branches/zip: Remove buf_block_t:magic_n.

buf_block_state_valid(): New macro for replacing the magic_n check

btr/btr0sea.c

@@ -356,7 +356,7 @@ btr_search_update_block_hash_info(
 
 	info->last_hash_succ = FALSE;
 
-	ut_a(block->magic_n == BUF_BLOCK_MAGIC_N);
+	ut_a(buf_block_state_valid(block));
 	ut_ad(info->magic_n == BTR_SEARCH_MAGIC_N);
 
 	if ((block->n_hash_helps > 0)

buf/buf0buf.c

@@ -603,8 +603,6 @@ buf_block_init(
 	buf_block_t*	block,	/* in: pointer to control block */
 	byte*		frame)	/* in: pointer to buffer frame */
 {
-	block->magic_n = 0;
-
 	block->state = BUF_BLOCK_NOT_USED;
 
 	block->frame = frame;
@@ -1783,8 +1781,6 @@ buf_page_init_for_backup_restore(
 	buf_block_t*	block)	/* in: block to init */
 {
 	/* Set the state of the block */
-	block->magic_n		= BUF_BLOCK_MAGIC_N;
-
 	buf_block_set_file_page(block, space, offset);
 
 	block->lock_hash_val	= 0;
@@ -1833,8 +1829,6 @@ buf_page_init(
 	ut_a(buf_block_get_state(block) != BUF_BLOCK_FILE_PAGE);
 
 	/* Set the state of the block */
-	block->magic_n		= BUF_BLOCK_MAGIC_N;
-
 	buf_block_set_file_page(block, space, offset);
 
 	block->check_index_page_at_flush = FALSE;

include/buf0buf.h

@@ -708,7 +708,6 @@ struct buf_block_struct{
 
 	/* 1. General fields */
 
-	ulint		magic_n;	/* magic number to check */
 	ulint		state;		/* state of the control block:
 					BUF_BLOCK_NOT_USED, ...; changing
 					this is only allowed when a thread
@@ -870,7 +869,10 @@ struct buf_block_struct{
 #endif /* UNIV_DEBUG_FILE_ACCESSES */
 };
 
-#define BUF_BLOCK_MAGIC_N	41526563
+/* Check if a block is in a valid state. */
+#define buf_block_state_valid(block)		\
+(buf_block_get_state(block) >= BUF_BLOCK_NOT_USED		\
+ && (buf_block_get_state(block) <= BUF_BLOCK_REMOVE_HASH))
 
 /* The buffer pool structure. NOTE! The definition appears here only for
 other modules of this directory (buf) to see it. Do not use from outside! */