ceph/src/boost/boost/beast/zlib/deflate_stream.hpp

   1 //
   2 // Copyright (c) 2016-2017 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 // Official repository: https://github.com/boostorg/beast
   8 //
   9
  10 #ifndef BOOST_BEAST_ZLIB_DEFLATE_STREAM_HPP
  11 #define BOOST_BEAST_ZLIB_DEFLATE_STREAM_HPP
  12
  13 #include <boost/beast/core/detail/config.hpp>
  14 #include <boost/beast/zlib/error.hpp>
  15 #include <boost/beast/zlib/zlib.hpp>
  16 #include <boost/beast/zlib/detail/deflate_stream.hpp>
  17 #include <algorithm>
  18 #include <cstdlib>
  19 #include <cstdint>
  20 #include <cstring>
  21 #include <memory>
  22
  23 namespace boost {
  24 namespace beast {
  25 namespace zlib {
  26
  27 // This is a derivative work based on Zlib, copyright below:
  28 /*
  29     Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
  30
  31     This software is provided 'as-is', without any express or implied
  32     warranty.  In no event will the authors be held liable for any damages
  33     arising from the use of this software.
  34
  35     Permission is granted to anyone to use this software for any purpose,
  36     including commercial applications, and to alter it and redistribute it
  37     freely, subject to the following restrictions:
  38
  39     1. The origin of this software must not be misrepresented; you must not
  40        claim that you wrote the original software. If you use this software
  41        in a product, an acknowledgment in the product documentation would be
  42        appreciated but is not required.
  43     2. Altered source versions must be plainly marked as such, and must not be
  44        misrepresented as being the original software.
  45     3. This notice may not be removed or altered from any source distribution.
  46
  47     Jean-loup Gailly        Mark Adler
  48     jloup@gzip.org          madler@alumni.caltech.edu
  49
  50     The data format used by the zlib library is described by RFCs (Request for
  51     Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
  52     (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
  53 */
  54
  55 /** Raw deflate compressor.
  56
  57     This is a port of zlib's "deflate" functionality to C++.
  58 */
  59 class deflate_stream
  60     : private detail::deflate_stream
  61 {
  62 public:
  63     /** Construct a default deflate stream.
  64
  65         Upon construction, the stream settings will be set
  66         to these default values:
  67
  68         @li `level = 6`
  69
  70         @li `windowBits = 15`
  71
  72         @li `memLevel = 8`
  73
  74         @li `strategy = Strategy::normal`
  75
  76         Although the stream is ready to be used immediately
  77         after construction, any required internal buffers are
  78         not dynamically allocated until needed.
  79     */
  80     deflate_stream()
  81     {
  82         reset(6, 15, DEF_MEM_LEVEL, Strategy::normal);
  83     }
  84
  85     /** Reset the stream and compression settings.
  86
  87         This function initializes the stream to the specified
  88         compression settings.
  89
  90         Although the stream is ready to be used immediately
  91         after a reset, any required internal buffers are not
  92         dynamically allocated until needed.
  93
  94         @note Any unprocessed input or pending output from
  95         previous calls are discarded.
  96     */
  97     void
  98     reset(
  99         int level,
 100         int windowBits,
 101         int memLevel,
 102         Strategy strategy)
 103     {
 104         doReset(level, windowBits, memLevel, strategy);
 105     }
 106
 107     /** Reset the stream without deallocating memory.
 108
 109         This function performs the equivalent of calling `clear`
 110         followed by `reset` with the same compression settings,
 111         without deallocating the internal buffers.
 112
 113         @note Any unprocessed input or pending output from
 114         previous calls are discarded.
 115     */
 116     void
 117     reset()
 118     {
 119         doReset();
 120     }
 121
 122     /** Clear the stream.
 123
 124         This function resets the stream and frees all dynamically
 125         allocated internal buffers. The compression settings are
 126         left unchanged.
 127
 128         @note Any unprocessed input or pending output from
 129         previous calls are discarded.
 130     */
 131     void
 132     clear()
 133     {
 134         doClear();
 135     }
 136
 137     /** Returns the upper limit on the size of a compressed block.
 138
 139         This function makes a conservative estimate of the maximum number
 140         of bytes needed to store the result of compressing a block of
 141         data based on the current compression level and strategy.
 142
 143         @param sourceLen The size of the uncompressed data.
 144
 145         @return The maximum number of resulting compressed bytes.
 146     */
 147     std::size_t
 148     upper_bound(std::size_t sourceLen) const
 149     {
 150         return doUpperBound(sourceLen);
 151     }
 152
 153     /** Fine tune internal compression parameters.
 154
 155         Compression parameters should only be tuned by someone who
 156         understands the algorithm used by zlib's deflate for searching
 157         for the best matching string, and even then only by the most
 158         fanatic optimizer trying to squeeze out the last compressed bit
 159         for their specific input data. Read the deflate.c source code
 160         (ZLib) for the meaning of the max_lazy, good_length, nice_length,
 161         and max_chain parameters.
