xref: /openbmc/linux/include/linux/zstd.h (revision e0c1b49f)
1 /* SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause */
2 /*
3  * Copyright (c) Yann Collet, Facebook, Inc.
4  * All rights reserved.
5  *
6  * This source code is licensed under both the BSD-style license (found in the
7  * LICENSE file in the root directory of https://github.com/facebook/zstd) and
8  * the GPLv2 (found in the COPYING file in the root directory of
9  * https://github.com/facebook/zstd). You may select, at your option, one of the
10  * above-listed licenses.
11  */
12 
13 #ifndef LINUX_ZSTD_H
14 #define LINUX_ZSTD_H
15 
16 /**
17  * This is a kernel-style API that wraps the upstream zstd API, which cannot be
18  * used directly because the symbols aren't exported. It exposes the minimal
19  * functionality which is currently required by users of zstd in the kernel.
20  * Expose extra functions from lib/zstd/zstd.h as needed.
21  */
22 
23 /* ======   Dependency   ====== */
24 #include <linux/types.h>
25 #include <linux/zstd_errors.h>
26 #include <linux/zstd_lib.h>
27 
28 /* ======   Helper Functions   ====== */
29 /**
30  * zstd_compress_bound() - maximum compressed size in worst case scenario
31  * @src_size: The size of the data to compress.
32  *
33  * Return:    The maximum compressed size in the worst case scenario.
34  */
35 size_t zstd_compress_bound(size_t src_size);
36 
37 /**
38  * zstd_is_error() - tells if a size_t function result is an error code
39  * @code:  The function result to check for error.
40  *
41  * Return: Non-zero iff the code is an error.
42  */
43 unsigned int zstd_is_error(size_t code);
44 
45 /**
46  * enum zstd_error_code - zstd error codes
47  */
48 typedef ZSTD_ErrorCode zstd_error_code;
49 
50 /**
51  * zstd_get_error_code() - translates an error function result to an error code
52  * @code:  The function result for which zstd_is_error(code) is true.
53  *
54  * Return: A unique error code for this error.
55  */
56 zstd_error_code zstd_get_error_code(size_t code);
57 
58 /**
59  * zstd_get_error_name() - translates an error function result to a string
60  * @code:  The function result for which zstd_is_error(code) is true.
61  *
62  * Return: An error string corresponding to the error code.
63  */
64 const char *zstd_get_error_name(size_t code);
65 
66 /**
67  * zstd_min_clevel() - minimum allowed compression level
68  *
69  * Return: The minimum allowed compression level.
70  */
71 int zstd_min_clevel(void);
72 
73 /**
74  * zstd_max_clevel() - maximum allowed compression level
75  *
76  * Return: The maximum allowed compression level.
77  */
78 int zstd_max_clevel(void);
79 
80 /* ======   Parameter Selection   ====== */
81 
82 /**
83  * enum zstd_strategy - zstd compression search strategy
84  *
85  * From faster to stronger. See zstd_lib.h.
86  */
87 typedef ZSTD_strategy zstd_strategy;
88 
89 /**
90  * struct zstd_compression_parameters - zstd compression parameters
91  * @windowLog:    Log of the largest match distance. Larger means more
92  *                compression, and more memory needed during decompression.
93  * @chainLog:     Fully searched segment. Larger means more compression,
94  *                slower, and more memory (useless for fast).
95  * @hashLog:      Dispatch table. Larger means more compression,
96  *                slower, and more memory.
97  * @searchLog:    Number of searches. Larger means more compression and slower.
98  * @searchLength: Match length searched. Larger means faster decompression,
99  *                sometimes less compression.
100  * @targetLength: Acceptable match size for optimal parser (only). Larger means
101  *                more compression, and slower.
102  * @strategy:     The zstd compression strategy.
103  *
104  * See zstd_lib.h.
105  */
106 typedef ZSTD_compressionParameters zstd_compression_parameters;
107 
108 /**
109  * struct zstd_frame_parameters - zstd frame parameters
110  * @contentSizeFlag: Controls whether content size will be present in the
111  *                   frame header (when known).
112  * @checksumFlag:    Controls whether a 32-bit checksum is generated at the
113  *                   end of the frame for error detection.
114  * @noDictIDFlag:    Controls whether dictID will be saved into the frame
115  *                   header when using dictionary compression.
116  *
117  * The default value is all fields set to 0. See zstd_lib.h.
118  */
119 typedef ZSTD_frameParameters zstd_frame_parameters;
120 
121 /**
122  * struct zstd_parameters - zstd parameters
123  * @cParams: The compression parameters.
124  * @fParams: The frame parameters.
