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/*
* 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_BYTE_ARRAY_UTILS_H
#define LATINIME_BYTE_ARRAY_UTILS_H
#include <cstdint>
#include "defines.h"
namespace latinime {
/**
* Utility methods for reading byte arrays.
*/
class ByteArrayUtils {
public:
/**
* Integer writing
*
* Each method write a corresponding size integer in a big endian manner.
*/
static AK_FORCE_INLINE void writeUintAndAdvancePosition(uint8_t *const buffer,
const uint32_t data, const int size, int *const pos) {
// size must be in 1 to 4.
ASSERT(size >= 1 && size <= 4);
switch (size) {
case 1:
ByteArrayUtils::writeUint8AndAdvancePosition(buffer, data, pos);
return;
case 2:
ByteArrayUtils::writeUint16AndAdvancePosition(buffer, data, pos);
return;
case 3:
ByteArrayUtils::writeUint24AndAdvancePosition(buffer, data, pos);
return;
case 4:
ByteArrayUtils::writeUint32AndAdvancePosition(buffer, data, pos);
return;
default:
break;
}
}
/**
* Integer reading
*
* Each method read a corresponding size integer in a big endian manner.
*/
static AK_FORCE_INLINE uint32_t readUint32(const uint8_t *const buffer, const int pos) {
return (buffer[pos] << 24) ^ (buffer[pos + 1] << 16)
^ (buffer[pos + 2] << 8) ^ buffer[pos + 3];
}
static AK_FORCE_INLINE uint32_t readUint24(const uint8_t *const buffer, const int pos) {
return (buffer[pos] << 16) ^ (buffer[pos + 1] << 8) ^ buffer[pos + 2];
}
static AK_FORCE_INLINE uint16_t readUint16(const uint8_t *const buffer, const int pos) {
return (buffer[pos] << 8) ^ buffer[pos + 1];
}
static AK_FORCE_INLINE uint8_t readUint8(const uint8_t *const buffer, const int pos) {
return buffer[pos];
}
static AK_FORCE_INLINE uint32_t readUint32AndAdvancePosition(
const uint8_t *const buffer, int *const pos) {
const uint32_t value = readUint32(buffer, *pos);
*pos += 4;
return value;
}
static AK_FORCE_INLINE int readSint24AndAdvancePosition(
const uint8_t *const buffer, int *const pos) {
const uint8_t value = readUint8(buffer, *pos);
if (value < 0x80) {
return readUint24AndAdvancePosition(buffer, pos);
} else {
(*pos)++;
return -(((value & 0x7F) << 16) ^ readUint16AndAdvancePosition(buffer, pos));
}
}
static AK_FORCE_INLINE uint32_t readUint24AndAdvancePosition(
const uint8_t *const buffer, int *const pos) {
const uint32_t value = readUint24(buffer, *pos);
*pos += 3;
return value;
}
static AK_FORCE_INLINE uint16_t readUint16AndAdvancePosition(
const uint8_t *const buffer, int *const pos) {
const uint16_t value = readUint16(buffer, *pos);
*pos += 2;
return value;
}
static AK_FORCE_INLINE uint8_t readUint8AndAdvancePosition(
const uint8_t *const buffer, int *const pos) {
return buffer[(*pos)++];
}
static AK_FORCE_INLINE uint32_t readUint(const uint8_t *const buffer,
const int size, const int pos) {
// size must be in 1 to 4.
ASSERT(size >= 1 && size <= 4);
switch (size) {
case 1:
return ByteArrayUtils::readUint8(buffer, pos);
case 2:
return ByteArrayUtils::readUint16(buffer, pos);
case 3:
return ByteArrayUtils::readUint24(buffer, pos);
case 4:
return ByteArrayUtils::readUint32(buffer, pos);
default:
return 0;
}
}
/**
* Code Point Reading
*
* 1 byte = bbbbbbbb match
* case 000xxxxx: xxxxx << 16 + next byte << 8 + next byte
* else: if 00011111 (= 0x1F) : this is the terminator. This is a relevant choice because
* unicode code points range from 0 to 0x10FFFF, so any 3-byte value starting with
* 00011111 would be outside unicode.
* else: iso-latin-1 code
* This allows for the whole unicode range to be encoded, including chars outside of
* the BMP. Also everything in the iso-latin-1 charset is only 1 byte, except control
* characters which should never happen anyway (and still work, but take 3 bytes).
*/
static AK_FORCE_INLINE int readCodePoint(const uint8_t *const buffer, const int pos) {
int p = pos;
return readCodePointAndAdvancePosition(buffer, nullptr /* codePointTable */, &p);
}
static AK_FORCE_INLINE int readCodePointAndAdvancePosition(
const uint8_t *const buffer, const int *const codePointTable, int *const pos) {
/*
* codePointTable is an array to convert the most frequent characters in this dictionary to
* 1 byte code points. It is only made of the original code points of the most frequent
* characters used in this dictionary. 0x20 - 0xFF is used for the 1 byte characters.
* The original code points are restored by picking the code points at the indices of the
* codePointTable. The indices are calculated by subtracting 0x20 from the firstByte.
