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astreamer.h
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1 /*-------------------------------------------------------------------------
2  *
3  * astreamer.h
4  *
5  * The "archive streamer" interface is intended to allow frontend code
6  * to stream from possibly-compressed archive files from any source and
7  * perform arbitrary actions based on the contents of those archives.
8  * Archive streamers are intended to be composable, and most tasks will
9  * require two or more archive streamers to complete. For instance,
10  * if the input is an uncompressed tar stream, a tar parser astreamer
11  * could be used to interpret it, and then an extractor astreamer could
12  * be used to write each archive member out to a file.
13  *
14  * In general, each archive streamer is relatively free to take whatever
15  * action it desires in the stream of chunks provided by the caller. It
16  * may do something simple, like write the archive to a file, perhaps after
17  * compressing it, but it can also do more complicated things, like
18  * annotating the byte stream to indicate which parts of the data
19  * correspond to tar headers or trailing padding, vs. which parts are
20  * payload data. A subsequent astreamer may use this information to
21  * make further decisions about how to process the data; for example,
22  * it might choose to modify the archive contents.
23  *
24  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
25  *
26  * IDENTIFICATION
27  * src/bin/pg_basebackup/astreamer.h
28  *-------------------------------------------------------------------------
29  */
30 
31 #ifndef ASTREAMER_H
32 #define ASTREAMER_H
33 
34 #include "common/compression.h"
35 #include "lib/stringinfo.h"
36 #include "pqexpbuffer.h"
37 
38 struct astreamer;
39 struct astreamer_ops;
40 typedef struct astreamer astreamer;
41 typedef struct astreamer_ops astreamer_ops;
42 
43 /*
44  * Each chunk of archive data passed to a astreamer is classified into one
45  * of these categories. When data is initially passed to an archive streamer,
46  * each chunk will be categorized as ASTREAMER_UNKNOWN, and the chunks can
47  * be of whatever size the caller finds convenient.
48  *
49  * If the archive is parsed (e.g. see astreamer_tar_parser_new()), then all
50  * chunks should be labelled as one of the other types listed here. In
51  * addition, there should be exactly one ASTREAMER_MEMBER_HEADER chunk and
52  * exactly one ASTREAMER_MEMBER_TRAILER chunk per archive member, even if
53  * that means a zero-length call. There can be any number of
54  * ASTREAMER_MEMBER_CONTENTS chunks in between those calls. There
55  * should exactly ASTREAMER_ARCHIVE_TRAILER chunk, and it should follow the
56  * last ASTREAMER_MEMBER_TRAILER chunk.
57  *
58  * In theory, we could need other classifications here, such as a way of
59  * indicating an archive header, but the "tar" format doesn't need anything
60  * else, so for the time being there's no point.
61  */
62 typedef enum
63 {
70 
71 /*
72  * Each chunk of data that is classified as ASTREAMER_MEMBER_HEADER,
73  * ASTREAMER_MEMBER_CONTENTS, or ASTREAMER_MEMBER_TRAILER should also
74  * pass a pointer to an instance of this struct. The details are expected
75  * to be present in the archive header and used to fill the struct, after
76  * which all subsequent calls for the same archive member are expected to
77  * pass the same details.
78  */
79 typedef struct
80 {
81  char pathname[MAXPGPATH];
83  mode_t mode;
87  bool is_link;
88  char linktarget[MAXPGPATH];
90 
91 /*
92  * Generally, each type of astreamer will define its own struct, but the
93  * first element should be 'astreamer base'. A astreamer that does not
94  * require any additional private data could use this structure directly.
95  *
96  * bbs_ops is a pointer to the astreamer_ops object which contains the
97  * function pointers appropriate to this type of astreamer.
98  *
99  * bbs_next is a pointer to the successor astreamer, for those types of
100  * astreamer which forward data to a successor. It need not be used and
101  * should be set to NULL when not relevant.
102  *
103  * bbs_buffer is a buffer for accumulating data for temporary storage. Each
104  * type of astreamer makes its own decisions about whether and how to use
105  * this buffer.
106  */
107 struct astreamer
108 {
112 };
113 
114 /*
115  * There are three callbacks for a astreamer. The 'content' callback is
116  * called repeatedly, as described in the astreamer_archive_context comments.
117  * Then, the 'finalize' callback is called once at the end, to give the
118  * astreamer a chance to perform cleanup such as closing files. Finally,
119  * because this code is running in a frontend environment where, as of this
120  * writing, there are no memory contexts, the 'free' callback is called to
121  * release memory. These callbacks should always be invoked using the static
122  * inline functions defined below.
123  */
125 {
126  void (*content) (astreamer *streamer, astreamer_member *member,
127  const char *data, int len,
129  void (*finalize) (astreamer *streamer);
130  void (*free) (astreamer *streamer);
131 };
132 
133 /* Send some content to a astreamer. */
134 static inline void
136  const char *data, int len,
138 {
139  Assert(streamer != NULL);
140  streamer->bbs_ops->content(streamer, member, data, len, context);
141 }
142 
143 /* Finalize a astreamer. */
144 static inline void
146 {
147  Assert(streamer != NULL);
148  streamer->bbs_ops->finalize(streamer);
149 }
150 
151 /* Free a astreamer. */
152 static inline void
154 {
155  Assert(streamer != NULL);
156  streamer->bbs_ops->free(streamer);
157 }
158 
159 /*
160  * This is a convenience method for use when implementing a astreamer; it is
161  * not for use by outside callers. It adds the amount of data specified by
162  * 'nbytes' to the astreamer's buffer and adjusts '*len' and '*data'
163  * accordingly.
