ceph/src/Beast/include/beast/zlib/inflate_stream.hpp

   1 //
   2 // Copyright (c) 2013-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
   3 //
   4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // This is a derivative work based on Zlib, copyright below:
   8 /*
   9     Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
  10
  11     This software is provided 'as-is', without any express or implied
  12     warranty.  In no event will the authors be held liable for any damages
  13     arising from the use of this software.
  14
  15     Permission is granted to anyone to use this software for any purpose,
  16     including commercial applications, and to alter it and redistribute it
  17     freely, subject to the following restrictions:
  18
  19     1. The origin of this software must not be misrepresented; you must not
  20        claim that you wrote the original software. If you use this software
  21        in a product, an acknowledgment in the product documentation would be
  22        appreciated but is not required.
  23     2. Altered source versions must be plainly marked as such, and must not be
  24        misrepresented as being the original software.
  25     3. This notice may not be removed or altered from any source distribution.
  26
  27     Jean-loup Gailly        Mark Adler
  28     jloup@gzip.org          madler@alumni.caltech.edu
  29
  30     The data format used by the zlib library is described by RFCs (Request for
  31     Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
  32     (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
  33 */
  34
  35 #ifndef BEAST_ZLIB_INFLATE_STREAM_HPP
  36 #define BEAST_ZLIB_INFLATE_STREAM_HPP
  37
  38 #include <beast/config.hpp>
  39 #include <beast/zlib/detail/inflate_stream.hpp>
  40
  41 namespace beast {
  42 namespace zlib {
  43
  44 /** Raw deflate stream decompressor.
  45
  46     This implements a raw deflate stream decompressor. The deflate
  47     protocol is a compression protocol described in
  48     "DEFLATE Compressed Data Format Specification version 1.3"
  49     located here: https://tools.ietf.org/html/rfc1951
  50
  51     The implementation is a refactored port to C++ of ZLib's "inflate".
  52     A more detailed description of ZLib is at http://zlib.net/.
  53
  54     Compression can be done in a single step if the buffers are large
  55     enough (for example if an input file is memory mapped), or can be done
  56     by repeated calls of the compression function. In the latter case, the
  57     application must provide more input and/or consume the output (providing
  58     more output space) before each call.
  59 */
  60 class inflate_stream
  61     : private detail::inflate_stream
  62 {
  63 public:
  64     /** Construct a raw deflate decompression stream.
  65
  66         The window size is set to the default of 15 bits.
  67     */
  68     inflate_stream() = default;
  69
  70     /** Reset the stream.
  71
  72         This puts the stream in a newly constructed state with
  73         the previously specified window size, but without de-allocating
  74         any dynamically created structures.
  75     */
  76     void
  77     reset()
  78     {
  79         doReset();
  80     }
  81
  82     /** Reset the stream.
  83
  84         This puts the stream in a newly constructed state with the
  85         specified window size, but without de-allocating any dynamically
  86         created structures.
  87     */
  88     void
  89     reset(int windowBits)
  90     {
  91         doReset(windowBits);
  92     }
  93
  94     /** Put the stream in a newly constructed state.
  95
  96         All dynamically allocated memory is de-allocated.
  97     */
  98     void
  99     clear()
 100     {
 101         doClear();
 102     }
 103
 104     /** Decompress input and produce output.
 105
 106         This function decompresses as much data as possible, and stops when
 107         the input buffer becomes empty or the output buffer becomes full. It
 108         may introduce some output latency (reading input without producing any
 109         output) except when forced to flush.
 110
 111         One or both of the following actions are performed:
 112
 113         @li Decompress more input starting at `zs.next_in` and update `zs.next_in`
 114         and `zs.avail_in` accordingly. If not all input can be processed (because
 115         there is not enough room in the output buffer), `zs.next_in` is updated
 116         and processing will resume at this point for the next call.
 117
 118         @li Provide more output starting at `zs.next_out` and update `zs.next_out`
 119         and `zs.avail_out` accordingly. `write` provides as much output as
 120         possible, until there is no more input data or no more space in the output
 121         buffer (see below about the flush parameter).
 122
 123         Before the call, the application should ensure that at least one of the
 124         actions is possible, by providing more input and/or consuming more output,
 125         and updating the values in `zs` accordingly. The application can consume
 126         the uncompressed output when it wants, for example when the output buffer
 127         is full (`zs.avail_out == 0`), or after each call. If `write` returns no
 128         error and with zero `zs.avail_out`, it must be called again after making
 129         room in the output buffer because there might be more output pending.
