[Qemu-devel] [PATCH 3/3] make path_combine() especially for filenames, not URLs

[Michael Tokarev]

Currently the two routines tries to "understand" and skip <protocol>:
prefix in path arguments are path_combine() and path_is_absolute()
(the latter isn't used anywhere but in the former).  This is wrong,
since notion of absolute path is, at least, protocol-specific.

The implementation is more wrong on windows where even non-absolute
paths but with drive name (d:foo) should be treated as absolute, as
in, one can't combine, say, c:\bar with d:foo forming c:\foo as
path_combine() currently does.

Introduce isslash() macro that works correctly on both windows and
unix, use it in is_windows_drive_prefix() (since any form of slash
can be used in constructs like //./), remove path_is_absolute() and
hardcode the trivial (but right) condition in path_combine(), and
simplify path_combine() further by removing <protocol>: handling
and unifying shash searching.

Signed-off-by: Michael Tokarev <address@hidden>
---
 block.c |   72 +++++++++++++++++++++-----------------------------------------
 1 files changed, 25 insertions(+), 47 deletions(-)

diff --git a/block.c b/block.c
index 42d6ff1..31a821d 100644
--- a/block.c
+++ b/block.c
@@ -71,6 +71,9 @@ static BlockDriverState *bs_snapshots;
 static int use_bdrv_whitelist;
 
 #ifdef _WIN32
+
+#define isslash(c) ((c) == '/' || (c) == '\\')
+
 static int is_windows_drive_prefix(const char *filename)
 {
     return (((filename[0] >= 'a' && filename[0] <= 'z') ||
@@ -83,11 +86,17 @@ int is_windows_drive(const char *filename)
     if (is_windows_drive_prefix(filename) &&
         filename[2] == '\0')
         return 1;
-    if (strstart(filename, "\\\\.\\", NULL) ||
-        strstart(filename, "//./", NULL))
-        return 1;
+    if (isslash(filename[0] && isslash(filename[1]) &&
+        filename[2] == '.' &&  isslash(filename[3]))
+        return 1; /* special case: windows device "//./" */
     return 0;
 }
+
+#else
+
+#define isslash(c) ((c) == '/')
+#define is_windows_drive_prefix(filename) (0)
+
 #endif
 
 /* check if the path starts with "<protocol>:"
@@ -115,61 +124,30 @@ static char *path_has_protocol(const char *path)
             (char*)p : NULL;
 }
 
-int path_is_absolute(const char *path)
-{
-    const char *p;
-#ifdef _WIN32
-    /* specific case for names like: "\\.\d:" */
-    if (*path == '/' || *path == '\\')
-        return 1;
-#endif
-    p = strchr(path, ':');
-    if (p)
-        p++;
-    else
-        p = path;
-#ifdef _WIN32
-    return (*p == '/' || *p == '\\');
-#else
-    return (*p == '/');
-#endif
-}
-
 /* if filename is absolute, just copy it to dest. Otherwise, build a
-   path to it by considering it is relative to base_path. URL are
-   supported. */
+   path to it by considering it is relative to base_path.
+   This is really about filenames not URLs - we don't support
+   <protocol>: prefix in filename since it makes no sense, especially
+   if the protocol in base_path is not the same as in filename.
+ */
 void path_combine(char *dest, int dest_size,
                   const char *base_path,
                   const char *filename)
 {
-    const char *p, *p1;
+    const char *p;
     int len;
 
     if (dest_size <= 0)
         return;
-    if (path_is_absolute(filename)) {
+    /* on windows, d:filename should be treated as absolute too */
+    if (isslash(filename[0]) || is_windows_drive_prefix(filename)) {
         pstrcpy(dest, dest_size, filename);
     } else {
-        p = strchr(base_path, ':');
-        if (p)
-            p++;
-        else
-            p = base_path;
-        p1 = strrchr(base_path, '/');
-#ifdef _WIN32
-        {
-            const char *p2;
-            p2 = strrchr(base_path, '\\');
-            if (!p1 || p2 > p1)
-                p1 = p2;
-        }
-#endif
-        if (p1)
-            p1++;
-        else
-            p1 = base_path;
-        if (p1 > p)
-            p = p1;
+        /* find last slash */
+        p = base_path + strlen(base_path);
+        while(p >= base_path && !isslash(*p))
+            --p;
+        p++;
         len = p - base_path;
         if (len > dest_size - 1)
             len = dest_size - 1;
-- 
1.7.2.3