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..2079f831d4ab6c3f43aa9d5ea771b8fba77772ad 100644
--- a/runtime/bin/directory_win.cc
+++ b/runtime/bin/directory_win.cc
@@ -9,7 +9,35 @@
 
 #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 = _snprintf(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 {
+      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);
@@ -17,43 +45,29 @@ static bool DeleteRecursively(const wchar_t* dir_name);
 
 
 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)) 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)) {
     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;
@@ -61,48 +75,42 @@ 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,
@@ -121,12 +129,10 @@ 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, path, &path_length);
+  if (path == NULL) {
     PostError(listing, dir_name);
-    free(path);
+    delete path;
     return false;
   }
 
@@ -134,25 +140,24 @@ static bool ListRecursively(const wchar_t* dir_name,
   HANDLE find_handle = FindFirstFileW(path, &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);
+    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;
   }
@@ -166,12 +171,12 @@ static bool ListRecursively(const wchar_t* dir_name,
     success = false;
     PostError(listing, dir_name);
   }
-  free(path);
+  delete path;
 
   return success;
 }
 
-
+// TODO(whesse): Finish adding PathBuffer, starting here.
 static bool DeleteFile(wchar_t* file_name,
                        wchar_t* path,
                        int path_length) {