 130
 131         The flush parameter may be `Flush::none`, `Flush::sync`, `Flush::finish`,
 132         `Flush::block`, or `Flush::trees`. `Flush::sync` requests to flush as much
 133         output as possible to the output buffer. `Flush::block` requests to stop if
 134         and when it gets to the next deflate block boundary. When decoding the
 135         zlib or gzip format, this will cause `write` to return immediately after
 136         the header and before the first block. When doing a raw inflate, `write` will
 137         go ahead and process the first block, and will return when it gets to the
 138         end of that block, or when it runs out of data.
 139
 140         The `Flush::block` option assists in appending to or combining deflate
 141         streams. Also to assist in this, on return `write` will set `zs.data_type`
 142         to the number of unused bits in the last byte taken from `zs.next_in`, plus
 143         64 if `write` is currently decoding the last block in the deflate stream,
 144         plus 128 if `write` returned immediately after decoding an end-of-block code
 145         or decoding the complete header up to just before the first byte of the
 146         deflate stream. The end-of-block will not be indicated until all of the
 147         uncompressed data from that block has been written to `zs.next_out`. The
 148         number of unused bits may in general be greater than seven, except when
 149         bit 7 of `zs.data_type` is set, in which case the number of unused bits
 150         will be less than eight. `zs.data_type` is set as noted here every time
 151         `write` returns for all flush options, and so can be used to determine the
 152         amount of currently consumed input in bits.
 153
 154         The `Flush::trees` option behaves as `Flush::block` does, but it also returns
 155         when the end of each deflate block header is reached, before any actual data
 156         in that block is decoded. This allows the caller to determine the length of
 157         the deflate block header for later use in random access within a deflate block.
 158         256 is added to the value of `zs.data_type` when `write` returns immediately
 159         after reaching the end of the deflate block header.
 160
 161         `write` should normally be called until it returns `error::end_of_stream` or
 162         another error. However if all decompression is to be performed in a single
 163         step (a single call of `write`), the parameter flush should be set to
 164         `Flush::finish`. In this case all pending input is processed and all pending
 165         output is flushed; `zs.avail_out` must be large enough to hold all of the
 166         uncompressed data for the operation to complete. (The size of the uncompressed
 167         data may have been saved by the compressor for this purpose.) The use of
 168         `Flush::finish` is not required to perform an inflation in one step. However
 169         it may be used to inform inflate that a faster approach can be used for the
 170         single call. `Flush::finish` also informs inflate to not maintain a sliding
 171         window if the stream completes, which reduces inflate's memory footprint.
 172         If the stream does not complete, either because not all of the stream is
 173         provided or not enough output space is provided, then a sliding window will be
 174         allocated and `write` can be called again to continue the operation as if
 175         `Flush::none` had been used.
 176
 177         In this implementation, `write` always flushes as much output as possible to
 178         the output buffer, and always uses the faster approach on the first call. So
 179         the effects of the flush parameter in this implementation are on the return value
 180         of `write` as noted below, when `write` returns early when `Flush::block` or
 181         `Flush::trees` is used, and when `write` avoids the allocation of memory for a
 182         sliding window when `Flush::finsih` is used.
 183
 184         If a preset dictionary is needed after this call,
 185         `write` sets `zs.adler` to the Adler-32 checksum of the dictionary chosen by
 186         the compressor and returns `error::need_dictionary`; otherwise it sets
 187         `zs.adler` to the Adler-32 checksum of all output produced so far (that is,
 188         `zs.total_out bytes`) and returns no error, `error::end_of_stream`, or an
 189         error code as described below. At the end of the stream, `write` checks that
 190         its computed adler32 checksum is equal to that saved by the compressor and
 191         returns `error::end_of_stream` only if the checksum is correct.
 192
 193         This function returns no error if some progress has been made (more input
 194         processed or more output produced), `error::end_of_stream` if the end of the
 195         compressed data has been reached and all uncompressed output has been produced,
 196         `error::need_dictionary` if a preset dictionary is needed at this point,
 197         `error::invalid_data` if the input data was corrupted (input stream not
 198         conforming to the zlib format or incorrect check value), `error::stream_error`
 199         if the stream structure was inconsistent (for example if `zs.next_in` or
 200         `zs.next_out` was null), `error::need_buffers` if no progress is possible or
 201         if there was not enough room in the output buffer when `Flush::finish` is
 202         used. Note that `error::need_buffers` is not fatal, and `write` can be called
 203         again with more input and more output space to continue decompressing.
 204     */
 205     void
 206     write(z_params& zs, Flush flush, error_code& ec)
 207     {
 208         doWrite(zs, flush, ec);
 209     }
 210 };
 211
 212 } // zlib
 213 } // beast
 214
 215 #endif