PostgreSQL Source Code: src/bin/pg_combinebackup/backup_label.c Source File

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backup_label.c
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1/*-------------------------------------------------------------------------
2 *
3 * Read and manipulate backup label files
4 *
5 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
6 * Portions Copyright (c) 1994, Regents of the University of California
7 *
8 * src/bin/pg_combinebackup/backup_label.c
9 *
10 *-------------------------------------------------------------------------
11 */
12#include "postgres_fe.h"
13
14#include <unistd.h>
15
16#include "access/xlogdefs.h"
17#include "backup_label.h"
18#include "common/file_perm.h"
19#include "common/logging.h"
20#include "write_manifest.h"
21
22static int get_eol_offset(StringInfo buf);
23static bool line_starts_with(char *s, char *e, char *match, char **sout);
24static bool parse_lsn(char *s, char *e, XLogRecPtr *lsn, char **c);
25static bool parse_tli(char *s, char *e, TimeLineID *tli);
26
27/*
28 * Parse a backup label file, starting at buf->cursor.
29 *
30 * We expect to find a START WAL LOCATION line, followed by a LSN, followed
31 * by a space; the resulting LSN is stored into *start_lsn.
32 *
33 * We expect to find a START TIMELINE line, followed by a TLI, followed by
34 * a newline; the resulting TLI is stored into *start_tli.
35 *
36 * We expect to find either both INCREMENTAL FROM LSN and INCREMENTAL FROM TLI
37 * or neither. If these are found, they should be followed by an LSN or TLI
38 * respectively and then by a newline, and the values will be stored into
39 * *previous_lsn and *previous_tli, respectively.
40 *
41 * Other lines in the provided backup_label data are ignored. filename is used
42 * for error reporting; errors are fatal.
43 */
44void
45 parse_backup_label(char *filename, StringInfo buf,
46 TimeLineID *start_tli, XLogRecPtr *start_lsn,
47 TimeLineID *previous_tli, XLogRecPtr *previous_lsn)
48{
49 int found = 0;
50
51 *start_tli = 0;
52 *start_lsn = InvalidXLogRecPtr;
53 *previous_tli = 0;
54 *previous_lsn = InvalidXLogRecPtr;
55
56 while (buf->cursor < buf->len)
57 {
58 char *s = &buf->data[buf->cursor];
59 int eo = get_eol_offset(buf);
60 char *e = &buf->data[eo];
61 char *c;
62
63 if (line_starts_with(s, e, "START WAL LOCATION: ", &s))
64 {
65 if (!parse_lsn(s, e, start_lsn, &c))
66 pg_fatal("%s: could not parse %s",
67 filename, "START WAL LOCATION");
68 if (c >= e || *c != ' ')
69 pg_fatal("%s: improper terminator for %s",
70 filename, "START WAL LOCATION");
71 found |= 1;
72 }
73 else if (line_starts_with(s, e, "START TIMELINE: ", &s))
74 {
75 if (!parse_tli(s, e, start_tli))
76 pg_fatal("%s: could not parse TLI for %s",
77 filename, "START TIMELINE");
78 if (*start_tli == 0)
79 pg_fatal("%s: invalid TLI", filename);
80 found |= 2;
81 }
82 else if (line_starts_with(s, e, "INCREMENTAL FROM LSN: ", &s))
83 {
84 if (!parse_lsn(s, e, previous_lsn, &c))
85 pg_fatal("%s: could not parse %s",
86 filename, "INCREMENTAL FROM LSN");
87 if (c >= e || *c != '\n')
88 pg_fatal("%s: improper terminator for %s",
89 filename, "INCREMENTAL FROM LSN");
90 found |= 4;
91 }
92 else if (line_starts_with(s, e, "INCREMENTAL FROM TLI: ", &s))
93 {
94 if (!parse_tli(s, e, previous_tli))
95 pg_fatal("%s: could not parse %s",
96 filename, "INCREMENTAL FROM TLI");
97 if (*previous_tli == 0)
98 pg_fatal("%s: invalid TLI", filename);
99 found |= 8;
100 }
101
102 buf->cursor = eo;
103 }
104
105 if ((found & 1) == 0)
106 pg_fatal("%s: could not find %s", filename, "START WAL LOCATION");
107 if ((found & 2) == 0)
108 pg_fatal("%s: could not find %s", filename, "START TIMELINE");
109 if ((found & 4) != 0 && (found & 8) == 0)
110 pg_fatal("%s: %s requires %s", filename,
111 "INCREMENTAL FROM LSN", "INCREMENTAL FROM TLI");
112 if ((found & 8) != 0 && (found & 4) == 0)
113 pg_fatal("%s: %s requires %s", filename,
114 "INCREMENTAL FROM TLI", "INCREMENTAL FROM LSN");
115}
116
117/*
118 * Write a backup label file to the output directory.
