diff --git a/libs/androidfw/StringPool.cpp b/libs/androidfw/StringPool.cpp
new file mode 100644
index 0000000..b59e906
--- /dev/null
+++ b/libs/androidfw/StringPool.cpp
@@ -0,0 +1,508 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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 <androidfw/BigBuffer.h>
+#include <androidfw/StringPool.h>
+
+#include <algorithm>
+#include <memory>
+#include <string>
+
+#include "android-base/logging.h"
+#include "androidfw/ResourceTypes.h"
+#include "androidfw/StringPiece.h"
+#include "androidfw/Util.h"
+
+using ::android::StringPiece;
+
+namespace android {
+
+StringPool::Ref::Ref() : entry_(nullptr) {
+}
+
+StringPool::Ref::Ref(const StringPool::Ref& rhs) : entry_(rhs.entry_) {
+  if (entry_ != nullptr) {
+    entry_->ref_++;
+  }
+}
+
+StringPool::Ref::Ref(StringPool::Entry* entry) : entry_(entry) {
+  if (entry_ != nullptr) {
+    entry_->ref_++;
+  }
+}
+
+StringPool::Ref::~Ref() {
+  if (entry_ != nullptr) {
+    entry_->ref_--;
+  }
+}
+
+StringPool::Ref& StringPool::Ref::operator=(const StringPool::Ref& rhs) {
+  if (rhs.entry_ != nullptr) {
+    rhs.entry_->ref_++;
+  }
+
+  if (entry_ != nullptr) {
+    entry_->ref_--;
+  }
+  entry_ = rhs.entry_;
+  return *this;
+}
+
+bool StringPool::Ref::operator==(const Ref& rhs) const {
+  return entry_->value == rhs.entry_->value;
+}
+
+bool StringPool::Ref::operator!=(const Ref& rhs) const {
+  return entry_->value != rhs.entry_->value;
+}
+
+const std::string* StringPool::Ref::operator->() const {
+  return &entry_->value;
+}
+
+const std::string& StringPool::Ref::operator*() const {
+  return entry_->value;
+}
+
+size_t StringPool::Ref::index() const {
+  // Account for the styles, which *always* come first.
+  return entry_->pool_->styles_.size() + entry_->index_;
+}
+
+const StringPool::Context& StringPool::Ref::GetContext() const {
+  return entry_->context;
+}
+
+StringPool::StyleRef::StyleRef() : entry_(nullptr) {
+}
+
+StringPool::StyleRef::StyleRef(const StringPool::StyleRef& rhs) : entry_(rhs.entry_) {
+  if (entry_ != nullptr) {
+    entry_->ref_++;
+  }
+}
+
+StringPool::StyleRef::StyleRef(StringPool::StyleEntry* entry) : entry_(entry) {
+  if (entry_ != nullptr) {
+    entry_->ref_++;
+  }
+}
+
+StringPool::StyleRef::~StyleRef() {
+  if (entry_ != nullptr) {
+    entry_->ref_--;
+  }
+}
+
+StringPool::StyleRef& StringPool::StyleRef::operator=(const StringPool::StyleRef& rhs) {
+  if (rhs.entry_ != nullptr) {
+    rhs.entry_->ref_++;
+  }
+
+  if (entry_ != nullptr) {
+    entry_->ref_--;
+  }
+  entry_ = rhs.entry_;
+  return *this;
+}
+
+bool StringPool::StyleRef::operator==(const StyleRef& rhs) const {
+  if (entry_->value != rhs.entry_->value) {
+    return false;
+  }
+
+  if (entry_->spans.size() != rhs.entry_->spans.size()) {
+    return false;
+  }
+
+  auto rhs_iter = rhs.entry_->spans.begin();
+  for (const Span& span : entry_->spans) {
+    const Span& rhs_span = *rhs_iter;
+    if (span.first_char != rhs_span.first_char || span.last_char != rhs_span.last_char ||
+        span.name != rhs_span.name) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool StringPool::StyleRef::operator!=(const StyleRef& rhs) const {
+  return !operator==(rhs);
+}
+
+const StringPool::StyleEntry* StringPool::StyleRef::operator->() const {
+  return entry_;
+}
+
+const StringPool::StyleEntry& StringPool::StyleRef::operator*() const {
+  return *entry_;
+}
+
+size_t StringPool::StyleRef::index() const {
+  return entry_->index_;
+}
+
+const StringPool::Context& StringPool::StyleRef::GetContext() const {
+  return entry_->context;
+}
+
+StringPool::Ref StringPool::MakeRef(const StringPiece& str) {
+  return MakeRefImpl(str, Context{}, true);
+}
+
+StringPool::Ref StringPool::MakeRef(const StringPiece& str, const Context& context) {
+  return MakeRefImpl(str, context, true);
+}
+
+StringPool::Ref StringPool::MakeRefImpl(const StringPiece& str, const Context& context,
