io: make MP_PATH_MAX private to win32 code

The win32 code is the only thing which actually needs this (and it's
used to make emulation of UTF-8 filename APIs easier).

1 files changed, 10 insertions, 0 deletions

diff --git a/osdep/io.c b/osdep/io.c
index 2e2603eb7f..c243b39de4 100644
--- a/osdep/io.c
+++ b/osdep/io.c
@@ -217,6 +217,16 @@ FILE *mp_fopen(const char *filename, const char *mode)
     return res;
 }
 
+// Windows' MAX_PATH/PATH_MAX/FILENAME_MAX is fixed to 260, but this limit
+// applies to unicode paths encoded with wchar_t (2 bytes on Windows). The UTF-8
+// version could end up bigger in memory. In the worst case each wchar_t is
+// encoded to 3 bytes in UTF-8, so in the worst case we have:
+//      wcslen(wpath) * 3 <= strlen(utf8path)
+// Thus we need MP_PATH_MAX as the UTF-8/char version of PATH_MAX.
+// Also make sure there's free space for the terminating \0.
+// (For codepoints encoded as UTF-16 surrogate pairs, UTF-8 has the same length.)
+#define MP_PATH_MAX (FILENAME_MAX * 3 + 1)
+
 struct mp_dir {
     DIR crap;   // must be first member
     _WDIR *wdir;