0 +1,49 @@
+@###############################################
+@#
+@# PX4 ROS compatible message source code
+@# generation for C++
+@#
+@# EmPy template for generating <msg>.h files
+@# Based on the original template for ROS
+@#
+@###############################################
+@# Start of Template
+@#
+@# Context:
+@#  - file_name_in (String) Source file
+@#  - spec (msggen.MsgSpec) Parsed specification of the .msg file
+@#  - search_path (dict) search paths for genmsg
+@#  - topics (List of String) topic names
+@#  - all_topics (List of String) all generated topic names (sorted)
+@###############################################
+
+@{
+import genmsg.msgs
+import json
+
+from px_generate_uorb_topic_helper import * # this is in Tools/
+
+uorb_struct = '%s_s'%name_snake_case
+
+sorted_fields = sorted(spec.parsed_fields(), key=sizeof_field_type, reverse=True)
+struct_size, padding_end_size = add_padding_bytes(sorted_fields, search_path)
+topic_fields = ["%s %s" % (convert_type(field.type, True), field.name) for field in sorted_fields]
+
+dependencies = []
+for field in spec.parsed_fields():
+    if not field.is_header:
+        type_name = field.type
+        # detect embedded types
+        sl_pos = type_name.find('/')
+        if sl_pos >= 0: # nested type
+            dependencies.append(field.base_type)
+}@
+
+{
+@# join all msg files in one line e.g: "float[3] position;float[3] velocity;bool armed;"
+		"fields": @( json.dumps(bytearray(";".join(topic_fields)+";", 'utf-8').decode('unicode_escape')) ),
+		"orb_ids": @( json.dumps([ all_topics.index(topic) for topic in topics]) ),
+		"main_orb_id": @( all_topics.index(name_snake_case) if name_snake_case in all_topics else -1 ),
+		"dependencies": @( json.dumps(list(set(dependencies))) ),
+		"name": "@( spec.full_name )"
+}

Tools/msg/templates/uorb/uORBTopics.cpp.em

@@ -8,7 +8,7 @@
 @#
 @# Context:
 @#  - msgs (List) list of all msg files
-@#  - multi_topics (List) list of all multi-topic names
+@#  - all_topics (List) list of all topic names (sorted)
 @###############################################
 /****************************************************************************
  *
@@ -50,9 +50,7 @@ msg_names = list(set([mn.replace(".msg", "") for mn in msgs])) # set() filters d
 msg_names.sort()
 msgs_count = len(msg_names)
 
-topic_names = list(set(topics)) # set() filters duplicates
+topics_count = len(all_topics)
-topic_names.sort()
-topics_count = len(topics)
 
 }@
 @[for msg_name in msg_names]@
@@ -60,8 +58,8 @@ topics_count = len(topics)
 @[end for]
 
 const constexpr struct orb_metadata *const uorb_topics_list[ORB_TOPICS_COUNT] = {
-@[for idx, topic_name in enumerate(topic_names, 1)]@
+@[for idx, topic_name in enumerate(all_topics, 1)]@
-	ORB_ID(@(topic_name))@[if idx != topic_names], @[end if]
+	ORB_ID(@(topic_name))@[if idx != all_topics], @[end if]
 @[end for]
 };
 

Tools/msg/templates/uorb/uORBTopics.hpp.em

@@ -7,7 +7,8 @@
 @# Start of Template
 @#
 @# Context:
-@#  - topics (List) list of all topic names
+@#  - msgs (List) list of all msg files
+@#  - all_topics (List) list of all topic names (sorted)
 @###############################################
 /****************************************************************************
  *
@@ -43,9 +44,7 @@
  ****************************************************************************/
 
 @{
-topics_count = len(topics)
+topics_count = len(all_topics)
-topic_names_all = list(set(topics)) # set() filters duplicates
-topic_names_all.sort()
 }@
 
 #pragma once
@@ -63,7 +62,7 @@ static constexpr size_t orb_topics_count() { return ORB_TOPICS_COUNT; }
 extern const struct orb_metadata *const *orb_get_topics() __EXPORT;
 
 enum class ORB_ID : orb_id_size_t {
-@[for idx, topic_name in enumerate(topic_names_all)]@
+@[for idx, topic_name in enumerate(all_topics)]@
 	@(topic_name) = @(idx),
 @[end for]
 	INVALID

msg/CMakeLists.txt

@@ -253,6 +253,7 @@ set(msg_source_out_path ${CMAKE_CURRENT_BINARY_DIR}/topics_sources)
 set(uorb_headers)
 set(uorb_sources)
 set(uorb_ucdr_headers)
+set(uorb_json_files)
 foreach(msg_file ${msg_files})
 	get_filename_component(msg ${msg_file} NAME_WE)
 
@@ -264,11 +265,9 @@ foreach(msg_file ${msg_files})
 	list(APPEND uorb_headers ${msg_out_path}/${msg}.h)
 	list(APPEND uorb_sources ${msg_source_out_path}/${msg}.cpp)
 	list(APPEND uorb_ucdr_headers ${ucdr_out_path}/${msg}.h)
+	list(APPEND uorb_json_files ${msg_source_out_path}/${msg}.json)
 endforeach()
 
-# set parent scope msg_files for other modules to consume (eg topic_listener)
-set(msg_files ${msg_files} PARENT_SCOPE)
-
 # Generate uORB headers
 add_custom_command(
 	OUTPUT
@@ -292,6 +291,44 @@ add_custom_command(
 	)
 add_custom_target(uorb_headers DEPENDS ${uorb_headers})
 
+add_custom_command(
+	OUTPUT
+		${uorb_json_files}
+	COMMAND ${PYTHON_EXECUTABLE} ${PX4_SOURCE_DIR}/Tools/msg/px_generate_uorb_topic_files.py
+		--json
+		-f ${msg_files}
+		-i ${CMAKE_CURRENT_SOURCE_DIR}
+		-o ${msg_source_out_path}
+		-e ${PX4_SOURCE_DIR}/Tools/msg/templates/uorb
+	DEPENDS
+		${msg_files}
+		${PX4_SOURCE_DIR}/Tools/msg/templates/uorb/msg.json.em
+		${PX4_SOURCE_DIR}/Tools/msg/px_generate_uorb_topic_files.py
+		${PX4_SOURCE_DIR}/Tools/msg/px_generate_uorb_topic_helper.py
+	COMMENT "Generating uORB json files"
+	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+	VERBATIM
+)
+add_custom_target(uorb_json_files DEPENDS ${uorb_json_files})
+
+set(uorb_message_fields_cpp_file ${msg_source_out_path}/uORBMessageFieldsGenerated.cpp)
+set(uorb_message_fields_header_file ${msg_out_path}/uORBMessageFieldsGenerated.hpp)
+add_custom_command(
+	OUTPUT
+		${uorb_message_fields_cpp_file}
+		${uorb_message_fields_header_file}
+	COMMAND ${PYTHON_EXECUTABLE} ${PX4_SOURCE_DIR}/Tools/msg/px_generate_uorb_compressed_fields.py
+		-f ${uorb_json_files}
+		--source-output-file ${uorb_message_fields_cpp_file}
+		--header-output-file ${uorb_message_fields_header_file}
+	DEPENDS
+		uorb_json_files
+		${PX4_SOURCE_DIR}/Tools/msg/px_generate_uorb_compressed_fields.py
+	COMMENT "Generating uORB compressed fields"
+	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+	VERBATIM
+)
+
 # Generate microcdr headers
 add_custom_command(
 	OUTPUT ${uorb_ucdr_headers}
@@ -334,7 +371,7 @@ add_custom_command(
 	VERBATIM
 	)
 
-add_library(uorb_msgs ${uorb_headers} ${msg_out_path}/uORBTopics.hpp ${uorb_sources} ${msg_source_out_path}/uORBTopics.cpp)
+add_library(uorb_msgs ${uorb_headers} ${msg_out_path}/uORBTopics.hpp ${uorb_sources} ${msg_source_out_path}/uORBTopics.cpp ${uorb_message_fields_cpp_file})
 target_link_libraries(uorb_msgs PRIVATE m)
 add_dependencies(uorb_msgs prebuild_targets uorb_headers)
 

platforms/common/uORB/CMakeLists.txt

@@ -54,6 +54,8 @@ set(SRCS_COMMON
 	uORBCommon.hpp
 	uORBCommunicator.hpp
 	uORBManager.hpp
+	uORBMessageFields.cpp
+	uORBMessageFields.hpp
 	uORBUtils.cpp
 	uORBUtils.hpp
 	uORBDeviceMaster.hpp
@@ -76,7 +78,7 @@ if (NOT DEFINED CONFIG_BUILD_FLAT AND "${PX4_PLATFORM}" MATCHES "nuttx")
 		${SRCS_COMMON}
 		${SRCS_KERNEL}
 		)
-	target_link_libraries(uORB_kernel PRIVATE cdev uorb_msgs nuttx_mm)
+	target_link_libraries(uORB_kernel PRIVATE cdev uorb_msgs nuttx_mm heatshrink)
 	target_compile_options(uORB_kernel PRIVATE ${MAX_CUSTOM_OPT_LEVEL} -D__KERNEL__)
 
