emo/busybox
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

libbb: split bb_get_chunk_from_file and bb_get_chunk_with_continuation

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

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);