Simplify implemmentation and invocation of block_is_zeros() function.

http_io.c

@@ -1796,7 +1796,7 @@ http_io_write_block(struct s3backer_store *const s3b, s3b_block_t block_num, con
         return EINVAL;
 
     // Detect zero blocks (if not done already by upper layer)
-    if (src != NULL && block_is_zeros(src, config->block_size))
+    if (src != NULL && block_is_zeros(src))
         src = NULL;
 
     // Don't write zero blocks when bitmap indicates empty until non-zero content is written

s3b_config.c

@@ -1711,8 +1711,8 @@ validate_config(int parse_only)
     config.num_blocks = (s3b_block_t)big_num_blocks;
 
     // Allocate zero block
-    if ((zero_block = calloc(1, config.block_size)) == NULL) {
-        warn("calloc");
+    if (init_zero_block(config.block_size) == -1) {
+        warn("init_zero_block");
         return -1;
     }
 

test_io.c

@@ -339,7 +339,7 @@ test_io_write_block(struct s3backer_store *const s3b, s3b_block_t block_num, con
     int r;
 
     // Check for zero block
-    if (src != NULL && memcmp(src, zero_block, config->block_size) == 0)
+    if (src != NULL && block_is_zeros(src))
         src = NULL;
 
     // Compute MD5

util.c

@@ -82,6 +82,7 @@ int log_enable_debug;
 
 // A block's worth of data containing only zero bytes
 const void *zero_block;
+static size_t zero_block_size;
 
 // stderr logging mutex
 static pthread_mutex_t stderr_log_mutex = PTHREAD_MUTEX_INITIALIZER;
@@ -259,21 +260,21 @@ bitmap_not(bitmap_t *bitmap, s3b_block_t num_blocks)
 }
 
 int
-block_is_zeros(const void *data, u_int block_size)
+init_zero_block(u_int block_size)
 {
-    static const u_long zero;
-    const u_int *ptr;
-    int i;
+    assert(zero_block == NULL);
+    if ((zero_block = calloc(1, block_size)) == NULL)
+        return -1;
+    zero_block_size = block_size;
+    return 0;
+}
 
-    if (block_size <= sizeof(zero))
-        return memcmp(data, &zero, block_size) == 0;
-    assert(block_size % sizeof(*ptr) == 0);
-    ptr = (const u_int *)data;
-    for (i = 0; i < block_size / sizeof(*ptr); i++) {
-        if (*ptr++ != 0)
-            return 0;
-    }
-    return 1;
+int
+block_is_zeros(const void *data)
+{
+    assert(zero_block != NULL);
+    assert(zero_block_size > 0);
+    return memcmp(data, zero_block, zero_block_size) == 0;
 }
 
 void

util.h

@@ -82,13 +82,14 @@ extern void describe_size(char *buf, int bmax, uintmax_t value);
 extern void syslog_logger(int level, const char *fmt, ...) __attribute__ ((__format__ (__printf__, 2, 3)));
 extern void stderr_logger(int level, const char *fmt, ...) __attribute__ ((__format__ (__printf__, 2, 3)));
 extern int find_string_in_table(const char *const *table, const char *value);
-extern int block_is_zeros(const void *data, u_int block_size);
+extern int block_is_zeros(const void *data);
 extern int snvprintf(char *buf, int bufsize, const char *format, ...) __attribute__ ((__format__ (__printf__, 3, 4)));
 extern char *prefix_log_format(int level, const char *fmt);
 extern void calculate_boundary_info(struct boundary_info *info, u_int block_size, const void *buf, size_t size, off_t offset);
 extern pid_t fork_off(const char *executable, char **argv);
 extern int add_string(struct string_array *array, const char *fmt, ...) __attribute__ ((__format__ (__printf__, 2, 3)));
 extern void free_strings(struct string_array *array);
+extern int init_zero_block(u_int block_size);
 
 // Bitmaps
 extern bitmap_t *bitmap_init(s3b_block_t num_blocks, int value);

zero_cache.c

@@ -367,7 +367,7 @@ zero_cache_read_block(struct s3backer_store *const s3b, s3b_block_t block_num, v
 
     // Update cache - if read was successful (or EEXIST case)
     if (r == 0 || (expect_etag != NULL && !strict && r == EEXIST && memcmp(expect_etag, zero_etag, MD5_DIGEST_LENGTH) == 0)) {
-        const int zero = block_is_zeros(dest, config->block_size);
+        const int zero = block_is_zeros(dest);
         pthread_mutex_lock(&priv->mutex);
         zero_cache_update_block(priv, block_num, zero);
         CHECK_RETURN(pthread_mutex_unlock(&priv->mutex));
@@ -382,12 +382,11 @@ zero_cache_write_block(struct s3backer_store *const s3b, s3b_block_t block_num,
   check_cancel_t *check_cancel, void *check_cancel_arg)
 {
     struct zero_cache_private *const priv = s3b->data;
-    struct zero_cache_conf *const config = priv->config;
     int known_zero;
     int r;
 
     // Detect zero blocks
-    if (src != NULL && block_is_zeros(src, config->block_size))
+    if (src != NULL && block_is_zeros(src))
         src = NULL;
     known_zero = src == NULL;