+                                        bool unique) {
+  if (unique) {
+    auto range = indexed_strings_.equal_range(str);
+    for (auto iter = range.first; iter != range.second; ++iter) {
+      if (context.priority == iter->second->context.priority) {
+        return Ref(iter->second);
+      }
+    }
+  }
+
+  std::unique_ptr<Entry> entry(new Entry());
+  entry->value = str.to_string();
+  entry->context = context;
+  entry->index_ = strings_.size();
+  entry->ref_ = 0;
+  entry->pool_ = this;
+
+  Entry* borrow = entry.get();
+  strings_.emplace_back(std::move(entry));
+  indexed_strings_.insert(std::make_pair(StringPiece(borrow->value), borrow));
+  return Ref(borrow);
+}
+
+StringPool::Ref StringPool::MakeRef(const Ref& ref) {
+  if (ref.entry_->pool_ == this) {
+    return ref;
+  }
+  return MakeRef(ref.entry_->value, ref.entry_->context);
+}
+
+StringPool::StyleRef StringPool::MakeRef(const StyleString& str) {
+  return MakeRef(str, Context{});
+}
+
+StringPool::StyleRef StringPool::MakeRef(const StyleString& str, const Context& context) {
+  std::unique_ptr<StyleEntry> entry(new StyleEntry());
+  entry->value = str.str;
+  entry->context = context;
+  entry->index_ = styles_.size();
+  entry->ref_ = 0;
+  for (const android::Span& span : str.spans) {
+    entry->spans.emplace_back(Span{MakeRef(span.name), span.first_char, span.last_char});
+  }
+
+  StyleEntry* borrow = entry.get();
+  styles_.emplace_back(std::move(entry));
+  return StyleRef(borrow);
+}
+
+StringPool::StyleRef StringPool::MakeRef(const StyleRef& ref) {
+  std::unique_ptr<StyleEntry> entry(new StyleEntry());
+  entry->value = ref.entry_->value;
+  entry->context = ref.entry_->context;
+  entry->index_ = styles_.size();
+  entry->ref_ = 0;
+  for (const Span& span : ref.entry_->spans) {
+    entry->spans.emplace_back(Span{MakeRef(*span.name), span.first_char, span.last_char});
+  }
+
+  StyleEntry* borrow = entry.get();
+  styles_.emplace_back(std::move(entry));
+  return StyleRef(borrow);
+}
+
+void StringPool::ReAssignIndices() {
+  // Assign the style indices.
+  const size_t style_len = styles_.size();
+  for (size_t index = 0; index < style_len; index++) {
+    styles_[index]->index_ = index;
+  }
+
+  // Assign the string indices.
+  const size_t string_len = strings_.size();
+  for (size_t index = 0; index < string_len; index++) {
+    strings_[index]->index_ = index;
+  }
+}
+
+void StringPool::Merge(StringPool&& pool) {
+  // First, change the owning pool for the incoming strings.
+  for (std::unique_ptr<Entry>& entry : pool.strings_) {
+    entry->pool_ = this;
+  }
+
+  // Now move the styles, strings, and indices over.
+  std::move(pool.styles_.begin(), pool.styles_.end(), std::back_inserter(styles_));
+  pool.styles_.clear();
+  std::move(pool.strings_.begin(), pool.strings_.end(), std::back_inserter(strings_));
+  pool.strings_.clear();
+  indexed_strings_.insert(pool.indexed_strings_.begin(), pool.indexed_strings_.end());
+  pool.indexed_strings_.clear();
+
+  ReAssignIndices();
+}
+
+void StringPool::HintWillAdd(size_t string_count, size_t style_count) {
+  strings_.reserve(strings_.size() + string_count);
+  styles_.reserve(styles_.size() + style_count);
+}
+
+void StringPool::Prune() {
+  const auto iter_end = indexed_strings_.end();
+  auto index_iter = indexed_strings_.begin();
+  while (index_iter != iter_end) {
+    if (index_iter->second->ref_ <= 0) {
+      index_iter = indexed_strings_.erase(index_iter);
+    } else {
+      ++index_iter;
+    }
+  }
+
+  auto end_iter2 =
+      std::remove_if(strings_.begin(), strings_.end(),
+                     [](const std::unique_ptr<Entry>& entry) -> bool { return entry->ref_ <= 0; });
+  auto end_iter3 = std::remove_if(
+      styles_.begin(), styles_.end(),
+      [](const std::unique_ptr<StyleEntry>& entry) -> bool { return entry->ref_ <= 0; });
+
+  // Remove the entries at the end or else we'll be accessing a deleted string from the StyleEntry.