 162     */
 163     void
 164     tune(
 165         int good_length,
 166         int max_lazy,
 167         int nice_length,
 168         int max_chain)
 169     {
 170         doTune(good_length, max_lazy, nice_length, max_chain);
 171     }
 172
 173     /** Compress input and write output.
 174
 175         This function compresses as much data as possible, and stops when
 176         the input buffer becomes empty or the output buffer becomes full.
 177         It may introduce some output latency (reading input without
 178         producing any output) except when forced to flush.
 179
 180         In each call, one or both of these actions are performed:
 181
 182         @li Compress more input starting at `zs.next_in` and update
 183         `zs.next_in` and `zs.avail_in` accordingly. If not all
 184         input can be processed (because there is not enough room in
 185         the output buffer), `zs.next_in` and `zs.avail_in` are updated
 186         and processing will resume at this point for the next call.
 187
 188         @li Provide more output starting at `zs.next_out` and update
 189         `zs.next_out` and `zs.avail_out` accordingly. This action is
 190         forced if the parameter flush is not `Flush::none`. Forcing
 191         flush frequently degrades the compression ratio, so this parameter
 192         should be set only when necessary (in interactive applications).
 193         Some output may be provided even if flush is not set.
 194
 195         Before the call, the application must ensure that at least one
 196         of the actions is possible, by providing more input and/or
 197         consuming more output, and updating `zs.avail_in` or `zs.avail_out`
 198         accordingly; `zs.avail_out` should never be zero before the call.
 199         The application can consume the compressed output when it wants,
 200         for example when the output buffer is full (`zs.avail_out == 0`),
 201         or after each call of `write`. If `write` returns no error
 202         with zero `zs.avail_out`, it must be called again after making
 203         room in the output buffer because there might be more output
 204         pending.
 205
 206         Normally the parameter flush is set to `Flush::none`, which allows
 207         deflate to decide how much data to accumulate before producing
 208         output, in order to maximize compression.
 209
 210         If the parameter flush is set to `Flush::sync`, all pending output
 211         is flushed to the output buffer and the output is aligned on a
 212         byte boundary, so that the decompressor can get all input data
 213         available so far. In particular `zs.avail_in` is zero after the
 214         call if enough output space has been provided before the call.
 215         Flushing may degrade compression for some compression algorithms
 216         and so it should be used only when necessary. This completes the
 217         current deflate block and follows it with an empty stored block
 218         that is three bits plus filler bits to the next byte, followed
 219         by the four bytes `{ 0x00, 0x00 0xff 0xff }`.
 220
 221         If flush is set to `Flush::partial`, all pending output is flushed
 222         to the output buffer, but the output is not aligned to a byte
 223         boundary. All of the input data so far will be available to the
 224         decompressor, as for Z_SYNC_FLUSH. This completes the current
 225         deflate block and follows it with an empty fixed codes block that
 226         is 10 bits long. This assures that enough bytes are output in order
 227         for the decompressor to finish the block before the empty fixed
 228         code block.
 229
 230         If flush is set to `Flush::block`, a deflate block is completed
 231         and emitted, as for `Flush::sync`, but the output is not aligned
 232         on a byte boundary, and up to seven bits of the current block are
 233         held to be written as the next byte after the next deflate block
 234         is completed. In this case, the decompressor may not be provided
 235         enough bits at this point in order to complete decompression of
 236         the data provided so far to the compressor. It may need to wait
 237         for the next block to be emitted. This is for advanced applications
 238         that need to control the emission of deflate blocks.
 239
 240         If flush is set to `Flush::full`, all output is flushed as with
 241         `Flush::sync`, and the compression state is reset so that
 242         decompression can restart from this point if previous compressed
 243         data has been damaged or if random access is desired. Using
 244         `Flush::full` too often can seriously degrade compression.
 245
 246         If `write` returns with `zs.avail_out == 0`, this function must
 247         be called again with the same value of the flush parameter and
 248         more output space (updated `zs.avail_out`), until the flush is
 249         complete (`write` returns with non-zero `zs.avail_out`). In the
 250         case of a `Flush::full`or `Flush::sync`, make sure that
 251         `zs.avail_out` is greater than six to avoid repeated flush markers
 252         due to `zs.avail_out == 0` on return.
 253
 254         If the parameter flush is set to `Flush::finish`, pending input
 255         is processed, pending output is flushed and deflate returns the
 256         error `error::end_of_stream` if there was enough output space;
 257         if deflate returns with no error, this function must be called
 258         again with `Flush::finish` and more output space (updated
 259         `zs.avail_out`) but no more input data, until it returns the
 260         error `error::end_of_stream` or another error. After `write` has
 261         returned the `error::end_of_stream` error, the only possible
 262         operations on the stream are to reset or destroy.
 263
 264         `Flush::finish` can be used immediately after initialization
 265         if all the compression is to be done in a single step. In this
 266         case, `zs.avail_out` must be at least value returned by
 267         `upper_bound` (see below). Then `write` is guaranteed to return
 268         the `error::end_of_stream` error. If not enough output space
 269         is provided, deflate will not return `error::end_of_stream`,
 270         and it must be called again as described above.
