Prevent success trying to open a zip-based file for writing, allow wr…

…iting from the stdio wrapper, minor comment fixup

examples/example8.cpp

@@ -4,7 +4,8 @@
 #include <ttvfs.h>
 #include <cstdio>
 
-// This example creates a VFS root to obtain a single file.
+// This example creates a VFS root to obtain a single file,
+// then deletes the root before using the file.
 // The file stays valid until the CountedPtr is destroyed.
 // You can use CountedPtr::content() to obtain a raw pointer,
 // but usually conversions are done automatically.

ttvfs_cfileapi/ttvfs_stdio.cpp

@@ -16,12 +16,6 @@ void ttvfs_setroot(ttvfs::Root *root)
 
 VFILE *vfopen(const char *fn, const char *mode)
 {
-    if (strchr(mode, 'w'))
-    {
-        assert(0 && "ttvfs_stdio: File writing via VFS not yet supported!");
-        return NULL;
-    }
-
     VFILE *vf = vfs->GetFile(fn);
     if (!vf || !vf->open(mode))
         return NULL;

ttvfs_cfileapi/ttvfs_stdio.h

@@ -6,13 +6,14 @@
 // * Define VFS_ENABLE_C_API to 1 to use ttvfs overrides.
 
 /*
-    This file is a minimal wrapper to replace the C API and std::ifstream.
-    Note that if you have an advanced needs, this wrapper API is not for you.
+    This file is a poor man's wrapper to replace the C API and std::ifstream.
+    Note that if you have any advanced needs, this wrapper API is not for you.
 
     To use it, go through your code and rename all FILE* to VFILE*,
     and fopen() and related to vfopen() (so just put a 'v' in front).
     Instead of std::ifstream, use InStream. If you use std::fstream for reading ONLY,
     also use InStream.
+    Make sure that a FILE* is not opened twice at any time - this is not supported.
 
     Note that the seek and tell functions do not offer 64 bit offsets in this API.
 */

ttvfs_zip/VFSFileZip.cpp

@@ -30,6 +30,8 @@ bool ZipFile::open(const char *mode /* = NULL */)
     _pos = 0;
     if(!mode)
         mode = "rb";
+    else if(strchr(mode, 'w') || strchr(mode, 'a'))
+        return false; // writing not yet supported
     if(_mode != mode)
     {
         delete [] _buf;