hex_filt.cpp

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/*
* Hex Encoder/Decoder
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/filters.h>
 
#include <botan/exceptn.h>
#include <botan/hex.h>
#include <botan/mem_ops.h>
#include <algorithm>
 
namespace Botan {
 
/**
* Size used for internal buffer in hex encoder/decoder
*/
const size_t HEX_CODEC_BUFFER_SIZE = 256;
 
/*
* Hex_Encoder Constructor
*/
Hex_Encoder::Hex_Encoder(bool breaks, size_t length, Case c) : m_casing(c), m_line_length(breaks ? length : 0) {
   m_in.resize(HEX_CODEC_BUFFER_SIZE);
   m_out.resize(2 * m_in.size());
}
 
/*
* Hex_Encoder Constructor
*/
Hex_Encoder::Hex_Encoder(Case c) : m_casing(c), m_line_length(0) {
   m_in.resize(HEX_CODEC_BUFFER_SIZE);
   m_out.resize(2 * m_in.size());
}
 
/*
* Encode and send a block
*/
void Hex_Encoder::encode_and_send(const uint8_t block[], size_t length) {
   hex_encode(cast_uint8_ptr_to_char(m_out.data()), block, length, m_casing == Uppercase);
 
   if(m_line_length == 0) {
      send(m_out, 2 * length);
   } else {
      size_t remaining = 2 * length;
      size_t offset = 0;
      while(remaining > 0) {
         const size_t sent = std::min(m_line_length - m_counter, remaining);
         send(&m_out[offset], sent);
         m_counter += sent;
         remaining -= sent;
         offset += sent;
         if(m_counter == m_line_length) {
            send('\n');
            m_counter = 0;
         }
      }
   }
}
 
/*
* Convert some data into hex format
*/
void Hex_Encoder::write(const uint8_t input[], size_t length) {
   const size_t initial_fill = std::min(m_in.size() - m_position, length);
   copy_mem(&m_in[m_position], input, initial_fill);
 
   if(m_position + length >= m_in.size()) {
      encode_and_send(m_in.data(), m_in.size());
      input += (m_in.size() - m_position);
      length -= (m_in.size() - m_position);
      while(length >= m_in.size()) {
         encode_and_send(input, m_in.size());
         input += m_in.size();
         length -= m_in.size();
      }
      copy_mem(m_in.data(), input, length);
      m_position = 0;
   }
   m_position += length;
}
 
/*
* Flush buffers
*/
void Hex_Encoder::end_msg() {
   encode_and_send(m_in.data(), m_position);
   if(m_counter > 0 && m_line_length > 0) {
      send('\n');
   }
   m_counter = m_position = 0;
}
 
/*
* Hex_Decoder Constructor
*/
Hex_Decoder::Hex_Decoder(Decoder_Checking c) : m_checking(c) {
   m_in.resize(HEX_CODEC_BUFFER_SIZE);
   m_out.resize(m_in.size() / 2);
}
 
namespace {
 
// Whitespace ignored by hex_char_to_bin() in hex.cpp. Dropping it before
// buffering keeps the decoder buffer bounded (see Hex_Decoder::write).
bool hex_ignorable_whitespace(uint8_t c) {
   return c == ' ' || c == '\t' || c == '\n' || c == '\r';
}
 
}  // namespace
 
/*
* Convert some data from hex format
*/
void Hex_Decoder::write(const uint8_t input[], size_t length) {
   const bool ignore_ws = (m_checking != FULL_CHECK);
 
   size_t pos = 0;
   while(pos < length) {
      // Drop ignored whitespace before buffering so a partial trailing nibble
      // stays next to its pair and the fixed buffer can't fill with whitespace.
      while(pos < length && m_position < m_in.size()) {
         const uint8_t c = input[pos++];
         if(ignore_ws && hex_ignorable_whitespace(c)) {
            continue;
         }
         m_in[m_position++] = c;
      }
 
      size_t consumed = 0;
      const size_t written =
         hex_decode(m_out.data(), cast_uint8_ptr_to_char(m_in.data()), m_position, consumed, ignore_ws);
 
      send(m_out, written);
 
      if(consumed != m_position) {
         copy_mem(m_in.data(), m_in.data() + consumed, m_position - consumed);
         m_position = m_position - consumed;
      } else {
         m_position = 0;
      }
   }
}
 
/*
* Flush buffers
*/
void Hex_Decoder::end_msg() {
   size_t consumed = 0;
   const size_t written =
      hex_decode(m_out.data(), cast_uint8_ptr_to_char(m_in.data()), m_position, consumed, m_checking != FULL_CHECK);
 
   send(m_out, written);
 
   const bool not_full_bytes = consumed != m_position;
 
   m_position = 0;
 
   if(not_full_bytes) {
      throw Invalid_Argument("Hex_Decoder: Input not full bytes");
   }
}
 
}  // namespace Botan