Add spellcheck and word suggestion to the prediction service

third_party/prediction/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h

+/*
+ * Copyright (C) 2013, 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.
+ */
+
+#ifndef LATINIME_BUFFER_WITH_EXTENDABLE_BUFFER_H
+#define LATINIME_BUFFER_WITH_EXTENDABLE_BUFFER_H
+
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+#include "third_party/prediction/defines.h"
+#include "third_party/prediction/suggest/policyimpl/dictionary/utils/byte_array_utils.h"
+#include "third_party/prediction/utils/byte_array_view.h"
+
+namespace latinime {
+
+// This is used as a buffer that can be extended for updatable dictionaries.
+// To optimize performance, raw pointer is directly used for reading buffer. The
+// position has to be
+// adjusted to access additional buffer. On the other hand, this class does not
+// provide writable
+// raw pointer but provides several methods that handle boundary checking for
+// writing data.
+class BufferWithExtendableBuffer {
+ public:
+  static const size_t DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE;
+
+  BufferWithExtendableBuffer(const ReadWriteByteArrayView originalBuffer,
+                             const int maxAdditionalBufferSize)
+      : mOriginalBuffer(originalBuffer),
+        mAdditionalBuffer(),
+        mUsedAdditionalBufferSize(0),
+        mMaxAdditionalBufferSize(maxAdditionalBufferSize) {}
+
+  // Without original buffer.
+  BufferWithExtendableBuffer(const int maxAdditionalBufferSize)
+      : mOriginalBuffer(),
+        mAdditionalBuffer(),
+        mUsedAdditionalBufferSize(0),
+        mMaxAdditionalBufferSize(maxAdditionalBufferSize) {}
+
+  AK_FORCE_INLINE int getTailPosition() const {
+    return mOriginalBuffer.size() + mUsedAdditionalBufferSize;
+  }
+
+  AK_FORCE_INLINE int getUsedAdditionalBufferSize() const {
+    return mUsedAdditionalBufferSize;
+  }
+
+  /**
+   * For reading.
+   */
+  AK_FORCE_INLINE bool isInAdditionalBuffer(const int position) const {
+    return position >= static_cast<int>(mOriginalBuffer.size());
+  }
+
+  // TODO: Resolve the issue that the address can be changed when the vector is
+  // resized.
+  // CAVEAT!: Be careful about array out of bound access with buffers
+  AK_FORCE_INLINE const uint8_t* getBuffer(
+      const bool usesAdditionalBuffer) const {
+    if (usesAdditionalBuffer) {
+      return mAdditionalBuffer.data();
+    } else {
+      return mOriginalBuffer.data();
+    }
+  }
+
+  uint32_t readUint(const int size, const int pos) const;
+
+  uint32_t readUintAndAdvancePosition(const int size, int* const pos) const;
+
+  void readCodePointsAndAdvancePosition(const int maxCodePointCount,
+                                        int* const outCodePoints,
+                                        int* outCodePointCount,
+                                        int* const pos) const;
+
+  AK_FORCE_INLINE int getOriginalBufferSize() const {
+    return mOriginalBuffer.size();
+  }
+
+  AK_FORCE_INLINE bool isNearSizeLimit() const {
+    return mAdditionalBuffer.size() >=
+           ((mMaxAdditionalBufferSize *
+             NEAR_BUFFER_LIMIT_THRESHOLD_PERCENTILE) /
+            100);
+  }
+
+  bool extend(const int size);
+
+  /**
+   * For writing.
+   *
+   * Writing is allowed for original buffer, already written region of
+   *additional buffer and the
+   * tail of additional buffer.
+   */
+  bool writeUint(const uint32_t data, const int size, const int pos);
+
+  bool writeUintAndAdvancePosition(const uint32_t data,
+                                   const int size,
+                                   int* const pos);
+
+  bool writeCodePointsAndAdvancePosition(const int* const codePoints,
+                                         const int codePointCount,
+                                         const bool writesTerminator,
+                                         int* const pos);
+
+  bool copy(const BufferWithExtendableBuffer* const sourceBuffer);
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BufferWithExtendableBuffer);
+
+  static const int NEAR_BUFFER_LIMIT_THRESHOLD_PERCENTILE;
+  static const size_t EXTEND_ADDITIONAL_BUFFER_SIZE_STEP;
+
+  const ReadWriteByteArrayView mOriginalBuffer;
+  std::vector<uint8_t> mAdditionalBuffer;
+  int mUsedAdditionalBufferSize;
+  const size_t mMaxAdditionalBufferSize;
+
+  // Return if the buffer is successfully extended or not.
+  bool extendBuffer(const size_t size);
+
+  // Returns if it is possible to write size-bytes from pos. When pos is at the
+  // tail position of
+  // the additional buffer, try extending the buffer.
+  bool checkAndPrepareWriting(const int pos, const int size);
+};
+}
+#endif /* LATINIME_BUFFER_WITH_EXTENDABLE_BUFFER_H */