*/
const uint8_t firstByte = readUint8(buffer, *pos);
if (firstByte < MINIMUM_ONE_BYTE_CHARACTER_VALUE) {
if (firstByte == CHARACTER_ARRAY_TERMINATOR) {
*pos += 1;
return NOT_A_CODE_POINT;
} else {
return readUint24AndAdvancePosition(buffer, pos);
}
} else {
*pos += 1;
if (codePointTable) {
return codePointTable[firstByte - MINIMUM_ONE_BYTE_CHARACTER_VALUE];
}
return firstByte;
}
}
/**
* String (array of code points) Reading
*
* Reads code points until the terminator is found.
*/
// Returns the length of the string.
static int readStringAndAdvancePosition(const uint8_t *const buffer,
const int maxLength, const int *const codePointTable, int *const outBuffer,
int *const pos) {
int length = 0;
int codePoint = readCodePointAndAdvancePosition(buffer, codePointTable, pos);
while (NOT_A_CODE_POINT != codePoint && length < maxLength) {
outBuffer[length++] = codePoint;
codePoint = readCodePointAndAdvancePosition(buffer, codePointTable, pos);
}
return length;
}
// Advances the position and returns the length of the string.
static int advancePositionToBehindString(
const uint8_t *const buffer, const int maxLength, int *const pos) {
int length = 0;
int codePoint = readCodePointAndAdvancePosition(buffer, nullptr /* codePointTable */, pos);
while (NOT_A_CODE_POINT != codePoint && length < maxLength) {
codePoint = readCodePointAndAdvancePosition(buffer, nullptr /* codePointTable */, pos);
length++;
}
return length;
}
/**
* String (array of code points) Writing
*/
static void writeCodePointsAndAdvancePosition(uint8_t *const buffer,
const int *const codePoints, const int codePointCount, const bool writesTerminator,
int *const pos) {
for (int i = 0; i < codePointCount; ++i) {
const int codePoint = codePoints[i];
if (codePoint == NOT_A_CODE_POINT || codePoint == CHARACTER_ARRAY_TERMINATOR) {
break;
} else if (codePoint < MINIMUM_ONE_BYTE_CHARACTER_VALUE
|| codePoint > MAXIMUM_ONE_BYTE_CHARACTER_VALUE) {
// three bytes character.
writeUint24AndAdvancePosition(buffer, codePoint, pos);
} else {
// one byte character.
writeUint8AndAdvancePosition(buffer, codePoint, pos);
}
}
if (writesTerminator) {
writeUint8AndAdvancePosition(buffer, CHARACTER_ARRAY_TERMINATOR, pos);
}
}
static int calculateRequiredByteCountToStoreCodePoints(const int *const codePoints,
const int codePointCount, const bool writesTerminator) {
int byteCount = 0;
for (int i = 0; i < codePointCount; ++i) {
const int codePoint = codePoints[i];
if (codePoint == NOT_A_CODE_POINT || codePoint == CHARACTER_ARRAY_TERMINATOR) {
break;
} else if (codePoint < MINIMUM_ONE_BYTE_CHARACTER_VALUE
|| codePoint > MAXIMUM_ONE_BYTE_CHARACTER_VALUE) {
// three bytes character.
byteCount += 3;
} else {
// one byte character.
byteCount += 1;
}
}
if (writesTerminator) {
// The terminator is one byte.
byteCount += 1;
}
return byteCount;
}
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(ByteArrayUtils);
static const uint8_t MINIMUM_ONE_BYTE_CHARACTER_VALUE;
static const uint8_t MAXIMUM_ONE_BYTE_CHARACTER_VALUE;
static const uint8_t CHARACTER_ARRAY_TERMINATOR;
static AK_FORCE_INLINE void writeUint32AndAdvancePosition(uint8_t *const buffer,
const uint32_t data, int *const pos) {
buffer[(*pos)++] = (data >> 24) & 0xFF;
buffer[(*pos)++] = (data >> 16) & 0xFF;
buffer[(*pos)++] = (data >> 8) & 0xFF;
buffer[(*pos)++] = data & 0xFF;
}
static AK_FORCE_INLINE void writeUint24AndAdvancePosition(uint8_t *const buffer,
const uint32_t data, int *const pos) {
buffer[(*pos)++] = (data >> 16) & 0xFF;
buffer[(*pos)++] = (data >> 8) & 0xFF;
buffer[(*pos)++] = data & 0xFF;
}
static AK_FORCE_INLINE void writeUint16AndAdvancePosition(uint8_t *const buffer,
const uint16_t data, int *const pos) {
buffer[(*pos)++] = (data >> 8) & 0xFF;
buffer[(*pos)++] = data & 0xFF;
}
static AK_FORCE_INLINE void writeUint8AndAdvancePosition(uint8_t *const buffer,
const uint8_t data, int *const pos) {
buffer[(*pos)++] = data & 0xFF;
}
};
} // namespace latinime
#endif /* LATINIME_BYTE_ARRAY_UTILS_H */
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