From 75217ec1e6a3122dfcab66187cf45b7f5e0b5465 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Sun, 3 Dec 2023 11:32:28 +1100
Subject: [PATCH] AP_Scripting: added readstring for uarts

this is much more efficient than reading a byte at a time
---
 libraries/AP_Scripting/docs/docs.lua          |  8 +++++++
 .../generator/description/bindings.desc       |  1 +
 libraries/AP_Scripting/lua_bindings.cpp       | 24 +++++++++++++++++++
 libraries/AP_Scripting/lua_bindings.h         |  1 +
 4 files changed, 34 insertions(+)

diff --git a/libraries/AP_Scripting/docs/docs.lua b/libraries/AP_Scripting/docs/docs.lua
index 856105481e..1d57957c7b 100644
--- a/libraries/AP_Scripting/docs/docs.lua
+++ b/libraries/AP_Scripting/docs/docs.lua
@@ -1140,6 +1140,14 @@ function AP_HAL__UARTDriver_ud:read() end
 ---@param baud_rate uint32_t_ud
 function AP_HAL__UARTDriver_ud:begin(baud_rate) end
 
+--[[
+  read count bytes from a uart and return as a lua string. Note
+  that the returned string can be shorter than the requested length
+--]]
+---@param count integer
+---@return string|nil
+function AP_HAL__UARTDriver_ud:readstring(count) end
+
 
 -- desc
 ---@class RC_Channel_ud
diff --git a/libraries/AP_Scripting/generator/description/bindings.desc b/libraries/AP_Scripting/generator/description/bindings.desc
index 3c0c37a7a9..74cc6c109d 100644
--- a/libraries/AP_Scripting/generator/description/bindings.desc
+++ b/libraries/AP_Scripting/generator/description/bindings.desc
@@ -357,6 +357,7 @@ include AP_SerialManager/AP_SerialManager.h
 ap_object AP_HAL::UARTDriver depends HAL_GCS_ENABLED
 ap_object AP_HAL::UARTDriver method begin void uint32_t 1U UINT32_MAX
 ap_object AP_HAL::UARTDriver method read int16_t
+ap_object AP_HAL::UARTDriver manual readstring AP_HAL__UARTDriver_readstring 1
 ap_object AP_HAL::UARTDriver method write uint32_t uint8_t'skip_check
 ap_object AP_HAL::UARTDriver method available uint32_t
 ap_object AP_HAL::UARTDriver method set_flow_control void AP_HAL::UARTDriver::flow_control'enum AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE AP_HAL::UARTDriver::FLOW_CONTROL_AUTO
diff --git a/libraries/AP_Scripting/lua_bindings.cpp b/libraries/AP_Scripting/lua_bindings.cpp
index 0059fb1150..a8637ed380 100644
--- a/libraries/AP_Scripting/lua_bindings.cpp
+++ b/libraries/AP_Scripting/lua_bindings.cpp
@@ -638,6 +638,30 @@ int AP_HAL__I2CDevice_read_registers(lua_State *L) {
     return success;
 }
 
+int AP_HAL__UARTDriver_readstring(lua_State *L) {
+    binding_argcheck(L, 2);
+
+    AP_HAL::UARTDriver * ud = *check_AP_HAL__UARTDriver(L, 1);
+
+    const uint16_t count = get_uint16_t(L, 2);
+    uint8_t *data = (uint8_t*)malloc(count);
+    if (data == nullptr) {
+        return 0;
+    }
+
+    const auto ret = ud->read(data, count);
+    if (ret < 0) {
+        free(data);
+        return 0;
+    }
+
+    // push to lua string
+    lua_pushlstring(L, (const char *)data, ret);
+    free(data);
+
+    return 1;
+}
+
 #if AP_SCRIPTING_CAN_SENSOR_ENABLED
 int lua_get_CAN_device(lua_State *L) {
 
diff --git a/libraries/AP_Scripting/lua_bindings.h b/libraries/AP_Scripting/lua_bindings.h
index 6bc459dc27..99e4f8a374 100644
--- a/libraries/AP_Scripting/lua_bindings.h
+++ b/libraries/AP_Scripting/lua_bindings.h
@@ -8,6 +8,7 @@ int lua_mission_receive(lua_State *L);
 int AP_Logger_Write(lua_State *L);
 int lua_get_i2c_device(lua_State *L);
 int AP_HAL__I2CDevice_read_registers(lua_State *L);
+int AP_HAL__UARTDriver_readstring(lua_State *L);
 int lua_get_CAN_device(lua_State *L);
 int lua_get_CAN_device2(lua_State *L);
 int lua_dirlist(lua_State *L);