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/*
* Copyright (C) 2011 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 ART_RUNTIME_LEB128_H_
#define ART_RUNTIME_LEB128_H_
#include "globals.h"
namespace art {
// Reads an unsigned LEB128 value, updating the given pointer to point
// just past the end of the read value. This function tolerates
// non-zero high-order bits in the fifth encoded byte.
static inline uint32_t DecodeUnsignedLeb128(const byte** data) {
const byte* ptr = *data;
int result = *(ptr++);
if (result > 0x7f) {
int cur = *(ptr++);
result = (result & 0x7f) | ((cur & 0x7f) << 7);
if (cur > 0x7f) {
cur = *(ptr++);
result |= (cur & 0x7f) << 14;
if (cur > 0x7f) {
cur = *(ptr++);
result |= (cur & 0x7f) << 21;
if (cur > 0x7f) {
// Note: We don't check to see if cur is out of range here,
// meaning we tolerate garbage in the four high-order bits.
cur = *(ptr++);
result |= cur << 28;
}
}
}
}
*data = ptr;
return static_cast<uint32_t>(result);
}
// Reads an unsigned LEB128 + 1 value. updating the given pointer to point
// just past the end of the read value. This function tolerates
// non-zero high-order bits in the fifth encoded byte.
// It is possible for this function to return -1.
static inline int32_t DecodeUnsignedLeb128P1(const byte** data) {
return DecodeUnsignedLeb128(data) - 1;
}
// Reads a signed LEB128 value, updating the given pointer to point
// just past the end of the read value. This function tolerates
// non-zero high-order bits in the fifth encoded byte.
static inline int32_t DecodeSignedLeb128(const byte** data) {
const byte* ptr = *data;
int32_t result = *(ptr++);
if (result <= 0x7f) {
result = (result << 25) >> 25;
} else {
int cur = *(ptr++);
result = (result & 0x7f) | ((cur & 0x7f) << 7);
if (cur <= 0x7f) {
result = (result << 18) >> 18;
} else {
cur = *(ptr++);
result |= (cur & 0x7f) << 14;
if (cur <= 0x7f) {
result = (result << 11) >> 11;
} else {
cur = *(ptr++);
result |= (cur & 0x7f) << 21;
if (cur <= 0x7f) {
result = (result << 4) >> 4;
} else {
// Note: We don't check to see if cur is out of range here,
// meaning we tolerate garbage in the four high-order bits.
cur = *(ptr++);
result |= cur << 28;
}
}
}
}
*data = ptr;
return result;
}
// Returns the number of bytes needed to encode the value in unsigned LEB128.
static inline uint32_t UnsignedLeb128Size(uint32_t data) {
uint32_t count = 0;
do {
data >>= 7;
count++;
} while (data != 0);
return count;
}
// Writes a 32-bit value in unsigned ULEB128 format.
// Returns the updated pointer.
static inline uint8_t* WriteUnsignedLeb128(uint8_t* ptr, uint32_t data) {
while (true) {
uint8_t out = data & 0x7f;
if (out != data) {
*ptr++ = out | 0x80;
data >>= 7;
} else {
*ptr++ = out;
break;
}
}
return ptr;
}
} // namespace art
#endif // ART_RUNTIME_LEB128_H_
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