+  strings_.erase(end_iter2, strings_.end());
+  styles_.erase(end_iter3, styles_.end());
+
+  ReAssignIndices();
+}
+
+template <typename E>
+static void SortEntries(
+    std::vector<std::unique_ptr<E>>& entries,
+    const std::function<int(const StringPool::Context&, const StringPool::Context&)>& cmp) {
+  using UEntry = std::unique_ptr<E>;
+
+  if (cmp != nullptr) {
+    std::sort(entries.begin(), entries.end(), [&cmp](const UEntry& a, const UEntry& b) -> bool {
+      int r = cmp(a->context, b->context);
+      if (r == 0) {
+        r = a->value.compare(b->value);
+      }
+      return r < 0;
+    });
+  } else {
+    std::sort(entries.begin(), entries.end(),
+              [](const UEntry& a, const UEntry& b) -> bool { return a->value < b->value; });
+  }
+}
+
+void StringPool::Sort(const std::function<int(const Context&, const Context&)>& cmp) {
+  SortEntries(styles_, cmp);
+  SortEntries(strings_, cmp);
+  ReAssignIndices();
+}
+
+template <typename T>
+static T* EncodeLength(T* data, size_t length) {
+  static_assert(std::is_integral<T>::value, "wat.");
+
+  constexpr size_t kMask = 1 << ((sizeof(T) * 8) - 1);
+  constexpr size_t kMaxSize = kMask - 1;
+  if (length > kMaxSize) {
+    *data++ = kMask | (kMaxSize & (length >> (sizeof(T) * 8)));
+  }
+  *data++ = length;
+  return data;
+}
+
+/**
+ * Returns the maximum possible string length that can be successfully encoded
+ * using 2 units of the specified T.
+ *    EncodeLengthMax<char> -> maximum unit length of 0x7FFF
+ *    EncodeLengthMax<char16_t> -> maximum unit length of 0x7FFFFFFF
+ **/
+template <typename T>
+static size_t EncodeLengthMax() {
+  static_assert(std::is_integral<T>::value, "wat.");
+
+  constexpr size_t kMask = 1 << ((sizeof(T) * 8 * 2) - 1);
+  constexpr size_t max = kMask - 1;
+  return max;
+}
+
+/**
+ * Returns the number of units (1 or 2) needed to encode the string length
+ * before writing the string.
+ */
+template <typename T>
+static size_t EncodedLengthUnits(size_t length) {
+  static_assert(std::is_integral<T>::value, "wat.");
+
+  constexpr size_t kMask = 1 << ((sizeof(T) * 8) - 1);
+  constexpr size_t kMaxSize = kMask - 1;
+  return length > kMaxSize ? 2 : 1;
+}
+
+const std::string kStringTooLarge = "STRING_TOO_LARGE";
+
+static bool EncodeString(const std::string& str, const bool utf8, BigBuffer* out,
+                         IDiagnostics* diag) {
+  if (utf8) {
+    const std::string& encoded = util::Utf8ToModifiedUtf8(str);
+    const ssize_t utf16_length =
+        utf8_to_utf16_length(reinterpret_cast<const uint8_t*>(encoded.data()), encoded.size());
+    CHECK(utf16_length >= 0);
+
+    // Make sure the lengths to be encoded do not exceed the maximum length that
+    // can be encoded using chars
+    if ((((size_t)encoded.size()) > EncodeLengthMax<char>()) ||
+        (((size_t)utf16_length) > EncodeLengthMax<char>())) {
+      diag->Error(DiagMessage() << "string too large to encode using UTF-8 "
+                                << "written instead as '" << kStringTooLarge << "'");
+
+      EncodeString(kStringTooLarge, utf8, out, diag);
+      return false;
+    }
+
+    const size_t total_size = EncodedLengthUnits<char>(utf16_length) +
+                              EncodedLengthUnits<char>(encoded.size()) + encoded.size() + 1;
+
+    char* data = out->NextBlock<char>(total_size);
+
+    // First encode the UTF16 string length.
+    data = EncodeLength(data, utf16_length);
+
+    // Now encode the size of the real UTF8 string.
