libwebp: Unicode command tools on Windows

Define macros in examples/unicode.h to use Unicode argv
on Windows. Keep char everywhere on Unix since it handles
UTF-8 without any change.

Impact:
 - All fopen () and SHCreateStreamOnFile(),
 - All fprintf() printing file paths,
 - All strcmp() used with "-",
 - File path parsing,
 - Gif reading.

Concerned executables from examples/ and extras/:
  anim_diff, anim_dump, vwebp, vwebp_sdl,
  cwebp, dwebp, gif2webp, img2webp,
  webpmux, webpinfo, webp_quality, get_disto

When compiled on Windows with Unicode enabled, webpmux and
img2webp will not work when used with an argument file and
will print "Reading arguments from a file is a feature
unavailable with Unicode binaries."

BUG=webp:398

Change-Id: Ic55d222a3ce1a715f9c4cce57ecbe2705d5ce317

examples/unicode.h

@@ -0,0 +1,101 @@
+// Copyright 2018 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS. All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+// -----------------------------------------------------------------------------
+//
+// Unicode support for Windows. The main idea is to maintain an array of Unicode
+// arguments (wargv) and use it only for file paths. The regular argv is used
+// for everything else.
+//
+// Author: Yannis Guyon (yguyon@google.com)
+
+#ifndef WEBP_EXAMPLES_UNICODE_H_
+#define WEBP_EXAMPLES_UNICODE_H_
+
+#if defined(_WIN32) && defined(_UNICODE)
+
+// wchar_t is used instead of TCHAR because we only perform additional work when
+// Unicode is enabled and because the output of CommandLineToArgvW() is wchar_t.
+
+#include <wchar.h>
+#include <windows.h>
+#include <shellapi.h>
+
+// Create a wchar_t array containing Unicode parameters.
+#define INIT_WARGV(ARGC, ARGV)                                                \
+  int wargc;                                                                  \
+  const W_CHAR** const wargv = CommandLineToArgvW(GetCommandLineW(), &wargc); \
+  do {                                                                        \
+    if (wargv == NULL || wargc != (ARGC)) {                                   \
+      fprintf(stderr, "Error: Unable to get Unicode arguments.\n");           \
+      FREE_WARGV_AND_RETURN(-1);                                              \
+    }                                                                         \
+  } while (0)
+
+// Use this to get a Unicode argument (e.g. file path).
+#define GET_WARGV(UNUSED, C) wargv[C]
+// For cases where argv is shifted by one compared to wargv.
+#define GET_WARGV_SHIFTED(UNUSED, C) wargv[(C) + 1]
+#define GET_WARGV_OR_NULL() wargv
+
+// Release resources. LocalFree() is needed after CommandLineToArgvW().
+#define FREE_WARGV() LOCAL_FREE((W_CHAR** const)wargv)
+#define LOCAL_FREE(WARGV)                  \
+  do {                                     \
+    if ((WARGV) != NULL) LocalFree(WARGV); \
+  } while (0)
+
+#define W_CHAR wchar_t  // WCHAR without underscore might already be defined.
+#define TO_W_CHAR(STR) (L##STR)
+
+#define WFOPEN(ARG, OPT) _wfopen((const W_CHAR*)ARG, TO_W_CHAR(OPT))
+
+#define WPRINTF(STR, ...) wprintf(TO_W_CHAR(STR), __VA_ARGS__)
+#define WFPRINTF(STDERR, STR, ...) fwprintf(STDERR, TO_W_CHAR(STR), __VA_ARGS__)
+
+#define WSTRLEN(FILENAME) wcslen((const W_CHAR*)FILENAME)
+#define WSTRCMP(FILENAME, STR) wcscmp((const W_CHAR*)FILENAME, TO_W_CHAR(STR))
+#define WSTRRCHR(FILENAME, STR) wcsrchr((const W_CHAR*)FILENAME, TO_W_CHAR(STR))
+#define WSNPRINTF(A, B, STR, ...) _snwprintf(A, B, TO_W_CHAR(STR), __VA_ARGS__)
+
+#else
+
+// Unicode file paths work as is on Unix platforms, and no extra work is done on
+// Windows either if Unicode is disabled.
+
+#define INIT_WARGV(ARGC, ARGV)
+
+#define GET_WARGV(ARGV, C) (ARGV)[C]
+#define GET_WARGV_SHIFTED(ARGV, C) (ARGV)[C]
+#define GET_WARGV_OR_NULL() NULL
+
+#define FREE_WARGV()
+#define LOCAL_FREE(WARGV)
+
+#define W_CHAR char
+#define TO_W_CHAR(STR) (STR)
+
+#define WFOPEN(ARG, OPT) fopen(ARG, OPT)
+
+#define WPRINTF(STR, ...) printf(STR, __VA_ARGS__)
+#define WFPRINTF(STDERR, STR, ...) fprintf(STDERR, STR, __VA_ARGS__)
+
+#define WSTRLEN(FILENAME) strlen(FILENAME)
+#define WSTRCMP(FILENAME, STR) strcmp(FILENAME, STR)
+#define WSTRRCHR(FILENAME, STR) strrchr(FILENAME, STR)
+#define WSNPRINTF(A, B, STR, ...) snprintf(A, B, STR, __VA_ARGS__)
+
+#endif  // defined(_WIN32) && defined(_UNICODE)
+
+// Don't forget to free wargv before returning (e.g. from main).
+#define FREE_WARGV_AND_RETURN(VALUE) \
+  do {                               \
+    FREE_WARGV();                    \
+    return (VALUE);                  \
+  } while (0)
+
+#endif  // WEBP_EXAMPLES_UNICODE_H_