Better name

src/small_allocator.c

@@ -35,7 +35,7 @@ typedef struct {
     uint8_t* base;            // backing store
     uint32_t size;            // total size
     BlockHeader* heap_start;  // first block
-    BlockHeader* next_fit;  // next-fit pointer
+    BlockHeader* next_alloc;  // start of free block search
 } SmallAllocator;
 
 /* --- Header helpers --- */
@@ -104,7 +104,7 @@ void small_allocator_init(SmallAllocator* a, void* backing_store, uint32_t size)
     first->prev = NULL_BLOCK;
 
     a->heap_start = first;
-    a->next_fit = first;
+    a->next_alloc = first;
 }
 
 static void maybe_split_block(SmallAllocator* a, BlockHeader* block, uint32_t size)
@@ -147,6 +147,7 @@ static void merge_with_next(SmallAllocator* a, BlockHeader* block)
     block->next = next->next;
     BlockHeader* nextnext = block_from_offset(a, next->next);
     if (nextnext) nextnext->prev = bh_offset(a, block);
+    // note - caller have to adjust next_alloc on return
 }
 
 void* small_alloc(SmallAllocator* a, uint32_t size)
@@ -156,7 +157,7 @@ void* small_alloc(SmallAllocator* a, uint32_t size)
     }
     size = ALIGN_UP(size);
 
-    BlockHeader* start = a->next_fit ? a->next_fit : a->heap_start;
+    BlockHeader* start = a->next_alloc ? a->next_alloc : a->heap_start;
     BlockHeader* curr = start;
 
     do {
@@ -164,7 +165,7 @@ void* small_alloc(SmallAllocator* a, uint32_t size)
             maybe_split_block(a, curr, size);
             block_set_used(curr);
             BlockHeader *next = block_from_offset(a, curr->next);
-            a->next_fit = next ? next : a->heap_start;;
+            a->next_alloc = next ? next : a->heap_start;;
             return (uint8_t*)curr + sizeof(BlockHeader);
         }
         BlockHeader *next = block_from_offset(a, curr->next);
@@ -194,9 +195,9 @@ void small_free(SmallAllocator* a, void* ptr)
     BlockHeader* prev = block_from_offset(a, block->prev);
     if (prev != NULL && block_is_free(prev)) {
         merge_with_next(a, prev);
-        a->next_fit = prev;
+        a->next_alloc = prev;
     } else {
-        a->next_fit = block;
+        a->next_alloc = block;
     }
 }
 
@@ -213,7 +214,7 @@ void debug_alloc(const SmallAllocator* a)
     puts("--debug end--");
 }
 
-[[gnu::aligned(16)]] char buff[1023 * 1023];
+[[gnu::aligned(16)]] char buff[1023];
 int main(void)
 {
     printf("bh size %zu\n", sizeof(BlockHeader));
@@ -223,15 +224,16 @@ int main(void)
 
     small_allocator_init(&a, buff, sizeof(buff));
     debug_alloc(&a);
-    ptrs[0] = small_alloc(&a, 32);
+    ptrs[0] = small_alloc(&a, 1023-16*2 - 144);
     ptrs[1] = small_alloc(&a, 80);
     ptrs[2] = small_alloc(&a, 32);
-    small_free(&a, ptrs[1]);
+    debug_alloc(&a);
+    small_free(&a, ptrs[0]);
     ptrs[3] = small_alloc(&a, 12);
     ptrs[4] = small_alloc(&a, 12);
     debug_alloc(&a);
 
-    small_free(&a, ptrs[0]);
+    small_free(&a, ptrs[1]);
     small_free(&a, ptrs[2]);
     small_free(&a, ptrs[3]);
     small_free(&a, ptrs[4]);