 	# User side library in nuttx kernel/protected build
@@ -102,9 +104,11 @@ else()
 	target_link_libraries(uORB PRIVATE cdev)
 endif()
 
-target_link_libraries(uORB PRIVATE uorb_msgs)
+target_link_libraries(uORB PRIVATE uorb_msgs heatshrink)
 target_compile_options(uORB PRIVATE ${MAX_CUSTOM_OPT_LEVEL})
 
 if(PX4_TESTING)
 	add_subdirectory(uORB_tests)
 endif()
+
+px4_add_functional_gtest(SRC uORBMessageFieldsTest.cpp LINKLIBS uORB)

platforms/common/uORB/uORB.cpp

@@ -40,6 +40,7 @@
 
 #include "uORBManager.hpp"
 #include "uORBCommon.hpp"
+#include "uORBMessageFields.hpp"
 
 
 #include <lib/drivers/device/Device.hpp>
@@ -196,7 +197,7 @@ int orb_get_interval(int handle, unsigned *interval)
 
 const char *orb_get_c_type(unsigned char short_type)
 {
-	// this matches with the uorb o_fields generator
+	// this matches with the uorb type_map_short python data
 	switch (short_type) {
 	case 0x82: return "int8_t";
 
@@ -239,25 +240,29 @@ void orb_print_message_internal(const orb_metadata *meta, const void *data, bool
 	const uint8_t *data_ptr = (const uint8_t *)data;
 	int data_offset = 0;
 
-	for (int format_idx = 0; meta->o_fields[format_idx] != 0;) {
+	// Find message format
-		const char *end_field = strchr(meta->o_fields + format_idx, ';');
+	char format_buffer[128];
+	uORB::MessageFormatReader format_reader(format_buffer, sizeof(format_buffer));
 
-		if (!end_field) {
+	if (!format_reader.readUntilFormat(meta->o_id)) {
-			PX4_ERR("Format error in %s", meta->o_fields);
+		PX4_ERR("Failed to get uorb format");
-			return;
+		return;
-		}
+	}
 
-		const char *c_type = orb_get_c_type(meta->o_fields[format_idx]);
+	int field_length = 0;
-		const int end_field_idx = end_field - meta->o_fields;
+
+	while (format_reader.readNextField(field_length)) {
+
+		const char *c_type = orb_get_c_type(format_buffer[0]);
 
 		int array_idx = -1;
 		int field_name_idx = -1;
 
-		for (int field_idx = format_idx; field_idx != end_field_idx; ++field_idx) {
+		for (int field_idx = 0; field_idx < field_length; ++field_idx) {
-			if (meta->o_fields[field_idx] == '[') {
+			if (format_buffer[field_idx] == '[') {
 				array_idx = field_idx + 1;
 
-			} else if (meta->o_fields[field_idx] == ' ') {
+			} else if (format_buffer[field_idx] == ' ') {
 				field_name_idx = field_idx + 1;
 				break;
 			}
@@ -266,19 +271,10 @@ void orb_print_message_internal(const orb_metadata *meta, const void *data, bool
 		int array_size = 1;
 
 		if (array_idx >= 0) {
-			array_size = strtol(meta->o_fields + array_idx, nullptr, 10);
+			array_size = strtol(format_buffer + array_idx, nullptr, 10);
 		}
 
-		char field_name[80];
+		const char *field_name = format_buffer + field_name_idx;
-		size_t field_name_len = end_field_idx - field_name_idx;
-
-		if (field_name_len >= sizeof(field_name)) {
-			PX4_ERR("field name too long %s (max: %u)", meta->o_fields, (unsigned)sizeof(field_name));
-			return;
-		}
-
-		memcpy(field_name, meta->o_fields + field_name_idx, field_name_len);
-		field_name[field_name_len] = '\0';
 
 		if (c_type) { // built-in type
 			bool dont_print = false;
@@ -458,17 +454,10 @@ void orb_print_message_internal(const orb_metadata *meta, const void *data, bool
 
 		} else {
 
-			// extract the topic name
+			// Get the topic name
-			char topic_name[80];
+			const size_t topic_name_len = array_size > 1 ? array_idx - 1 : field_name_idx - 1;
-			const size_t topic_name_len = array_size > 1 ? array_idx - format_idx - 1 : field_name_idx - format_idx - 1;
+			format_buffer[topic_name_len] = '\0';
-
+			const char *topic_name = format_buffer;
-			if (topic_name_len >= sizeof(topic_name)) {
-				PX4_ERR("topic name too long in %s (max: %u)", meta->o_name, (unsigned)sizeof(topic_name));
-				return;
-			}
-
-			memcpy(topic_name, meta->o_fields + format_idx, topic_name_len);
-			topic_name[topic_name_len] = '\0';
 
 			// find the metadata
 			const orb_metadata *const *topics = orb_get_topics();
@@ -499,7 +488,5 @@ void orb_print_message_internal(const orb_metadata *meta, const void *data, bool
 				data_offset += found_topic->o_size;
 			}
 		}
-
-		format_idx = end_field_idx + 1;
 	}
 }

platforms/common/uORB/uORB.h

@@ -51,7 +51,6 @@ struct orb_metadata {
 	const char    *o_name;              /**< unique object name */
 	const uint16_t o_size;              /**< object size */
 	const uint16_t o_size_no_padding;   /**< object size w/o padding at the end (for logger) */
-	const char    *o_fields;            /**< semicolon separated list of fields (with type) */
 	orb_id_size_t  o_id;                /**< ORB_ID enum */
 };
 
@@ -100,15 +99,13 @@ typedef const struct orb_metadata *orb_id_t;
  * @param _name		The name of the topic.
  * @param _struct	The structure the topic provides.
  * @param _size_no_padding	Struct size w/o padding at the end
- * @param _fields	All fields in a semicolon separated list e.g: "float[3] position;bool armed"
  * @param _orb_id_enum	ORB ID enum e.g.: ORB_ID::vehicle_status
  */
-#define ORB_DEFINE(_name, _struct, _size_no_padding, _fields, _orb_id_enum)		\
+#define ORB_DEFINE(_name, _struct, _size_no_padding, _orb_id_enum)		\
 	const struct orb_metadata __orb_##_name = {	\
 		#_name,					\
 		sizeof(_struct),		\
 		_size_no_padding,			\
-		_fields,				\
 		_orb_id_enum				\
 	}; struct hack
 
@@ -236,7 +233,7 @@ extern int	orb_set_interval(int handle, unsigned interval) __EXPORT;
 extern int	orb_get_interval(int handle, unsigned *interval) __EXPORT;
 
 /**
- * Returns the C type string from a short type in o_fields metadata, or nullptr
+ * Returns the C type string from a short type in message fields metadata, or nullptr
  * if not a short type
  */
 const char *orb_get_c_type(unsigned char short_type);
@@ -248,7 +245,6 @@ const char *orb_get_c_type(unsigned char short_type);
  */
 void orb_print_message_internal(const struct orb_metadata *meta, const void *data, bool print_topic_name);
 
