path.c

   1 /*
   2  * I'm tired of doing "vsnprintf()" etc just to open a
   3  * file, so here's a "return static buffer with printf"
   4  * interface for paths.
   5  *
   6  * It's obviously not thread-safe. Sue me. But it's quite
   7  * useful for doing things like
   8  *
   9  *   f = open(mkpath("%s/%s.git", base, name), O_RDONLY);
  10  *
  11  * which is what it's designed for.
  12  */
  13 #include "cache.h"
  14
  15 static char pathname[PATH_MAX];
  16 static char bad_path[] = "/bad-path/";
  17
  18 static char *cleanup_path(char *path)
  19 {
  20         /* Clean it up */
  21         if (!memcmp(path, "./", 2)) {
  22                 path += 2;
  23                 while (*path == '/')
  24                         path++;
  25         }
  26         return path;
  27 }
  28
  29 char *mkpath(const char *fmt, ...)
  30 {
  31         va_list args;
  32         unsigned len;
  33
  34         va_start(args, fmt);
  35         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  36         va_end(args);
  37         if (len >= PATH_MAX)
  38                 return bad_path;
  39         return cleanup_path(pathname);
  40 }
  41
  42 char *git_path(const char *fmt, ...)
  43 {
  44         const char *git_dir = gitenv(GIT_DIR_ENVIRONMENT) ? : DEFAULT_GIT_DIR_ENVIRONMENT;
  45         va_list args;
  46         unsigned len;
  47
  48         len = strlen(git_dir);
  49         if (len > PATH_MAX-100)
  50                 return bad_path;
  51         memcpy(pathname, git_dir, len);
  52         if (len && git_dir[len-1] != '/')
  53                 pathname[len++] = '/';
  54         va_start(args, fmt);
  55         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
  56         va_end(args);
  57         if (len >= PATH_MAX)
  58                 return bad_path;
  59         return cleanup_path(pathname);
  60 }
  61
  62
  63 /* git_mkstemp() - create tmp file honoring TMPDIR variable */
  64 int git_mkstemp(char *path, size_t len, const char *template)
  65 {
  66         char *env, *pch = path;
  67
  68         if ((env = getenv("TMPDIR")) == NULL) {
  69                 strcpy(pch, "/tmp/");
  70                 len -= 5;
  71                 pch += 5;
  72         } else {
  73                 size_t n = snprintf(pch, len, "%s/", env);
  74
  75                 len -= n;
  76                 pch += n;
  77         }
  78
  79         safe_strncpy(pch, template, len);
  80
  81         return mkstemp(path);
  82 }
  83
  84
  85 char *safe_strncpy(char *dest, const char *src, size_t n)
  86 {
  87         strncpy(dest, src, n);
  88         dest[n - 1] = '\0';
  89
  90         return dest;
  91 }