164 lines
4.7 KiB
C
164 lines
4.7 KiB
C
/*
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* Copyright (C) 2008 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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* Functions for interpreting LEB128 (little endian base 128) values
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*/
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#ifndef LIBDEX_LEB128_H_
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#define LIBDEX_LEB128_H_
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#include "DexFile.h"
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/*
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* Reads an unsigned LEB128 value, updating the given pointer to point
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* just past the end of the read value. This function tolerates
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* non-zero high-order bits in the fifth encoded byte.
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*/
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DEX_INLINE int readUnsignedLeb128(const u1** pStream) {
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const u1* ptr = *pStream;
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int result = *(ptr++);
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if (result > 0x7f) {
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int cur = *(ptr++);
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result = (result & 0x7f) | ((cur & 0x7f) << 7);
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if (cur > 0x7f) {
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cur = *(ptr++);
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result |= (cur & 0x7f) << 14;
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if (cur > 0x7f) {
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cur = *(ptr++);
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result |= (cur & 0x7f) << 21;
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if (cur > 0x7f) {
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/*
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* Note: We don't check to see if cur is out of
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* range here, meaning we tolerate garbage in the
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* high four-order bits.
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*/
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cur = *(ptr++);
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result |= cur << 28;
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}
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}
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}
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}
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*pStream = ptr;
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return result;
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}
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/*
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* Reads a signed LEB128 value, updating the given pointer to point
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* just past the end of the read value. This function tolerates
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* non-zero high-order bits in the fifth encoded byte.
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*/
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DEX_INLINE int readSignedLeb128(const u1** pStream) {
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const u1* ptr = *pStream;
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int result = *(ptr++);
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if (result <= 0x7f) {
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result = (result << 25) >> 25;
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} else {
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int cur = *(ptr++);
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result = (result & 0x7f) | ((cur & 0x7f) << 7);
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if (cur <= 0x7f) {
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result = (result << 18) >> 18;
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} else {
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cur = *(ptr++);
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result |= (cur & 0x7f) << 14;
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if (cur <= 0x7f) {
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result = (result << 11) >> 11;
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} else {
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cur = *(ptr++);
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result |= (cur & 0x7f) << 21;
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if (cur <= 0x7f) {
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result = (result << 4) >> 4;
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} else {
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/*
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* Note: We don't check to see if cur is out of
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* range here, meaning we tolerate garbage in the
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* high four-order bits.
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*/
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cur = *(ptr++);
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result |= cur << 28;
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}
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}
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}
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}
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*pStream = ptr;
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return result;
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}
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/*
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* Reads an unsigned LEB128 value, updating the given pointer to point
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* just past the end of the read value and also indicating whether the
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* value was syntactically valid. The only syntactically *invalid*
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* values are ones that are five bytes long where the final byte has
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* any but the low-order four bits set. Additionally, if the limit is
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* passed as non-NULL and bytes would need to be read past the limit,
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* then the read is considered invalid.
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*/
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int readAndVerifyUnsignedLeb128(const u1** pStream, const u1* limit,
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bool* okay);
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/*
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* Reads a signed LEB128 value, updating the given pointer to point
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* just past the end of the read value and also indicating whether the
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* value was syntactically valid. The only syntactically *invalid*
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* values are ones that are five bytes long where the final byte has
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* any but the low-order four bits set. Additionally, if the limit is
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* passed as non-NULL and bytes would need to be read past the limit,
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* then the read is considered invalid.
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*/
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int readAndVerifySignedLeb128(const u1** pStream, const u1* limit, bool* okay);
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/*
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* Writes a 32-bit value in unsigned ULEB128 format.
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*
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* Returns the updated pointer.
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*/
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DEX_INLINE u1* writeUnsignedLeb128(u1* ptr, u4 data)
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{
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while (true) {
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u1 out = data & 0x7f;
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if (out != data) {
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*ptr++ = out | 0x80;
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data >>= 7;
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} else {
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*ptr++ = out;
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break;
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}
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}
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return ptr;
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}
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/*
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* Returns the number of bytes needed to encode "val" in ULEB128 form.
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*/
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DEX_INLINE int unsignedLeb128Size(u4 data)
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{
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int count = 0;
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do {
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data >>= 7;
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count++;
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} while (data != 0);
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return count;
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}
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#endif
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