125  */
126 typedef ZSTD_parameters zstd_parameters;
127 
128 /**
129  * zstd_get_params() - returns zstd_parameters for selected level
130  * @level:              The compression level
131  * @estimated_src_size: The estimated source size to compress or 0
132  *                      if unknown.
133  *
134  * Return:              The selected zstd_parameters.
135  */
136 zstd_parameters zstd_get_params(int level,
137 	unsigned long long estimated_src_size);
138 
139 /* ======   Single-pass Compression   ====== */
140 
141 typedef ZSTD_CCtx zstd_cctx;
142 
143 /**
144  * zstd_cctx_workspace_bound() - max memory needed to initialize a zstd_cctx
145  * @parameters: The compression parameters to be used.
146  *
147  * If multiple compression parameters might be used, the caller must call
148  * zstd_cctx_workspace_bound() for each set of parameters and use the maximum
149  * size.
150  *
151  * Return:      A lower bound on the size of the workspace that is passed to
152  *              zstd_init_cctx().
153  */
154 size_t zstd_cctx_workspace_bound(const zstd_compression_parameters *parameters);
155 
156 /**
157  * zstd_init_cctx() - initialize a zstd compression context
158  * @workspace:      The workspace to emplace the context into. It must outlive
159  *                  the returned context.
160  * @workspace_size: The size of workspace. Use zstd_cctx_workspace_bound() to
161  *                  determine how large the workspace must be.
162  *
163  * Return:          A zstd compression context or NULL on error.
164  */
165 zstd_cctx *zstd_init_cctx(void *workspace, size_t workspace_size);
166 
167 /**
168  * zstd_compress_cctx() - compress src into dst with the initialized parameters
169  * @cctx:         The context. Must have been initialized with zstd_init_cctx().
170  * @dst:          The buffer to compress src into.
171  * @dst_capacity: The size of the destination buffer. May be any size, but
172  *                ZSTD_compressBound(srcSize) is guaranteed to be large enough.
173  * @src:          The data to compress.
174  * @src_size:     The size of the data to compress.
175  * @parameters:   The compression parameters to be used.
176  *
177  * Return:        The compressed size or an error, which can be checked using
178  *                zstd_is_error().
179  */
180 size_t zstd_compress_cctx(zstd_cctx *cctx, void *dst, size_t dst_capacity,
181 	const void *src, size_t src_size, const zstd_parameters *parameters);
182 
183 /* ======   Single-pass Decompression   ====== */
184 
185 typedef ZSTD_DCtx zstd_dctx;
186 
187 /**
188  * zstd_dctx_workspace_bound() - max memory needed to initialize a zstd_dctx
189  *
190  * Return: A lower bound on the size of the workspace that is passed to
191  *         zstd_init_dctx().
192  */
193 size_t zstd_dctx_workspace_bound(void);
194 
195 /**
196  * zstd_init_dctx() - initialize a zstd decompression context
197  * @workspace:      The workspace to emplace the context into. It must outlive
198  *                  the returned context.
199  * @workspace_size: The size of workspace. Use zstd_dctx_workspace_bound() to
200  *                  determine how large the workspace must be.
201  *
202  * Return:          A zstd decompression context or NULL on error.
203  */
204 zstd_dctx *zstd_init_dctx(void *workspace, size_t workspace_size);
205 
206 /**
207  * zstd_decompress_dctx() - decompress zstd compressed src into dst
208  * @dctx:         The decompression context.
209  * @dst:          The buffer to decompress src into.
210  * @dst_capacity: The size of the destination buffer. Must be at least as large
211  *                as the decompressed size. If the caller cannot upper bound the
212  *                decompressed size, then it's better to use the streaming API.
213  * @src:          The zstd compressed data to decompress. Multiple concatenated
214  *                frames and skippable frames are allowed.
215  * @src_size:     The exact size of the data to decompress.
216  *
217  * Return:        The decompressed size or an error, which can be checked using
218  *                zstd_is_error().
219  */
220 size_t zstd_decompress_dctx(zstd_dctx *dctx, void *dst, size_t dst_capacity,
221 	const void *src, size_t src_size);
222 
223 /* ======   Streaming Buffers   ====== */
224 
225 /**
226  * struct zstd_in_buffer - input buffer for streaming
227  * @src:  Start of the input buffer.
228  * @size: Size of the input buffer.
229  * @pos:  Position where reading stopped. Will be updated.
230  *        Necessarily 0 <= pos <= size.
231  *
232  * See zstd_lib.h.
233  */
234 typedef ZSTD_inBuffer zstd_in_buffer;
235 
236 /**
237  * struct zstd_out_buffer - output buffer for streaming
238  * @dst:  Start of the output buffer.
