| /* |
| * Copyright (C) 2017 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. |
| */ |
| |
| #pragma once |
| |
| #include "dex_format.h" |
| |
| // LEB128 encode/decode helpers: |
| // https://source.android.com/devices/tech/dalvik/dex-format.html |
| |
| namespace dex { |
| |
| // Reads an unsigned LEB128 value, updating the given pointer to |
| // point just past the end of the read value. |
| inline u4 ReadULeb128(const u1** pptr) { |
| const u1* ptr = *pptr; |
| u4 result = *(ptr++); |
| |
| if (result > 0x7f) { |
| u4 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) { |
| // 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; |
| } |
| } |
| } |
| } |
| |
| *pptr = ptr; |
| return result; |
| } |
| |
| // Reads a signed LEB128 value, updating the given pointer to |
| // point just past the end of the read value. |
| inline s4 ReadSLeb128(const u1** pptr) { |
| const u1* ptr = *pptr; |
| s4 result = *(ptr++); |
| |
| if (result <= 0x7f) { |
| result = (result << 25) >> 25; |
| } else { |
| s4 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; |
| } |
| } |
| } |
| } |
| |
| *pptr = ptr; |
| return result; |
| } |
| |
| // Writes a 32-bit value in unsigned ULEB128 format. |
| // Returns the updated pointer. |
| inline u1* WriteULeb128(u1* ptr, u4 data) { |
| for (;;) { |
| u1 out = data & 0x7f; |
| if (out != data) { |
| *ptr++ = out | 0x80; |
| data >>= 7; |
| } else { |
| *ptr++ = out; |
| break; |
| } |
| } |
| return ptr; |
| } |
| |
| // Writes a 32-bit value in signed ULEB128 format. |
| // Returns the updated pointer. |
| inline u1* WriteSLeb128(u1* ptr, s4 value) { |
| u4 extra_bits = static_cast<u4>(value ^ (value >> 31)) >> 6; |
| u1 out = value & 0x7f; |
| while (extra_bits != 0u) { |
| *ptr++ = out | 0x80; |
| value >>= 7; |
| out = value & 0x7f; |
| extra_bits >>= 7; |
| } |
| *ptr++ = out; |
| return ptr; |
| } |
| |
| } // namespace dex |