aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/libpq/src/common/compression.c
blob: 47b18b8c6007daec2ccc3ce8d91ef0453ef24963 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
/*-------------------------------------------------------------------------
 *
 * compression.c
 *
 * Shared code for compression methods and specifications.
 *
 * A compression specification specifies the parameters that should be used
 * when performing compression with a specific algorithm. The simplest
 * possible compression specification is an integer, which sets the
 * compression level.
 *
 * Otherwise, a compression specification is a comma-separated list of items,
 * each having the form keyword or keyword=value.
 *
 * Currently, the supported keywords are "level", "long", and "workers".
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *		  src/common/compression.c
 *-------------------------------------------------------------------------
 */

#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif

#ifdef USE_ZSTD
#error #include <zstd.h>
#endif
#ifdef HAVE_LIBZ
#include <zlib.h>
#endif

#include "common/compression.h"

static int	expect_integer_value(char *keyword, char *value,
								 pg_compress_specification *result);
static bool expect_boolean_value(char *keyword, char *value,
								 pg_compress_specification *result);

/*
 * Look up a compression algorithm by name. Returns true and sets *algorithm
 * if the name is recognized. Otherwise returns false.
 */
bool
parse_compress_algorithm(char *name, pg_compress_algorithm *algorithm)
{
	if (strcmp(name, "none") == 0)
		*algorithm = PG_COMPRESSION_NONE;
	else if (strcmp(name, "gzip") == 0)
		*algorithm = PG_COMPRESSION_GZIP;
	else if (strcmp(name, "lz4") == 0)
		*algorithm = PG_COMPRESSION_LZ4;
	else if (strcmp(name, "zstd") == 0)
		*algorithm = PG_COMPRESSION_ZSTD;
	else
		return false;
	return true;
}

/*
 * Get the human-readable name corresponding to a particular compression
 * algorithm.
 */
const char *
get_compress_algorithm_name(pg_compress_algorithm algorithm)
{
	switch (algorithm)
	{
		case PG_COMPRESSION_NONE:
			return "none";
		case PG_COMPRESSION_GZIP:
			return "gzip";
		case PG_COMPRESSION_LZ4:
			return "lz4";
		case PG_COMPRESSION_ZSTD:
			return "zstd";
			/* no default, to provoke compiler warnings if values are added */
	}
	Assert(false);
	return "???";				/* placate compiler */
}

/*
 * Parse a compression specification for a specified algorithm.
 *
 * See the file header comments for a brief description of what a compression
 * specification is expected to look like.
 *
 * On return, all fields of the result object will be initialized.
 * In particular, result->parse_error will be NULL if no errors occurred
 * during parsing, and will otherwise contain an appropriate error message.
 * The caller may free this error message string using pfree, if desired.
 * Note, however, even if there's no parse error, the string might not make
 * sense: e.g. for gzip, level=12 is not sensible, but it does parse OK.
 *
 * The compression level is assigned by default if not directly specified
 * by the specification.
 *
 * Use validate_compress_specification() to find out whether a compression
 * specification is semantically sensible.
 */
void
parse_compress_specification(pg_compress_algorithm algorithm, char *specification,
							 pg_compress_specification *result)
{
	int			bare_level;
	char	   *bare_level_endp;

	/* Initial setup of result object. */
	result->algorithm = algorithm;
	result->options = 0;
	result->parse_error = NULL;

	/*
	 * Assign a default level depending on the compression method.  This may
	 * be enforced later.
	 */
	switch (result->algorithm)
	{
		case PG_COMPRESSION_NONE:
			result->level = 0;
			break;
		case PG_COMPRESSION_LZ4:
#ifdef USE_LZ4
			result->level = 0;	/* fast compression mode */
#else
			result->parse_error =
				psprintf(_("this build does not support compression with %s"),
						 "LZ4");
#endif
			break;
		case PG_COMPRESSION_ZSTD:
#ifdef USE_ZSTD
			result->level = ZSTD_CLEVEL_DEFAULT;
#else
			result->parse_error =
				psprintf(_("this build does not support compression with %s"),
						 "ZSTD");
#endif
			break;
		case PG_COMPRESSION_GZIP:
#ifdef HAVE_LIBZ
			result->level = Z_DEFAULT_COMPRESSION;
#else
			result->parse_error =
				psprintf(_("this build does not support compression with %s"),
						 "gzip");
#endif
			break;
	}

	/* If there is no specification, we're done already. */
	if (specification == NULL)
		return;

