Use a PathBuffer class in dart:io directory lister.

runtime/bin/directory_win.cc

Index: runtime/bin/directory_win.cc
diff --git a/runtime/bin/directory_win.cc b/runtime/bin/directory_win.cc
index 9d8f6f31935d30691c4344acc8354d300dfef835..24d98f70eaf18e54b5caec609cf54ef518a28570 100644
--- a/runtime/bin/directory_win.cc
+++ b/runtime/bin/directory_win.cc
@@ -9,51 +9,78 @@
 
 #include "bin/log.h"
 
-// Forward declaration.
+class PathBuffer {
+ public:
+  PathBuffer() : length(0) { }
+
+  wchar_t data[MAX_PATH + 1];
+  int length;
+
+  bool Add(const wchar_t* name) {
+    size_t written = _snwprintf(data + length,
+                               MAX_PATH - length,
+                               L"%s",
+                               name);
+    data[MAX_PATH] = L'\0';
+    if (written == wcsnlen(name, MAX_PATH + 1)) {
+      length += written;
+      return true;
+    } else {
+      SetLastError(ERROR_BUFFER_OVERFLOW);
+      return false;
+    }
+  }
+
+  void Reset(int new_length) {
+    length = new_length;
+    data[length] = L'\0';
+  }
+};
+
+
+// Forward declarations.
 static bool ListRecursively(const wchar_t* dir_name,
                             bool recursive,
                             DirectoryListing* listing);
 static bool DeleteRecursively(const wchar_t* dir_name);
 
 
+static void PostError(DirectoryListing* listing,
+                      const wchar_t* dir_name) {
+  const char* utf8_path = StringUtils::WideToUtf8(dir_name);
+  listing->HandleError(utf8_path);
+  free(const_cast<char*>(utf8_path));
+}
+
+
 static bool HandleDir(wchar_t* dir_name,
-                      wchar_t* path,
-                      int path_length,
+                      PathBuffer* path,
                       bool recursive,
                       DirectoryListing* listing) {
-  if (wcscmp(dir_name, L".") != 0 &&
-      wcscmp(dir_name, L"..") != 0) {
-    size_t written = _snwprintf(path + path_length,
-                                MAX_PATH - path_length,
-                                L"%s",
-                                dir_name);
-    if (written != wcslen(dir_name)) {
-      return false;
-    }
-    char* utf8_path = StringUtils::WideToUtf8(path);
-    bool ok = listing->HandleDirectory(utf8_path);
-    free(utf8_path);
-    if (!ok) return ok;
-    if (recursive) {
-      return ListRecursively(path, recursive, listing);
-    }
+  if (wcscmp(dir_name, L".") == 0) return true;
+  if (wcscmp(dir_name, L"..") == 0) return true;
+  if (!path->Add(dir_name)) {
+    PostError(listing, path->data);
+    return false;
+  }
+  char* utf8_path = StringUtils::WideToUtf8(path->data);
+  bool ok = listing->HandleDirectory(utf8_path);
+  free(utf8_path);
+  if (!ok) return ok;
+  if (recursive) {
+    return ListRecursively(path->data, recursive, listing);
   }
-  return true;
 }
 
 
 static bool HandleFile(wchar_t* file_name,
-                       wchar_t* path,
-                       int path_length,
+                       PathBuffer* path,
                        DirectoryListing* listing) {
-  size_t written = _snwprintf(path + path_length,
-                              MAX_PATH - path_length,
-                              L"%s",
-                              file_name);
-  if (written != wcslen(file_name)) {
+  if (!path->Add(file_name)) {
+    PostError(listing, path->data);
     return false;
-  };
-  char* utf8_path = StringUtils::WideToUtf8(path);
+  }
+  char* utf8_path = StringUtils::WideToUtf8(path->data);
   bool ok = listing->HandleFile(utf8_path);
   free(utf8_path);
   return ok;
@@ -61,55 +88,42 @@ static bool HandleFile(wchar_t* file_name,
 
