PostgreSQL Source Code  git master
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros
stringinfo.h
Go to the documentation of this file.
1 /*-------------------------------------------------------------------------
2  *
3  * stringinfo.h
4  * Declarations/definitions for "StringInfo" functions.
5  *
6  * StringInfo 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 palloc().
9  *
10  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
11  * Portions Copyright (c) 1994, Regents of the University of California
12  *
13  * src/include/lib/stringinfo.h
14  *
15  *-------------------------------------------------------------------------
16  */
17 #ifndef STRINGINFO_H
18 #define STRINGINFO_H
19 
20 /*-------------------------
21  * StringInfoData holds information about an extensible string.
22  * data is the current buffer for the string (allocated with palloc).
23  * len is the current string length. There is guaranteed to be
24  * a terminating '\0' at data[len], although this is not very
25  * useful when the string holds binary data rather than text.
26  * maxlen is the allocated size in bytes of 'data', i.e. the maximum
27  * string size (including the terminating '\0' char) that we can
28  * currently store in 'data' without having to reallocate
29  * more space. We must always have maxlen > len.
30  * cursor is initialized to zero by makeStringInfo or initStringInfo,
31  * but is not otherwise touched by the stringinfo.c routines.
32  * Some routines use it to scan through a StringInfo.
33  *-------------------------
34  */
35 typedef struct StringInfoData
36 {
37  char *data;
38  int len;
39  int maxlen;
40  int cursor;
42 
44 
45 
46 /*------------------------
47  * There are two ways to create a StringInfo object initially:
48  *
49  * StringInfo stringptr = makeStringInfo();
50  * Both the StringInfoData and the data buffer are palloc'd.
51  *
52  * StringInfoData string;
53  * initStringInfo(&string);
54  * The data buffer is palloc'd but the StringInfoData is just local.
55  * This is the easiest approach for a StringInfo object that will
56  * only live as long as the current routine.
57  *
58  * To destroy a StringInfo, pfree() the data buffer, and then pfree() the
59  * StringInfoData if it was palloc'd. There's no special support for this.
60  *
61  * NOTE: some routines build up a string using StringInfo, and then
62  * release the StringInfoData but return the data string itself to their
63  * caller. At that point the data string looks like a plain palloc'd
64  * string.
65  *-------------------------
66  */
67 
68 /*------------------------
69  * makeStringInfo
70  * Create an empty 'StringInfoData' & return a pointer to it.
71  */
72 extern StringInfo makeStringInfo(void);
73 
74 /*------------------------
75  * initStringInfo
76  * Initialize a StringInfoData struct (with previously undefined contents)
77  * to describe an empty string.
78  */
79 extern void initStringInfo(StringInfo str);
80 
81 /*------------------------
82  * resetStringInfo
83  * Clears the current content of the StringInfo, if any. The
84  * StringInfo remains valid.
85  */
86 extern void resetStringInfo(StringInfo str);
87 
88 /*------------------------
89  * appendStringInfo
90  * Format text data under the control of fmt (an sprintf-style format string)
91  * and append it to whatever is already in str. More space is allocated
92  * to str if necessary. This is sort of like a combination of sprintf and
93  * strcat.
94  */
95 extern void appendStringInfo(StringInfo str, const char *fmt,...) pg_attribute_printf(2, 3);
96 
97 /*------------------------
98  * appendStringInfoVA
99  * Attempt to format text data under the control of fmt (an sprintf-style
100  * format string) and append it to whatever is already in str. If successful
101  * return zero; if not (because there's not enough space), return an estimate
102  * of the space needed, without modifying str. Typically the caller should
103  * pass the return value to enlargeStringInfo() before trying again; see
104  * appendStringInfo for standard usage pattern.
105  */
106 extern int appendStringInfoVA(StringInfo str, const char *fmt, va_list args) pg_attribute_printf(2, 0);
107 
108 /*------------------------
109  * appendStringInfoString
110  * Append a null-terminated string to str.
111  * Like appendStringInfo(str, "%s", s) but faster.
112  */
113 extern void appendStringInfoString(StringInfo str, const char *s);
114 
115 /*------------------------
116  * appendStringInfoChar
117  * Append a single byte to str.
118  * Like appendStringInfo(str, "%c", ch) but much faster.
119  */
120 extern void appendStringInfoChar(StringInfo str, char ch);
121 
122 /*------------------------
123  * appendStringInfoCharMacro
124  * As above, but a macro for even more speed where it matters.
125  * Caution: str argument will be evaluated multiple times.
126  */
127 #define appendStringInfoCharMacro(str,ch) \
128  (((str)->len + 1 >= (str)->maxlen) ? \
129  appendStringInfoChar(str, ch) : \
130  (void)((str)->data[(str)->len] = (ch), (str)->data[++(str)->len] = '\0'))
131 
132 /*------------------------
133  * appendStringInfoSpaces
134  * Append a given number of spaces to str.
135  */
136 extern void appendStringInfoSpaces(StringInfo str, int count);
137 
138 /*------------------------
139  * appendBinaryStringInfo
140  * Append arbitrary binary data to a StringInfo, allocating more space
141  * if necessary.
142  */
143 extern void appendBinaryStringInfo(StringInfo str,
144  const char *data, int datalen);
145 
146 /*------------------------
147  * enlargeStringInfo
148  * Make sure a StringInfo's buffer can hold at least 'needed' more bytes.
149  */
150 extern void enlargeStringInfo(StringInfo str, int needed);
151 
152 #endif /* STRINGINFO_H */
struct StringInfoData StringInfoData
void int appendStringInfoVA(StringInfo str, const char *fmt, va_list args) pg_attribute_printf(2
StringInfoData * StringInfo
Definition: stringinfo.h:43
void appendStringInfoSpaces(StringInfo str, int count)
Definition: stringinfo.c:187
void resetStringInfo(StringInfo str)
Definition: stringinfo.c:62
#define pg_attribute_printf(f, a)
Definition: c.h:639
void appendStringInfo(StringInfo str, const char *fmt,...) pg_attribute_printf(2
void int void appendStringInfoString(StringInfo str, const char *s)
Definition: stringinfo.c:157
void appendBinaryStringInfo(StringInfo str, const char *data, int datalen)
Definition: stringinfo.c:208
void appendStringInfoChar(StringInfo str, char ch)
Definition: stringinfo.c:169
void enlargeStringInfo(StringInfo str, int needed)
Definition: stringinfo.c:245
StringInfo makeStringInfo(void)
Definition: stringinfo.c:28
void initStringInfo(StringInfo str)
Definition: stringinfo.c:46