Memory alignment, better realloc impl

axl_memory.c

@@ -12,11 +12,18 @@ struct mb_header
 
 typedef struct mb_header mb_header;
 
-#define MB_HEADER_SIZE sizeof(mb_header)
-
 static mb_header* root = NULL;
 static mb_header* nomad = NULL;
 
+#define AXL_ALIGNMENT 8
+
+static inline u32 axl_align(u32 size)
+{
+    return (size + (AXL_ALIGNMENT - 1)) & ~(AXL_ALIGNMENT - 1);
+}
+
+#define MB_HEADER_SIZE axl_align(sizeof(mb_header))
+
 void* axl_memset(void* ptr, i8 c, u32 n)
 {
     if(ptr)
@@ -46,7 +53,12 @@ void axl_init(void)
     }
 }
 
-mb_header* axl_find_mb(u32 req_size)
+static inline mb_header* axl_get_mb_header(void* ptr)
+{
+    return (mb_header*)((u8*)ptr - MB_HEADER_SIZE);
+}
+
+static mb_header* axl_find_mb(u32 req_size)
 {
     mb_header* block = nomad ? nomad : root; 
     mb_header* start = block;
@@ -76,28 +88,42 @@ mb_header* axl_find_mb(u32 req_size)
     return NULL;
 }
 
-void axl_split_mb(mb_header* block, u32 size)
+static b8 axl_split_mb(mb_header* block, u32 size)
 {
-    if(block->size > size + MB_HEADER_SIZE)
+    if(block->size > size)
     {
-        mb_header* new_block = (mb_header*)((u8*)block + MB_HEADER_SIZE + size);
+        if(block->size - size >= MB_HEADER_SIZE + AXL_ALIGNMENT)
-        new_block->size = block->size - size - MB_HEADER_SIZE;
-        new_block->is_free = true; 
-        new_block->next = block->next;
-        new_block->prev = block;
-
-        if(new_block->next)
         {
-            new_block->next->prev = new_block;
+            mb_header* new_block = (mb_header*)((u8*)block + MB_HEADER_SIZE + size);
-        }
+            new_block->size = block->size - size - MB_HEADER_SIZE;
+            new_block->is_free = true; 
+            new_block->next = block->next;
+            new_block->prev = block;
 
-        block->size = size; 
+            if(new_block->next)
-        block->next = new_block;
+            {
+                new_block->next->prev = new_block;
+            }
+
+            block->size = size; 
+            block->next = new_block;
+
+            return true;
+        }
     }
+
+    return false;
 }
 
 void* axl_malloc(u32 size)
 {
+    if(size == 0)
+    {
+        return NULL;
+    }
+
+    size = axl_align(size);
+
     if(size > AXL_HEAP_SIZE - MB_HEADER_SIZE)
     {
         return NULL;
@@ -122,6 +148,52 @@ void* axl_malloc(u32 size)
     return (void*)((u8*)free_block + MB_HEADER_SIZE);
 }
 
+void* axl_memcpy(void* dst, const void* src, u32 count)
+{
+    for(u32 i = 0; i < count; i++)
+    {
+        *((u8*)dst + i) = *((u8*)src + i);
+    }
+
+    return dst;
+}
+
+void* axl_realloc(void* ptr, u32 size)
+{
+    if(size == 0)
+    {
+        axl_free(ptr);
+        return NULL;
+    }
+
+    size = axl_align(size);
+
+    if(!ptr)
+    {
+        return axl_malloc(size);
+    }
+
+    mb_header* old = axl_get_mb_header(ptr);
+    if(axl_split_mb(old, size))
+    {
+        return ptr;
+    }  
+
+    void* new = axl_malloc(size);
+
+    if(!new)
+    {
+        return NULL;
+    }
+
+    size = size < old->size ? size : old->size;
+    axl_memcpy(new, ptr, size);
+
+    axl_free(ptr);
+
+    return new;
+}
+
 void axl_free(void* ptr)
 {
     if(!ptr)
@@ -129,7 +201,7 @@ void axl_free(void* ptr)
         return;
     }
 
-    mb_header* block = (mb_header*)((u8*)ptr - MB_HEADER_SIZE);
+    mb_header* block = axl_get_mb_header(ptr);
     mb_header* next_block = block->next;
     mb_header* prev_block = block->prev;
     block->is_free = true; 

axl_memory.h

@@ -9,6 +9,7 @@
 
 void    axl_init(void);
 void*   axl_malloc(u32 size);
+void*   axl_realloc(void* ptr, u32 size);
 void*   axl_memset(void* ptr, i8 c, u32 n);
 void    axl_free(void* ptr);
 

makefile

@@ -1,11 +1,11 @@
 CC = clang
 CFLAGS = -Wall -Wextra -Werror -pedantic -std=c11 -nostdlib -static -Oz -ffreestanding
 LDFLAGS = -Wl,/SUBSYSTEM:CONSOLE,/ENTRY:_start -fuse-ld=lld
-LIBS = -lkernel32 -luser32
+LIBS = -lkernel32
 SOURCES = main.c axl_memory.c
 TARGET = prog.exe
 
-all: $(TARGET)
+all: clean $(TARGET)
 
 $(TARGET): $(SOURCES) 
 	$(CC) $(CFLAGS) $(SOURCES) -o $(TARGET) $(LDFLAGS) $(LIBS)