 
 static bool HandleEntry(LPWIN32_FIND_DATAW find_file_data,
-                        wchar_t* path,
-                        int path_length,
+                        PathBuffer* path,
                         bool recursive,
                         DirectoryListing* listing) {
   DWORD attributes = find_file_data->dwFileAttributes;
   if ((attributes & FILE_ATTRIBUTE_DIRECTORY) != 0) {
     return HandleDir(find_file_data->cFileName,
                      path,
-                     path_length,
                      recursive,
                      listing);
   } else {
-    return HandleFile(find_file_data->cFileName, path, path_length, listing);
+    return HandleFile(find_file_data->cFileName, path, listing);
   }
 }
 
 
-// ComputeFullSearchPath must be called with a path array of size at
-// least MAX_PATH.
-static bool ComputeFullSearchPath(const wchar_t* dir_name,
-                                  wchar_t* path,
-                                  int* path_length) {
+static PathBuffer* ComputeFullSearchPath(const wchar_t* dir_name) {
   // GetFullPathName only works in a multi-threaded environment if
   // SetCurrentDirectory is not used. We currently have no plan for
   // exposing SetCurrentDirectory.
-  size_t written = GetFullPathNameW(dir_name, MAX_PATH, path, NULL);
+  PathBuffer* path = new PathBuffer();
+
+  size_t written = GetFullPathNameW(dir_name, MAX_PATH + 1, path->data, NULL);
   // GetFullPathName only accepts input strings of size less than
   // MAX_PATH and returns 0 to indicate failure for paths longer than
   // that. Therefore the path buffer is always big enough.
   if (written == 0 || written > MAX_PATH) {
-    return false;
+    delete path;
+    return NULL;
   }
-  *path_length = written;
-  written = _snwprintf(path + *path_length,
-                       MAX_PATH - *path_length,
-                       L"%s",
-                       L"\\*");
-  if (written != 2) {
-    return false;
+  path->length = written;
+  if (path->Add(L"\\*")) {
+    return path;
+  } else {
+    delete path;
+    return NULL;
   }
-  *path_length += written;
-  return true;
-}
-
-static void PostError(DirectoryListing* listing,
-                      const wchar_t* dir_name) {
-  const char* utf8_path = StringUtils::WideToUtf8(dir_name);
-  listing->HandleError(utf8_path);
-  free(const_cast<char*>(utf8_path));
 }
 
 
@@ -121,38 +135,35 @@ static bool ListRecursively(const wchar_t* dir_name,
   // recursive traversal. path_length does not always equal
   // strlen(path) but indicates the current prefix of path that is the
   // path of the current directory in the traversal.
-  wchar_t* path = static_cast<wchar_t*>(malloc(MAX_PATH * sizeof(wchar_t)));
-  int path_length = 0;
-  bool valid = ComputeFullSearchPath(dir_name, path, &path_length);
-  if (!valid) {
+  PathBuffer* path = ComputeFullSearchPath(dir_name);
+  if (path == NULL) {
     PostError(listing, dir_name);
-    free(path);
+    delete path;
     return false;
   }
 
   WIN32_FIND_DATAW find_file_data;
-  HANDLE find_handle = FindFirstFileW(path, &find_file_data);
+  HANDLE find_handle = FindFirstFileW(path->data, &find_file_data);
 
   // Adjust the path by removing the '*' used for the search.
-  path_length -= 1;
-  path[path_length] = '\0';
+  path->Reset(path->length - 1);
 
   if (find_handle == INVALID_HANDLE_VALUE) {
-    PostError(listing, path);
-    free(path);
+    PostError(listing, path->data);
+    delete path;
     return false;
   }
 