	/* As a special case, the specification can be a bare integer. */
	bare_level = strtol(specification, &bare_level_endp, 10);
	if (specification != bare_level_endp && *bare_level_endp == '\0')
	{
		result->level = bare_level;
		return;
	}

	/* Look for comma-separated keyword or keyword=value entries. */
	while (1)
	{
		char	   *kwstart;
		char	   *kwend;
		char	   *vstart;
		char	   *vend;
		int			kwlen;
		int			vlen;
		bool		has_value;
		char	   *keyword;
		char	   *value;

		/* Figure start, end, and length of next keyword and any value. */
		kwstart = kwend = specification;
		while (*kwend != '\0' && *kwend != ',' && *kwend != '=')
			++kwend;
		kwlen = kwend - kwstart;
		if (*kwend != '=')
		{
			vstart = vend = NULL;
			vlen = 0;
			has_value = false;
		}
		else
		{
			vstart = vend = kwend + 1;
			while (*vend != '\0' && *vend != ',')
				++vend;
			vlen = vend - vstart;
			has_value = true;
		}

		/* Reject empty keyword. */
		if (kwlen == 0)
		{
			result->parse_error =
				pstrdup(_("found empty string where a compression option was expected"));
			break;
		}

		/* Extract keyword and value as separate C strings. */
		keyword = palloc(kwlen + 1);
		memcpy(keyword, kwstart, kwlen);
		keyword[kwlen] = '\0';
		if (!has_value)
			value = NULL;
		else
		{
			value = palloc(vlen + 1);
			memcpy(value, vstart, vlen);
			value[vlen] = '\0';
		}

		/* Handle whatever keyword we found. */
		if (strcmp(keyword, "level") == 0)
		{
			result->level = expect_integer_value(keyword, value, result);

			/*
			 * No need to set a flag in "options", there is a default level
			 * set at least thanks to the logic above.
			 */
		}
		else if (strcmp(keyword, "workers") == 0)
		{
			result->workers = expect_integer_value(keyword, value, result);
			result->options |= PG_COMPRESSION_OPTION_WORKERS;
		}
		else if (strcmp(keyword, "long") == 0)
		{
			result->long_distance = expect_boolean_value(keyword, value, result);
			result->options |= PG_COMPRESSION_OPTION_LONG_DISTANCE;
		}
		else
			result->parse_error =
				psprintf(_("unrecognized compression option: \"%s\""), keyword);

		/* Release memory, just to be tidy. */
		pfree(keyword);
		if (value != NULL)
			pfree(value);

		/*
		 * If we got an error or have reached the end of the string, stop.
		 *
		 * If there is no value, then the end of the keyword might have been
		 * the end of the string. If there is a value, then the end of the
		 * keyword cannot have been the end of the string, but the end of the
		 * value might have been.
		 */
		if (result->parse_error != NULL ||
			(vend == NULL ? *kwend == '\0' : *vend == '\0'))
			break;

		/* Advance to next entry and loop around. */
		specification = vend == NULL ? kwend + 1 : vend + 1;
	}
}

/*
 * Parse 'value' as an integer and return the result.
 *
 * If parsing fails, set result->parse_error to an appropriate message
 * and return -1.
 */
static int
expect_integer_value(char *keyword, char *value, pg_compress_specification *result)
{
	int			ivalue;
	char	   *ivalue_endp;

	if (value == NULL)
	{
		result->parse_error =
			psprintf(_("compression option \"%s\" requires a value"),
					 keyword);
		return -1;
	}

	ivalue = strtol(value, &ivalue_endp, 10);
	if (ivalue_endp == value || *ivalue_endp != '\0')
	{
		result->parse_error =
			psprintf(_("value for compression option \"%s\" must be an integer"),
					 keyword);
		return -1;
	}
	return ivalue;
}

/*
 * Parse 'value' as a boolean and return the result.
 *
 * If parsing fails, set result->parse_error to an appropriate message
 * and return -1.  The caller must check result->parse_error to determine if
 * the call was successful.
 *
 * Valid values are: yes, no, on, off, 1, 0.
 *
 * Inspired by ParseVariableBool().
 */
static bool
expect_boolean_value(char *keyword, char *value, pg_compress_specification *result)
{
	if (value == NULL)
		return true;

	if (pg_strcasecmp(value, "yes") == 0)
		return true;
	if (pg_strcasecmp(value, "on") == 0)
		return true;
	if (pg_strcasecmp(value, "1") == 0)
		return true;

	if (pg_strcasecmp(value, "no") == 0)
		return false;
	if (pg_strcasecmp(value, "off") == 0)
		return false;
	if (pg_strcasecmp(value, "0") == 0)
		return false;

	result->parse_error =
		psprintf(_("value for compression option \"%s\" must be a Boolean value"),
				 keyword);
	return false;
}

