1/*-------------------------------------------------------------------------
2 *
3 * pqexpbuffer.h
4 * Declarations/definitions for "PQExpBuffer" functions.
5 *
6 * PQExpBuffer provides an indefinitely-extensible string data type.
7 * It can be used to buffer either ordinary C strings (null-terminated text)
8 * or arbitrary binary data. All storage is allocated with malloc().
9 *
10 * This module is essentially the same as the backend's StringInfo data type,
11 * but it is intended for use in frontend libpq and client applications.
12 * Thus, it does not rely on palloc() nor elog().
13 *
14 * It does rely on vsnprintf(); if configure finds that libc doesn't provide
15 * a usable vsnprintf(), then a copy of our own implementation of it will
16 * be linked into libpq.
17 *
18 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
19 * Portions Copyright (c) 1994, Regents of the University of California
20 *
21 * src/interfaces/libpq/pqexpbuffer.h
22 *
23 *-------------------------------------------------------------------------
24 */
25#ifndef PQEXPBUFFER_H
26#define PQEXPBUFFER_H
27
28/*-------------------------
29 * PQExpBufferData holds information about an extensible string.
30 * data is the current buffer for the string (allocated with malloc).
31 * len is the current string length. There is guaranteed to be
32 * a terminating '\0' at data[len], although this is not very
33 * useful when the string holds binary data rather than text.
34 * maxlen is the allocated size in bytes of 'data', i.e. the maximum
35 * string size (including the terminating '\0' char) that we can
36 * currently store in 'data' without having to reallocate
37 * more space. We must always have maxlen > len.
38 *
39 * An exception occurs if we failed to allocate enough memory for the string
40 * buffer. In that case data points to a statically allocated empty string,
41 * and len = maxlen = 0.
42 *-------------------------
43 */
44typedef struct PQExpBufferData
45{
46 char *data;
47 size_t len;
48 size_t maxlen;
49} PQExpBufferData;
50
51typedef PQExpBufferData *PQExpBuffer;
52
53/*------------------------
54 * Test for a broken (out of memory) PQExpBuffer.
55 * When a buffer is "broken", all operations except resetting or deleting it
56 * are no-ops.
57 *------------------------
58 */
59#define PQExpBufferBroken(str) \
60 ((str) == NULL || (str)->maxlen == 0)
61
62/*------------------------
63 * Same, but for use when using a static or local PQExpBufferData struct.
64 * For that, a null-pointer test is useless and may draw compiler warnings.
65 *------------------------
66 */
67#define PQExpBufferDataBroken(buf) \
68 ((buf).maxlen == 0)
69
70/*------------------------
71 * Initial size of the data buffer in a PQExpBuffer.
72 * NB: this must be large enough to hold error messages that might
73 * be returned by PQrequestCancel().
74 *------------------------
75 */
76#define INITIAL_EXPBUFFER_SIZE 256
77
78/*------------------------
79 * There are two ways to create a PQExpBuffer object initially:
80 *
81 * PQExpBuffer stringptr = createPQExpBuffer();
82 * Both the PQExpBufferData and the data buffer are malloc'd.
83 *
84 * PQExpBufferData string;
85 * initPQExpBuffer(&string);
86 * The data buffer is malloc'd but the PQExpBufferData is presupplied.
87 * This is appropriate if the PQExpBufferData is a field of another
88 * struct.
89 *-------------------------
90 */
91
92/*------------------------
93 * createPQExpBuffer
94 * Create an empty 'PQExpBufferData' & return a pointer to it.
95 */
96extern PQExpBuffer createPQExpBuffer(void);
97
98/*------------------------
99 * initPQExpBuffer
100 * Initialize a PQExpBufferData struct (with previously undefined contents)
101 * to describe an empty string.
102 */
103extern void initPQExpBuffer(PQExpBuffer str);
104
105/*------------------------
106 * To destroy a PQExpBuffer, use either:
107 *
108 * destroyPQExpBuffer(str);
109 * free()s both the data buffer and the PQExpBufferData.
110 * This is the inverse of createPQExpBuffer().
111 *
112 * termPQExpBuffer(str)
113 * free()s the data buffer but not the PQExpBufferData itself.
114 * This is the inverse of initPQExpBuffer().
115 *
116 * NOTE: some routines build up a string using PQExpBuffer, and then
117 * release the PQExpBufferData but return the data string itself to their
118 * caller. At that point the data string looks like a plain malloc'd
119 * string.
120 */
121extern void destroyPQExpBuffer(PQExpBuffer str);
122extern void termPQExpBuffer(PQExpBuffer str);
123
124/*------------------------
125 * resetPQExpBuffer
126 * Reset a PQExpBuffer to empty
127 *
128 * Note: if possible, a "broken" PQExpBuffer is returned to normal.
129 */
130extern void resetPQExpBuffer(PQExpBuffer str);
131
132/*------------------------
133 * enlargePQExpBuffer
134 * Make sure there is enough space for 'needed' more bytes in the buffer
135 * ('needed' does not include the terminating null).
136 *
137 * Returns 1 if OK, 0 if failed to enlarge buffer. (In the latter case
138 * the buffer is left in "broken" state.)
139 */
140extern int enlargePQExpBuffer(PQExpBuffer str, size_t needed);
141
142/*------------------------
143 * printfPQExpBuffer
144 * Format text data under the control of fmt (an sprintf-like format string)
145 * and insert it into str. More space is allocated to str if necessary.
146 * This is a convenience routine that does the same thing as
147 * resetPQExpBuffer() followed by appendPQExpBuffer().
148 */
149extern void printfPQExpBuffer(PQExpBuffer str, const char *fmt,...) pg_attribute_printf(2, 3);
150
151/*------------------------
152 * appendPQExpBuffer
153 * Format text data under the control of fmt (an sprintf-like format string)
154 * and append it to whatever is already in str. More space is allocated
155 * to str if necessary. This is sort of like a combination of sprintf and
156 * strcat.
157 */
158extern void appendPQExpBuffer(PQExpBuffer str, const char *fmt,...) pg_attribute_printf(2, 3);
159
160/*------------------------
161 * appendPQExpBufferStr
162 * Append the given string to a PQExpBuffer, allocating more space
163 * if necessary.
164 */
165extern void appendPQExpBufferStr(PQExpBuffer str, const char *data);
166
167/*------------------------
168 * appendPQExpBufferChar
169 * Append a single byte to str.
170 * Like appendPQExpBuffer(str, "%c", ch) but much faster.
171 */
172extern void appendPQExpBufferChar(PQExpBuffer str, char ch);
173
174/*------------------------
175 * appendBinaryPQExpBuffer
176 * Append arbitrary binary data to a PQExpBuffer, allocating more space
177 * if necessary.
178 */
179extern void appendBinaryPQExpBuffer(PQExpBuffer str,
180 const char *data, size_t datalen);
181
182#endif /* PQEXPBUFFER_H */
183