164  */
165 static inline void
166 astreamer_buffer_bytes(astreamer *streamer, const char **data, int *len,
167  int nbytes)
168 {
169  Assert(nbytes <= *len);
170 
171  appendBinaryStringInfo(&streamer->bbs_buffer, *data, nbytes);
172  *len -= nbytes;
173  *data += nbytes;
174 }
175 
176 /*
177  * This is a convenience method for use when implementing a astreamer; it is
178  * not for use by outsider callers. It attempts to add enough data to the
179  * astreamer's buffer to reach a length of target_bytes and adjusts '*len'
180  * and '*data' accordingly. It returns true if the target length has been
181  * reached and false otherwise.
182  */
183 static inline bool
184 astreamer_buffer_until(astreamer *streamer, const char **data, int *len,
185  int target_bytes)
186 {
187  int buflen = streamer->bbs_buffer.len;
188 
189  if (buflen >= target_bytes)
190  {
191  /* Target length already reached; nothing to do. */
192  return true;
193  }
194 
195  if (buflen + *len < target_bytes)
196  {
197  /* Not enough data to reach target length; buffer all of it. */
198  astreamer_buffer_bytes(streamer, data, len, *len);
199  return false;
200  }
201 
202  /* Buffer just enough to reach the target length. */
203  astreamer_buffer_bytes(streamer, data, len, target_bytes - buflen);
204  return true;
205 }
206 
207 /*
208  * Functions for creating astreamer objects of various types. See the header
209  * comments for each of these functions for details.
210  */
211 extern astreamer *astreamer_plain_writer_new(char *pathname, FILE *file);
212 extern astreamer *astreamer_gzip_writer_new(char *pathname, FILE *file,
213  pg_compress_specification *compress);
214 extern astreamer *astreamer_extractor_new(const char *basepath,
215  const char *(*link_map) (const char *),
216  void (*report_output_file) (const char *));
217 
220  pg_compress_specification *compress);
223  pg_compress_specification *compress);
228 
229 #endif
static void astreamer_free(astreamer *streamer)
Definition: astreamer.h:153
static void astreamer_content(astreamer *streamer, astreamer_member *member, const char *data, int len, astreamer_archive_context context)
Definition: astreamer.h:135
astreamer * astreamer_plain_writer_new(char *pathname, FILE *file)
static bool astreamer_buffer_until(astreamer *streamer, const char **data, int *len, int target_bytes)
Definition: astreamer.h:184
astreamer * astreamer_zstd_compressor_new(astreamer *next, pg_compress_specification *compress)
astreamer * astreamer_gzip_decompressor_new(astreamer *next)
astreamer * astreamer_tar_parser_new(astreamer *next)
Definition: astreamer_tar.c:93
astreamer * astreamer_extractor_new(const char *basepath, const char *(*link_map)(const char *), void(*report_output_file)(const char *))
astreamer * astreamer_lz4_decompressor_new(astreamer *next)
astreamer * astreamer_tar_archiver_new(astreamer *next)
astreamer * astreamer_tar_terminator_new(astreamer *next)
astreamer * astreamer_lz4_compressor_new(astreamer *next, pg_compress_specification *compress)
Definition: astreamer_lz4.c:72
astreamer * astreamer_gzip_writer_new(char *pathname, FILE *file, pg_compress_specification *compress)
static void astreamer_finalize(astreamer *streamer)
Definition: astreamer.h:145
astreamer * astreamer_zstd_decompressor_new(astreamer *next)
astreamer_archive_context
Definition: astreamer.h:63
@ ASTREAMER_MEMBER_HEADER
Definition: astreamer.h:65
@ ASTREAMER_MEMBER_CONTENTS
Definition: astreamer.h:66
@ ASTREAMER_MEMBER_TRAILER
Definition: astreamer.h:67
@ ASTREAMER_ARCHIVE_TRAILER
Definition: astreamer.h:68
@ ASTREAMER_UNKNOWN
Definition: astreamer.h:64
static void astreamer_buffer_bytes(astreamer *streamer, const char **data, int *len, int nbytes)
Definition: astreamer.h:166
static int32 next
Definition: blutils.c:219
#define Assert(condition)
Definition: c.h:863
#define MAXPGPATH
const void size_t len
const void * data
tree context
Definition: radixtree.h:1835
void appendBinaryStringInfo(StringInfo str, const void *data, int datalen)
Definition: stringinfo.c:230
pgoff_t size
Definition: astreamer.h:82
void(* content)(astreamer *streamer, astreamer_member *member, const char *data, int len, astreamer_archive_context context)
Definition: astreamer.h:126
void(* finalize)(astreamer *streamer)
Definition: astreamer.h:129
void(* free)(astreamer *streamer)
Definition: astreamer.h:130
StringInfoData bbs_buffer
Definition: astreamer.h:111
const astreamer_ops * bbs_ops
Definition: astreamer.h:109
astreamer * bbs_next
Definition: astreamer.h:110
int gid_t
Definition: win32_port.h:245
#define pgoff_t
Definition: win32_port.h:207
int uid_t
Definition: win32_port.h:244