-
 __END_DECLS
 
 /* Diverse uORB header defines */ //XXX: move to better location

platforms/common/uORB/uORBMessageFields.cpp

@@ -0,0 +1,342 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2023 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+
+#include "uORBMessageFields.hpp"
+
+#include <px4_platform_common/log.h>
+
+namespace uORB
+{
+
+MessageFormatReader::State MessageFormatReader::readMore()
+{
+	if (_state == State::Complete || _state == State::Failure) {
+		return _state;
+	}
+
+	if (_buffer_length == _buffer_capacity) {
+		_state = State::Failure;
+		PX4_ERR("buffer too small");
+		return _state;
+	}
+
+	const uint8_t *compressed_formats = orb_compressed_message_formats();
+	const unsigned compressed_formats_size = orb_compressed_message_formats_size();
+
+	if (_buffer_length == 0 && _compressed_formats_idx == compressed_formats_size) {
+		_state = State::Complete;
+		return _state;
+	}
+
+	const unsigned max_num_iterations = 5; // Safeguard, we're not expected to do more than a few iterations
+
+	for (unsigned iteration = 0; iteration < max_num_iterations; ++iteration) {
+		switch (_state) {
+		case State::ReadOrbIDs: {
+				int num_orb_ids = _buffer[0];
+				const unsigned orb_ids_size = 1 + num_orb_ids * sizeof(orb_id_size_t);
+
+				if (_buffer_length > orb_ids_size) {
+					int num_dependent_orb_ids = _buffer[orb_ids_size];
+					const unsigned orb_ids_dependent_size = 1 + num_dependent_orb_ids * sizeof(orb_id_size_t);
+
+					if (_buffer_length >= orb_ids_size + orb_ids_dependent_size) {
+
+						orb_id_size_t orb_id;
+						_state = State::ReadingFormat;
+						_format_length = 0;
+
+						_orb_ids.clear();
+
+						for (int i = 0; i < num_orb_ids; ++i) {
+							memcpy(&orb_id, &_buffer[1 + sizeof(orb_id_size_t) * i], sizeof(orb_id_size_t));
+							_orb_ids.push_back(orb_id);
+						}
+
+						_orb_ids_dependencies.clear();
+
+						for (int i = 0; i < num_dependent_orb_ids; ++i) {
+							memcpy(&orb_id, &_buffer[orb_ids_size + 1 + sizeof(orb_id_size_t) * i],
+							       sizeof(orb_id_size_t));
+							_orb_ids_dependencies.push_back(orb_id);
+						}
+
+						memmove(_buffer, _buffer + orb_ids_size + orb_ids_dependent_size,
+							_buffer_length - orb_ids_size - orb_ids_dependent_size);
+						_buffer_length -= orb_ids_size + orb_ids_dependent_size;
+
+						return State::ReadOrbIDs;
+					}
+				}
+
+				if (_buffer_length == _buffer_capacity) {
+					_state = State::Failure;
+					PX4_ERR("buffer too small");
+					return _state;
+				}
+
+				break;
+			}
+
+		case State::ReadingFormat: {
+				const bool got_new_data = _format_length < _buffer_length;
+
+				for (; _format_length < _buffer_length; ++_format_length) {
+					if (_buffer[_format_length] == '\0') {
+						_state = State::FormatComplete;
+						return _state;
+					}
+				}
+
+				if (got_new_data) {
+					return _state;
+				}
+			}
+			break;
+
+		case State::FormatComplete:
+			if (_format_length != 0) {
+				PX4_ERR("Invalid API calls"); // Missing call to clearFormatFromBuffer or clearFormatAndRestoreLeftover
+				_state = State::Failure;
+				return _state;
+			}
+
+			_state = State::ReadOrbIDs;
+			break;
+
+		case State::Failure:
+		case State::Complete:
+			return _state;
+		}
+
+		// Decompress more data
+		size_t count = 0;
+
+		if (heatshrink_decoder_sink(&_hsd, &compressed_formats[_compressed_formats_idx],
+					    compressed_formats_size - _compressed_formats_idx, &count) < 0) {
+			_state = State::Failure;
+			return _state;
+		}
+
+		_compressed_formats_idx += count;
+
+		if (_compressed_formats_idx == compressed_formats_size) {
+			const HSD_finish_res fres = heatshrink_decoder_finish(&_hsd);
+
+			if (fres != HSDR_FINISH_MORE && fres != HSDR_FINISH_DONE) {
+				_state = State::Failure;
+				return _state;
+			}
+		}
+
+		const HSD_poll_res pres = heatshrink_decoder_poll(&_hsd, reinterpret_cast<uint8_t *>(&_buffer[_buffer_length]),
+					  _buffer_capacity - _buffer_length, &count);
+		_buffer_length += count;
+
+		if (HSDR_POLL_EMPTY != pres && HSDR_POLL_MORE != pres) {
+			_state = State::Failure;
+			return _state;
+		}
+
+		if (_compressed_formats_idx == compressed_formats_size) {
+			const HSD_finish_res fres = heatshrink_decoder_finish(&_hsd);
+
+			if (HSDR_FINISH_DONE != fres && HSDR_FINISH_MORE != fres) {
+				_state = State::Failure;
+				return _state;
+			}
+		}
+
+	}
+
+	// Not expected to get here
+	PX4_ERR("logic error");
+	_state = State::Failure;
+	return _state;
+}
+
+void MessageFormatReader::clearFormatFromBuffer()
+{
+	if (_state == State::FormatComplete) {
+		++_format_length; // Include null char
+		memmove(_buffer, _buffer + _format_length, _buffer_length - _format_length);
+		_buffer_length -= _format_length;
+
+	} else {
+		// Full buffer is occupied with format
+		_buffer_length = 0;
+	}
+
+	_format_length = 0;
+}
+
+int MessageFormatReader::expandMessageFormat(char *format, unsigned len, unsigned buf_len)
+{
+	++len; // Include null char
+
+	int format_idx = 0;
+
+	while (format[format_idx] != 0) {
+
+		const char *c_type = orb_get_c_type(format[format_idx]);
+
+		if (c_type) {
+			// Replace 1 char type with expanded c_type
+			const int c_type_len = (int)strlen(c_type);
+
+			if (len + c_type_len - 1 > buf_len) {
+				return -1;
+			}
+
+			memmove(format + format_idx + c_type_len, format + format_idx + 1, len - format_idx - 1);
+			memcpy(format + format_idx, c_type, c_type_len);
+			format_idx += c_type_len - 1;
+			len += c_type_len - 1;
+		}
+
+		// Go to next field
+		const char *end_field = strchr(format + format_idx, ';');
+
+		if (!end_field) {
+			PX4_ERR("Format error in %s", format);
+			return -1;
+		}
+
+		format_idx = (int)(end_field - format + 1);
+	}
+
+	if (format_idx + 1 != (int)len) {
+		PX4_ERR("logic error");
+		return -1;
+	}
+
+	return format_idx;
+}
+
+bool MessageFormatReader::readUntilFormat(orb_id_size_t orb_id)
+{
+	bool done = false;
+	bool found_format = false;
+
+	while (!done && !found_format) {
+		switch (readMore()) {
+		case State::ReadOrbIDs:
+			for (const orb_id_size_t current_orb_id : orbIDs()) {
+				if (current_orb_id == orb_id) {
+					found_format = true;
+				}
+			}
+
+			break;
+
+		case State::ReadingFormat:
+		case State::FormatComplete:
+			clearFormatFromBuffer();
+			break;
+
+		case State::Complete:
+		case State::Failure:
+			done = true;
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	return found_format;
+}
+
+bool MessageFormatReader::readNextField(int &field_length)
+{
+	if (field_length > 0) {
+		// Move left-over part to beginning
+		++field_length; // include null
+		memmove(_buffer, _buffer + field_length, _buffer_length - field_length);
+		_buffer_length -= field_length;
+		_format_length -= field_length;
+	}
+
+	auto findFieldEnd = [&]() {
+		// Find ';'
+		bool found = false;
+
+		for (field_length = 0; field_length < (int)_format_length; ++field_length) {
+			if (_buffer[field_length] == ';') {
+				_buffer[field_length] = '\0';
+				found = true;
+				break;
+			}
+		}
+
+		return found;
+	};
+
+	// We might still have a field in the buffer
+	if (findFieldEnd()) {
+		return true;
+	}
+
+	bool done = false;
+	bool ret = false;
+
+	while (!done) {
+		switch (readMore()) {
+		case State::ReadingFormat:
+			if (findFieldEnd()) {
+				ret = true;
+				done = true;
+			}
+
+			break;
+
+		case State::FormatComplete: {
+				ret = findFieldEnd(); // Expected to return true here
+				done = true;
+				break;
+			}
+
+		case State::ReadOrbIDs: // Arrived at the next format -> we're done
+		case State::Complete:
+		case State::Failure:
+			done = true;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+
+} // namespace uORB

