--- mem_align.c	2002/03/21 00:28:33	1.3
+++ mem_align.c	2002/03/24 18:18:40	1.4
@@ -6,21 +6,55 @@
 {
 	uint8_t *mem_ptr;
   
-	if(alignment == 0)
+	if(!alignment)
 	{
-		if((mem_ptr = (uint8_t *) malloc(size + 1)) != NULL) {
+
+		/* We have not to satisfy any alignment */
+		if((mem_ptr = (uint8_t *) malloc(size + 1)) != NULL)
+		{
+
+			/* Store (mem_ptr - "real allocated memory") in *(mem_ptr-1) */
 			*mem_ptr = 0;
+
+			/* Return the mem_ptr pointer */
 			return (void *) mem_ptr++;
+
 		}
+
 	}
 	else
 	{
 		uint8_t *tmp;
 	
-		if((tmp = (uint8_t *) malloc(size + alignment)) != NULL) {
+		/*
+		 * Allocate the required size memory + alignment so we
+		 * can realign the data if necessary
+		 */
+
+		if((tmp = (uint8_t *) malloc(size + alignment)) != NULL)
+		{
+
+			/* Align the tmp pointer */
 			mem_ptr = (uint8_t *)((uint32_t)(tmp + alignment - 1)&(~(uint32_t)(alignment - 1)));
+
+			/*
+			 * Special case where malloc have already satisfied the alignment
+			 * We must add alignment to mem_ptr because we must store
+			 * (mem_ptr - tmp) in *(mem_ptr-1)
+			 * If we do not add alignment to mem_ptr then *(mem_ptr-1) points
+			 * to a forbidden memory space
+			 */
+			if(mem_ptr == tmp) mem_ptr += alignment;
+
+			/*
+			 * (mem_ptr - tmp) is stored in *(mem_ptr-1) so we are able to retrieve
+			 * the real malloc block allocated and free it in xvid_free
+			 */
 			*(mem_ptr - 1) = (uint8_t)(mem_ptr - tmp);
+
+			/* Return the aligned pointer */
 			return (void *) mem_ptr;
+
 		}
 	}
 
@@ -31,10 +65,7 @@
 void xvid_free(void *mem_ptr)
 {
 
-	uint8_t *real_ptr;
-
-	real_ptr = (uint8_t*)mem_ptr;
-
-	free(real_ptr - *(real_ptr -1));
+	/* *(mem_ptr - 1) give us the offset to the real malloc block */
+	free((uint8_t*)mem_ptr - *((uint8_t*)mem_ptr - 1));
 
 }