+  int path_length = path->length;
   bool success = HandleEntry(&find_file_data,
                              path,
-                             path_length,
                              recursive,
                              listing);
 
   while ((FindNextFileW(find_handle, &find_file_data) != 0)) {
+    path->Reset(path_length);  // HandleEntry adds the entry name to path.
     success = HandleEntry(&find_file_data,
                           path,
-                          path_length,
                           recursive,
                           listing) && success;
   }
@@ -166,24 +177,16 @@ static bool ListRecursively(const wchar_t* dir_name,
     success = false;
     PostError(listing, dir_name);
   }
-  free(path);
+  delete path;
 
   return success;
 }
 
 
-static bool DeleteFile(wchar_t* file_name,
-                       wchar_t* path,
-                       int path_length) {
-  size_t written = _snwprintf(path + path_length,
-                              MAX_PATH - path_length,
-                              L"%s",
-                              file_name);
-  if (written != wcslen(file_name)) {
-    return false;
-  }
+static bool DeleteFile(wchar_t* file_name, PathBuffer* path) {
+  if (!path->Add(file_name)) return false;
 
-  if (DeleteFileW(path) != 0) {
+  if (DeleteFileW(path->data) != 0) {
     return true;
   }
 
@@ -191,7 +194,7 @@ static bool DeleteFile(wchar_t* file_name,
   // again. This mirrors Linux/Mac where a directory containing read-only files
   // can still be recursively deleted.
   if (GetLastError() == ERROR_ACCESS_DENIED) {
-    DWORD attributes = GetFileAttributesW(path);
+    DWORD attributes = GetFileAttributesW(path->data);
     if (attributes == INVALID_FILE_ATTRIBUTES) {
       return false;
     }
@@ -199,11 +202,11 @@ static bool DeleteFile(wchar_t* file_name,
     if ((attributes & FILE_ATTRIBUTE_READONLY) == FILE_ATTRIBUTE_READONLY) {
       attributes &= ~FILE_ATTRIBUTE_READONLY;
 
-      if (SetFileAttributesW(path, attributes) == 0) {
+      if (SetFileAttributesW(path->data, attributes) == 0) {
         return false;
       }
 
-      return DeleteFileW(path) != 0;
+      return DeleteFileW(path->data) != 0;
     }
   }
 
@@ -211,33 +214,20 @@ static bool DeleteFile(wchar_t* file_name,
 }
 
 
-static bool DeleteDir(wchar_t* dir_name,
-                      wchar_t* path,
-                      int path_length) {
-  if (wcscmp(dir_name, L".") != 0 &&
-      wcscmp(dir_name, L"..") != 0) {
-    size_t written = _snwprintf(path + path_length,
-                                MAX_PATH - path_length,
-                                L"%s",
-                                dir_name);
-    if (written != wcslen(dir_name)) {
-      return false;
-    }
-    return DeleteRecursively(path);
-  }
-  return true;
+static bool DeleteDir(wchar_t* dir_name, PathBuffer* path) {
+  if (wcscmp(dir_name, L".") == 0) return true;
+  if (wcscmp(dir_name, L"..") == 0) return true;
+  return path->Add(dir_name) && DeleteRecursively(path->data);
 }
 
 
-static bool DeleteEntry(LPWIN32_FIND_DATAW find_file_data,
-                        wchar_t* path,
-                        int path_length) {
+static bool DeleteEntry(LPWIN32_FIND_DATAW find_file_data, PathBuffer* path) {
   DWORD attributes = find_file_data->dwFileAttributes;
 
   if ((attributes & FILE_ATTRIBUTE_DIRECTORY) != 0) {
-    return DeleteDir(find_file_data->cFileName, path, path_length);
+    return DeleteDir(find_file_data->cFileName, path);
   } else {
-    return DeleteFile(find_file_data->cFileName, path, path_length);
+    return DeleteFile(find_file_data->cFileName, path);
   }
 }
 
@@ -257,33 +247,29 @@ static bool DeleteRecursively(const wchar_t* dir_name) {
   // recursive traversal. path_length does not always equal
   // strlen(path) but indicates the current prefix of path that is the
   // path of the current directory in the traversal.
-  wchar_t* path = static_cast<wchar_t*>(malloc(MAX_PATH * sizeof(wchar_t)));
-  int path_length = 0;
-  bool valid = ComputeFullSearchPath(dir_name, path, &path_length);
-  if (!valid) {
-    free(path);
-    return false;
-  }
+  PathBuffer* path = ComputeFullSearchPath(dir_name);
+  if (path == NULL) return false;
 
