eliminate rc_scratch_buffer_t (#287)

src/rcheevos/alloc.c

@@ -5,7 +5,7 @@
 
 void* rc_alloc_scratch(void* pointer, int32_t* offset, uint32_t size, uint32_t alignment, rc_scratch_t* scratch, uint32_t scratch_object_pointer_offset)
 {
-  rc_scratch_buffer_t* buffer;
+  void* data;
 
   /* if we have a real buffer, then allocate the data there */
   if (pointer)
@@ -19,49 +19,13 @@ void* rc_alloc_scratch(void* pointer, int32_t* offset, uint32_t size, uint32_t a
   }
 
   /* find a scratch buffer to hold the temporary data */
-  buffer = &scratch->buffer;
-  do {
-    const uint32_t aligned_buffer_offset = (buffer->offset + alignment - 1) & ~(alignment - 1);
-    if (aligned_buffer_offset < sizeof(buffer->buffer)) {
-      const uint32_t remaining = sizeof(buffer->buffer) - aligned_buffer_offset;
-
-      if (remaining >= size) {
-        /* claim the required space from an existing buffer */
-        return rc_alloc(buffer->buffer, &buffer->offset, size, alignment, NULL, -1);
-      }
-    }
-
-    if (!buffer->next)
-      break;
-
-    buffer = buffer->next;
-  } while (1);
-
-  /* not enough space in any existing buffer, allocate more */
-  if (size > (uint32_t)sizeof(buffer->buffer)) {
-    /* caller is asking for more than we can fit in a standard rc_scratch_buffer_t.
-     * leverage the fact that the buffer is the last field and extend its size.
-     * this chunk will be exactly large enough to hold the needed data, and since offset
-     * will exceed sizeof(buffer->buffer), it will never be eligible to hold anything else.
-     */
-    const size_t needed = sizeof(rc_scratch_buffer_t) - sizeof(buffer->buffer) + size;
-    buffer->next = (rc_scratch_buffer_t*)malloc(needed);
-  }
-  else {
-    buffer->next = (rc_scratch_buffer_t*)malloc(sizeof(rc_scratch_buffer_t));
-  }
-
-  if (!buffer->next) {
+  data = rc_buffer_alloc(&scratch->buffer, size);
+  if (!data) {
     *offset = RC_OUT_OF_MEMORY;
     return NULL;
   }
 
-  buffer = buffer->next;
-  buffer->offset = 0;
-  buffer->next = NULL;
-
-  /* claim the required space from the new buffer */
-  return rc_alloc(buffer->buffer, &buffer->offset, size, alignment, NULL, -1);
+  return data;
 }
 
 void* rc_alloc(void* pointer, int32_t* offset, uint32_t size, uint32_t alignment, rc_scratch_t* scratch, uint32_t scratch_object_pointer_offset) {
@@ -137,9 +101,8 @@ void rc_init_parse_state(rc_parse_state_t* parse, void* buffer, lua_State* L, in
   parse->L = L;
   parse->funcs_ndx = funcs_ndx;
   parse->buffer = buffer;
-  parse->scratch.buffer.offset = 0;
-  parse->scratch.buffer.next = NULL;
   parse->scratch.strings = NULL;
+  rc_buffer_init(&parse->scratch.buffer);
   memset(&parse->scratch.objs, 0, sizeof(parse->scratch.objs));
   parse->first_memref = 0;
   parse->variables = 0;
@@ -151,12 +114,5 @@ void rc_init_parse_state(rc_parse_state_t* parse, void* buffer, lua_State* L, in
 
 void rc_destroy_parse_state(rc_parse_state_t* parse)
 {
-  rc_scratch_buffer_t* buffer = parse->scratch.buffer.next;
-  rc_scratch_buffer_t* next;
-
-  while (buffer) {
-    next = buffer->next;
-    free(buffer);
-    buffer = next;
-  }
+  rc_buffer_destroy(&parse->scratch.buffer);
 }

src/rcheevos/rc_internal.h

@@ -2,6 +2,7 @@
 #define RC_INTERNAL_H
 
 #include "rc_runtime_types.h"
+#include "../rc_util.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -39,15 +40,8 @@ RC_ALLOW_ALIGN(char)
 /* force alignment to 4 bytes on 32-bit systems, or 8 bytes on 64-bit systems */
 #define RC_ALIGN(n) (((n) + (sizeof(void*)-1)) & ~(sizeof(void*)-1))
 
-typedef struct rc_scratch_buffer {
-  struct rc_scratch_buffer* next;
-  int32_t offset;
-  uint8_t buffer[512 - 16];
-}
-rc_scratch_buffer_t;
-
 typedef struct {
-  rc_scratch_buffer_t buffer;
+  rc_buffer_t buffer;
   rc_scratch_string_t* strings;
 
   struct objs {

src/rcheevos/richpresence.c

@@ -279,7 +279,6 @@ static void rc_rebalance_richpresence_lookup_rebuild(rc_richpresence_lookup_item
 static void rc_rebalance_richpresence_lookup(rc_richpresence_lookup_item_t** root, rc_parse_state_t* parse)
 {
   rc_richpresence_lookup_item_t** items;
-  rc_scratch_buffer_t* buffer;
   int index;
   int size;
 
@@ -288,39 +287,20 @@ static void rc_rebalance_richpresence_lookup(rc_richpresence_lookup_item_t** roo
   if (count < 3)
     return;
 
-  /* allocate space for the flattened list - prefer scratch memory if available */
+  /* allocate space for the flattened list in scratch memory */
   size = count * sizeof(rc_richpresence_lookup_item_t*);
-  buffer = &parse->scratch.buffer;
-  do {
-    const int aligned_offset = RC_ALIGN(buffer->offset);
-    const int remaining = sizeof(buffer->buffer) - aligned_offset;
-
-    if (remaining >= size) {
-      items = (rc_richpresence_lookup_item_t**)&buffer->buffer[aligned_offset];
-      break;
-    }
-
-    buffer = buffer->next;
-    if (buffer == NULL) {
-      /* could not find large enough block of scratch memory; allocate. if allocation fails,
-       * we can still use the unbalanced tree, so just bail out */
-      items = (rc_richpresence_lookup_item_t**)malloc(size);
-      if (items == NULL)
-        return;
+  items = (rc_richpresence_lookup_item_t**)rc_buffer_alloc(&parse->scratch.buffer, size);
 
-      break;
-    }
-  } while (1);
+  /* if allocation fails, we can still use the unbalanced tree, so just bail out */
+  if (items == NULL)
+    return;
 
   /* flatten the list */
   index = 0;
   rc_rebalance_richpresence_lookup_get_items(*root, items, &index);
 
   /* and rebuild it as a balanced tree */
   rc_rebalance_richpresence_lookup_rebuild(root, items, 0, count - 1);
-
-  if (buffer == NULL)
-    free(items);
 }
 
 static void rc_insert_richpresence_lookup_item(rc_richpresence_lookup_t* lookup,