239  * @size: Size of the output buffer.
240  * @pos:  Position where writing stopped. Will be updated.
241  *        Necessarily 0 <= pos <= size.
242  *
243  * See zstd_lib.h.
244  */
245 typedef ZSTD_outBuffer zstd_out_buffer;
246 
247 /* ======   Streaming Compression   ====== */
248 
249 typedef ZSTD_CStream zstd_cstream;
250 
251 /**
252  * zstd_cstream_workspace_bound() - memory needed to initialize a zstd_cstream
253  * @cparams: The compression parameters to be used for compression.
254  *
255  * Return:   A lower bound on the size of the workspace that is passed to
256  *           zstd_init_cstream().
257  */
258 size_t zstd_cstream_workspace_bound(const zstd_compression_parameters *cparams);
259 
260 /**
261  * zstd_init_cstream() - initialize a zstd streaming compression context
262  * @parameters        The zstd parameters to use for compression.
263  * @pledged_src_size: If params.fParams.contentSizeFlag == 1 then the caller
264  *                    must pass the source size (zero means empty source).
265  *                    Otherwise, the caller may optionally pass the source
266  *                    size, or zero if unknown.
267  * @workspace:        The workspace to emplace the context into. It must outlive
268  *                    the returned context.
269  * @workspace_size:   The size of workspace.
270  *                    Use zstd_cstream_workspace_bound(params->cparams) to
271  *                    determine how large the workspace must be.
272  *
273  * Return:            The zstd streaming compression context or NULL on error.
274  */
275 zstd_cstream *zstd_init_cstream(const zstd_parameters *parameters,
276 	unsigned long long pledged_src_size, void *workspace, size_t workspace_size);
277 
278 /**
279  * zstd_reset_cstream() - reset the context using parameters from creation
280  * @cstream:          The zstd streaming compression context to reset.
281  * @pledged_src_size: Optionally the source size, or zero if unknown.
282  *
283  * Resets the context using the parameters from creation. Skips dictionary
284  * loading, since it can be reused. If `pledged_src_size` is non-zero the frame
285  * content size is always written into the frame header.
286  *
287  * Return:            Zero or an error, which can be checked using
288  *                    zstd_is_error().
289  */
290 size_t zstd_reset_cstream(zstd_cstream *cstream,
291 	unsigned long long pledged_src_size);
292 
293 /**
294  * zstd_compress_stream() - streaming compress some of input into output
295  * @cstream: The zstd streaming compression context.
296  * @output:  Destination buffer. `output->pos` is updated to indicate how much
297  *           compressed data was written.
298  * @input:   Source buffer. `input->pos` is updated to indicate how much data
299  *           was read. Note that it may not consume the entire input, in which
300  *           case `input->pos < input->size`, and it's up to the caller to
301  *           present remaining data again.
302  *
303  * The `input` and `output` buffers may be any size. Guaranteed to make some
304  * forward progress if `input` and `output` are not empty.
305  *
306  * Return:   A hint for the number of bytes to use as the input for the next
307  *           function call or an error, which can be checked using
308  *           zstd_is_error().
309  */
310 size_t zstd_compress_stream(zstd_cstream *cstream, zstd_out_buffer *output,
311 	zstd_in_buffer *input);
312 
313 /**
314  * zstd_flush_stream() - flush internal buffers into output
315  * @cstream: The zstd streaming compression context.
316  * @output:  Destination buffer. `output->pos` is updated to indicate how much
317  *           compressed data was written.
318  *
319  * zstd_flush_stream() must be called until it returns 0, meaning all the data
320  * has been flushed. Since zstd_flush_stream() causes a block to be ended,
321  * calling it too often will degrade the compression ratio.
322  *
323  * Return:   The number of bytes still present within internal buffers or an
324  *           error, which can be checked using zstd_is_error().
325  */
326 size_t zstd_flush_stream(zstd_cstream *cstream, zstd_out_buffer *output);
327 
328 /**
329  * zstd_end_stream() - flush internal buffers into output and end the frame
330  * @cstream: The zstd streaming compression context.
331  * @output:  Destination buffer. `output->pos` is updated to indicate how much
332  *           compressed data was written.
333  *
334  * zstd_end_stream() must be called until it returns 0, meaning all the data has
335  * been flushed and the frame epilogue has been written.
336  *
337  * Return:   The number of bytes still present within internal buffers or an
338  *           error, which can be checked using zstd_is_error().