119 *
120 * This will be identical to the provided backup_label file, except that the
121 * INCREMENTAL FROM LSN and INCREMENTAL FROM TLI lines will be omitted.
122 *
123 * The new file will be checksummed using the specified algorithm. If
124 * mwriter != NULL, it will be added to the manifest.
125 */
126void
127 write_backup_label(char *output_directory, StringInfo buf,
128 pg_checksum_type checksum_type, manifest_writer *mwriter)
129{
130 char output_filename[MAXPGPATH];
131 int output_fd;
132 pg_checksum_context checksum_ctx;
133 uint8 checksum_payload[PG_CHECKSUM_MAX_LENGTH];
134 int checksum_length;
135
136 pg_checksum_init(&checksum_ctx, checksum_type);
137
138 snprintf(output_filename, MAXPGPATH, "%s/backup_label", output_directory);
139
140 if ((output_fd = open(output_filename,
141 O_WRONLY | O_CREAT | O_EXCL | PG_BINARY,
142 pg_file_create_mode)) < 0)
143 pg_fatal("could not open file \"%s\": %m", output_filename);
144
145 while (buf->cursor < buf->len)
146 {
147 char *s = &buf->data[buf->cursor];
148 int eo = get_eol_offset(buf);
149 char *e = &buf->data[eo];
150
151 if (!line_starts_with(s, e, "INCREMENTAL FROM LSN: ", NULL) &&
152 !line_starts_with(s, e, "INCREMENTAL FROM TLI: ", NULL))
153 {
154 ssize_t wb;
155
156 wb = write(output_fd, s, e - s);
157 if (wb != e - s)
158 {
159 if (wb < 0)
160 pg_fatal("could not write file \"%s\": %m", output_filename);
161 else
162 pg_fatal("could not write file \"%s\": wrote %d of %d",
163 output_filename, (int) wb, (int) (e - s));
164 }
165 if (pg_checksum_update(&checksum_ctx, (uint8 *) s, e - s) < 0)
166 pg_fatal("could not update checksum of file \"%s\"",
167 output_filename);
168 }
169
170 buf->cursor = eo;
171 }
172
173 if (close(output_fd) != 0)
174 pg_fatal("could not close file \"%s\": %m", output_filename);
175
176 checksum_length = pg_checksum_final(&checksum_ctx, checksum_payload);
177
178 if (mwriter != NULL)
179 {
180 struct stat sb;
181
182 /*
183 * We could track the length ourselves, but must stat() to get the
184 * mtime.
185 */
186 if (stat(output_filename, &sb) < 0)
187 pg_fatal("could not stat file \"%s\": %m", output_filename);
188 add_file_to_manifest(mwriter, "backup_label", sb.st_size,
189 sb.st_mtime, checksum_type,
190 checksum_length, checksum_payload);
191 }
192}
193
194/*
195 * Return the offset at which the next line in the buffer starts, or there
196 * is none, the offset at which the buffer ends.
197 *
198 * The search begins at buf->cursor.
199 */
200static int
201 get_eol_offset(StringInfo buf)
202{
203 int eo = buf->cursor;
204
205 while (eo < buf->len)
206 {
207 if (buf->data[eo] == '\n')
208 return eo + 1;
209 ++eo;
210 }
211
212 return eo;
213}
214
215/*
216 * Test whether the line that runs from s to e (inclusive of *s, but not
217 * inclusive of *e) starts with the match string provided, and return true
218 * or false according to whether or not this is the case.
219 *
220 * If the function returns true and if *sout != NULL, stores a pointer to the
221 * byte following the match into *sout.
