mirror of
https://github.com/wpilibsuite/allwpilib
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134 lines
3.3 KiB
C++
134 lines
3.3 KiB
C++
/*----------------------------------------------------------------------------*/
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/* Copyright (c) FIRST 2015. All Rights Reserved. */
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/* Open Source Software - may be modified and shared by FRC teams. The code */
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/* must be accompanied by the FIRST BSD license file in the root directory of */
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/* the project. */
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/*----------------------------------------------------------------------------*/
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#include "nt_leb128.h"
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#include "nt_raw_istream.h"
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namespace NtImpl {
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/**
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* size_uleb128 - get size of unsigned LEB128 data
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* @val: value
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*
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* Determine the number of bytes required to encode an unsigned LEB128 datum.
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* The algorithm is taken from Appendix C of the DWARF 3 spec. For information
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* on the encodings refer to section "7.6 - Variable Length Data". Return
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* the number of bytes required.
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*/
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std::size_t
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size_uleb128(unsigned long val)
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{
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std::size_t count = 0;
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do {
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val >>= 7;
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++count;
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} while (val != 0);
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return count;
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}
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/**
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* write_uleb128 - write unsigned LEB128 data
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* @addr: the address where the ULEB128 data is to be stored
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* @val: value to be stored
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*
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* Encode an unsigned LEB128 encoded datum. The algorithm is taken
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* from Appendix C of the DWARF 3 spec. For information on the
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* encodings refer to section "7.6 - Variable Length Data". Return
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* the number of bytes written.
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*/
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std::size_t
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write_uleb128(char* addr, unsigned long val)
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{
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std::size_t count = 0;
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do {
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unsigned char byte = val & 0x7f;
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val >>= 7;
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if (val != 0)
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byte |= 0x80; // mark this byte to show that more bytes will follow
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*((unsigned char *)addr) = byte;
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addr++;
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count++;
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} while (val != 0);
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return count;
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}
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/**
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* read_uleb128 - read unsigned LEB128 data
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* @addr: the address where the ULEB128 data is stored
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* @ret: address to store the result
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*
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* Decode an unsigned LEB128 encoded datum. The algorithm is taken
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* from Appendix C of the DWARF 3 spec. For information on the
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* encodings refer to section "7.6 - Variable Length Data". Return
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* the number of bytes read.
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*/
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std::size_t
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read_uleb128(char* addr, unsigned long* ret)
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{
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unsigned long result = 0;
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int shift = 0;
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std::size_t count = 0;
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while (1)
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{
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unsigned char byte = *((unsigned char *)addr);
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addr++;
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count++;
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result |= (byte & 0x7f) << shift;
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shift += 7;
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if (!(byte & 0x80))
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break;
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}
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*ret = result;
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return count;
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}
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/**
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* read_uleb128 - read unsigned LEB128 data from a stream
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* @is: the input stream where the ULEB128 data is to be read from
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* @ret: address to store the result
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*
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* Decode an unsigned LEB128 encoded datum. The algorithm is taken
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* from Appendix C of the DWARF 3 spec. For information on the
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* encodings refer to section "7.6 - Variable Length Data". Return
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* false on stream error, true on success.
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*/
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bool
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read_uleb128(raw_istream& is, unsigned long* ret)
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{
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unsigned long result = 0;
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int shift = 0;
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while (1)
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{
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unsigned char byte;
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if (!is.read((char*)&byte, 1))
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return false;
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result |= (byte & 0x7f) << shift;
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shift += 7;
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if (!(byte & 0x80))
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break;
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}
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*ret = result;
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return true;
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}
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} // namespace NtImpl
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