Refactor UniqueNameHelper to use an adapter pattern for code sharing.

content/renderer/unique_name_helper.cc

-// Copyright 2017 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "content/renderer/unique_name_helper.h"
-
-#include <vector>
-
-#include "base/containers/adapters.h"
-#include "base/logging.h"
-#include "base/strings/string_number_conversions.h"
-#include "base/strings/string_piece.h"
-#include "content/renderer/render_frame_impl.h"
-#include "content/renderer/render_frame_proxy.h"
-#include "third_party/WebKit/public/web/WebLocalFrame.h"
-
-namespace content {
-
-namespace {
-
-const std::string& UniqueNameForFrame(blink::WebFrame* frame) {
-  return frame->IsWebLocalFrame()
-             ? RenderFrameImpl::FromWebFrame(frame)->unique_name()
-             : RenderFrameProxy::FromWebFrame(frame)->unique_name();
-}
-
-bool UniqueNameExists(blink::WebFrame* top, const std::string& candidate) {
-  // This method is currently O(N), where N = number of frames in the tree.
-
-  // Before recalculating or checking unique name, we set m_uniqueName
-  // to an empty string (so the soon-to-be-removed name does not count
-  // as a collision).  This means that uniqueNameExists would return
-  // false positives when called with an empty |name|.
-  DCHECK(!candidate.empty());
-
-  for (blink::WebFrame* frame = top; frame; frame = frame->TraverseNext()) {
-    if (UniqueNameForFrame(frame) == candidate)
-      return true;
-  }
-
-  return false;
-}
-
-std::string GenerateCandidate(blink::WebFrame* parent, blink::WebFrame* child) {
-  constexpr char kFramePathPrefix[] = "<!--framePath ";
-  constexpr int kFramePathPrefixLength = 14;
-  constexpr int kFramePathSuffixLength = 3;
-
-  std::string new_name(kFramePathPrefix);
-
-  // Find the nearest parent that has a frame with a path in it.
-  std::vector<blink::WebFrame*> chain;
-  for (blink::WebFrame* frame = parent; frame; frame = frame->Parent()) {
-    base::StringPiece name = UniqueNameForFrame(frame);
-    if (name.starts_with(kFramePathPrefix) && name.ends_with("-->") &&
-        kFramePathPrefixLength + kFramePathSuffixLength < name.size()) {
-      name.substr(kFramePathPrefixLength,
-                  name.size() - kFramePathPrefixLength - kFramePathSuffixLength)
-          .AppendToString(&new_name);
-      break;
-    }
-    chain.push_back(frame);
-  }
-
-  for (auto* frame : base::Reversed(chain)) {
-    new_name += '/';
-    new_name += UniqueNameForFrame(frame);
-  }
-
-  int child_count = 0;
-  for (blink::WebFrame* frame = parent->FirstChild(); frame;
-       frame = frame->NextSibling()) {
-    ++child_count;
-  }
-
-  // When generating a candidate, a null |child| means that this is the
-  // candidate name for a child frame that's not yet attached.
-  new_name += "/<!--frame";
-  new_name += base::IntToString(child_count - (child ? 1 : 0));
-  new_name += "-->-->";
-
-  // NOTE: This name might not be unique - see http://crbug.com/588800.
-  return new_name;
-}
-
-std::string GenerateFramePosition(blink::WebFrame* parent,
-                                  blink::WebFrame* child) {
-  // This method is currently O(N), where N = number of frames in the tree.
-
-  std::string position_string("<!--framePosition");
-
-  while (parent) {
-    int position_in_parent = 0;
-    blink::WebFrame* sibling = parent->FirstChild();
-    while (sibling != child) {
-      sibling = sibling->NextSibling();
-      ++position_in_parent;
-    }
-
-    position_string += '-';
-    position_string += base::IntToString(position_in_parent);
-
-    child = parent;
-    parent = parent->Parent();
-  }
-
-  // NOTE: The generated string is not guaranteed to be unique, but should
-  // have a better chance of being unique than the string generated by
-  // GenerateCandidate, because we embed extra information into the string:
-  // 1) we walk the full chain of ancestors, all the way to the main frame
-  // 2) we use frame-position-within-parent (aka |position_in_parent|)
-  //    instead of sibling-count.
-  return position_string;
-}
-
-std::string AppendUniqueSuffix(blink::WebFrame* top,
-                               const std::string& prefix,
-                               const std::string& likely_unique_suffix) {
-  // This should only be called if the |prefix| isn't unique, as this is
-  // otherwise pointless work.
-  DCHECK(UniqueNameExists(top, prefix));
-
-  // We want unique name to be stable across page reloads - this is why
-  // we use a deterministic |number_of_tries| rather than a random number
-  // (a random number would be more likely to avoid a collision, but
-  // would change after every page reload).
-  int number_of_retries = 0;
-
-  // Keep trying |prefix| + |likely_unique_suffix| + |number_of_tries|
-  // concatenations until we get a truly unique name.
-  std::string candidate(prefix);
-  candidate += likely_unique_suffix;
-  candidate += '/';
-  while (true) {
-    size_t current_length = candidate.size();
-    candidate += base::IntToString(number_of_retries++);
-    candidate += "-->";
-    if (!UniqueNameExists(top, candidate))
-      break;
-    candidate.resize(current_length);
-  }
-  return candidate;
-}
-
-std::string CalculateNewName(blink::WebFrame* parent,
-                             blink::WebFrame* child,
-                             const std::string& name) {
-  blink::WebFrame* top = parent->Top();
-  if (!name.empty() && !UniqueNameExists(top, name) && name != "_blank")
-    return name;
-
-  std::string candidate = GenerateCandidate(parent, child);
-  if (!UniqueNameExists(top, candidate))
-    return candidate;
-
-  std::string likely_unique_suffix = GenerateFramePosition(parent, child);
-  return AppendUniqueSuffix(top, candidate, likely_unique_suffix);
-}
-
-}  // namespace
-
-UniqueNameHelper::UniqueNameHelper(RenderFrameImpl* render_frame)
-    : render_frame_(render_frame) {}
-
-UniqueNameHelper::~UniqueNameHelper() {}
-
-std::string UniqueNameHelper::GenerateNameForNewChildFrame(
-    blink::WebFrame* parent,
-    const std::string& name) {
-  return CalculateNewName(parent, nullptr, name);
-}
-
-void UniqueNameHelper::UpdateName(const std::string& name) {
-  // The unique name of the main frame is always the empty string.
-  if (!GetWebFrame()->Parent())
-    return;
-  // It's important to clear this before calculating a new name, as the
-  // calculation checks for collisions with existing unique names.
-  unique_name_.clear();
-  unique_name_ = CalculateNewName(GetWebFrame()->Parent(), GetWebFrame(), name);
-}
-
-blink::WebLocalFrame* UniqueNameHelper::GetWebFrame() const {
-  return render_frame_->GetWebFrame();
-}
-
-}  // namespace content