HTML MessagePort as mojo::MessagePipeHandle

content/browser/android/string_message_codec.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/browser/android/string_message_codec.h"
+
+#include <vector>
+
+#include "base/logging.h"
+
+namespace content {
+namespace {
+
+const uint32_t kVarIntShift = 7;
+const uint32_t kVarIntMask = (1 << kVarIntShift) - 1;
+
+const uint8_t kVersionTag = 0xFF;
+const uint8_t kPaddingTag = '\0';
+const uint8_t kOneByteStringTag = '"';
+const uint8_t kTwoByteStringTag = 'c';
+
+const uint32_t kVersion = 10;
+
+static size_t BytesNeededForUint32(uint32_t value) {
+  size_t result = 0;
+  do {
+    result++;
+    value >>= kVarIntShift;
+  } while (value);
+  return result;
+}
+
+void WriteUint8(uint8_t value, std::vector<uint8_t>* buffer) {
+  buffer->push_back(value);
+}
+
+void WriteUint32(uint32_t value, std::vector<uint8_t>* buffer) {
+  for (;;) {
+    uint8_t b = (value & kVarIntMask);
+    value >>= kVarIntShift;
+    if (!value) {
+      WriteUint8(b, buffer);
+      break;
+    }
+    WriteUint8(b | (1 << kVarIntShift), buffer);
+  }
+}
+
+void WriteBytes(const char* bytes, size_t num_bytes,
+                std::vector<uint8_t>* buffer) {
+  buffer->insert(buffer->end(), bytes, bytes + num_bytes);
+}
+
+bool ReadUint8(const uint8_t** ptr, const uint8_t* end, uint8_t* value) {
+  if (*ptr >= end)
+    return false;
+  *value = *(*ptr)++;
+  return true;
+}
+
+bool ReadUint32(const uint8_t** ptr, const uint8_t* end, uint32_t* value) {
+  *value = 0;
+  uint8_t current_byte;
+  int shift = 0;
+  do {
+    if (*ptr >= end)
+      return false;
+    current_byte = *(*ptr)++;
+    *value |= (static_cast<uint32_t>(current_byte & kVarIntMask) << shift);
+    shift += kVarIntShift;
+  } while (current_byte & (1 << kVarIntShift));
+  return true;
+}
+
+bool ContainsOnlyLatin1(const base::string16& data) {
+  base::char16 x = 0;
+  for (base::char16 c : data)
+    x |= c;
+  return !(x & 0xFF00);
+}
+
+} // namespace
+
+base::string16 EncodeStringMessage(const base::string16& data) {
+  std::vector<uint8_t> buffer;
+  WriteUint8(kVersionTag, &buffer);
+  WriteUint32(kVersion, &buffer);
+
+  if (ContainsOnlyLatin1(data)) {
+    std::string data_latin1(data.begin(), data.end());
+    WriteUint8(kOneByteStringTag, &buffer);
+    WriteUint32(data_latin1.size(), &buffer);
+    WriteBytes(data_latin1.c_str(), data_latin1.size(), &buffer);
+  } else {
+    size_t num_bytes = data.size() * sizeof(base::char16);
+    if ((buffer.size() + 1 + BytesNeededForUint32(num_bytes)) & 1)
+      WriteUint8(kPaddingTag, &buffer);
+    WriteUint8(kTwoByteStringTag, &buffer);
+    WriteUint32(num_bytes, &buffer);
+    WriteBytes(reinterpret_cast<const char*>(data.data()), num_bytes, &buffer);
+  }
+
+  base::string16 result;
+  size_t result_num_bytes = (buffer.size() + 1) & ~1;
+  result.resize(result_num_bytes / 2);
+  uint8_t* destination = reinterpret_cast<uint8_t*>(&result[0]);
+  memcpy(destination, &buffer[0], buffer.size());
+  return result;
+}
+
+bool DecodeStringMessage(const base::string16& encoded_data,
+                         base::string16* result) {
+  size_t num_bytes = encoded_data.size() * 2;
+
+  const uint8_t* ptr = reinterpret_cast<const uint8_t*>(&encoded_data[0]);
+  const uint8_t* end = ptr + num_bytes;
+
+  uint8_t tag;
+  if (!ReadUint8(&ptr, end, &tag) || tag != kVersionTag)
+    return false;
+
+  uint32_t version;
+  if (!ReadUint32(&ptr, end, &version))
+    return false;
+
+  do {
+    if (!ReadUint8(&ptr, end, &tag))
+      return false;
+  } while (tag == kPaddingTag);
+
+  switch (tag) {
+    case kOneByteStringTag: {
+      uint32_t num_bytes;
+      if (!ReadUint32(&ptr, end, &num_bytes))
+        return false;
+      result->assign(reinterpret_cast<const char*>(ptr),
+                     reinterpret_cast<const char*>(ptr) + num_bytes);
+      return true;
+    }
+    case kTwoByteStringTag: {
+      uint32_t num_bytes;
+      if (!ReadUint32(&ptr, end, &num_bytes))
+        return false;
+      result->assign(reinterpret_cast<const base::char16*>(ptr), num_bytes / 2);
+      return true;
+    }
+  }
+
+  DLOG(WARNING) << "Unexpected tag: " << tag;
+  return false;
+}
+
+}  // namespace content