branches/zip: Reduce internal memory fragmentation.

mem_alloc2(): New macro.  This is a variant of mem_alloc() that
returns the allocated size, which is equal to or greater than
the requested size.

mem_alloc_func(): Add the output parameter *size for the allocated size.
When it is set, adjust the parameter passed to mem_heap_alloc().

rec_copy_prefix_to_buf_old(), rec_copy_prefix_to_buf(): Use mem_alloc2()
instead of mem_alloc().

include/mem0mem.h

@@ -199,7 +199,8 @@ Macro for memory buffer allocation */
 
 #define mem_zalloc(N)	memset(mem_alloc(N), 0, (N));
 
-#define mem_alloc(N)	mem_alloc_func((N), __FILE__, __LINE__)
+#define mem_alloc(N)	mem_alloc_func((N), NULL, __FILE__, __LINE__)
+#define mem_alloc2(N,S)	mem_alloc_func((N), (S), __FILE__, __LINE__)
 /*******************************************************************
 NOTE: Use the corresponding macro instead of this function.
 Allocates a single buffer of memory from the dynamic memory of
@@ -210,7 +211,9 @@ void*
 mem_alloc_func(
 /*===========*/
 					/* out, own: free storage */
-	ulint		n,		/* in: desired number of bytes */
+	ulint		n,		/* in: requested size in bytes */
+	ulint*		size,		/* out: allocated size in bytes,
+					or NULL */
 	const char*	file_name,	/* in: file name where created */
 	ulint		line);		/* in: line where created */
 

include/mem0mem.ic

@@ -496,6 +496,8 @@ mem_alloc_func(
 /*===========*/
 					/* out, own: free storage */
 	ulint		n,		/* in: desired number of bytes */
+	ulint*		size,		/* out: allocated size in bytes,
+					or NULL */
 	const char*	file_name,	/* in: file name where created */
 	ulint		line)		/* in: line where created */
 {
@@ -509,6 +511,18 @@ mem_alloc_func(
 	first block and thus we can calculate the pointer to the heap from
 	the pointer to the buffer when we free the memory buffer. */
 
+	if (UNIV_LIKELY_NULL(size)) {
+		/* Adjust the allocation to the actual size of the
+		memory block. */
+		ulint	m = mem_block_get_len(heap)
+			- mem_block_get_free(heap);
+#ifdef UNIV_MEM_DEBUG
+		m -= MEM_FIELD_HEADER_SIZE + MEM_FIELD_TRAILER_SIZE;
+#endif /* UNIV_MEM_DEBUG */
+		ut_ad(m >= n);
+		*size = n = m;
+	}
+
 	buf = mem_heap_alloc(heap, n);
 
 	ut_a((byte*)heap == (byte*)buf - MEM_BLOCK_HEADER_SIZE

rem/rem0rec.c

@@ -1260,8 +1260,7 @@ rec_copy_prefix_to_buf_old(
 			mem_free(*buf);
 		}
 
-		*buf = mem_alloc(prefix_len);
-		*buf_size = prefix_len;
+		*buf = mem_alloc2(prefix_len, buf_size);
 	}
 
 	ut_memcpy(*buf, rec - area_start, prefix_len);
@@ -1378,8 +1377,7 @@ rec_copy_prefix_to_buf(
 			mem_free(*buf);
 		}
 
-		*buf = mem_alloc(prefix_len);
-		*buf_size = prefix_len;
+		*buf = mem_alloc2(prefix_len, buf_size);
 	}
 
 	memcpy(*buf, lens + 1, prefix_len);