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_alpm_archive_fgets: optimize EOL search

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Instead of iterating character by character, use memchr() calls to
hopefully speed up the search. A newline is the most likely culprit, so
search for that first followed by a NULL byte if there was no newline in
the buffer.

Signed-off-by: Dan McGee <dan@archlinux.org>
This commit is contained in:
Dan McGee 2011-09-27 17:37:27 -05:00
parent 89fe19f3e1
commit a27bdcfe51
1 changed files with 17 additions and 17 deletions
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34
lib/libalpm/util.c
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@ -918,16 +918,16 @@ int _alpm_test_checksum(const char *filepath, const char *expected,
/* Note: does NOT handle sparse files on purpose for speed. */ /* Note: does NOT handle sparse files on purpose for speed. */
int _alpm_archive_fgets(struct archive *a, struct archive_read_buffer *b) int _alpm_archive_fgets(struct archive *a, struct archive_read_buffer *b)
{ {
char *i = NULL;
int64_t offset;
int done = 0;
/* ensure we start populating our line buffer at the beginning */ /* ensure we start populating our line buffer at the beginning */
b->line_offset = b->line; b->line_offset = b->line;
while(1) { while(1) {
size_t block_remaining;
char *eol;
/* have we processed this entire block? */ /* have we processed this entire block? */
if(b->block + b->block_size == b->block_offset) { if(b->block + b->block_size == b->block_offset) {
int64_t offset;
if(b->ret == ARCHIVE_EOF) { if(b->ret == ARCHIVE_EOF) {
/* reached end of archive on the last read, now we are out of data */ /* reached end of archive on the last read, now we are out of data */
goto cleanup; goto cleanup;
@ -937,20 +937,20 @@ int _alpm_archive_fgets(struct archive *a, struct archive_read_buffer *b)
b->ret = archive_read_data_block(a, (void *)&b->block, b->ret = archive_read_data_block(a, (void *)&b->block,
&b->block_size, &offset); &b->block_size, &offset);
b->block_offset = b->block; b->block_offset = b->block;
block_remaining = b->block_size;
/* error, cleanup */ /* error, cleanup */
if(b->ret < ARCHIVE_OK) { if(b->ret < ARCHIVE_OK) {
goto cleanup; goto cleanup;
} }
} else {
block_remaining = b->block + b->block_size - b->block_offset;
} }
/* loop through the block looking for EOL characters */ /* look through the block looking for EOL characters */
for(i = b->block_offset; i < (b->block + b->block_size); i++) { eol = memchr(b->block_offset, '\n', block_remaining);
/* check if read value was null or newline */ if(!eol) {
if(*i == '\0' || *i == '\n') { eol = memchr(b->block_offset, '\0', block_remaining);
done = 1;
break;
}
} }
/* allocate our buffer, or ensure our existing one is big enough */ /* allocate our buffer, or ensure our existing one is big enough */
@ -960,8 +960,8 @@ int _alpm_archive_fgets(struct archive *a, struct archive_read_buffer *b)
b->line_size = b->block_size + 1; b->line_size = b->block_size + 1;
b->line_offset = b->line; b->line_offset = b->line;
} else { } else {
size_t needed = (size_t)((b->line_offset - b->line) size_t new = eol ? (eol - b->block_offset) : block_remaining;
+ (i - b->block_offset) + 1); size_t needed = (size_t)((b->line_offset - b->line) + new + 1);
if(needed > b->max_line_size) { if(needed > b->max_line_size) {
b->ret = -ERANGE; b->ret = -ERANGE;
goto cleanup; goto cleanup;
@ -978,11 +978,11 @@ int _alpm_archive_fgets(struct archive *a, struct archive_read_buffer *b)
} }
} }
if(done) { if(eol) {
size_t len = (size_t)(i - b->block_offset); size_t len = (size_t)(eol - b->block_offset);
memcpy(b->line_offset, b->block_offset, len); memcpy(b->line_offset, b->block_offset, len);
b->line_offset[len] = '\0'; b->line_offset[len] = '\0';
b->block_offset = ++i; b->block_offset = eol + 1;
/* this is the main return point; from here you can read b->line */ /* this is the main return point; from here you can read b->line */
return ARCHIVE_OK; return ARCHIVE_OK;
} else { } else {
@ -990,7 +990,7 @@ int _alpm_archive_fgets(struct archive *a, struct archive_read_buffer *b)
size_t len = (size_t)(b->block + b->block_size - b->block_offset); size_t len = (size_t)(b->block + b->block_size - b->block_offset);
memcpy(b->line_offset, b->block_offset, len); memcpy(b->line_offset, b->block_offset, len);
b->line_offset += len; b->line_offset += len;
b->block_offset = i; b->block_offset = b->block + b->block_size;
/* there was no new data, return what is left; saved ARCHIVE_EOF will be /* there was no new data, return what is left; saved ARCHIVE_EOF will be
* returned on next call */ * returned on next call */
if(len == 0) { if(len == 0) {