+    data = EncodeLength(data, encoded.size());
+    strncpy(data, encoded.data(), encoded.size());
+
+  } else {
+    const std::u16string encoded = util::Utf8ToUtf16(str);
+    const ssize_t utf16_length = encoded.size();
+
+    // Make sure the length to be encoded does not exceed the maximum possible
+    // length that can be encoded
+    if (((size_t)utf16_length) > EncodeLengthMax<char16_t>()) {
+      diag->Error(DiagMessage() << "string too large to encode using UTF-16 "
+                                << "written instead as '" << kStringTooLarge << "'");
+
+      EncodeString(kStringTooLarge, utf8, out, diag);
+      return false;
+    }
+
+    // Total number of 16-bit words to write.
+    const size_t total_size = EncodedLengthUnits<char16_t>(utf16_length) + encoded.size() + 1;
+
+    char16_t* data = out->NextBlock<char16_t>(total_size);
+
+    // Encode the actual UTF16 string length.
+    data = EncodeLength(data, utf16_length);
+    const size_t byte_length = encoded.size() * sizeof(char16_t);
+
+    // NOTE: For some reason, strncpy16(data, entry->value.data(),
+    // entry->value.size()) truncates the string.
+    memcpy(data, encoded.data(), byte_length);
+
+    // The null-terminating character is already here due to the block of data
+    // being set to 0s on allocation.
+  }
+
+  return true;
+}
+
+bool StringPool::Flatten(BigBuffer* out, const StringPool& pool, bool utf8, IDiagnostics* diag) {
+  bool no_error = true;
+  const size_t start_index = out->size();
+  android::ResStringPool_header* header = out->NextBlock<android::ResStringPool_header>();
+  header->header.type = util::HostToDevice16(android::RES_STRING_POOL_TYPE);
+  header->header.headerSize = util::HostToDevice16(sizeof(*header));
+  header->stringCount = util::HostToDevice32(pool.size());
+  header->styleCount = util::HostToDevice32(pool.styles_.size());
+  if (utf8) {
+    header->flags |= android::ResStringPool_header::UTF8_FLAG;
+  }
+
+  uint32_t* indices = pool.size() != 0 ? out->NextBlock<uint32_t>(pool.size()) : nullptr;
+  uint32_t* style_indices =
+      pool.styles_.size() != 0 ? out->NextBlock<uint32_t>(pool.styles_.size()) : nullptr;
+
+  const size_t before_strings_index = out->size();
+  header->stringsStart = before_strings_index - start_index;
+
+  // Styles always come first.
+  for (const std::unique_ptr<StyleEntry>& entry : pool.styles_) {
+    *indices++ = out->size() - before_strings_index;
+    no_error = EncodeString(entry->value, utf8, out, diag) && no_error;
+  }
+
+  for (const std::unique_ptr<Entry>& entry : pool.strings_) {
+    *indices++ = out->size() - before_strings_index;
+    no_error = EncodeString(entry->value, utf8, out, diag) && no_error;
+  }
+
+  out->Align4();
+
+  if (style_indices != nullptr) {
+    const size_t before_styles_index = out->size();
+    header->stylesStart = util::HostToDevice32(before_styles_index - start_index);
+
+    for (const std::unique_ptr<StyleEntry>& entry : pool.styles_) {
+      *style_indices++ = out->size() - before_styles_index;
+
+      if (!entry->spans.empty()) {
+        android::ResStringPool_span* span =
+            out->NextBlock<android::ResStringPool_span>(entry->spans.size());
+        for (const Span& s : entry->spans) {
+          span->name.index = util::HostToDevice32(s.name.index());
+          span->firstChar = util::HostToDevice32(s.first_char);
+          span->lastChar = util::HostToDevice32(s.last_char);
+          span++;
+        }
+      }
+
+      uint32_t* spanEnd = out->NextBlock<uint32_t>();
+      *spanEnd = android::ResStringPool_span::END;
+    }
+
+    // The error checking code in the platform looks for an entire
+    // ResStringPool_span structure worth of 0xFFFFFFFF at the end
+    // of the style block, so fill in the remaining 2 32bit words
+    // with 0xFFFFFFFF.
+    const size_t padding_length =
+        sizeof(android::ResStringPool_span) - sizeof(android::ResStringPool_span::name);
+    uint8_t* padding = out->NextBlock<uint8_t>(padding_length);
+    memset(padding, 0xff, padding_length);
+    out->Align4();
+  }
+  header->header.size = util::HostToDevice32(out->size() - start_index);
+  return no_error;
+}
+
+bool StringPool::FlattenUtf8(BigBuffer* out, const StringPool& pool, IDiagnostics* diag) {
+  return Flatten(out, pool, true, diag);
+}
+
+bool StringPool::FlattenUtf16(BigBuffer* out, const StringPool& pool, IDiagnostics* diag) {
+  return Flatten(out, pool, false, diag);
+}
+
+}  // namespace android