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vi: fix backward search with GNU regex

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With FEATURE_VI_REGEX_SEARCH enabled backward searches don't work.
This is problematic on distros that enable regexes, such as Tiny
Core Linux and Fedora.

When calling GNU re_search() with a negative range parameter
(indicating a backward search) the start offset must be set to
the end of the area being searched.

The return value of re_search() is the offset of the matched pattern
from the start of the area being searched.  For a successful search
(positive return value) char_search() can return the pointer to
the start of the area plus the offset.

FEATURE_VI_REGEX_SEARCH isn't enabled by default but when it is:

function                                             old     new   delta
char_search                                          256     247      -9
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-9)               Total: -9 bytes

Signed-off-by: Andrey Dobrovolsky <andrey.dobrovolsky.odessa@gmail.com>
Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Ron Yorston 2021-06-21 11:30:39 +01:00 committed by Denys Vlasenko
parent ac4786ba00
commit 51358757c7
1 changed files with 13 additions and 20 deletions
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33
editors/vi.c
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@ -2376,9 +2376,7 @@ static char *char_search(char *p, const char *pat, int dir_and_range)
struct re_pattern_buffer preg;
const char *err;
char *q;
int i;
int size;
int range;
int i, size, range, start;
re_syntax_options = RE_SYNTAX_POSIX_EXTENDED;
if (ignorecase)
@ -2403,31 +2401,26 @@ static char *char_search(char *p, const char *pat, int dir_and_range)
// RANGE could be negative if we are searching backwards
range = q - p;
q = p;
size = range;
if (range < 0) {
size = -size;
q = p - size;
if (q < text)
q = text;
size = -range;
start = size;
} else {
size = range;
start = 0;
}
q = p - start;
if (q < text)
q = text;
// search for the compiled pattern, preg, in p[]
// range < 0: search backward
// range > 0: search forward
// 0 < start < size
// range < 0, start == size: search backward
// range > 0, start == 0: search forward
// re_search() < 0: not found or error
// re_search() >= 0: index of found pattern
// struct pattern char int int int struct reg
// re_search(*pattern_buffer, *string, size, start, range, *regs)
i = re_search(&preg, q, size, /*start:*/ 0, range, /*struct re_registers*:*/ NULL);
i = re_search(&preg, q, size, start, range, /*struct re_registers*:*/ NULL);
regfree(&preg);
if (i < 0)
return NULL;
if (dir_and_range > 0) // FORWARD?
p = p + i;
else
p = p - i;
return p;
return i < 0 ? NULL : q + i;
}
# else
# if ENABLE_FEATURE_VI_SETOPTS