339  */
340 size_t zstd_end_stream(zstd_cstream *cstream, zstd_out_buffer *output);
341 
342 /* ======   Streaming Decompression   ====== */
343 
344 typedef ZSTD_DStream zstd_dstream;
345 
346 /**
347  * zstd_dstream_workspace_bound() - memory needed to initialize a zstd_dstream
348  * @max_window_size: The maximum window size allowed for compressed frames.
349  *
350  * Return:           A lower bound on the size of the workspace that is passed
351  *                   to zstd_init_dstream().
352  */
353 size_t zstd_dstream_workspace_bound(size_t max_window_size);
354 
355 /**
356  * zstd_init_dstream() - initialize a zstd streaming decompression context
357  * @max_window_size: The maximum window size allowed for compressed frames.
358  * @workspace:       The workspace to emplace the context into. It must outlive
359  *                   the returned context.
360  * @workspaceSize:   The size of workspace.
361  *                   Use zstd_dstream_workspace_bound(max_window_size) to
362  *                   determine how large the workspace must be.
363  *
364  * Return:           The zstd streaming decompression context.
365  */
366 zstd_dstream *zstd_init_dstream(size_t max_window_size, void *workspace,
367 	size_t workspace_size);
368 
369 /**
370  * zstd_reset_dstream() - reset the context using parameters from creation
371  * @dstream: The zstd streaming decompression context to reset.
372  *
373  * Resets the context using the parameters from creation. Skips dictionary
374  * loading, since it can be reused.
375  *
376  * Return:   Zero or an error, which can be checked using zstd_is_error().
377  */
378 size_t zstd_reset_dstream(zstd_dstream *dstream);
379 
380 /**
381  * zstd_decompress_stream() - streaming decompress some of input into output
382  * @dstream: The zstd streaming decompression context.
383  * @output:  Destination buffer. `output.pos` is updated to indicate how much
384  *           decompressed data was written.
385  * @input:   Source buffer. `input.pos` is updated to indicate how much data was
386  *           read. Note that it may not consume the entire input, in which case
387  *           `input.pos < input.size`, and it's up to the caller to present
388  *           remaining data again.
389  *
390  * The `input` and `output` buffers may be any size. Guaranteed to make some
391  * forward progress if `input` and `output` are not empty.
392  * zstd_decompress_stream() will not consume the last byte of the frame until
393  * the entire frame is flushed.
394  *
395  * Return:   Returns 0 iff a frame is completely decoded and fully flushed.
396  *           Otherwise returns a hint for the number of bytes to use as the
397  *           input for the next function call or an error, which can be checked
398  *           using zstd_is_error(). The size hint will never load more than the
399  *           frame.
400  */
401 size_t zstd_decompress_stream(zstd_dstream *dstream, zstd_out_buffer *output,
402 	zstd_in_buffer *input);
403 
404 /* ======   Frame Inspection Functions ====== */
405 
406 /**
407  * zstd_find_frame_compressed_size() - returns the size of a compressed frame
408  * @src:      Source buffer. It should point to the start of a zstd encoded
409  *            frame or a skippable frame.
410  * @src_size: The size of the source buffer. It must be at least as large as the
411  *            size of the frame.
412  *
413  * Return:    The compressed size of the frame pointed to by `src` or an error,
414  *            which can be check with zstd_is_error().
415  *            Suitable to pass to ZSTD_decompress() or similar functions.
416  */
417 size_t zstd_find_frame_compressed_size(const void *src, size_t src_size);
418 
419 /**
420  * struct zstd_frame_params - zstd frame parameters stored in the frame header
421  * @frameContentSize: The frame content size, or ZSTD_CONTENTSIZE_UNKNOWN if not
422  *                    present.
423  * @windowSize:       The window size, or 0 if the frame is a skippable frame.
424  * @blockSizeMax:     The maximum block size.
425  * @frameType:        The frame type (zstd or skippable)
426  * @headerSize:       The size of the frame header.
427  * @dictID:           The dictionary id, or 0 if not present.
428  * @checksumFlag:     Whether a checksum was used.
429  *
430  * See zstd_lib.h.
431  */
432 typedef ZSTD_frameHeader zstd_frame_header;
433 
434 /**
435  * zstd_get_frame_header() - extracts parameters from a zstd or skippable frame
436  * @params:   On success the frame parameters are written here.
437  * @src:      The source buffer. It must point to a zstd or skippable frame.
438  * @src_size: The size of the source buffer.
439  *
440  * Return:    0 on success. If more data is required it returns how many bytes
441  *            must be provided to make forward progress. Otherwise it returns
442  *            an error, which can be checked using zstd_is_error().
443  */
444 size_t zstd_get_frame_header(zstd_frame_header *params, const void *src,
445 	size_t src_size);
446 
447 #endif  /* LINUX_ZSTD_H */
448