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/*------------------------------------------------------------------------- * * 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) 1996-2012, 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,...) /* This extension allows gcc to check the format string */ __attribute__((format(PG_PRINTF_ATTRIBUTE, 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,...) /* This extension allows gcc to check the format string */ __attribute__((format(PG_PRINTF_ATTRIBUTE, 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 */