hex.cpp

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/*
* Hex Encoding and Decoding
* (C) 2010,2020 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/hex.h>
 
#include <botan/exceptn.h>
#include <botan/mem_ops.h>
#include <botan/internal/charset.h>
#include <botan/internal/ct_utils.h>
#include <botan/internal/fmt.h>
 
namespace Botan {
 
namespace {
 
char hex_encode_nibble(uint8_t n, bool uppercase) {
   BOTAN_DEBUG_ASSERT(n <= 15);
 
   const auto in_09 = CT::Mask<uint8_t>::is_lt(n, 10);
 
   const char c_09 = n + '0';
   const char c_af = n + (uppercase ? 'A' : 'a') - 10;
 
   return in_09.select(c_09, c_af);
}
 
}  // namespace
 
void hex_encode(char output[], const uint8_t input[], size_t input_length, bool uppercase) {
   for(size_t i = 0; i != input_length; ++i) {
      const uint8_t n0 = (input[i] >> 4) & 0xF;
      const uint8_t n1 = (input[i]) & 0xF;
 
      output[2 * i] = hex_encode_nibble(n0, uppercase);
      output[2 * i + 1] = hex_encode_nibble(n1, uppercase);
   }
}
 
std::string hex_encode(const uint8_t input[], size_t input_length, bool uppercase) {
   std::string output(2 * input_length, 0);
 
   if(input_length) {
      hex_encode(&output.front(), input, input_length, uppercase);
   }
 
   return output;
}
 
namespace {
 
uint8_t hex_char_to_bin(char input) {
   const uint8_t c = static_cast<uint8_t>(input);
 
   const auto is_alpha_upper = CT::Mask<uint8_t>::is_within_range(c, uint8_t('A'), uint8_t('F'));
   const auto is_alpha_lower = CT::Mask<uint8_t>::is_within_range(c, uint8_t('a'), uint8_t('f'));
   const auto is_decimal = CT::Mask<uint8_t>::is_within_range(c, uint8_t('0'), uint8_t('9'));
 
   const auto is_whitespace =
      CT::Mask<uint8_t>::is_any_of(c, {uint8_t(' '), uint8_t('\t'), uint8_t('\n'), uint8_t('\r')});
 
   const uint8_t c_upper = c - uint8_t('A') + 10;
   const uint8_t c_lower = c - uint8_t('a') + 10;
   const uint8_t c_decim = c - uint8_t('0');
 
   uint8_t ret = 0xFF;  // default value
 
   ret = is_alpha_upper.select(c_upper, ret);
   ret = is_alpha_lower.select(c_lower, ret);
   ret = is_decimal.select(c_decim, ret);
   ret = is_whitespace.select(0x80, ret);
 
   return ret;
}
 
}  // namespace
 
size_t hex_decode(uint8_t output[], const char input[], size_t input_length, size_t& input_consumed, bool ignore_ws) {
   uint8_t* out_ptr = output;
   bool top_nibble = true;
 
   clear_mem(output, input_length / 2);
 
   for(size_t i = 0; i != input_length; ++i) {
      const uint8_t bin = hex_char_to_bin(input[i]);
 
      if(bin >= 0x10) {
         if(bin == 0x80 && ignore_ws) {
            continue;
         }
 
         throw Invalid_Argument(fmt("hex_decode: invalid character '{}'", format_char_for_display(input[i])));
      }
 
      if(top_nibble) {
         *out_ptr |= bin << 4;
      } else {
         *out_ptr |= bin;
      }
 
      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 uint8_t 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(uint8_t 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 Invalid_Argument("hex_decode: input did not have full bytes");
   }
 
   return written;
}
 
size_t hex_decode(uint8_t output[], std::string_view input, bool ignore_ws) {
   return hex_decode(output, input.data(), input.length(), ignore_ws);
}
 
size_t hex_decode(std::span<uint8_t> output, std::string_view input, bool ignore_ws) {
   return hex_decode(output.data(), input.data(), input.length(), ignore_ws);
}
 
secure_vector<uint8_t> hex_decode_locked(const char input[], size_t input_length, bool ignore_ws) {
   secure_vector<uint8_t> bin(1 + input_length / 2);
 
   size_t written = hex_decode(bin.data(), input, input_length, ignore_ws);
 
   bin.resize(written);
   return bin;
}
 
secure_vector<uint8_t> hex_decode_locked(std::string_view input, bool ignore_ws) {
   return hex_decode_locked(input.data(), input.size(), ignore_ws);
}
 
std::vector<uint8_t> hex_decode(const char input[], size_t input_length, bool ignore_ws) {
   std::vector<uint8_t> bin(1 + input_length / 2);
 
   size_t written = hex_decode(bin.data(), input, input_length, ignore_ws);
 
   bin.resize(written);
   return bin;
}
 
std::vector<uint8_t> hex_decode(std::string_view input, bool ignore_ws) {
   return hex_decode(input.data(), input.size(), ignore_ws);
}
 
}  // namespace Botan