platforms/common/uORB/uORBMessageFields.hpp

@@ -0,0 +1,157 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2023 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#pragma once
+
+#include <uORB/topics/uORBMessageFieldsGenerated.hpp>
+#include <uORB/uORB.h>
+#include <containers/Array.hpp>
+#include <cstring>
+
+#define HEATSHRINK_DYNAMIC_ALLOC 0
+#include <lib/heatshrink/heatshrink/heatshrink_decoder.h>
+
+namespace uORB
+{
+
+class MessageFormatReader
+{
+public:
+	enum class State {
+		ReadOrbIDs,
+		ReadingFormat,
+		FormatComplete,
+		Failure,
+		Complete
+	};
+
+	MessageFormatReader(char *buffer, unsigned buffer_capacity)
+		: _buffer(buffer), _buffer_capacity(buffer_capacity)
+	{
+		heatshrink_decoder_reset(&_hsd);
+		static_assert(orb_compressed_heatshrink_window_length == HEATSHRINK_STATIC_WINDOW_BITS, "window length mismatch");
+		static_assert(orb_compressed_heatshrink_lookahead_length == HEATSHRINK_STATIC_LOOKAHEAD_BITS,
+			      "lookahead length mismatch");
+		_buffer[0] = 0;
+	}
+
+	/**
+	 * Read and decompress more data into the given buffer (from the constructor).
+	 * Call iteratively until completed or a failure happens.
+	 * @return current state
+	 */
+	State readMore();
+
+	/**
+	 * Read until the start of a format given an ORB ID
+	 * @return true on success
+	 */
+	bool readUntilFormat(orb_id_size_t orb_id);
+
+	/**
+	 * Iteratively read fields for the current format
+	 * @param field_length [in,out] field length, set to 0 initially
+	 * @return true while there is a field
+	 */
+	bool readNextField(int &field_length);
+
+	/**
+	 * Current length of the buffer
+	 */
+	uint32_t bufferLength() const { return _buffer_length; }
+	/**
+	 * Clear the buffer during ReadingFormat (if it does not need to be accumulated) or FormatComplete.
+	 * After FormatComplete either this or clearFormatAndRestoreLeftover must be called.
+	 */
+	void clearFormatFromBuffer();
+
+	/**
+	 * When FormatComplete, this can be called to move the remaining part after the format to the end of the buffer,
+	 * allowing the buffer to be modified.
+	 * @return length of the left-over part.
+	 */
+	unsigned moveLeftoverToBufferEnd()
+	{
+		_buffer_length -= _format_length + 1;
+		memmove(_buffer + _buffer_capacity - _buffer_length, _buffer + _format_length + 1, _buffer_length);
+		return _buffer_length;
+	}
+	/**
+	 * After calling moveLeftoverToBufferEnd(), this must be called.
+	 */
+	void clearFormatAndRestoreLeftover()
+	{
+		memmove(_buffer, _buffer + _buffer_capacity - _buffer_length, _buffer_length);
+		_format_length = 0;
+	}
+
+	/**
+	 * Get the (partial if ReadingFormat or complete if FormatComplete) format length in the buffer
+	 */
+	unsigned formatLength() const { return _format_length; }
+
+	/**
+	 * In ReadOrbIDs, ReadingFormat or FormatComplete states, this returns the orb ID's accociated with the format.
+	 */
+	const px4::Array<orb_id_size_t, orb_compressed_max_num_orb_ids> &orbIDs() const { return _orb_ids; }
+	/**
+	 * In ReadOrbIDs, ReadingFormat or FormatComplete states, this returns the dependent orb ID's accociated with the
+	 * format (for nested format definitions).
+	 */
+	const px4::Array<orb_id_size_t, orb_compressed_max_num_orb_id_dependencies> &orbIDsDependencies() const { return _orb_ids_dependencies; }
+
+	/**
+	 * Expand a tokenized format (after decompressing it)
+	 * @param format tokenized format, expanded in-place
+	 * @param len Length of the format, format[len] == '\0' must hold
+	 * @param buf_len total length of format. Must be long enough for expanded format.
+	 * @return expanded format length, or <0 on error
+	 */
+	static int expandMessageFormat(char *format, unsigned len, unsigned buf_len);
+
+private:
+	State _state{State::ReadOrbIDs};
+	px4::Array<orb_id_size_t, orb_compressed_max_num_orb_ids> _orb_ids;
+	px4::Array<orb_id_size_t, orb_compressed_max_num_orb_id_dependencies> _orb_ids_dependencies;
+
+	unsigned _compressed_formats_idx{0};
+	char *_buffer{nullptr};
+	const unsigned _buffer_capacity;
+	uint32_t _buffer_length{0};
+	unsigned _format_length{0};
+
+	heatshrink_decoder _hsd;
+};
+
+
+} // namespace uORB

platforms/common/uORB/uORBMessageFieldsTest.cpp

@@ -0,0 +1,234 @@
+/****************************************************************************
+ *
+ *   Copyright (C) 2023 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#include "uORBMessageFields.hpp"
+
+#include <gtest/gtest.h>
+#include <containers/Bitset.hpp>
+#include <px4_platform_common/param.h>
+#include <uORB/topics/uORBTopics.hpp>
+
+#include <string>
+
+// To run: make tests TESTFILTER=uORBMessageFields
+
+class uORBMessageFieldsTest : public ::testing::Test
+{
+public:
+	void SetUp() override
+	{
+		param_control_autosave(false);
+	}
+};
+
+TEST_F(uORBMessageFieldsTest, decompressed_formats_match)
+{
+	char buffer[1500];
+	uORB::MessageFormatReader format_reader(buffer, sizeof(buffer));
+
+	px4::Bitset<ORB_TOPICS_COUNT> formats_found;
+	px4::Bitset<ORB_TOPICS_COUNT> dependencies;
+
+	static const char *all_formats[] = ORB_DECOMPRESSED_MESSAGE_FIELDS;
+	int format_idx = 0;
+
+	bool done = false;
+
+	while (!done) {
+		switch (format_reader.readMore()) {
+		case uORB::MessageFormatReader::State::FormatComplete: {
+				const unsigned format_length = format_reader.formatLength();
+				EXPECT_GT(format_length, 0);
+
+				// Move the left-over (the part after the format if any) to the end of the buffer
+				const unsigned leftover_length = format_reader.moveLeftoverToBufferEnd();
+
+				for (const orb_id_size_t orb_id : format_reader.orbIDs()) {
+					// Ensure each orb_id is set only once
+					EXPECT_FALSE(formats_found[orb_id]);
+					formats_found.set(orb_id);
+					dependencies.set(orb_id, false); // Clear dependency
+				}
+
+				for (const orb_id_size_t orb_id : format_reader.orbIDsDependencies()) {
+					dependencies.set(orb_id);
+				}
+
+				// Compare format
+				ASSERT_LT(format_idx, sizeof(all_formats) / sizeof(all_formats[0]));
+				const std::string format(buffer, format_length);
+				const std::string format_expected(all_formats[format_idx]);
+				EXPECT_EQ(format, format_expected);
+
+				const int ret = uORB::MessageFormatReader::expandMessageFormat(buffer, format_length,
+						sizeof(buffer) - leftover_length);
+				EXPECT_GE(ret, 0);
+				++format_idx;
+
+				// Move left-over back
+				format_reader.clearFormatAndRestoreLeftover();
+				break;
+			}
+			break;
+
+		case uORB::MessageFormatReader::State::Failure:
+			PX4_ERR("Failed to read formats");
+			done = true;
+			ASSERT_FALSE(true);
+			break;
+
+		case uORB::MessageFormatReader::State::Complete:
+			done = true;
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	// Check that all formats are found
+	for (size_t i = 0; i < formats_found.size(); ++i) {
+		EXPECT_TRUE(formats_found[i]);
+	}
+
+	// Expect dependencies to be cleared. If this is not the case, the format ordering is incorrect.
+	EXPECT_EQ(dependencies.count(), 0);
+}
+
+TEST_F(uORBMessageFieldsTest, decompress_formats_iterative)
+{
+	char buffer[64];
+	uORB::MessageFormatReader format_reader(buffer, sizeof(buffer));
+
+	px4::Bitset<ORB_TOPICS_COUNT> formats_found;
+
+	static const char *all_formats[] = ORB_DECOMPRESSED_MESSAGE_FIELDS;
+	int format_idx = 0;
+	std::string current_format;
+
+	bool done = false;
+
+	while (!done) {
+		switch (format_reader.readMore()) {
+		case uORB::MessageFormatReader::State::ReadingFormat:
+			current_format += std::string(buffer, format_reader.formatLength());
+			format_reader.clearFormatFromBuffer();
+			break;
+
+		case uORB::MessageFormatReader::State::FormatComplete: {
+				current_format += std::string(buffer, format_reader.formatLength());
+				format_reader.clearFormatFromBuffer();
+
+				EXPECT_FALSE(current_format.empty());
+
+				for (const orb_id_size_t orb_id : format_reader.orbIDs()) {
+					// Ensure each orb_id is set only once
+					EXPECT_FALSE(formats_found[orb_id]);
+					formats_found.set(orb_id);
+				}
+
+				// Compare format
+				ASSERT_LT(format_idx, sizeof(all_formats) / sizeof(all_formats[0]));
+				const std::string format_expected(all_formats[format_idx]);
+				EXPECT_EQ(current_format, format_expected);
+
+				++format_idx;
+				current_format.clear();
+				break;
+			}
+			break;
+
+		case uORB::MessageFormatReader::State::Failure:
+			PX4_ERR("Failed to read formats");
+			done = true;
+			ASSERT_FALSE(true);
+			break;
+
+		case uORB::MessageFormatReader::State::Complete:
+			done = true;
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	// Check that all formats are found
+	for (size_t i = 0; i < formats_found.size(); ++i) {
+		EXPECT_TRUE(formats_found[i]);
+	}
+}
+
+TEST_F(uORBMessageFieldsTest, decompress_formats_buffer_too_short)
+{
+	char buffer[64];
+	static_assert(uORB::orb_tokenized_fields_max_length > sizeof(buffer), "Test expects smaller buffer");
+	uORB::MessageFormatReader format_reader(buffer, sizeof(buffer));
+
+	bool done = false;
+
+	while (!done) {
+		switch (format_reader.readMore()) {
+		case uORB::MessageFormatReader::State::Failure:
+		case uORB::MessageFormatReader::State::Complete:
+			done = true;
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	EXPECT_EQ(format_reader.readMore(), uORB::MessageFormatReader::State::Failure);
+}
+
+TEST_F(uORBMessageFieldsTest, decompress_specific_format)
+{
+	char format[512];
+	char buffer[128];
+	uORB::MessageFormatReader format_reader(buffer, sizeof(buffer));
+
+	ASSERT_TRUE(format_reader.readUntilFormat((orb_id_size_t)ORB_ID::orb_test));
+
+	int field_length = 0;
+	int format_length = 0;
+
+	while (format_reader.readNextField(field_length)) {
+		format_length += snprintf(format + format_length, sizeof(buffer) - format_length - 1, "%s;", buffer);
+	}
+
+	ASSERT_GT(uORB::MessageFormatReader::expandMessageFormat(format, format_length, sizeof(format)), 0);
+
+	const std::string expected_format = "uint64_t timestamp;int32_t val;uint8_t[4] _padding0;";
+	ASSERT_EQ(expected_format, format);
+}