   WIN32_FIND_DATAW find_file_data;
-  HANDLE find_handle = FindFirstFileW(path, &find_file_data);
+  HANDLE find_handle = FindFirstFileW(path->data, &find_file_data);
 
   // Adjust the path by removing the '*' used for the search.
-  path_length -= 1;
-  path[path_length] = '\0';
+  int path_length = path->length - 1;
+  path->Reset(path_length);
 
   if (find_handle == INVALID_HANDLE_VALUE) {
-    free(path);
+    delete path;
     return false;
   }
 
-  bool success = DeleteEntry(&find_file_data, path, path_length);
+  bool success = DeleteEntry(&find_file_data, path);
 
   while ((FindNextFileW(find_handle, &find_file_data) != 0) && success) {
-    success = success && DeleteEntry(&find_file_data, path, path_length);
+    path->Reset(path_length);  // DeleteEntry adds to the path.
+    success = success && DeleteEntry(&find_file_data, path);
   }
 
-  free(path);
+  delete path;
 
   if ((GetLastError() != ERROR_NO_MORE_FILES) ||
       (FindClose(find_handle) == 0) ||
@@ -362,52 +348,51 @@ char* Directory::CreateTemp(const char* const_template) {
   // dir_template.  Creates this directory, with a default security
   // descriptor inherited from its parent directory.
   // The return value must be freed by the caller.
-  wchar_t* path = static_cast<wchar_t*>(malloc(MAX_PATH * sizeof(wchar_t)));
-  int path_length;
+  PathBuffer* path = new PathBuffer();
   if (0 == strncmp(const_template, "", 1)) {
-    path_length = GetTempPathW(MAX_PATH, path);
-    if (path_length == 0) {
-      free(path);
+    path->length = GetTempPathW(MAX_PATH, path->data);
+    if (path->length == 0) {
+      delete path;
       return NULL;
     }
   } else {
     const wchar_t* system_template = StringUtils::Utf8ToWide(const_template);
-    _snwprintf(path, MAX_PATH, L"%s", system_template);
+    path->Add(system_template);
     free(const_cast<wchar_t*>(system_template));
-    path_length = wcslen(path);
   }
   // Length of tempdir-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx is 44.
-  if (path_length > MAX_PATH - 44) {
-    free(path);
+  if (path->length > MAX_PATH - 44) {
+    delete path;
     return NULL;
   }
-  if ((path)[path_length - 1] == L'\\') {
+  if ((path->data)[path->length - 1] == L'\\') {
     // No base name for the directory - use "tempdir".
-    _snwprintf(path + path_length, MAX_PATH - path_length, L"tempdir");
-    path_length = wcslen(path);
+    path->Add(L"tempdir");
   }
 
   UUID uuid;
   RPC_STATUS status = UuidCreateSequential(&uuid);
   if (status != RPC_S_OK && status != RPC_S_UUID_LOCAL_ONLY) {
-    free(path);
+    delete path;
     return NULL;
   }
   RPC_WSTR uuid_string;
   status = UuidToStringW(&uuid, &uuid_string);
   if (status != RPC_S_OK) {
-    free(path);
+    delete path;
     return NULL;
   }
 
-  _snwprintf(path + path_length, MAX_PATH - path_length, L"-%s", uuid_string);
+  path->Add(L"-");
+  // RPC_WSTR is an unsigned short*, so we cast to wchar_t*.
+  path->Add(reinterpret_cast<wchar_t*>(uuid_string));
   RpcStringFreeW(&uuid_string);
-  if (!CreateDirectoryW(path, NULL)) {
-    free(path);
+  if (!CreateDirectoryW(path->data, NULL)) {
+    delete path;
     return NULL;
   }
-  char* result = StringUtils::WideToUtf8(path);
-  free(path);
+  char* result = StringUtils::WideToUtf8(path->data);
+  delete path;
   return result;
 }