stringinfo.h

关系型数据库 Postgresql 6.5.2

/*-------------------------------------------------------------------------
 *
 * stringinfo.h
 *	  Declarations/definitions for "StringInfo" functions.
 *
 * StringInfo 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 palloc().
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 * $Id: stringinfo.h,v 1.13 1999/05/26 12:56:27 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef STRINGINFO_H
#define STRINGINFO_H

/*-------------------------
 * StringInfoData holds information about an extensible string.
 *		data	is the current buffer for the string (allocated with palloc).
 *		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.
 *-------------------------
 */
typedef struct StringInfoData
{
	char	   *data;
	int			len;
	int			maxlen;
} StringInfoData;

typedef StringInfoData *StringInfo;


/*------------------------
 * There are two ways to create a StringInfo object initially:
 *
 * StringInfo stringptr = makeStringInfo();
 *		Both the StringInfoData and the data buffer are palloc'd.
 *
 * StringInfoData string;
 * initStringInfo(&string);
 *		The data buffer is palloc'd but the StringInfoData is just local.
 *		This is the easiest approach for a StringInfo object that will
 *		only live as long as the current routine.
 *
 * To destroy a StringInfo, pfree() the data buffer, and then pfree() the
 * StringInfoData if it was palloc'd.  There's no special support for this.
 *
 * NOTE: some routines build up a string using StringInfo, and then
 * release the StringInfoData but return the data string itself to their
 * caller.	At that point the data string looks like a plain palloc'd
 * string.
 *-------------------------
 */

#ifdef NOT_USED
/*------------------------
 * makeStringInfo
 * Create an empty 'StringInfoData' & return a pointer to it.
 */
extern StringInfo makeStringInfo(void);
#endif

/*------------------------
 * initStringInfo
 * Initialize a StringInfoData struct (with previously undefined contents)
 * to describe an empty string.
 */
extern void initStringInfo(StringInfo str);

/*------------------------
 * appendStringInfo
 * 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.
 * CAUTION: the current implementation has a 1K limit on the amount of text
 * generated in a single call (not on the total string length).
 */
extern void appendStringInfo(StringInfo str, const char *fmt,...);

/*------------------------
 * appendStringInfoChar
 * Append a single byte to str.
 * Like appendStringInfo(str, "%c", ch) but much faster.
 */
extern void appendStringInfoChar(StringInfo str, char ch);

/*------------------------
 * appendBinaryStringInfo
 * Append arbitrary binary data to a StringInfo, allocating more space
 * if necessary.
 */
extern void appendBinaryStringInfo(StringInfo str,
					   const char *data, int datalen);

/*------------------------
 * stringStringInfo
 * Return the string itself or "<>" if it is NULL.
 * This is just a convenience macro used by many callers of appendStringInfo.
 */
#define stringStringInfo(s) (((s) == NULL) ? "<>" : (s))

#endif	 /* STRINGINFO_H */