Current File : //usr/include/pgsql/internal/pqexpbuffer.h
/*-------------------------------------------------------------------------
*
* pqexpbuffer.h
* Declarations/definitions for "PQExpBuffer" functions.
*
* PQExpBuffer provides an indefinitely-extensible string data type.
* It can be used to buffer either ordinary C strings (null-terminated text)
* or arbitrary binary data. All storage is allocated with malloc().
*
* This module is essentially the same as the backend's StringInfo data type,
* but it is intended for use in frontend libpq and client applications.
* Thus, it does not rely on palloc() nor elog().
*
* It does rely on vsnprintf(); if configure finds that libc doesn't provide
* a usable vsnprintf(), then a copy of our own implementation of it will
* be linked into libpq.
*
* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/interfaces/libpq/pqexpbuffer.h
*
*-------------------------------------------------------------------------
*/
#ifndef PQEXPBUFFER_H
#define PQEXPBUFFER_H
/*-------------------------
* PQExpBufferData holds information about an extensible string.
* data is the current buffer for the string (allocated with malloc).
* len is the current string length. There is guaranteed to be
* a terminating '\0' at data[len], although this is not very
* useful when the string holds binary data rather than text.
* maxlen is the allocated size in bytes of 'data', i.e. the maximum
* string size (including the terminating '\0' char) that we can
* currently store in 'data' without having to reallocate
* more space. We must always have maxlen > len.
*
* An exception occurs if we failed to allocate enough memory for the string
* buffer. In that case data points to a statically allocated empty string,
* and len = maxlen = 0.
*-------------------------
*/
typedef struct PQExpBufferData
{
char *data;
size_t len;
size_t maxlen;
} PQExpBufferData;
typedef PQExpBufferData *PQExpBuffer;
/*------------------------
* Test for a broken (out of memory) PQExpBuffer.
* When a buffer is "broken", all operations except resetting or deleting it
* are no-ops.
*------------------------
*/
#define PQExpBufferBroken(str) \
((str) == NULL || (str)->maxlen == 0)
/*------------------------
* Same, but for use when using a static or local PQExpBufferData struct.
* For that, a null-pointer test is useless and may draw compiler warnings.
*------------------------
*/
#define PQExpBufferDataBroken(buf) \
((buf).maxlen == 0)
/*------------------------
* Initial size of the data buffer in a PQExpBuffer.
* NB: this must be large enough to hold error messages that might
* be returned by PQrequestCancel().
*------------------------
*/
#define INITIAL_EXPBUFFER_SIZE 256
/*------------------------
* There are two ways to create a PQExpBuffer object initially:
*
* PQExpBuffer stringptr = createPQExpBuffer();
* Both the PQExpBufferData and the data buffer are malloc'd.
*
* PQExpBufferData string;
* initPQExpBuffer(&string);
* The data buffer is malloc'd but the PQExpBufferData is presupplied.
* This is appropriate if the PQExpBufferData is a field of another
* struct.
*-------------------------
*/
/*------------------------
* createPQExpBuffer
* Create an empty 'PQExpBufferData' & return a pointer to it.
*/
extern PQExpBuffer createPQExpBuffer(void);
/*------------------------
* initPQExpBuffer
* Initialize a PQExpBufferData struct (with previously undefined contents)
* to describe an empty string.
*/
extern void initPQExpBuffer(PQExpBuffer str);
/*------------------------
* To destroy a PQExpBuffer, use either:
*
* destroyPQExpBuffer(str);
* free()s both the data buffer and the PQExpBufferData.
* This is the inverse of createPQExpBuffer().
*
* termPQExpBuffer(str)
* free()s the data buffer but not the PQExpBufferData itself.
* This is the inverse of initPQExpBuffer().
*
* NOTE: some routines build up a string using PQExpBuffer, and then
* release the PQExpBufferData but return the data string itself to their
* caller. At that point the data string looks like a plain malloc'd
* string.
*/
extern void destroyPQExpBuffer(PQExpBuffer str);
extern void termPQExpBuffer(PQExpBuffer str);
/*------------------------
* resetPQExpBuffer
* Reset a PQExpBuffer to empty
*
* Note: if possible, a "broken" PQExpBuffer is returned to normal.
*/
extern void resetPQExpBuffer(PQExpBuffer str);
/*------------------------
* enlargePQExpBuffer
* Make sure there is enough space for 'needed' more bytes in the buffer
* ('needed' does not include the terminating null).
*
* Returns 1 if OK, 0 if failed to enlarge buffer. (In the latter case
* the buffer is left in "broken" state.)
*/
extern int enlargePQExpBuffer(PQExpBuffer str, size_t needed);
/*------------------------
* printfPQExpBuffer
* Format text data under the control of fmt (an sprintf-like format string)
* and insert it into str. More space is allocated to str if necessary.
* This is a convenience routine that does the same thing as
* resetPQExpBuffer() followed by appendPQExpBuffer().
*/
extern void printfPQExpBuffer(PQExpBuffer str, const char *fmt,...) pg_attribute_printf(2, 3);
/*------------------------
* appendPQExpBuffer
* Format text data under the control of fmt (an sprintf-like format string)
* and append it to whatever is already in str. More space is allocated
* to str if necessary. This is sort of like a combination of sprintf and
* strcat.
*/
extern void appendPQExpBuffer(PQExpBuffer str, const char *fmt,...) pg_attribute_printf(2, 3);
/*------------------------
* appendPQExpBufferStr
* Append the given string to a PQExpBuffer, allocating more space
* if necessary.
*/
extern void appendPQExpBufferStr(PQExpBuffer str, const char *data);
/*------------------------
* appendPQExpBufferChar
* Append a single byte to str.
* Like appendPQExpBuffer(str, "%c", ch) but much faster.
*/
extern void appendPQExpBufferChar(PQExpBuffer str, char ch);
/*------------------------
* appendBinaryPQExpBuffer
* Append arbitrary binary data to a PQExpBuffer, allocating more space
* if necessary.
*/
extern void appendBinaryPQExpBuffer(PQExpBuffer str,
const char *data, size_t datalen);
#endif /* PQEXPBUFFER_H */
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