BlockCompressionCodecSnappy.cc

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/* -*- c++ -*-
 * Copyright (C) 2007-2015 Hypertable, Inc.
 *
 * This file is part of Hypertable.
 *
 * Hypertable is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 3 of the
 * License, or any later version.
 *
 * Hypertable is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */


#include <Common/Compat.h>

#include "BlockCompressionCodecSnappy.h"

#include <Common/DynamicBuffer.h>
#include <Common/Logger.h>
#include <Common/Checksum.h>

using namespace Hypertable;

void
BlockCompressionCodecSnappy::deflate(const DynamicBuffer &input,
    DynamicBuffer &output, BlockHeader &header, size_t reserve) {
  output.reserve(header.encoded_length()+snappy::MaxCompressedLength(input.fill())+reserve);
  size_t outlen;
  snappy::RawCompress((const char *)input.base, input.fill(), 
                (char *)output.base+header.encoded_length(), &outlen);

  HT_ASSERT(outlen+reserve <= output.size);

  /* check for an incompressible block */
  if (outlen >= input.fill()) {
    header.set_compression_type(NONE);
    memcpy(output.base+header.encoded_length(), input.base, input.fill());
    header.set_data_length(input.fill());
    header.set_data_zlength(input.fill());
  }
  else {
    header.set_compression_type(SNAPPY);
    header.set_data_length(input.fill());
    header.set_data_zlength(outlen);
  }

  header.set_data_checksum(fletcher32(output.base + header.encoded_length(),
                header.get_data_zlength()));

  output.ptr = output.base;
  header.encode(&output.ptr);
  output.ptr += header.get_data_zlength();
}


void
BlockCompressionCodecSnappy::inflate(const DynamicBuffer &input,
    DynamicBuffer &output, BlockHeader &header) {
  const uint8_t *msg_ptr = input.base;
  size_t remaining = input.fill();

  header.decode(&msg_ptr, &remaining);

  if (header.get_data_zlength() > remaining)
    HT_THROWF(Error::BLOCK_COMPRESSOR_BAD_HEADER, "Block decompression error, "
              "header zlength = %lu, actual = %lu",
              (Lu)header.get_data_zlength(), (Lu)remaining);

  uint32_t checksum = fletcher32(msg_ptr, header.get_data_zlength());

  if (checksum != header.get_data_checksum())
    HT_THROWF(Error::BLOCK_COMPRESSOR_CHECKSUM_MISMATCH, "Compressed block "
              "checksum mismatch header=%lx, computed=%lx",
              (Lu)header.get_data_checksum(), (Lu)checksum);

  try {
    output.reserve(header.get_data_length());

    // check compress bit
    if (header.get_compression_type() == NONE)
      memcpy(output.base, msg_ptr, header.get_data_length());
    else {
      if (!snappy::RawUncompress((const char *)msg_ptr, 
                header.get_data_zlength(), (char *)output.base))
        HT_THROWF(Error::BLOCK_COMPRESSOR_INFLATE_ERROR, "%s", 
                "Compressed block inflate error");
    }

    output.ptr = output.base + header.get_data_length();
  }
  catch (Exception &e) {
    output.free();
    throw;
  }
}