/*
 * Returns NULL if the compression specification string was syntactically
 * valid and semantically sensible.  Otherwise, returns an error message.
 *
 * Does not test whether this build of PostgreSQL supports the requested
 * compression method.
 */
char *
validate_compress_specification(pg_compress_specification *spec)
{
	int			min_level = 1;
	int			max_level = 1;
	int			default_level = 0;

	/* If it didn't even parse OK, it's definitely no good. */
	if (spec->parse_error != NULL)
		return spec->parse_error;

	/*
	 * Check that the algorithm expects a compression level and it is within
	 * the legal range for the algorithm.
	 */
	switch (spec->algorithm)
	{
		case PG_COMPRESSION_GZIP:
			max_level = 9;
#ifdef HAVE_LIBZ
			default_level = Z_DEFAULT_COMPRESSION;
#endif
			break;
		case PG_COMPRESSION_LZ4:
			max_level = 12;
			default_level = 0;	/* fast mode */
			break;
		case PG_COMPRESSION_ZSTD:
#ifdef USE_ZSTD
			max_level = ZSTD_maxCLevel();
			min_level = ZSTD_minCLevel();
			default_level = ZSTD_CLEVEL_DEFAULT;
#endif
			break;
		case PG_COMPRESSION_NONE:
			if (spec->level != 0)
				return psprintf(_("compression algorithm \"%s\" does not accept a compression level"),
								get_compress_algorithm_name(spec->algorithm));
			break;
	}

	if ((spec->level < min_level || spec->level > max_level) &&
		spec->level != default_level)
		return psprintf(_("compression algorithm \"%s\" expects a compression level between %d and %d (default at %d)"),
						get_compress_algorithm_name(spec->algorithm),
						min_level, max_level, default_level);

	/*
	 * Of the compression algorithms that we currently support, only zstd
	 * allows parallel workers.
	 */
	if ((spec->options & PG_COMPRESSION_OPTION_WORKERS) != 0 &&
		(spec->algorithm != PG_COMPRESSION_ZSTD))
	{
		return psprintf(_("compression algorithm \"%s\" does not accept a worker count"),
						get_compress_algorithm_name(spec->algorithm));
	}

	/*
	 * Of the compression algorithms that we currently support, only zstd
	 * supports long-distance mode.
	 */
	if ((spec->options & PG_COMPRESSION_OPTION_LONG_DISTANCE) != 0 &&
		(spec->algorithm != PG_COMPRESSION_ZSTD))
	{
		return psprintf(_("compression algorithm \"%s\" does not support long-distance mode"),
						get_compress_algorithm_name(spec->algorithm));
	}

	return NULL;
}

#ifdef FRONTEND

/*
 * Basic parsing of a value specified through a command-line option, commonly
 * -Z/--compress.
 *
 * The parsing consists of a METHOD:DETAIL string fed later to
 * parse_compress_specification().  This only extracts METHOD and DETAIL.
 * If only an integer is found, the method is implied by the value specified.
 */
void
parse_compress_options(const char *option, char **algorithm, char **detail)
{
	char	   *sep;
	char	   *endp;
	long		result;

	/*
	 * Check whether the compression specification consists of a bare integer.
	 *
	 * For backward-compatibility, assume "none" if the integer found is zero
	 * and "gzip" otherwise.
	 */
	result = strtol(option, &endp, 10);
	if (*endp == '\0')
	{
		if (result == 0)
		{
			*algorithm = pstrdup("none");
			*detail = NULL;
		}
		else
		{
			*algorithm = pstrdup("gzip");
			*detail = pstrdup(option);
		}
		return;
	}

	/*
	 * Check whether there is a compression detail following the algorithm
	 * name.
	 */
	sep = strchr(option, ':');
	if (sep == NULL)
	{
		*algorithm = pstrdup(option);
		*detail = NULL;
	}
	else
	{
		char	   *alg;

		alg = palloc((sep - option) + 1);
		memcpy(alg, option, sep - option);
		alg[sep - option] = '\0';

		*algorithm = alg;
		*detail = pstrdup(sep + 1);
	}
}
#endif							/* FRONTEND */