 271
 272         `write` returns no error if some progress has been made (more
 273         input processed or more output produced), `error::end_of_stream`
 274         if all input has been consumed and all output has been produced
 275         (only when flush is set to `Flush::finish`), `error::stream_error`
 276         if the stream state was inconsistent (for example if `zs.next_in`
 277         or `zs.next_out` was `nullptr`), `error::need_buffers` if no
 278         progress is possible (for example `zs.avail_in` or `zs.avail_out`
 279         was zero). Note that `error::need_buffers` is not fatal, and
 280         `write` can be called again with more input and more output space
 281         to continue compressing.
 282     */
 283     void
 284     write(
 285         z_params& zs,
 286         Flush flush,
 287         error_code& ec)
 288     {
 289         doWrite(zs, flush, ec);
 290     }
 291
 292     /** Update the compression level and strategy.
 293
 294         This function dynamically updates the compression level and
 295         compression strategy. The interpretation of level and strategy
 296         is as in @ref reset. This can be used to switch between compression
 297         and straight copy of the input data, or to switch to a different kind
 298         of input data requiring a different strategy. If the compression level
 299         is changed, the input available so far is compressed with the old level
 300         (and may be flushed); the new level will take effect only at the next
 301         call of @ref write.
 302
 303         Before the call of `params`, the stream state must be set as for a
 304         call of @ref write, since the currently available input may have to be
 305         compressed and flushed. In particular, `zs.avail_out` must be non-zero.
 306
 307         @return `Z_OK` if success, `Z_STREAM_ERROR` if the source stream state
 308         was inconsistent or if a parameter was invalid, `error::need_buffers`
 309         if `zs.avail_out` was zero.
 310     */
 311     void
 312     params(
 313         z_params& zs,
 314         int level,
 315         Strategy strategy,
 316         error_code& ec)
 317     {
 318         doParams(zs, level, strategy, ec);
 319     }
 320
 321     /** Return bits pending in the output.
 322
 323         This function returns the number of bytes and bits of output
 324         that have been generated, but not yet provided in the available
 325         output. The bytes not provided would be due to the available
 326         output space having being consumed. The number of bits of output
 327         not provided are between 0 and 7, where they await more bits to
 328         join them in order to fill out a full byte. If pending or bits
 329         are `nullptr`, then those values are not set.
 330
 331         @return `Z_OK` if success, or `Z_STREAM_ERROR` if the source
 332         stream state was inconsistent.
 333     */
 334     void
 335     pending(unsigned *value, int *bits)
 336     {
 337         doPending(value, bits);
 338     }
 339
 340     /** Insert bits into the compressed output stream.
 341
 342         This function inserts bits in the deflate output stream. The
 343         intent is that this function is used to start off the deflate
 344         output with the bits leftover from a previous deflate stream when
 345         appending to it. As such, this function can only be used for raw
 346         deflate, and must be used before the first `write` call after an
 347         initialization. `bits` must be less than or equal to 16, and that
 348         many of the least significant bits of `value` will be inserted in
 349         the output.
 350
 351         @return `error::need_buffers` if there was not enough room in
 352         the internal buffer to insert the bits.
 353     */
 354     void
 355     prime(int bits, int value, error_code& ec)
 356     {
 357         return doPrime(bits, value, ec);
 358     }
 359 };
 360
 361 /** Returns the upper limit on the size of a compressed block.
 362
 363     This function makes a conservative estimate of the maximum number
 364     of bytes needed to store the result of compressing a block of
 365     data.
 366
 367     @param bytes The size of the uncompressed data.
 368
 369     @return The maximum number of resulting compressed bytes.
 370 */
 371 std::size_t
 372 deflate_upper_bound(std::size_t bytes);
 373
 374 /*  For the default windowBits of 15 and memLevel of 8, this function returns
 375     a close to exact, as well as small, upper bound on the compressed size.
 376     They are coded as constants here for a reason--if the #define's are
 377     changed, then this function needs to be changed as well.  The return
 378     value for 15 and 8 only works for those exact settings.
 379
 380     For any setting other than those defaults for windowBits and memLevel,
 381     the value returned is a conservative worst case for the maximum expansion
 382     resulting from using fixed blocks instead of stored blocks, which deflate
 383     can emit on compressed data for some combinations of the parameters.
 384
 385     This function could be more sophisticated to provide closer upper bounds for
 386     every combination of windowBits and memLevel.  But even the conservative
 387     upper bound of about 14% expansion does not seem onerous for output buffer
 388     allocation.
 389 */
 390 inline
 391 std::size_t
 392 deflate_upper_bound(std::size_t bytes)
 393 {
 394     return bytes +
 395         ((bytes + 7) >> 3) +
 396         ((bytes + 63) >> 6) + 5 +
 397         6;
 398 }
 399
 400 } // zlib
 401 } // beast
 402 } // boost
 403
 404 #endif