platforms/ros2/include/uORB/uORB.h

@@ -46,7 +46,6 @@ struct orb_metadata {
 	const char *o_name;		/**< unique object name */
 	const uint16_t o_size;		/**< object size */
 	const uint16_t o_size_no_padding;	/**< object size w/o padding at the end (for logger) */
-	const char *o_fields;		/**< semicolon separated list of fields (with type) */
 	uint8_t o_id;			/**< ORB_ID enum */
 };
 

src/include/containers/Array.hpp

@@ -99,6 +99,12 @@ public:
 	const T *begin() const { return &_items[0]; }
 	const T *end() const { return &_items[_size]; }
 
+	void clear()
+	{
+		_size = 0;
+		_overflow = false;
+	}
+
 private:
 	T        _items[N];
 	size_t      _size{0};

src/lib/CMakeLists.txt

@@ -51,6 +51,7 @@ add_subdirectory(dataman_client EXCLUDE_FROM_ALL)
 add_subdirectory(drivers EXCLUDE_FROM_ALL)
 add_subdirectory(field_sensor_bias_estimator EXCLUDE_FROM_ALL)
 add_subdirectory(geo EXCLUDE_FROM_ALL)
+add_subdirectory(heatshrink EXCLUDE_FROM_ALL)
 add_subdirectory(hysteresis EXCLUDE_FROM_ALL)
 add_subdirectory(l1 EXCLUDE_FROM_ALL)
 add_subdirectory(led EXCLUDE_FROM_ALL)

src/lib/heatshrink/CMakeLists.txt

@@ -0,0 +1,43 @@
+############################################################################
+#
+#   Copyright (c) 2023 PX4 Development Team. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name PX4 nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################################
+
+px4_add_git_submodule(TARGET git_heatshrink PATH heatshrink)
+
+px4_add_library(heatshrink
+	heatshrink/heatshrink_decoder.c
+)
+
+target_compile_options(heatshrink PRIVATE
+	${MAX_CUSTOM_OPT_LEVEL}
+	-DHEATSHRINK_DYNAMIC_ALLOC=0)
+

