git/interpolate.c
Jim Meyering 8e0f70033b Avoid unnecessary "if-before-free" tests.
This change removes all obvious useless if-before-free tests.
E.g., it replaces code like this:

        if (some_expression)
                free (some_expression);

with the now-equivalent:

        free (some_expression);

It is equivalent not just because POSIX has required free(NULL)
to work for a long time, but simply because it has worked for
so long that no reasonable porting target fails the test.
Here's some evidence from nearly 1.5 years ago:

    http://www.winehq.org/pipermail/wine-patches/2006-October/031544.html

FYI, the change below was prepared by running the following:

  git ls-files -z | xargs -0 \
  perl -0x3b -pi -e \
    's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*NULL)?\s*\)\s+(free\s*\(\s*\1\s*\))/$2/s'

Note however, that it doesn't handle brace-enclosed blocks like
"if (x) { free (x); }".  But that's ok, since there were none like
that in git sources.

Beware: if you do use the above snippet, note that it can
produce syntactically invalid C code.  That happens when the
affected "if"-statement has a matching "else".
E.g., it would transform this

  if (x)
    free (x);
  else
    foo ();

into this:

  free (x);
  else
    foo ();

There were none of those here, either.

If you're interested in automating detection of the useless
tests, you might like the useless-if-before-free script in gnulib:
[it *does* detect brace-enclosed free statements, and has a --name=S
 option to make it detect free-like functions with different names]

  http://git.sv.gnu.org/gitweb/?p=gnulib.git;a=blob;f=build-aux/useless-if-before-free

Addendum:
  Remove one more (in imap-send.c), spotted by Jean-Luc Herren <jlh@gmx.ch>.

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2008-02-22 14:14:40 -08:00

104 lines
2.1 KiB
C

/*
* Copyright 2006 Jon Loeliger
*/
#include "git-compat-util.h"
#include "interpolate.h"
void interp_set_entry(struct interp *table, int slot, const char *value)
{
char *oldval = table[slot].value;
char *newval = NULL;
free(oldval);
if (value)
newval = xstrdup(value);
table[slot].value = newval;
}
void interp_clear_table(struct interp *table, int ninterps)
{
int i;
for (i = 0; i < ninterps; i++) {
interp_set_entry(table, i, NULL);
}
}
/*
* Convert a NUL-terminated string in buffer orig
* into the supplied buffer, result, whose length is reslen,
* performing substitutions on %-named sub-strings from
* the table, interps, with ninterps entries.
*
* Example interps:
* {
* { "%H", "example.org"},
* { "%port", "123"},
* { "%%", "%"},
* }
*
* Returns the length of the substituted string (not including the final \0).
* Like with snprintf, if the result is >= reslen, then it overflowed.
*/
unsigned long interpolate(char *result, unsigned long reslen,
const char *orig,
const struct interp *interps, int ninterps)
{
const char *src = orig;
char *dest = result;
unsigned long newlen = 0;
const char *name, *value;
unsigned long namelen, valuelen;
int i;
char c;
while ((c = *src)) {
if (c == '%') {
/* Try to match an interpolation string. */
for (i = 0; i < ninterps; i++) {
name = interps[i].name;
namelen = strlen(name);
if (strncmp(src, name, namelen) == 0)
break;
}
/* Check for valid interpolation. */
if (i < ninterps) {
value = interps[i].value;
if (!value) {
src += namelen;
continue;
}
valuelen = strlen(value);
if (newlen + valuelen < reslen) {
/* Substitute. */
memcpy(dest, value, valuelen);
dest += valuelen;
}
newlen += valuelen;
src += namelen;
continue;
}
}
/* Straight copy one non-interpolation character. */
if (newlen + 1 < reslen)
*dest++ = *src;
src++;
newlen++;
}
/* XXX: the previous loop always keep room for the ending NUL,
we just need to check if there was room for a NUL in the first place */
if (reslen > 0)
*dest = '\0';
return newlen;
}