From 161982b53e91125c858b1c2bf6bf78ba935c7e16 Mon Sep 17 00:00:00 2001
From: Gary Ott <ottman001@hotmail.com>
Date: Tue, 14 Jul 2020 11:09:05 +0100
Subject: [PATCH] Added code to jsuGetFreeStack() for ESP32 and introduced
 ESP_STACK_SIZE constant.

---
 boards/ESP32.py      |  1 +
 src/jsutils.c        | 14 ++++++++++++++
 src/jsutils.h        |  4 ++++
 targets/esp32/main.c | 14 ++++++++++++--
 4 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/boards/ESP32.py b/boards/ESP32.py
index 5ed735df19..a693e0879b 100755
--- a/boards/ESP32.py
+++ b/boards/ESP32.py
@@ -37,6 +37,7 @@
    ],
    'makefile' : [
      'DEFINES+=-DESP_PLATFORM -DESP32=1',
+     'DEFINES+=-DESP_STACK_SIZE=25000',
      'DEFINES+=-DJSVAR_MALLOC', # Allocate space for variables at jsvInit time
      'ESP32_FLASH_MAX=1572864'
    ]
diff --git a/src/jsutils.c b/src/jsutils.c
index c59e270d33..1cd568f9ec 100644
--- a/src/jsutils.c
+++ b/src/jsutils.c
@@ -869,6 +869,20 @@ size_t jsuGetFreeStack() {
   const uint32_t max_stack = 1000000; // give it 1 megabyte of stack
   if (count>max_stack) return 0;
   return max_stack - count;
+#elif defined(ESP32)
+  char ptr; // this is on the stack
+
+  //RTOS task stacks work the opposite way to what you may expect.
+  //Early entries are in higher memory locations.
+  //Later entries are in lower memory locations.
+
+  
+  uint32_t stackPos   = (uint32_t)&ptr;
+  uint32_t stackStart = (uint32_t)espruino_stackHighPtr - ESP_STACK_SIZE;
+
+  if (stackPos < stackStart) return 0; // should never happen, but just in case of overflow!
+  
+  return stackPos - stackStart;
 #else
   // stack depth seems pretty platform-specific :( Default to a value that disables it
   return 1000000; // no stack depth check on this platform
diff --git a/src/jsutils.h b/src/jsutils.h
index 79057b2535..e3fba7614b 100755
--- a/src/jsutils.h
+++ b/src/jsutils.h
@@ -530,4 +530,8 @@ void srand(unsigned int seed);
 /** get the amount of free stack we have, in bytes */
 size_t jsuGetFreeStack();
 
+#ifdef ESP32
+  void *espruino_stackHighPtr;  //Used by jsuGetFreeStack
+#endif
+
 #endif /* JSUTILS_H_ */
diff --git a/targets/esp32/main.c b/targets/esp32/main.c
index c0e9e55bcc..598d7ce708 100644
--- a/targets/esp32/main.c
+++ b/targets/esp32/main.c
@@ -30,6 +30,8 @@
 
 #include "jsvar.h"
 
+extern void *espruino_stackHighPtr;  //Name spaced because this has to be a global variable.
+                                     //Used in jsuGetFreeStack().
 
 extern void initialise_wifi(void);
 
@@ -43,6 +45,14 @@ static void uartTask(void *data) {
 
 static void espruinoTask(void *data) {
   int heapVars;
+
+#ifdef ESP32
+    espruino_stackHighPtr = &heapVars;  //Ignore the name, 'heapVars' is on the stack!
+                          //I didn't use another variable becaue this function never ends so
+                          //all variables declared here consume stack space that is never freed. 
+#endif
+
+
   PWMInit();
   RMTInit();
   SPIChannelsInit();
@@ -101,10 +111,10 @@ int app_main(void)
 #ifdef RTOS
   queues_init();
   tasks_init();
-  task_init(espruinoTask,"EspruinoTask",25000,5,0);
+  task_init(espruinoTask,"EspruinoTask", ESP_STACK_SIZE, 5, 0);
   task_init(uartTask,"ConsoleTask",2200,20,0);
 #else
-  xTaskCreatePinnedToCore(&espruinoTask, "espruinoTask", 25000, NULL, 5, NULL, 0);
+  xTaskCreatePinnedToCore(&espruinoTask, "espruinoTask", ESP_STACK_SIZE, NULL, 5, NULL, 0);
   xTaskCreatePinnedToCore(&uartTask,"uartTask",2200,NULL,20,NULL,0);
 #endif
   return 0;