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fiemap copy: simplify post-loop logic; improve comments

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* src/copy.c (extent_copy): Avoid duplication in post-loop
extend-to-desired-length code.
This commit is contained in:
Jim Meyering
2011-01-27 19:00:48 +01:00
parent f4473df430
commit cfbeeafd4a
1 changed files with 15 additions and 29 deletions
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44
src/copy.c
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@@ -268,8 +268,8 @@ extent_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
while (ext_len)
{
/* Avoid reading into the holes if the left extent
length is shorter than the buffer size. */
/* Don't read from a following hole if EXT_LEN
is smaller than the buffer size. */
buf_size = MIN (ext_len, buf_size);
ssize_t n_read = read (src_fd, buf, buf_size);
@@ -285,7 +285,7 @@ extent_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
if (n_read == 0)
{
/* Record number of bytes read from the previous extent. */
/* Record number of bytes read from this extent-at-EOF. */
last_read_size = last_ext_len - ext_len;
break;
}
@@ -306,33 +306,19 @@ extent_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
}
while (! scan.hit_final_extent);
/* If a file ends up with holes, the sum of the last extent logical offset
and the read-returned size or the last extent length will be shorter than
the actual size of the file. Use ftruncate to extend the length of the
destination file if make_holes, or write zeros up to the actual size of the
file. */
if (make_holes)
/* When the source file ends with a hole, the sum of the last extent start
offset and (the read-returned size or the last extent length) is smaller
than the actual size of the file. In that case, extend the destination
file to the required length. When MAKE_HOLES is set, use ftruncate;
otherwise, use write_zeros. */
uint64_t eof_hole_len = (src_total_size - last_ext_start
- (last_read_size ? last_read_size : last_ext_len));
if (eof_hole_len && (make_holes
? ftruncate (dest_fd, src_total_size)
: ! write_zeros (dest_fd, eof_hole_len)))
{
if (last_ext_start + last_read_size < src_total_size)
{
if (ftruncate (dest_fd, src_total_size) < 0)
{
error (0, errno, _("failed to extend %s"), quote (dst_name));
return false;
}
}
}
else
{
if (last_ext_start + last_ext_len < src_total_size)
{
uint64_t holes_len = src_total_size - last_ext_start - last_ext_len;
if (0 < holes_len)
{
if (! write_zeros (dest_fd, holes_len))
return false;
}
}
error (0, errno, _("failed to extend %s"), quote (dst_name));
return false;
}
return true;