/* | |

* 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 | |

#define _LIBDEX_LEB128 | |

#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 |