[PATCH] tmpdir.c (path_search_alloc): New function.

[John Darrington <john@darrington.wattle.id.au>]

* lib/tmpdir.c (path_search_alloc): Define new function similar to
path_search,  but which allocates the buffer for the result instead
of relying on the caller to preallocate it.
*lib/tmpdir.h (path_search_alloc): Declare it.
---
 lib/tmpdir.c | 127 +++++++++++++++++++++++++++++++++++----------------
 lib/tmpdir.h |   6 +++
 2 files changed, 93 insertions(+), 40 deletions(-)

diff --git a/lib/tmpdir.c b/lib/tmpdir.c
index 28ff99f58..70ab7007f 100644
--- a/lib/tmpdir.c
+++ b/lib/tmpdir.c
@@ -83,43 +83,23 @@ direxists (const char *dir)
   return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
 }
 
-/* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
-   non-null and exists, uses it; otherwise uses the first of $TMPDIR,
-   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
-   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
-   doesn't exist, none of the searched dirs exists, or there's not
-   enough space in TMPL. */
-int
-path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
-             bool try_tmpdir)
+
+static int
+__path_search (char *tmpl, const char **dirx, const char *pfx, bool try_tmpdir)
 {
   const char *d;
-  size_t dlen, plen;
-  bool add_slash;
-
-  if (!pfx || !pfx[0])
-    {
-      pfx = "file";
-      plen = 4;
-    }
-  else
-    {
-      plen = strlen (pfx);
-      if (plen > 5)
-        plen = 5;
-    }
 
   if (try_tmpdir)
     {
       d = __libc_secure_getenv ("TMPDIR");
       if (d != NULL && direxists (d))
-        dir = d;
-      else if (dir != NULL && direxists (dir))
+        *dirx = d;
+      else if (*dirx != NULL && direxists (*dirx))
         /* nothing */ ;
       else
-        dir = NULL;
+        *dirx = NULL;
     }
-  if (dir == NULL)
+  if (*dirx == NULL)
     {
 #if defined _WIN32 && ! defined __CYGWIN__
       char dirbuf[PATH_MAX];
@@ -131,26 +111,63 @@ path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
          directory (unless $TMPDIR is set).  */
       retval = GetTempPath (PATH_MAX, dirbuf);
       if (retval > 0 && retval < PATH_MAX && direxists (dirbuf))
-        dir = dirbuf;
+        *dirx = dirbuf;
       else
 #endif
-      if (direxists (P_tmpdir))
-        dir = P_tmpdir;
-      else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
-        dir = "/tmp";
-      else
-        {
-          __set_errno (ENOENT);
-          return -1;
-        }
+        if (direxists (P_tmpdir))
+          *dirx = P_tmpdir;
+        else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
+          *dirx = "/tmp";
+        else
+          {
+            __set_errno (ENOENT);
+            return -1;
+          }
     }
 
-  dlen = strlen (dir);
+  return 0;
+}
+
+static void
+__impute_lengths (const char *pfx, const char *dir, size_t *plen, size_t *dlen, bool *add_slash)
+{
+  if (!pfx || !pfx[0])
+    {
+      pfx = "file";
+      *plen = 4;
+    }
+  else
+    {
+      *plen = strlen (pfx);
+      if (*plen > 5)
+        *plen = 5;
+    }
+
+  *dlen = strlen (dir);
 #ifdef __VMS
-  add_slash = 0;
+  *add_slash = 0;
 #else
-  add_slash = dlen != 0 && !ISSLASH (dir[dlen - 1]);
+  *add_slash = *dlen != 0 && !ISSLASH (dir[*dlen - 1]);
 #endif
+}
+
+/* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
+   non-null and exists, uses it; otherwise uses the first of $TMPDIR,
+   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
+   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
+   doesn't exist, none of the searched dirs exists, or there's not
+   enough space in TMPL. */
+int
+path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
+             bool try_tmpdir)
+{
+  if (0 != __path_search (tmpl, &dir, pfx, try_tmpdir))
+    return -1;
+
+  size_t plen;
+  size_t dlen;
+  bool add_slash;
+  __impute_lengths (pfx, dir, &plen, &dlen, &add_slash);
 
   /* check we have room for "${dir}/${pfx}XXXXXX\0" */
   if (tmpl_len < dlen + add_slash + plen + 6 + 1)
@@ -163,3 +180,33 @@ path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
   sprintf (tmpl + dlen, &"/%.*sXXXXXX"[!add_slash], (int) plen, pfx);
   return 0;
 }
+
+
+/* Like path_search, but this function will allocate TMPL and fill
+   TMPL_LEN with the allocated length.   The caller must free TMPL when
+   no longer required.  */
+int
+path_search_alloc (char **tmpl, size_t *tmpl_len, const char *dir, const char *pfx,
+             bool try_tmpdir)
+{
+  if (0 != __path_search (*tmpl, &dir, pfx, try_tmpdir))
+    return -1;
+
+  size_t plen;
+  size_t dlen;
+  bool add_slash;
+  __impute_lengths (pfx, dir, &plen, &dlen, &add_slash);
+
+  /* check we have room for "${dir}/${pfx}XXXXXX\0" */
+  *tmpl = malloc (dlen + add_slash + plen + 6 + 1);
+  if (!*tmpl)
+    {
+      __set_errno (ENOMEM);
+      return -1;
+    }
+  *tmpl_len = dlen + add_slash + plen + 6 + 1;
+
+  memcpy (*tmpl, dir, dlen);
+  sprintf (*tmpl + dlen, &"/%.*sXXXXXX"[!add_slash], (int) plen, pfx);
+  return 0;
+}
diff --git a/lib/tmpdir.h b/lib/tmpdir.h
index 4d694a3d9..28c62fcc2 100644
--- a/lib/tmpdir.h
+++ b/lib/tmpdir.h
@@ -24,3 +24,9 @@
    doesn't exist, none of the searched dirs exists, or there's not
    enough space in TMPL. */
 extern int path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx, bool try_tmpdir);
+
+/* Like path_search, except that TMPL is allocated automatically.
+   TMPL may not be null.  *TMPL must be freed by the caller, when no longer needed.
+   After calling this function *TMPL_LEN will be set to the lenght of *TMPL.  */
+extern int path_search_alloc (char **tmpl, size_t *tmpl_len, const char *dir, const char *pfx,
+                       bool try_tmpdir);
-- 
2.20.1