1 files changed, 168 insertions, 0 deletions
diff --git a/src/main/native/windows/util.cc b/src/main/native/windows/util.cc
new file mode 100644
index 0000000000..8f43fe7b74
--- /dev/null
+++ b/src/main/native/windows/util.cc
@@ -0,0 +1,168 @@
+// Copyright 2016 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <windows.h>
+
+#include <algorithm>
+#include <functional>
+#include <memory>
+#include <string>
+
+#include "src/main/native/windows/util.h"
+
+namespace bazel {
+namespace windows {
+
+using std::function;
+using std::string;
+using std::unique_ptr;
+using std::wstring;
+
+string GetLastErrorString(const string& cause) {
+  DWORD last_error = GetLastError();
+  if (last_error == 0) {
+    return "";
+  }
+
+  LPSTR message;
+  DWORD size = FormatMessageA(
+      FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
+          FORMAT_MESSAGE_IGNORE_INSERTS,
+      NULL, last_error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+      (LPSTR)&message, 0, NULL);
+
+  if (size == 0) {
+    char buf[256];
+    snprintf(buf, sizeof(buf),
+             "%s: Error %d (cannot format message due to error %d)",
+             cause.c_str(), last_error, GetLastError());
+    buf[sizeof(buf) - 1] = 0;
+  }
+
+  string result = string(message);
+  LocalFree(message);
+  return cause + ": " + result;
+}
+
+static void QuotePath(const string& path, string* result) {
+  *result = string("\"") + path + "\"";
+}
+
+static bool IsSeparator(char c) { return c == '/' || c == '\\'; }
+
+static bool HasSeparator(const string& s) {
+  return s.find_first_of('/') != string::npos ||
+         s.find_first_of('\\') != string::npos;
+}
+
+static bool Contains(const string& s, const char* substr) {
+  return s.find(substr) != string::npos;
+}
+
+string AsShortPath(string path, function<wstring()> path_as_wstring,
+                   string* result) {
+  if (path.empty()) {
+    result->clear();
+    return "";
+  }
+  if (path[0] == '"') {
+    return string("path should not be quoted");
+  }
+  if (IsSeparator(path[0])) {
+    return string("path='") + path + "' is absolute";
+  }
+  if (Contains(path, "/./") || Contains(path, "\\.\\") ||
+      Contains(path, "/..") || Contains(path, "\\..")) {
+    return string("path='") + path + "' is not normalized";
+  }
+  if (path.size() >= MAX_PATH && !HasSeparator(path)) {
+    return string("path='") + path + "' is just a file name but too long";
+  }
+  if (HasSeparator(path) &&
+      !(isalpha(path[0]) && path[1] == ':' && IsSeparator(path[2]))) {
+    return string("path='") + path + "' is not an absolute path";
+  }
+  // At this point we know the path is either just a file name (shorter than
+  // MAX_PATH), or an absolute, normalized, Windows-style path (of any length).
+
+  std::replace(path.begin(), path.end(), '/', '\\');
+  // Fast-track: the path is already short.
+  if (path.size() < MAX_PATH) {
+    *result = path;
+    return "";
+  }
+  // At this point we know that the path is at least MAX_PATH long and that it's
+  // absolute, normalized, and Windows-style.
+
+  // Retrieve string as UTF-16 path, add "\\?\" prefix.
+  wstring wlong = wstring(L"\\\\?\\") + path_as_wstring();
+
+  // Experience shows that:
+  // - GetShortPathNameW's result has a "\\?\" prefix if and only if the input
+  //   did too (though this behavior is not documented on MSDN)
+  // - CreateProcess{A,W} only accept an executable of MAX_PATH - 1 length
+  // Therefore for our purposes the acceptable shortened length is
+  // MAX_PATH + 4 (null-terminated). That is, MAX_PATH - 1 for the shortened
+  // path, plus a potential "\\?\" prefix that's only there if `wlong` also had
+  // it and which we'll omit from `result`, plus a null terminator.
+  static const size_t kMaxShortPath = MAX_PATH + 4;
+
+  WCHAR wshort[kMaxShortPath];
+  DWORD wshort_size = ::GetShortPathNameW(wlong.c_str(), NULL, 0);
+  if (wshort_size == 0) {
+    return GetLastErrorString(string("GetShortPathName failed (path=") + path +
+                              ")");
+  }
+
+  if (wshort_size >= kMaxShortPath) {
+    return string("GetShortPathName would not shorten the path enough (path=") +
+           path + ")";
+  }
+  GetShortPathNameW(wlong.c_str(), wshort, kMaxShortPath);
+
+  // Convert the result to UTF-8.
+  char mbs_short[MAX_PATH];
+  size_t mbs_size = wcstombs(
+      mbs_short,
+      wshort + 4,  // we know it has a "\\?\" prefix, because `wlong` also did
+      MAX_PATH);
+  if (mbs_size < 0 || mbs_size >= MAX_PATH) {
+    return string("wcstombs failed (path=") + path + ")";
+  }
+  mbs_short[mbs_size] = 0;
+
+  *result = mbs_short;
+  return "";
+}
+
+string AsExecutablePathForCreateProcess(const string& path,
+                                        function<wstring()> path_as_wstring,
+                                        string* result) {
+  if (path.empty()) {
+    return string("path should not be empty");
+  }
+  string error = AsShortPath(path, path_as_wstring, result);
+  if (error.empty()) {
+    // Quote the path in case it's something like "c:\foo\app name.exe".
+    // Do this unconditionally, there's no harm in quoting. Quotes are not
+    // allowed inside paths so we don't need to escape quotes.
+    QuotePath(*result, result);
+  }
+  return error;
+}
+
+}  // namespace windows
+}  // namespace bazel