src/lib/heatshrink/heatshrink

@@ -0,0 +1 @@
+Subproject commit 052e6de72f67f1777198bce98f3de62f7f3c16a0

src/lib/heatshrink/heatshrink_encode.py

@@ -0,0 +1,422 @@
+import ctypes
+from enum import Enum
+
+
+# Note: this implementation directly follows the heatshrink_encoder.c code
+# (it's neither expected to be very efficient, nor is it pythonic)
+
+# Enum
+class HSE_state(ctypes.c_int):
+    HSES_NOT_FULL = 0
+    HSES_FILLED = 1
+    HSES_SEARCH = 2
+    HSES_YIELD_TAG_BIT = 3
+    HSES_YIELD_LITERAL = 4
+    HSES_YIELD_BR_INDEX = 5
+    HSES_YIELD_BR_LENGTH = 6
+    HSES_SAVE_BACKLOG = 7
+    HSES_FLUSH_BITS = 8
+    HSES_DONE = 9
+
+
+# Constants
+FLAG_IS_FINISHING = 0x01
+MATCH_NOT_FOUND = 0xFFFF
+
+HEATSHRINK_LITERAL_MARKER = 0x01
+HEATSHRINK_BACKREF_MARKER = 0x00
+
+
+# Structs
+class output_info(ctypes.Structure):
+    _fields_ = [
+        ("buf", ctypes.POINTER(ctypes.c_uint8)),
+        ("buf_size", ctypes.c_size_t),
+        ("output_size", ctypes.POINTER(ctypes.c_size_t))
+    ]
+
+
+# Functions
+def add_tag_bit(hse, oi, tag):
+    push_bits(hse, 1, tag, oi)
+
+
+def push_bits(hse, count, bits, oi):
+    assert count <= 8
+    current_byte = ctypes.c_uint8(hse.current_byte)
+    bit_index = ctypes.c_uint8(hse.bit_index)
+    for i in range(count - 1, -1, -1):
+        bit = bits & (1 << i)
+        if bit:
+            current_byte.value |= bit_index.value
+        bit_index.value >>= 1
+        if bit_index.value == 0:
+            bit_index.value = 0x80
+            oi.buf[oi.output_size[0]] = current_byte.value
+            oi.output_size[0] += 1
+            current_byte.value = 0
+    hse.current_byte = current_byte.value
+    hse.bit_index = bit_index.value
+
+
+def push_literal_byte(hse, oi):
+    processed_offset = hse.match_scan_index - 1
+    input_offset = get_input_offset(hse) + processed_offset
+    c = hse.buffer[input_offset]
+    push_bits(hse, 8, c, oi)
+
+
+# Define necessary structures and enums
+class heatshrink_encoder(ctypes.Structure):
+    _fields_ = [
+        ("input_size", ctypes.c_uint16),
+        ("match_scan_index", ctypes.c_uint16),
+        ("match_length", ctypes.c_uint16),
+        ("match_pos", ctypes.c_uint16),
+        ("outgoing_bits", ctypes.c_uint16),
+        ("outgoing_bits_count", ctypes.c_uint8),
+        ("flags", ctypes.c_uint8),
+        ("state", ctypes.c_uint8),
+        ("current_byte", ctypes.c_uint8),
+        ("bit_index", ctypes.c_uint8),
+
+        ("buffer", ctypes.POINTER(ctypes.c_uint8)),
+    ]
+
+    def __init__(self, window_size=8, lookahead_size=4):
+        super().__init__()
+        self.window_size = window_size
+        self.lookahead_size = lookahead_size
+        self.search_index = hs_index(window_size)
+        self.buffer = (ctypes.c_uint8 * (2 << window_size))()
+        self.bit_index = 0x80
+
+
+class hs_index(ctypes.Structure):
+    _fields_ = [("index", ctypes.POINTER(ctypes.c_int16))]
+
+    def __init__(self, window_size):
+        super().__init__()
+        self.index = (ctypes.c_int16 * (2 << window_size))()
+
+
+class HSE_sink_res(Enum):
+    HSER_SINK_OK = 0
+    HSER_SINK_ERROR_NULL = -1
+    HSER_SINK_ERROR_MISUSE = -2
+
+
+class HSE_poll_res(Enum):
+    HSER_POLL_EMPTY = 0
+    HSER_POLL_MORE = 1
+    HSER_POLL_ERROR_NULL = -1
+    HSER_POLL_ERROR_MISUSE = -2
+
+
+class HSE_finish_res(Enum):
+    HSER_FINISH_DONE = 0
+    HSER_FINISH_MORE = 1
+    HSER_FINISH_ERROR_NULL = -1
+
+
+def is_finishing(hse):
+    return hse.flags & FLAG_IS_FINISHING
+
+
+def can_take_byte(oi):
+    return oi.output_size[0] < oi.buf_size
+
+
+def get_input_buffer_size(hse):
+    return 1 << hse.window_size
+
+
+def get_lookahead_size(hse):
+    return 1 << hse.lookahead_size
+
+
+def get_input_offset(hse):
+    return get_input_buffer_size(hse)
+
+
+def heatshrink_encoder_sink(hse, in_buf, size, input_size):
+    if hse is None or in_buf is None or input_size is None:
+        return HSE_sink_res.HSER_SINK_ERROR_NULL
+
+    if is_finishing(hse):
+        return HSE_sink_res.HSER_SINK_ERROR_MISUSE
+
+    if hse.state != HSE_state.HSES_NOT_FULL:
+        return HSE_sink_res.HSER_SINK_ERROR_MISUSE
+
+    write_offset = get_input_offset(hse) + hse.input_size
+    ibs = get_input_buffer_size(hse)
+    rem = ibs - hse.input_size
+    cp_sz = min(rem, size)
+
+    for i in range(cp_sz):
+        hse.buffer[write_offset + i] = in_buf[i]
+    input_size.value = cp_sz
+    hse.input_size += cp_sz
+
+    if cp_sz == rem:
+        hse.state = HSE_state.HSES_FILLED
+
+    return HSE_sink_res.HSER_SINK_OK
+
+
+def do_indexing(hse):
+    # Build an index array I that contains flattened linked lists
+    # for the previous instances of every byte in the buffer.
+
+    hsi = hse.search_index
+    last = [0xffff] * 256
+    buf = hse.buffer
+    index = hsi.index
+    input_offset = get_input_offset(hse)
+    end = input_offset + hse.input_size
+
+    for i in range(0, end):
+        v = buf[i]
+        lv = last[v]
+        index[i] = lv
+        last[v] = i
+
+
+def heatshrink_encoder_poll(hse, out_buf, out_buf_size, output_size):
+    if hse is None or out_buf is None or output_size is None:
+        return HSE_poll_res.HSER_POLL_ERROR_NULL
+
+    if out_buf_size == 0:
+        return HSE_poll_res.HSER_POLL_ERROR_MISUSE
+
+    output_size[0] = 0
+    oi = output_info()
+    oi.buf = out_buf
+    oi.buf_size = out_buf_size
+    oi.output_size = output_size
+
+    while True:
+        in_state = hse.state
+        if in_state == HSE_state.HSES_NOT_FULL:
+            return HSE_poll_res.HSER_POLL_EMPTY
+        elif in_state == HSE_state.HSES_DONE:
+            return HSE_poll_res.HSER_POLL_EMPTY
+        elif in_state == HSE_state.HSES_FILLED:
+            do_indexing(hse)
+            hse.state = HSE_state.HSES_SEARCH
+        elif in_state == HSE_state.HSES_SEARCH:
+            hse.state = st_step_search(hse)
+        elif in_state == HSE_state.HSES_YIELD_TAG_BIT:
+            hse.state = st_yield_tag_bit(hse, oi)
+        elif in_state == HSE_state.HSES_YIELD_LITERAL:
+            hse.state = st_yield_literal(hse, oi)
+        elif in_state == HSE_state.HSES_YIELD_BR_INDEX:
+            hse.state = st_yield_br_index(hse, oi)
+        elif in_state == HSE_state.HSES_YIELD_BR_LENGTH:
+            hse.state = st_yield_br_length(hse, oi)
+        elif in_state == HSE_state.HSES_SAVE_BACKLOG:
+            hse.state = st_save_backlog(hse)
+        elif in_state == HSE_state.HSES_FLUSH_BITS:
+            hse.state = st_flush_bit_buffer(hse, oi)
+        else:
+            return HSE_poll_res.HSER_POLL_ERROR_MISUSE
+
+        if hse.state == in_state:
+            if oi.output_size == oi.buf_size:
+                return HSE_poll_res.HSER_POLL_MORE
+
+
+def heatshrink_encoder_finish(hse):
+    hse.flags |= FLAG_IS_FINISHING
+    if hse.state == HSE_state.HSES_NOT_FULL:
+        hse.state = HSE_state.HSES_FILLED
+    if hse.state == HSE_state.HSES_DONE:
+        return HSE_finish_res.HSER_FINISH_DONE
+    return HSE_finish_res.HSER_FINISH_MORE
+
+
+def st_step_search(hse):
+    window_length = get_input_buffer_size(hse)
+    lookahead_sz = get_lookahead_size(hse)
+    msi = hse.match_scan_index
+
+    fin = is_finishing(hse)
+    if msi > hse.input_size - (1 if fin else lookahead_sz):
+        return HSE_state.HSES_FLUSH_BITS if fin else HSE_state.HSES_SAVE_BACKLOG
+
+    input_offset = get_input_offset(hse)
+    end = input_offset + msi
+    start = end - window_length
+
+    max_possible = lookahead_sz if hse.input_size - msi >= lookahead_sz else hse.input_size - msi
+
+    match_pos, match_length = find_longest_match(hse, start, end, max_possible)
+
+    if match_pos == MATCH_NOT_FOUND:
+        hse.match_scan_index += 1
+        hse.match_length = 0
+        return HSE_state.HSES_YIELD_TAG_BIT
+    else:
+        hse.match_pos = match_pos
+        hse.match_length = match_length
+        return HSE_state.HSES_YIELD_TAG_BIT
+
+
+def find_longest_match(hse, start, end, maxlen):
+    buf = hse.buffer
+
+    match_maxlen = 0
+    match_index = MATCH_NOT_FOUND
+
+    needlepoint = end
+
+    pos = hse.search_index.index[end]
+    buf_needlepoint_maxlen = buf[needlepoint + match_maxlen]
+    while pos >= start:
+
+        if buf[pos + match_maxlen] != buf_needlepoint_maxlen:
+            pos = hse.search_index.index[pos]
+            continue
+
+        length = 1
+        for length in range(1, maxlen):
+            if buf[pos + length] != buf[needlepoint + length]:
+                break
+        if length > match_maxlen:
+            match_maxlen = length
+            match_index = pos
+            buf_needlepoint_maxlen = buf[needlepoint + match_maxlen]
+            if length == maxlen:
+                break  # won't find better
+
+        pos = hse.search_index.index[pos]
+
+    break_even_point = 1 + hse.window_size + hse.lookahead_size
+
+    if match_maxlen > (break_even_point // 8):
+        return end - match_index, match_maxlen
+    return MATCH_NOT_FOUND, 0
+
+
+def push_outgoing_bits(hse, oi):
+    if hse.outgoing_bits_count > 8:
+        count = 8
+        bits = hse.outgoing_bits >> (hse.outgoing_bits_count - 8)
+    else:
+        count = hse.outgoing_bits_count
+        bits = hse.outgoing_bits
+
+    if count > 0:
+        push_bits(hse, count, bits, oi)
+        hse.outgoing_bits_count -= count
+    return count
+
+
+def st_yield_tag_bit(hse, oi):
+    if can_take_byte(oi):
+        if hse.match_length == 0:
+            add_tag_bit(hse, oi, HEATSHRINK_LITERAL_MARKER)
+            return HSE_state.HSES_YIELD_LITERAL
+        else:
+            add_tag_bit(hse, oi, HEATSHRINK_BACKREF_MARKER)
+            hse.outgoing_bits = hse.match_pos - 1
+            hse.outgoing_bits_count = hse.window_size
+            return HSE_state.HSES_YIELD_BR_INDEX
+    else:
+        return HSE_state.HSES_YIELD_TAG_BIT
+
+
+def st_yield_literal(hse, oi):
+    if can_take_byte(oi):
+        push_literal_byte(hse, oi)
+        return HSE_state.HSES_SEARCH
+    else:
+        return HSE_state.HSES_YIELD_LITERAL
+
+
+def st_yield_br_index(hse, oi):
+    if can_take_byte(oi):
+        if push_outgoing_bits(hse, oi) > 0:
+            return HSE_state.HSES_YIELD_BR_INDEX
+        else:
+            hse.outgoing_bits = hse.match_length - 1
+            hse.outgoing_bits_count = hse.lookahead_size
+            return HSE_state.HSES_YIELD_BR_LENGTH
+    else:
+        return HSE_state.HSES_YIELD_BR_INDEX
+
+
+def st_yield_br_length(hse, oi):
+    if can_take_byte(oi):
+        if push_outgoing_bits(hse, oi) > 0:
+            return HSE_state.HSES_YIELD_BR_LENGTH
+        else:
+            hse.match_scan_index += hse.match_length
+            hse.match_length = 0
+            return HSE_state.HSES_SEARCH
+    else:
+        return HSE_state.HSES_YIELD_BR_LENGTH
+
+
+def st_save_backlog(hse):
+    save_backlog(hse)
+    return HSE_state.HSES_NOT_FULL
+
+
+def st_flush_bit_buffer(hse, oi):
+    if hse.bit_index == 0x80:
+        return HSE_state.HSES_DONE
+    elif can_take_byte(oi):
+        oi.buf[oi.output_size[0]] = hse.current_byte
+        oi.output_size[0] += 1
+        return HSE_state.HSES_DONE
+    else:
+        return HSE_state.HSES_FLUSH_BITS
+
+
+def save_backlog(hse):
+    input_buf_sz = get_input_buffer_size(hse)
+
+    msi = hse.match_scan_index
+
+    rem = input_buf_sz - msi  # unprocessed bytes
+    shift_sz = input_buf_sz + rem
+
+    for i in range(shift_sz):
+        hse.buffer[i] = hse.buffer[input_buf_sz - rem + i]
+
+    hse.match_scan_index = 0
+    hse.input_size -= input_buf_sz - rem
+
+
+def encode(data, window_size, lookahead_size):
+    hse = heatshrink_encoder(window_size, lookahead_size)
+    input_buf = (ctypes.c_uint8 * len(data))()
+    for i, d in enumerate(data):
+        input_buf[i] = d
+    in_size = len(input_buf)
+
+    out_buf_size = 4 * in_size  # set output buffer size a bit larger
+    out_buf = (ctypes.c_uint8 * out_buf_size)()
+
+    sunk = 0
+    ret = []
+    while sunk < in_size:
+        input_size = ctypes.c_size_t(in_size)
+        heatshrink_encoder_sink(hse, input_buf, in_size - sunk, input_size)
+        input_buf = input_buf[input_size.value:]
+        sunk += input_size.value
+        if sunk == in_size:
+            heatshrink_encoder_finish(hse)
+
+        poll_res = HSE_poll_res.HSER_POLL_MORE
+        while poll_res == HSE_poll_res.HSER_POLL_MORE:
+            output_size = (ctypes.c_size_t * 1)()
+            poll_res = heatshrink_encoder_poll(hse, out_buf, out_buf_size, output_size)
+            ret += list(out_buf)[0:output_size[0]]
+
+        if sunk == in_size:
+            heatshrink_encoder_finish(hse)
+    return ret
+

