AP_Logger: support logging of files contents

this allows us to see key internal data in log files

libraries/AP_Logger/AP_Logger.cpp

@@ -1358,6 +1358,11 @@ void AP_Logger::io_thread(void)
         if (++counter % 4 == 0) {
             hal.util->log_stack_info();
         }
+#if HAL_LOGGER_FILE_CONTENTS_ENABLED
+        if (counter % 100 == 0) {
+            file_content_update();
+        }
+#endif
     }
 }
 
@@ -1439,6 +1444,80 @@ bool AP_Logger::log_while_disarmed(void) const
     return false;
 }
 
+#if HAL_LOGGER_FILE_CONTENTS_ENABLED
+/*
+  log the content of a file in FILE log messages
+ */
+void AP_Logger::log_file_content(const char *filename)
+{
+    WITH_SEMAPHORE(file_content.sem);
+    auto *file = new file_list;
+    if (file == nullptr) {
+        return;
+    }
+    file->filename = filename;
+    if (file_content.head == nullptr) {
+        file_content.tail = file_content.head = file;
+        file_content.fd = -1;
+    } else {
+        file_content.tail->next = file;
+        file_content.tail = file;
+    }
+}
+
+/*
+  periodic call to log file content
+ */
+void AP_Logger::file_content_update(void)
+{
+    auto *file = file_content.head;
+    if (file == nullptr) {
+        return;
+    }
+
+    // remove a file structure from the linked list
+    auto remove_from_list = [this,file]()
+    { 
+        WITH_SEMAPHORE(file_content.sem);
+        file_content.head = file->next;
+        if (file_content.tail == file) {
+            file_content.tail = file_content.head;
+        }
+        delete file;
+        file_content.fd = -1;
+    };
+
+    if (file_content.fd == -1) {
+        // open a new file
+        file_content.fd  = AP::FS().open(file->filename, O_RDONLY);
+        if (file_content.fd == -1) {
+            remove_from_list();
+            return;
+        }
+        file_content.offset = 0;
+    }
+
+    struct log_File pkt {
+        LOG_PACKET_HEADER_INIT(LOG_FILE_MSG),
+    };
+    strncpy_noterm(pkt.filename, file->filename, sizeof(pkt.filename));
+    const auto length = AP::FS().read(file_content.fd, pkt.data, sizeof(pkt.data));
+    if (length <= 0) {
+        AP::FS().close(file_content.fd);
+        remove_from_list();
+        return;
+    }
+    pkt.offset = file_content.offset;
+    pkt.length = length;
+    if (WriteBlock_first_succeed(&pkt, sizeof(pkt))) {
+        file_content.offset += length;
+    } else {
+        // seek back ready for another try
+        AP::FS().lseek(file_content.fd, file_content.offset, SEEK_SET);
+    }
+}
+#endif // HAL_LOGGER_FILE_CONTENTS_ENABLED
+
 namespace AP {
 
 AP_Logger &logger()

libraries/AP_Logger/AP_Logger.h

@@ -67,6 +67,10 @@
 
 #endif
 
+#ifndef HAL_LOGGER_FILE_CONTENTS_ENABLED
+#define HAL_LOGGER_FILE_CONTENTS_ENABLED HAL_LOGGING_FILESYSTEM_ENABLED
+#endif
+
 #include <AP_HAL/AP_HAL.h>
 #include <AP_AHRS/AP_AHRS.h>
 #include <AP_AHRS/AP_AHRS_DCM.h>
@@ -85,7 +89,6 @@
 
 #include "LoggerMessageWriter.h"
 
-
 class AP_Logger_Backend;
 class AP_AHRS;
 class AP_AHRS_View;
@@ -464,6 +467,9 @@ public:
         return _log_start_count;
     }
 
+    // add a filename to list of files to log. The name must be a constant string, not allocated
+    void log_file_content(const char *name);
+
 protected:
 
     const struct LogStructure *_structures;
@@ -550,6 +556,21 @@ private:
     void start_io_thread(void);
     void io_thread();
 
+#if HAL_LOGGER_FILE_CONTENTS_ENABLED
+    // support for logging file content
+    struct file_list {
+        struct file_list *next;
+        const char *filename;
+    };
+    struct {
+        struct file_list *head, *tail;
+        int fd;
+        uint16_t offset;
+        HAL_Semaphore sem;
+    } file_content;
+    void file_content_update(void);
+#endif
+    
     /* support for retrieving logs via mavlink: */
 
     enum class TransferActivity {

libraries/AP_Logger/LogStructure.h

@@ -687,6 +687,14 @@ struct PACKED log_STAK {
     char name[16];
 };
 
+struct PACKED log_File {
+    LOG_PACKET_HEADER;
+    char filename[16];
+    uint16_t offset;
+    uint16_t length;
+    char data[64];
+};
+
 // FMT messages define all message formats other than FMT
 // UNIT messages define units which can be referenced by FMTU messages
 // FMTU messages associate types (e.g. centimeters/second/second) to FMT message fields
@@ -1318,6 +1326,8 @@ LOG_STRUCTURE_FROM_VISUALODOM \
       "PSCD", "Qffffffff", "TimeUS,TPD,PD,DVD,TVD,VD,DAD,TAD,AD", "smmnnnooo", "F00000000" }, \
     { LOG_STAK_MSG, sizeof(log_STAK), \
       "STAK", "QBBHHN", "TimeUS,Id,Pri,Total,Free,Name", "s#----", "F-----", true }, \
+    { LOG_FILE_MSG, sizeof(log_File), \
+      "FILE",   "NhhZ",       "FileName,Offset,Length,Data", "----", "----" }, \
 LOG_STRUCTURE_FROM_AIS \
 
 // message types 0 to 63 reserved for vehicle specific use
@@ -1396,6 +1406,7 @@ enum LogMessages : uint8_t {
     LOG_IDS_FROM_PRECLAND,
     LOG_IDS_FROM_AIS,
     LOG_STAK_MSG,
+    LOG_FILE_MSG,
 
     _LOG_LAST_MSG_
 };