ceph/src/compressor/snappy/SnappyCompressor.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2015 Haomai Wang <haomaiwang@gmail.com>
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15 #ifndef CEPH_SNAPPYCOMPRESSOR_H
  16 #define CEPH_SNAPPYCOMPRESSOR_H
  17
  18 #include <snappy.h>
  19 #include <snappy-sinksource.h>
  20 #include "include/buffer.h"
  21 #include "compressor/Compressor.h"
  22
  23 class CEPH_BUFFER_API BufferlistSource : public snappy::Source {
  24   bufferlist::iterator pb;
  25   size_t remaining;
  26
  27  public:
  28   explicit BufferlistSource(bufferlist::iterator _pb, size_t _input_len)
  29     : pb(_pb),
  30       remaining(_input_len) {
  31     remaining = std::min(remaining, (size_t)pb.get_remaining());
  32   }
  33   size_t Available() const override {
  34     return remaining;
  35   }
  36   const char *Peek(size_t *len) override {
  37     const char *data = NULL;
  38     *len = 0;
  39     size_t avail = Available();
  40     if (avail) {
  41       auto ptmp = pb;
  42       *len = ptmp.get_ptr_and_advance(avail, &data);
  43     }
  44     return data;
  45   }
  46   void Skip(size_t n) override {
  47     assert(n <= remaining);
  48     pb.advance(n);
  49     remaining -= n;
  50   }
  51
  52   bufferlist::iterator get_pos() const {
  53     return pb;
  54   }
  55 };
  56
  57 class SnappyCompressor : public Compressor {
  58  public:
  59   SnappyCompressor() : Compressor(COMP_ALG_SNAPPY, "snappy") {}
  60
  61   int compress(const bufferlist &src, bufferlist &dst) override {
  62     BufferlistSource source(const_cast<bufferlist&>(src).begin(), src.length());
  63     bufferptr ptr = buffer::create_page_aligned(
  64       snappy::MaxCompressedLength(src.length()));
  65     snappy::UncheckedByteArraySink sink(ptr.c_str());
  66     snappy::Compress(&source, &sink);
  67     dst.append(ptr, 0, sink.CurrentDestination() - ptr.c_str());
  68     return 0;
  69   }
  70
  71   int decompress(const bufferlist &src, bufferlist &dst) override {
  72     bufferlist::iterator i = const_cast<bufferlist&>(src).begin();
  73     return decompress(i, src.length(), dst);
  74   }
  75
  76   int decompress(bufferlist::iterator &p,
  77                  size_t compressed_len,
  78                  bufferlist &dst) override {
  79     snappy::uint32 res_len = 0;
  80     BufferlistSource source_1(p, compressed_len);
  81     if (!snappy::GetUncompressedLength(&source_1, &res_len)) {
  82       return -1;
  83     }
  84     BufferlistSource source_2(p, compressed_len);
  85     bufferptr ptr(res_len);
  86     if (snappy::RawUncompress(&source_2, ptr.c_str())) {
  87       p = source_2.get_pos();
  88       dst.append(ptr);
  89       return 0;
  90     }
  91     return -2;
  92   }
  93 };
  94
  95 #endif