222 */
223static bool
224 line_starts_with(char *s, char *e, char *match, char **sout)
225{
226 while (s < e && *match != '0円' && *s == *match)
227 ++s, ++match;
228
229 if (*match == '0円' && sout != NULL)
230 *sout = s;
231
232 return (*match == '0円');
233}
234
235/*
236 * Parse an LSN starting at s and not stopping at or before e. The return value
237 * is true on success and otherwise false. On success, stores the result into
238 * *lsn and sets *c to the first character that is not part of the LSN.
239 */
240static bool
241 parse_lsn(char *s, char *e, XLogRecPtr *lsn, char **c)
242{
243 char save = *e;
244 int nchars;
245 bool success;
246 unsigned hi;
247 unsigned lo;
248
249 *e = '0円';
250 success = (sscanf(s, "%X/%08X%n", &hi, &lo, &nchars) == 2);
251 *e = save;
252
253 if (success)
254 {
255 *lsn = ((XLogRecPtr) hi) << 32 | (XLogRecPtr) lo;
256 *c = s + nchars;
257 }
258
259 return success;
260}
261
262/*
263 * Parse a TLI starting at s and stopping at or before e. The return value is
264 * true on success and otherwise false. On success, stores the result into
265 * *tli. If the first character that is not part of the TLI is anything other
266 * than a newline, that is deemed a failure.
267 */
268static bool
269 parse_tli(char *s, char *e, TimeLineID *tli)
270{
271 char save = *e;
272 int nchars;
273 bool success;
274
275 *e = '0円';
276 success = (sscanf(s, "%u%n", tli, &nchars) == 1);
277 *e = save;
278
279 if (success && s[nchars] != '\n')
280 success = false;
281
282 return success;
283}
static int get_eol_offset(StringInfo buf)
Definition: backup_label.c:201
void parse_backup_label(char *filename, StringInfo buf, TimeLineID *start_tli, XLogRecPtr *start_lsn, TimeLineID *previous_tli, XLogRecPtr *previous_lsn)
Definition: backup_label.c:45
static bool parse_lsn(char *s, char *e, XLogRecPtr *lsn, char **c)
Definition: backup_label.c:241
static bool line_starts_with(char *s, char *e, char *match, char **sout)
Definition: backup_label.c:224
void write_backup_label(char *output_directory, StringInfo buf, pg_checksum_type checksum_type, manifest_writer *mwriter)
Definition: backup_label.c:127
static bool parse_tli(char *s, char *e, TimeLineID *tli)
Definition: backup_label.c:269
uint8_t uint8
Definition: c.h:536
#define PG_BINARY
Definition: c.h:1272
int pg_checksum_final(pg_checksum_context *context, uint8 *output)
int pg_checksum_update(pg_checksum_context *context, const uint8 *input, size_t len)
int pg_checksum_init(pg_checksum_context *context, pg_checksum_type type)
#define PG_CHECKSUM_MAX_LENGTH
pg_checksum_type
char * output_filename
Definition: ecpg.c:24
int pg_file_create_mode
Definition: file_perm.c:19
static bool success
Definition: initdb.c:187
#define close(a)
Definition: win32.h:12
#define write(a, b, c)
Definition: win32.h:14
#define pg_fatal(...)
#define MAXPGPATH
const void size_t len
static char * filename
Definition: pg_dumpall.c:120
static char * buf
Definition: pg_test_fsync.c:72
#define snprintf
Definition: port.h:239
c
char * c
Definition: preproc-cursor.c:31
e
e
Definition: preproc-init.c:82
Definition: write_manifest.c:28
Definition: win32_port.h:255
__time64_t st_mtime
Definition: win32_port.h:265
__int64 st_size
Definition: win32_port.h:263
#define stat
Definition: win32_port.h:274
void add_file_to_manifest(manifest_writer *mwriter, const char *manifest_path, uint64 size, time_t mtime, pg_checksum_type checksum_type, int checksum_length, uint8 *checksum_payload)
Definition: write_manifest.c:76
uint64 XLogRecPtr
Definition: xlogdefs.h:21
#define InvalidXLogRecPtr
Definition: xlogdefs.h:28
uint32 TimeLineID
Definition: xlogdefs.h:62

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