libpqxx
The C++ client library for PostgreSQL
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blob.hxx
1/* Binary Large Objects interface.
2 *
3 * Read or write large objects, stored in their own storage on the server.
4 *
5 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/largeobject instead.
6 *
7 * Copyright (c) 2000-2024, Jeroen T. Vermeulen.
8 *
9 * See COPYING for copyright license. If you did not receive a file called
10 * COPYING with this source code, please notify the distributor of this
11 * mistake, or contact the author.
12 */
13#ifndef PQXX_H_BLOB
14#define PQXX_H_BLOB
15
16#if !defined(PQXX_HEADER_PRE)
17# error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
18#endif
19
20#include <cstdint>
21
22#if defined(PQXX_HAVE_PATH)
23# include <filesystem>
24#endif
25
26// C++20: Assume support.
27#if __has_include(<ranges>)
28# include <ranges>
29#endif
30
31// C++20: Assume support.
32#if __has_include(<span>)
33# include <span>
34#endif
35
36#include "pqxx/dbtransaction.hxx"
37
38
39namespace pqxx
40{
54class PQXX_LIBEXPORT blob
55{
56public:
58
62 [[nodiscard]] static oid create(dbtransaction &, oid = 0);
63
65 static void remove(dbtransaction &, oid);
66
68 [[nodiscard]] static blob open_r(dbtransaction &, oid);
69 // Open blob for writing. Any attempt to read from it will fail.
70 [[nodiscard]] static blob open_w(dbtransaction &, oid);
71 // Open blob for reading and/or writing.
72 [[nodiscard]] static blob open_rw(dbtransaction &, oid);
73
75
78 blob() = default;
79
81 blob(blob &&);
83 blob &operator=(blob &&);
84
85 blob(blob const &) = delete;
86 blob &operator=(blob const &) = delete;
87 ~blob();
88
90
96 static constexpr std::size_t chunk_limit = 0x7fffffff;
97
99
107 std::size_t read(bytes &buf, std::size_t size);
108
109#if defined(PQXX_HAVE_SPAN)
111
116 template<std::size_t extent = std::dynamic_extent>
117 std::span<std::byte> read(std::span<std::byte, extent> buf)
118 {
119 return buf.subspan(0, raw_read(std::data(buf), std::size(buf)));
120 }
121#endif // PQXX_HAVE_SPAN
122
123#if defined(PQXX_HAVE_CONCEPTS) && defined(PQXX_HAVE_SPAN)
125
130 template<binary DATA> std::span<std::byte> read(DATA &buf)
131 {
132 return {std::data(buf), raw_read(std::data(buf), std::size(buf))};
133 }
134#else // PQXX_HAVE_CONCEPTS && PQXX_HAVE_SPAN
136
148 template<typename ALLOC> bytes_view read(std::vector<std::byte, ALLOC> &buf)
149 {
150 return {std::data(buf), raw_read(std::data(buf), std::size(buf))};
151 }
152#endif // PQXX_HAVE_CONCEPTS && PQXX_HAVE_SPAN
153
154#if defined(PQXX_HAVE_CONCEPTS)
156
174 template<binary DATA> void write(DATA const &data)
175 {
176 raw_write(std::data(data), std::size(data));
177 }
178#else
180
198 template<typename DATA> void write(DATA const &data)
199 {
200 raw_write(std::data(data), std::size(data));
201 }
202#endif
203
205
211 void resize(std::int64_t size);
212
214 [[nodiscard]] std::int64_t tell() const;
215
217
218 std::int64_t seek_abs(std::int64_t offset = 0);
220
224 std::int64_t seek_rel(std::int64_t offset = 0);
226
230 std::int64_t seek_end(std::int64_t offset = 0);
231
233
236 static oid from_buf(dbtransaction &tx, bytes_view data, oid id = 0);
237
239
241 static void append_from_buf(dbtransaction &tx, bytes_view data, oid id);
242
244 [[nodiscard]] static oid from_file(dbtransaction &, char const path[]);
245
246#if defined(PQXX_HAVE_PATH) && !defined(_WIN32)
248
251 [[nodiscard]] static oid
252 from_file(dbtransaction &tx, std::filesystem::path const &path)
253 {
254 return from_file(tx, path.c_str());
255 }
256#endif
257
259
262 static oid from_file(dbtransaction &, char const path[], oid);
263
264#if defined(PQXX_HAVE_PATH) && !defined(_WIN32)
266
272 static oid
273 from_file(dbtransaction &tx, std::filesystem::path const &path, oid id)
274 {
275 return from_file(tx, path.c_str(), id);
276 }
277#endif
278
280
283 static void to_buf(dbtransaction &, oid, bytes &, std::size_t max_size);
284
286
292 static std::size_t append_to_buf(
293 dbtransaction &tx, oid id, std::int64_t offset, bytes &buf,
294 std::size_t append_max);
295
297 static void to_file(dbtransaction &, oid, char const path[]);
298
299#if defined(PQXX_HAVE_PATH) && !defined(_WIN32)
301
304 static void
305 to_file(dbtransaction &tx, oid id, std::filesystem::path const &path)
306 {
307 to_file(tx, id, path.c_str());
308 }
309#endif
310
312
323 void close();
324
325private:
326 PQXX_PRIVATE blob(connection &conn, int fd) noexcept :
327 m_conn{&conn}, m_fd{fd}
328 {}
329 static PQXX_PRIVATE blob open_internal(dbtransaction &, oid, int);
330 static PQXX_PRIVATE pqxx::internal::pq::PGconn *
331 raw_conn(pqxx::connection *) noexcept;
332 static PQXX_PRIVATE pqxx::internal::pq::PGconn *
333 raw_conn(pqxx::dbtransaction const &) noexcept;
334 static PQXX_PRIVATE std::string errmsg(connection const *);
335 static PQXX_PRIVATE std::string errmsg(dbtransaction const &tx)
336 {
337 return errmsg(&tx.conn());
338 }
339 PQXX_PRIVATE std::string errmsg() const { return errmsg(m_conn); }
340 PQXX_PRIVATE std::int64_t seek(std::int64_t offset, int whence);
341 std::size_t raw_read(std::byte buf[], std::size_t size);
342 void raw_write(std::byte const buf[], std::size_t size);
343
344 connection *m_conn = nullptr;
345 int m_fd = -1;
346};
347} // namespace pqxx
348#endif
Definition blob.hxx:55
void write(DATA const &data)
Write data large object, at the current position.
Definition blob.hxx:198
blob()=default
You can default-construct a blob, but it won't do anything useful.
bytes_view read(std::vector< std::byte, ALLOC > &buf)
Read up to std::size(buf) bytes from the object.
Definition blob.hxx:148
Connection to a database.
Definition connection.hxx:230
Abstract transaction base class: bracket transactions on the database.
Definition dbtransaction.hxx:54
The home of all libpqxx classes, functions, templates, etc.
Definition array.cxx:27
std::vector< std::string_view > to_buf(char *here, char const *end, TYPE... value)
Convert multiple values to strings inside a single buffer.
Definition strconv.hxx:492
std::conditional< has_generic_bytes_char_traits, std::basic_string< std::byte >, std::basic_string< std::byte, byte_char_traits > >::type bytes
Type alias for a container containing bytes.
Definition util.hxx:375
unsigned int oid
PostgreSQL database row identifier.
Definition libpq-forward.hxx:33
std::conditional< has_generic_bytes_char_traits, std::basic_string_view< std::byte >, std::basic_string_view< std::byte, byte_char_traits > >::type bytes_view
Type alias for a view of bytes.
Definition util.hxx:385