[switch_utils.c] fix switch_cut_path() function for both slash and back slash in path

[sunlin7]

Hi,
This change try to rewrite the switch_cut_path() function, for continue search the next sep with preview stopping position, while the original function will always try both two path-seps from beginning.
The new implemention will

1. fix problem to deal some path like a\\b/c with both back slash and slash.
   $ mkdir a\\b/ && cd a\\b/ && git clone URL_FS
   Original function will give unexpect value b while new implemention will return expect value a\\b.

2. reduce about 40% calling timing.
   $ gcc -std=c11 test-switch_cut_path.c && ./a.out
func[0] take time 9 s
func[1] take time 15 s

The testing code is

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
const char *switch_cut_path(const char *in) {
  const char *p, *ret = in;
  const char delims[] = "/\\";
  const char *i;

  if (in) {
    for (i = delims; *i; i++) {
      p = in;
      while ((p = strchr(p, *i)) != 0) {
        ret = ++p;
      }
    }
    return ret;
  } else {
    return NULL;
  }
}

const char *switch_cut_path_new(const char *in) {
  const char *p = in, *ret = in;

  if (NULL == in) {
    return NULL;
  }
  while ((p = strchr(ret, '/')) != NULL) {
    ret = ++p;
  }
  while ((p = strchr(ret, '\\')) != NULL) {
    ret = ++p;
  }
  return ret;
}

int main(int argc, char *argv[])
{
  char seps[] = "/\\";
  char path[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
  const char *(*funcs[])(const char *) = {switch_cut_path_new, switch_cut_path};
  for (int i = 0; i < sizeof(funcs)/sizeof(funcs[0]); i++) {
    time_t t1 = time(NULL);
    for (int j = 0; j < 1024 * 1024 * 200; j++) {
      int idx = j % sizeof(path);
      char orig = path[idx];
      path[idx] = '/';
      funcs[i](path);
      path[idx] = '\\';
      funcs[i](path);
      path[idx] = orig;
    }
    time_t t2 = time(NULL);
    printf("func[%d] take time %ld s\n", i, t2 - t1);
  }
  return 0;
}

[sunlin7]

@andywolk Could you help to review this change please? Thanks

[mjerris]

This changes behavior of the function when either using mixed / and \ or when using unix delims on windows. If you want to optimize this function the first step would be to do a set of unit tests including those scenarios. Is there a compelling reason to optimize this function, if so please provide some detail of the scenario that has this function being called frequently

[mjerris]

any optimization or refactoring type changes should start with a complete set of unit tests to confirm we don’t break anything in the process.

[sunlin7]

@mjerris I turn on all level log, and the switch_cut_path() will be called for each log printing, so I try to make the calling faster.
The changes has updated for adding test cases in the tests/unit/switch_utils.c.
Please notice that the new implemention will give correct result for path like a\\b/c, while original function maybe has problem.
Here's an example:
$ makedir -p a\\b/ &&　touch a\\b/c
original switch_cut_path("a\\b/c") return "b/c"
new switch_cut_path("a\\b/c") return "c"

[mjerris]

does the new way will break cutting unix style paths on windows?

[sunlin7]

Hi @mjerris The updated changes won't break cutting unix style paths on windows. The changes didn't depend on the macro WIN32, always search for both / and \\, ack like it's preview version.

[sunlin7]

The unit testing case will verify it's behavior.

freeswitch/tests/unit/switch_utils.c

Lines 65 to 68 in c1f6041

	fst_check_string_equals(switch_cut_path("switch-cut-path"), "switch-cut-path");
	fst_check_string_equals(switch_cut_path("switch/cut-path"), "cut-path");
	fst_check_string_equals(switch_cut_path("switch/cut\\path"), "path");
	fst_check_string_equals(switch_cut_path("switch\\cut/path"), "path");

[sunlin7]

@mjerris The new version released days ago, shall we merge this bug fix then it will get wide testing before next release? Thanks

[sunlin7]

@mjerris Could you review this bug fix please? It will fix the incorrect path spliting on *nix, and keep behavior on Windows.