move lv_draw_buf to lv_mem as lv_mem_buf

This way they can be used as general purpose buffers not only for drawing

src/lv_misc/lv_mem.c

@@ -9,6 +9,7 @@
  *********************/
 #include "lv_mem.h"
 #include "lv_math.h"
+#include "lv_gc.h"
 #include <string.h>
 
 #if LV_MEM_CUSTOM != 0
@@ -375,6 +376,73 @@ uint32_t lv_mem_get_size(const void * data)
 
 #endif /*LV_ENABLE_GC*/
 
+/**
+ * Get a temporal buffer with the given size.
+ * @param size the required size
+ */
+void * lv_mem_buf_get(uint32_t size)
+{
+    /*Try to find a free buffer with suitable size */
+    uint8_t i;
+    for(i = 0; i < LV_MEM_BUF_MAX_NUM; i++) {
+        if(_lv_mem_buf[i].used == 0 && _lv_mem_buf[i].size >= size) {
+            _lv_mem_buf[i].used = 1;
+            return  _lv_mem_buf[i].p;
+        }
+    }
+
+    /*Reallocate a free buffer*/
+    for(i = 0; i < LV_MEM_BUF_MAX_NUM; i++) {
+        if(_lv_mem_buf[i].used == 0) {
+            _lv_mem_buf[i].used = 1;
+            _lv_mem_buf[i].size = size;
+            /*if this fails you probably need to increase your LV_MEM_SIZE/heap size*/
+            _lv_mem_buf[i].p = lv_mem_realloc(_lv_mem_buf[i].p, size);
+            if(_lv_mem_buf[i].p == NULL) {
+                LV_LOG_ERROR("lv_mem_buf_get: Out of memory, can't allocate a new  buffer (increase your LV_MEM_SIZE/heap size)")
+            }
+            return  _lv_mem_buf[i].p;
+        }
+    }
+
+    LV_LOG_ERROR("lv_mem_buf_get: no free buffer. Increase LV_DRAW_BUF_MAX_NUM.");
+
+    return NULL;
+}
+
+/**
+ * Release a memory buffer
+ * @param p buffer to release
+ */
+void lv_mem_buf_release(void * p)
+{
+    uint8_t i;
+    for(i = 0; i < LV_MEM_BUF_MAX_NUM; i++) {
+        if(_lv_mem_buf[i].p == p) {
+            _lv_mem_buf[i].used = 0;
+            return;
+        }
+    }
+
+    LV_LOG_ERROR("lv_mem_buf_release: p is not a known buffer")
+}
+
+/**
+ * Free all memory buffers
+ */
+void lv_mem_buf_free_all(void)
+{
+    uint8_t i;
+    for(i = 0; i < LV_MEM_BUF_MAX_NUM; i++) {
+        if(_lv_mem_buf[i].p) {
+            lv_mem_free(_lv_mem_buf[i].p);
+            _lv_mem_buf[i].p = NULL;
+            _lv_mem_buf[i].used = 0;
+            _lv_mem_buf[i].size = 0;
+        }
+    }
+}
+
 /**********************
  *   STATIC FUNCTIONS
  **********************/