Add properties to SDL_IOStreams returned by IOFromMem

include/SDL3/SDL_iostream.h

@@ -291,6 +291,13 @@ extern SDL_DECLSPEC SDL_IOStream * SDLCALL SDL_IOFromFile(const char *file, cons
  * buffer, you should use SDL_IOFromConstMem() with a read-only buffer of
  * memory instead.
  *
+ * The following properties will be set at creation time by SDL:
+ *
+ * - `SDL_PROP_IOSTREAM_MEMORY_POINTER`: this will be the `mem` parameter that
+ *   was passed to this function.
+ * - `SDL_PROP_IOSTREAM_MEMORY_SIZE_NUMBER`: this will be the `size` parameter
+ *   that was passed to this function.
+ *
  * \param mem a pointer to a buffer to feed an SDL_IOStream stream.
  * \param size the buffer size, in bytes.
  * \returns a pointer to a new SDL_IOStream structure or NULL on failure; call
@@ -308,6 +315,9 @@ extern SDL_DECLSPEC SDL_IOStream * SDLCALL SDL_IOFromFile(const char *file, cons
  */
 extern SDL_DECLSPEC SDL_IOStream * SDLCALL SDL_IOFromMem(void *mem, size_t size);
 
+#define SDL_PROP_IOSTREAM_MEMORY_POINTER "SDL.iostream.memory.base"
+#define SDL_PROP_IOSTREAM_MEMORY_SIZE_NUMBER  "SDL.iostream.memory.size"
+
 /**
  * Use this function to prepare a read-only memory buffer for use with
  * SDL_IOStream.
@@ -325,6 +335,13 @@ extern SDL_DECLSPEC SDL_IOStream * SDLCALL SDL_IOFromMem(void *mem, size_t size)
  * If you need to write to a memory buffer, you should use SDL_IOFromMem()
  * with a writable buffer of memory instead.
  *
+ * The following properties will be set at creation time by SDL:
+ *
+ * - `SDL_PROP_IOSTREAM_MEMORY_POINTER`: this will be the `mem` parameter that
+ *   was passed to this function.
+ * - `SDL_PROP_IOSTREAM_MEMORY_SIZE_NUMBER`: this will be the `size` parameter
+ *   that was passed to this function.
+ *
  * \param mem a pointer to a read-only buffer to feed an SDL_IOStream stream.
  * \param size the buffer size, in bytes.
  * \returns a pointer to a new SDL_IOStream structure or NULL on failure; call

src/file/SDL_iostream.c

@@ -793,6 +793,12 @@ SDL_IOStream *SDL_IOFromMem(void *mem, size_t size)
     SDL_IOStream *iostr = SDL_OpenIO(&iface, iodata);
     if (!iostr) {
         SDL_free(iodata);
+    } else {
+        const SDL_PropertiesID props = SDL_GetIOProperties(iostr);
+        if (props) {
+            SDL_SetPointerProperty(props, SDL_PROP_IOSTREAM_MEMORY_POINTER, mem);
+            SDL_SetNumberProperty(props, SDL_PROP_IOSTREAM_MEMORY_SIZE_NUMBER, size);
+        }
     }
     return iostr;
 }
@@ -827,6 +833,12 @@ SDL_IOStream *SDL_IOFromConstMem(const void *mem, size_t size)
     SDL_IOStream *iostr = SDL_OpenIO(&iface, iodata);
     if (!iostr) {
         SDL_free(iodata);
+    } else {
+        const SDL_PropertiesID props = SDL_GetIOProperties(iostr);
+        if (props) {
+            SDL_SetPointerProperty(props, SDL_PROP_IOSTREAM_MEMORY_POINTER, (void *)mem);
+            SDL_SetNumberProperty(props, SDL_PROP_IOSTREAM_MEMORY_SIZE_NUMBER, size);
+        }
     }
     return iostr;
 }