maint: refactor copy to use is_nul()

* src/dd.c: Move is_nul() from here to ...
* src/system.h: ... here
* src/copy.c (sparse_copy): Adjust to use the refactored is_nul()

1 files changed, 7 insertions, 26 deletions

diff --git a/src/copy.c b/src/copy.c
index 541ca20cb..f63a72696 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -152,13 +152,12 @@ sparse_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
              uintmax_t max_n_read, off_t *total_n_read,
              bool *last_write_made_hole)
 {
-  typedef uintptr_t word;
   *last_write_made_hole = false;
   *total_n_read = 0;
 
   while (max_n_read)
     {
-      word *wp = NULL;
+      bool make_hole = false;
 
       ssize_t n_read = read (src_fd, buf, MIN (max_n_read, buf_size));
       if (n_read < 0)
@@ -175,11 +174,10 @@ sparse_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
 
       if (make_holes)
         {
-          char *cp;
-
-          /* Sentinel to stop loop.  */
+          /* Sentinel required by is_nul().  */
           buf[n_read] = '\1';
 #ifdef lint
+          typedef uintptr_t word;
           /* Usually, buf[n_read] is not the byte just before a "word"
              (aka uintptr_t) boundary.  In that case, the word-oriented
              test below (*wp++ == 0) would read some uninitialized bytes
@@ -189,35 +187,17 @@ sparse_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
           memset (buf + n_read + 1, 0, sizeof (word) - 1);
 #endif
 
-          /* Find first nonzero *word*, or the word with the sentinel.  */
-
-          wp = (word *) buf;
-          while (*wp++ == 0)
-            continue;
-
-          /* Find the first nonzero *byte*, or the sentinel.  */
-
-          cp = (char *) (wp - 1);
-          while (*cp++ == 0)
-            continue;
-
-          if (cp <= buf + n_read)
-            /* Clear to indicate that a normal write is needed. */
-            wp = NULL;
-          else
+          if ((make_hole = is_nul (buf, n_read)))
             {
-              /* We found the sentinel, so the whole input block was zero.
-                 Make a hole.  */
               if (lseek (dest_fd, n_read, SEEK_CUR) < 0)
                 {
                   error (0, errno, _("cannot lseek %s"), quote (dst_name));
                   return false;
                 }
-              *last_write_made_hole = true;
             }
         }
 
-      if (!wp)
+      if (!make_hole)
         {
           size_t n = n_read;
           if (full_write (dest_fd, buf, n) != n)
@@ -225,13 +205,14 @@ sparse_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
               error (0, errno, _("writing %s"), quote (dst_name));
               return false;
             }
-          *last_write_made_hole = false;
 
           /* It is tempting to return early here upon a short read from a
              regular file.  That would save the final read syscall for each
              file.  Unfortunately that doesn't work for certain files in
              /proc with linux kernels from at least 2.6.9 .. 2.6.29.  */
         }
+
+      *last_write_made_hole = make_hole;
     }
 
   return true;