hex.cpp

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/*
* Hex Encoding and Decoding
* (C) 2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
 
#include <botan/hex.h>
#include <botan/mem_ops.h>
#include <stdexcept>
 
namespace Botan {
 
void hex_encode(char output[],
                const byte input[],
                size_t input_length,
                bool uppercase)
   {
   static const byte BIN_TO_HEX_UPPER[16] = {
      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
      'A', 'B', 'C', 'D', 'E', 'F' };
 
   static const byte BIN_TO_HEX_LOWER[16] = {
      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
      'a', 'b', 'c', 'd', 'e', 'f' };
 
   const byte* tbl = uppercase ? BIN_TO_HEX_UPPER : BIN_TO_HEX_LOWER;
 
   for(size_t i = 0; i != input_length; ++i)
      {
      byte x = input[i];
      output[2*i  ] = tbl[(x >> 4) & 0x0F];
      output[2*i+1] = tbl[(x     ) & 0x0F];
      }
   }
 
std::string hex_encode(const MemoryRegion<byte>& input,
                       bool uppercase)
   {
   return hex_encode(&input[0], input.size(), uppercase);
   }
 
std::string hex_encode(const byte input[],
                       size_t input_length,
                       bool uppercase)
   {
   std::string output(2 * input_length, 0);
 
   if(input_length)
      hex_encode(&output[0], input, input_length, uppercase);
 
   return output;
   }
 
size_t hex_decode(byte output[],
                  const char input[],
                  size_t input_length,
                  size_t& input_consumed,
                  bool ignore_ws)
   {
   /*
   * Mapping of hex characters to either their binary equivalent
   * or to an error code.
   *  If valid hex (0-9 A-F a-f), the value.
   *  If whitespace, then 0x80
   *  Otherwise 0xFF
   * Warning: this table assumes ASCII character encodings
   */
 
   static const byte HEX_TO_BIN[256] = {
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x80,
      0x80, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0x80, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x01,
      0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
      0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x0A, 0x0B, 0x0C,
      0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 
   byte* out_ptr = output;
   bool top_nibble = true;
 
   clear_mem(output, input_length / 2);
 
   for(size_t i = 0; i != input_length; ++i)
      {
      const byte bin = HEX_TO_BIN[static_cast<byte>(input[i])];
 
      if(bin >= 0x10)
         {
         if(bin == 0x80 && ignore_ws)
            continue;
 
         std::string bad_char(1, input[i]);
         if(bad_char == "\t")
           bad_char = "\\t";
         else if(bad_char == "\n")
           bad_char = "\\n";
 
         throw std::invalid_argument(
           std::string("hex_decode: invalid hex character '") +
           bad_char + "'");
         }
 
      *out_ptr |= bin << (top_nibble*4);
 
      top_nibble = !top_nibble;
      if(top_nibble)
         ++out_ptr;
      }
 
   input_consumed = input_length;
   size_t written = (out_ptr - output);
 
   /*
   * We only got half of a byte at the end; zap the half-written
   * output and mark it as unread
   */
   if(!top_nibble)
      {
      *out_ptr = 0;
      input_consumed -= 1;
      }
 
   return written;
   }
 
size_t hex_decode(byte output[],
                  const char input[],
                  size_t input_length,
                  bool ignore_ws)
   {
   size_t consumed = 0;
   size_t written = hex_decode(output, input, input_length,
                               consumed, ignore_ws);
 
   if(consumed != input_length)
      throw std::invalid_argument("hex_decode: input did not have full bytes");
 
   return written;
   }
 
size_t hex_decode(byte output[],
                  const std::string& input,
                  bool ignore_ws)
   {
   return hex_decode(output, &input[0], input.length(), ignore_ws);
   }
 
SecureVector<byte> hex_decode(const char input[],
                              size_t input_length,
                              bool ignore_ws)
   {
   SecureVector<byte> bin(1 + input_length / 2);
 
   size_t written = hex_decode(&bin[0],
                               input,
                               input_length,
                               ignore_ws);
 
   bin.resize(written);
   return bin;
   }
 
SecureVector<byte> hex_decode(const std::string& input,
                              bool ignore_ws)
   {
   return hex_decode(&input[0], input.size(), ignore_ws);
   }
 
}