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libbb: split bb_get_chunk_from_file and bb_get_chunk_with_continuation

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This also moves bb_get_chunk_with_continuation into its sole user,
parse_config.c.
This allows to optimize both functions separately,
they need to be optimized for speed.
(this need was highlighted by slow modprobe caused in part by slow
bb_get_chunk_with_continuation in config parser).

function                                             old     new   delta
bb_get_chunk_from_file                                 7     130    +123
config_read                                          457     558    +101
bb_get_chunk_with_continuation                       194       -    -194
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 2/0 up/down: 224/-194)           Total: 30 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2011-06-17 03:37:43 +02:00
parent 901a53baec
commit a1a448347e
3 changed files with 56 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/libbb.h
View File

@ -730,8 +730,12 @@ extern void xclose(int fd) FAST_FUNC;
/* Reads and prints to stdout till eof, then closes FILE. Exits on error: */
extern void xprint_and_close_file(FILE *file) FAST_FUNC;
/* Reads a line from a text file, up to a newline or NUL byte, inclusive.
* Returns malloc'ed char*. If end is NULL '\n' isn't considered
* end of line. If end isn't NULL, length of the chunk is stored in it.
* Returns NULL if EOF/error.
*/
extern char *bb_get_chunk_from_file(FILE *file, int *end) FAST_FUNC;
extern char *bb_get_chunk_with_continuation(FILE *file, int *end, int *lineno) FAST_FUNC;
/* Reads up to (and including) TERMINATING_STRING: */
extern char *xmalloc_fgets_str(FILE *file, const char *terminating_string) FAST_FUNC RETURNS_MALLOC;
/* Same, with limited max size, and returns the length (excluding NUL): */

42
libbb/get_line_from_file.c
View File

@ -11,45 +11,24 @@
#include "libbb.h"
/* This function reads an entire line from a text file, up to a newline
* or NUL byte, inclusive. It returns a malloc'ed char * which
* must be free'ed by the caller. If end is NULL '\n' isn't considered
* end of line. If end isn't NULL, length of the chunk is stored in it.
* If lineno is not NULL, *lineno is incremented for each line,
* and also trailing '\' is recognized as line continuation.
*
* Returns NULL if EOF/error. */
char* FAST_FUNC bb_get_chunk_with_continuation(FILE *file, int *end, int *lineno)
char* FAST_FUNC bb_get_chunk_from_file(FILE *file, int *end)
{
int ch;
int idx = 0;
unsigned idx = 0;
char *linebuf = NULL;
int linebufsz = 0;
while ((ch = getc(file)) != EOF) {
/* grow the line buffer as necessary */
if (idx >= linebufsz) {
linebufsz += 256;
linebuf = xrealloc(linebuf, linebufsz);
}
if (!(idx & 0xff))
linebuf = xrealloc(linebuf, idx + 0x100);
linebuf[idx++] = (char) ch;
if (!ch)
if (ch == '\0')
break;
if (end && ch == '\n')
break;
if (end && ch == '\n') {
if (lineno == NULL)
break;
(*lineno)++;
if (idx < 2 || linebuf[idx-2] != '\\')
break;
idx -= 2;
}
}
if (end) {
if (end)
*end = idx;
/* handle corner case when the file is not ended with '\n' */
if (ch == EOF && lineno != NULL)
(*lineno)++;
}
if (linebuf) {
// huh, does fgets discard prior data on error like this?
// I don't think so....
@ -63,11 +42,6 @@ char* FAST_FUNC bb_get_chunk_with_continuation(FILE *file, int *end, int *lineno
return linebuf;
}
char* FAST_FUNC bb_get_chunk_from_file(FILE *file, int *end)
{
return bb_get_chunk_with_continuation(file, end, NULL);
}
/* Get line, including trailing \n if any */
char* FAST_FUNC xmalloc_fgets(FILE *file)
{

52
libbb/parse_config.c
View File

@ -104,6 +104,44 @@ void FAST_FUNC config_close(parser_t *parser)
}
}
/* This function reads an entire line from a text file, up to a newline
* or NUL byte, exclusive. It returns a malloc'ed char*.
* *lineno is incremented for each line.
* Trailing '\' is recognized as line continuation.
* Returns NULL if EOF/error.
*/
static char* get_line_with_continuation(FILE *file, int *lineno)
{
int ch;
unsigned idx = 0;
char *linebuf = NULL;
while ((ch = getc(file)) != EOF) {
/* grow the line buffer as necessary */
if (!(idx & 0xff))
linebuf = xrealloc(linebuf, idx + 0x101);
if (ch == '\n')
ch = '\0';
linebuf[idx] = (char) ch;
if (ch == '\0') {
(*lineno)++;
if (idx == 0 || linebuf[idx-1] != '\\')
break;
idx--; /* go back to '/' */
continue;
}
idx++;
}
if (ch == EOF) {
/* handle corner case when the file is not ended with '\n' */
(*lineno)++;
if (linebuf)
linebuf[idx] = '\0';
}
return linebuf;
}
/*
0. If parser is NULL return 0.
1. Read a line from config file. If nothing to read then return 0.
@ -132,28 +170,24 @@ int FAST_FUNC config_read(parser_t *parser, char **tokens, unsigned flags, const
{
char *line;
int ntokens, mintokens;
int t, len;
int t;
if (!parser)
return 0;
ntokens = (uint8_t)flags;
mintokens = (uint8_t)(flags >> 8);
if (parser == NULL)
return 0;
again:
memset(tokens, 0, sizeof(tokens[0]) * ntokens);
config_free_data(parser);
/* Read one line (handling continuations with backslash) */
line = bb_get_chunk_with_continuation(parser->fp, &len, &parser->lineno);
line = get_line_with_continuation(parser->fp, &parser->lineno);
if (line == NULL)
return 0;
parser->line = line;
/* Strip trailing line-feed if any */
if (len && line[len-1] == '\n')
line[len-1] = '\0';
/* Skip token in the start of line? */
if (flags & PARSE_TRIM)
line += strspn(line, delims + 1);