src/modules/logger/CMakeLists.txt

@@ -35,6 +35,7 @@ px4_add_module(
 	MODULE modules__logger
 	MAIN logger
 	PRIORITY "SCHED_PRIORITY_MAX-30"
+	STACK_MAIN 2500
 	COMPILE_FLAGS
 		${MAX_CUSTOM_OPT_LEVEL}
 		-Wno-cast-align # TODO: fix and enable

src/modules/logger/logger.cpp

@@ -44,12 +44,14 @@
 #include <stdlib.h>
 #include <time.h>
 
+#include <uORB/uORBMessageFields.hpp>
 #include <uORB/Publication.hpp>
 #include <uORB/topics/uORBTopics.hpp>
 #include <uORB/topics/parameter_update.h>
 #include <uORB/topics/vehicle_command_ack.h>
 #include <uORB/topics/battery_status.h>
 
+#include <containers/Bitset.hpp>
 #include <drivers/drv_hrt.h>
 #include <mathlib/math/Limits.hpp>
 #include <px4_platform/cpuload.h>
@@ -1659,156 +1661,134 @@ void Logger::write_console_output()
 
 }
 
-void Logger::write_format(LogType type, const orb_metadata &meta, WrittenFormats &written_formats,
-			  ulog_message_format_s &msg, int subscription_index, int level)
-{
-	if (level > 3) {
-		// precaution: limit recursion level. If we land here it's either a bug or nested topic definitions. In the
-		// latter case, increase the maximum level.
-		PX4_ERR("max recursion level reached (%i)", level);
-		return;
-	}
-
-	// check if we already wrote the format: either if at a previous _subscriptions index or in written_formats
-	for (const auto &written_format : written_formats) {
-		if (written_format == &meta) {
-			PX4_DEBUG("already added: %s", meta.o_name);
-			return;
-		}
-	}
-
-	for (int i = 0; i < subscription_index; ++i) {
-		if (_subscriptions[i].get_topic() == &meta) {
-			PX4_DEBUG("already in _subscriptions: %s", meta.o_name);
-			return;
-		}
-	}
-
-	PX4_DEBUG("writing format for %s", meta.o_name);
-
-	// Write the current format (we don't need to check if we already added it to written_formats)
-	int format_len = snprintf(msg.format, sizeof(msg.format), "%s:", meta.o_name);
-
-	for (int format_idx = 0; meta.o_fields[format_idx] != 0;) {
-		const char *end_field = strchr(meta.o_fields + format_idx, ';');
-
-		if (!end_field) {
-			PX4_ERR("Format error in %s", meta.o_fields);
-			return;
-		}
-
-		const char *c_type = orb_get_c_type(meta.o_fields[format_idx]);
-
-		if (c_type) {
-			format_len += snprintf(msg.format + format_len, sizeof(msg.format) - format_len, "%s", c_type);
-			++format_idx;
-		}
-
-		int len = end_field - (meta.o_fields + format_idx) + 1;
-
-		if (len >= (int)sizeof(msg.format) - format_len) {
-			PX4_WARN("skip topic %s, format string is too large, max is %zu", meta.o_name,
-				 sizeof(ulog_message_format_s::format));
-			return;
-		}
-
-		memcpy(msg.format + format_len, meta.o_fields + format_idx, len);
-		format_len += len;
-		format_idx += len;
-	}
-
-	msg.format[format_len] = '\0';
-	size_t msg_size = sizeof(msg) - sizeof(msg.format) + format_len;
-	msg.msg_size = msg_size - ULOG_MSG_HEADER_LEN;
-
-	write_message(type, &msg, msg_size);
-
-	if (level > 1 && !written_formats.push_back(&meta)) {
-		PX4_ERR("Array too small");
-	}
-
-	// Now go through the fields and check for nested type usages.
-	// o_fields looks like this for example: "<chr> timestamp;<chr>[5] array;"
-	const char *fmt = meta.o_fields;
-
-	while (fmt && *fmt) {
-		// extract the type name
-		char type_name[64];
-		const char *space = strchr(fmt, ' ');
-
-		if (!space) {
-			PX4_ERR("invalid format %s", fmt);
-			break;
-		}
-
-		const char *array_start = strchr(fmt, '['); // check for an array
-
-		int type_length;
-
-		if (array_start && array_start < space) {
-			type_length = array_start - fmt;
-
-		} else {
-			type_length = space - fmt;
-		}
-
-		if (type_length >= (int)sizeof(type_name)) {
-			PX4_ERR("buf len too small");
-			break;
-		}
-
-		memcpy(type_name, fmt, type_length);
-		type_name[type_length] = '\0';
-
-		// ignore built-in types
-		if (orb_get_c_type(type_name[0]) == nullptr) {
-
-			// find orb meta for type
-			const orb_metadata *const *topics = orb_get_topics();
-			const orb_metadata *found_topic = nullptr;
-
-			for (size_t i = 0; i < orb_topics_count(); i++) {
-				if (strcmp(topics[i]->o_name, type_name) == 0) {
-					found_topic = topics[i];
-				}
-			}
-
-			if (found_topic) {
-
-				write_format(type, *found_topic, written_formats, msg, subscription_index, level + 1);
-
-			} else {
-				PX4_ERR("No definition for topic %s found", fmt);
-			}
-		}
-
-		fmt = strchr(fmt, ';');
-
-		if (fmt) { ++fmt; }
-	}
-}
-
 void Logger::write_formats(LogType type)
 {
 	_writer.lock();
 
