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/*
* Copyright (C) 2008 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.
*/
/*
* Functions for interpreting LEB128 (little endian base 128) values
*/
#ifndef LIBDEX_LEB128_H_
#define LIBDEX_LEB128_H_
#include "DexFile.h"
/*
* 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.
*/
DEX_INLINE int readUnsignedLeb128(const u1** pStream) {
const u1* ptr = *pStream;
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
* high four-order bits.
*/
cur = *(ptr++);
result |= cur << 28;
}
}
}
}
*pStream = ptr;
return result;
}
/*
* 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.
*/
DEX_INLINE int readSignedLeb128(const u1** pStream) {
const u1* ptr = *pStream;
int 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
* high four-order bits.
*/
cur = *(ptr++);
result |= cur << 28;
}
}
}
}
*pStream = ptr;
return result;
}
/*
* Reads an unsigned LEB128 value, updating the given pointer to point
* just past the end of the read value and also indicating whether the
* value was syntactically valid. The only syntactically *invalid*
* values are ones that are five bytes long where the final byte has
* any but the low-order four bits set. Additionally, if the limit is
* passed as non-NULL and bytes would need to be read past the limit,
* then the read is considered invalid.
*/
int readAndVerifyUnsignedLeb128(const u1** pStream, const u1* limit,
bool* okay);
/*
* Reads a signed LEB128 value, updating the given pointer to point
* just past the end of the read value and also indicating whether the
* value was syntactically valid. The only syntactically *invalid*
* values are ones that are five bytes long where the final byte has
* any but the low-order four bits set. Additionally, if the limit is
* passed as non-NULL and bytes would need to be read past the limit,
* then the read is considered invalid.
*/
int readAndVerifySignedLeb128(const u1** pStream, const u1* limit, bool* okay);
/*
* Writes a 32-bit value in unsigned ULEB128 format.
*
* Returns the updated pointer.
*/
DEX_INLINE u1* writeUnsignedLeb128(u1* ptr, u4 data)
{
while (true) {
u1 out = data & 0x7f;
if (out != data) {
*ptr++ = out | 0x80;
data >>= 7;
} else {
*ptr++ = out;
break;
}
}
return ptr;
}
/*
* Returns the number of bytes needed to encode "val" in ULEB128 form.
*/
DEX_INLINE int unsignedLeb128Size(u4 data)
{
int count = 0;
do {
data >>= 7;
count++;
} while (data != 0);
return count;
}
#endif
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