-	// both of these are large and thus we need to be careful in terms of stack size requirements
+	// This is large and thus we need to be careful in terms of stack size requirements
 	ulog_message_format_s msg;
-	WrittenFormats written_formats;
 
-	// write all subscribed formats
+	// Write all subscribed formats
 	int sub_count = _num_subscriptions;
 
 	if (type == LogType::Mission) {
 		sub_count = _num_mission_subs;
 	}
 
+	// Keep a bitset of all required formats (nested definitions are added later on to the bitset)
+	px4::Bitset<ORB_TOPICS_COUNT> formats_to_write;
+
 	for (int i = 0; i < sub_count; ++i) {
 		const LoggerSubscription &sub = _subscriptions[i];
-		write_format(type, *sub.get_topic(), written_formats, msg, i);
+
+		if (sub.get_topic()->o_id < formats_to_write.size()) {
+			formats_to_write.set(sub.get_topic()->o_id);
+
+		} else {
+			PX4_ERR("logic error");
+		}
 	}
 
-	write_format(type, *_event_subscription.get_topic(), written_formats, msg, sub_count);
+	formats_to_write.set(_event_subscription.get_topic()->o_id);
+
+
+	static_assert(sizeof(msg.format) > uORB::orb_tokenized_fields_max_length, "uORB message definition too long");
+	uORB::MessageFormatReader format_reader(msg.format, sizeof(msg.format));
+	bool done = false;
+
+	while (!done) {
+		switch (format_reader.readMore()) {
+		case uORB::MessageFormatReader::State::FormatComplete: {
+				unsigned format_length = format_reader.formatLength();
+				// Move the left-over (the part after the format if any) to the end of the buffer
+				const unsigned leftover_length = format_reader.moveLeftoverToBufferEnd();
+
+				bool needs_expansion = true;
+				int last_name_length = 0;
+				bool format_error = false;
+
+				for (const orb_id_size_t orb_id : format_reader.orbIDs()) {
+					if (orb_id >= formats_to_write.size() || !formats_to_write[orb_id]) {
+						continue;
+					}
+
+					// Make sure to write dependencies too
+					for (const orb_id_size_t orb_id_dep : format_reader.orbIDsDependencies()) {
+						formats_to_write.set(orb_id_dep);
+					}
+
+					formats_to_write.set(orb_id, false);
+					const orb_metadata &meta = *get_orb_meta((ORB_ID) orb_id);
+
+					PX4_DEBUG("writing format for %s", meta.o_name);
+
+					// Expand if needed (first time only)
+					if (needs_expansion) {
+						const int ret = uORB::MessageFormatReader::expandMessageFormat(msg.format, format_length,
+								sizeof(msg.format) - leftover_length);
+
+						if (ret < 0) {
+							PX4_ERR("Format %s error (too long?)", meta.o_name);
+							format_error = true;
+
+						} else {
+							format_length = ret;
+						}
+
+						needs_expansion = false;
+					}
+
+					// Prepend format name and ':'
+					const int name_length = strlen(meta.o_name) + 1; // + 1 for ':'
+
+					if (format_length + name_length - last_name_length + 1 > sizeof(msg.format) - leftover_length) {
+						PX4_ERR("Format %s too long", meta.o_name);
+						format_error = true;
+					}
+
+					if (format_error) {
+						break;
+					}
+
+					if (last_name_length != name_length) {
+						memmove(msg.format + name_length, msg.format + last_name_length,
+							format_length + 1 - last_name_length);
+						msg.format[name_length - 1] = ':';
+						format_length += name_length - last_name_length;
+						last_name_length = name_length;
+					}
+
+					memcpy(msg.format, meta.o_name, name_length - 1);
+
+					size_t msg_size = sizeof(msg) - sizeof(msg.format) + format_length;
+					msg.msg_size = msg_size - ULOG_MSG_HEADER_LEN;
+					write_message(type, &msg, msg_size);
+				}
+
+				// Move left-over back
+				format_reader.clearFormatAndRestoreLeftover();
+				break;
+			}
+			break;
+
+		case uORB::MessageFormatReader::State::Failure:
+			PX4_ERR("Failed to read formats");
+			done = true;
+			break;
+
+		case uORB::MessageFormatReader::State::Complete:
+			done = true;
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	if (formats_to_write.count() > 0) {
+		// Getting here is a bug. Maybe the ordering of nested formats is not as expected?
+		PX4_ERR("Not all formats written");
+	}
 
 	_writer.unlock();
 }

src/modules/logger/logger.h

@@ -236,11 +236,6 @@ private:
 	 */
 	void write_header(LogType type);
 
-	/// Array to store written formats for nested definitions (only)
-	using WrittenFormats = Array < const orb_metadata *, 20 >;
-
-	void write_format(LogType type, const orb_metadata &meta, WrittenFormats &written_formats, ulog_message_format_s &msg,
-			  int subscription_index, int level = 1);
 	void write_formats(LogType type);
 
 	/**

src/modules/logger/messages.h

@@ -116,7 +116,7 @@ struct ulog_message_format_s {
 	uint16_t msg_size; ///< size of message - ULOG_MSG_HEADER_LEN
 	uint8_t msg_type = static_cast<uint8_t>(ULogMessageType::FORMAT);
 
-	char format[1500];
+	char format[1600];
 };
 
 /**

src/modules/replay/Replay.cpp

@@ -47,6 +47,7 @@
 #include <px4_platform_common/time.h>
 #include <px4_platform_common/shutdown.h>
 #include <lib/parameters/param.h>
+#include <uORB/uORBMessageFields.hpp>
 
 #include <cstring>
 #include <float.h>
@@ -391,33 +392,30 @@ Replay::readFormat(std::ifstream &file, uint16_t msg_size)
 }
 
 
-string Replay::parseOrbFields(const string &fields)
+string Replay::getOrbFields(const orb_metadata *meta)
 {
-	string ret{};
+	char format[3000];
+	char buffer[512];
+	uORB::MessageFormatReader format_reader(buffer, sizeof(buffer));
 
-	// convert o_fields from "<chr> timestamp;<chr>[5] array;" to "uint64_t timestamp;int8_t[5] array;"
+	if (!format_reader.readUntilFormat(meta->o_id)) {
-	for (int format_idx = 0; format_idx < (int)fields.length();) {
+		PX4_ERR("failed to find format for topic %s", meta->o_name);
-		const char *end_field = strchr(fields.c_str() + format_idx, ';');
+		return "";
-
-		if (!end_field) {
-			PX4_ERR("Format error in %s", fields.c_str());
-			return "";
-		}
-
-		const char *c_type = orb_get_c_type(fields[format_idx]);
-
-		if (c_type) {
-			string str_type = c_type;
-			ret += str_type;
-			++format_idx;
-		}
-
-		int len = end_field - (fields.c_str() + format_idx) + 1;
-		ret += fields.substr(format_idx, len);
-		format_idx += len;
 	}
 
-	return ret;
+	int field_length = 0;
+	int format_length = 0;
+
+	while (format_reader.readNextField(field_length)) {
+		format_length += snprintf(format + format_length, sizeof(buffer) - format_length - 1, "%s;", buffer);
+	}
+
+	if (uORB::MessageFormatReader::expandMessageFormat(format, format_length, sizeof(format)) < 0) {
+		PX4_ERR("failed to expand message format for %s", meta->o_name);
+		return "";
+	}
+
+	return format;
 }
 
 bool
@@ -455,7 +453,7 @@ Replay::readAndAddSubscription(std::ifstream &file, uint16_t msg_size)
 	// FIXME: this should check recursively, all used nested types
 	string file_format = _file_formats[topic_name];
 
-	const string orb_fields = parseOrbFields(orb_meta->o_fields);
+	const string orb_fields = getOrbFields(orb_meta);
 
 	if (file_format != orb_fields) {
 		// check if we have a compatibility conversion available

src/modules/replay/Replay.hpp

@@ -297,7 +297,7 @@ private:
 	void setUserParams(const char *filename);
 	void readDynamicParams(const char *filename);
 
-	std::string parseOrbFields(const std::string &fields);
+	std::string getOrbFields(const orb_metadata *meta);
 
 	static char *_replay_file;
 };