自学教程：C++ vsnprintf函数代码示例

voidsafe_fprintf(FILE *f, const char *fmt, ...){	char fmtbuff_stack[256]; /* Place to format the printf() string. */	char outbuff[256]; /* Buffer for outgoing characters. */	char *fmtbuff_heap; /* If fmtbuff_stack is too small, we use malloc */	char *fmtbuff;  /* Pointer to fmtbuff_stack or fmtbuff_heap. */	int fmtbuff_length;	int length, n;	va_list ap;	const char *p;	unsigned i;	wchar_t wc;	char try_wc;	/* Use a stack-allocated buffer if we can, for speed and safety. */	fmtbuff_heap = NULL;	fmtbuff_length = sizeof(fmtbuff_stack);	fmtbuff = fmtbuff_stack;	/* Try formatting into the stack buffer. */	va_start(ap, fmt);	length = vsnprintf(fmtbuff, fmtbuff_length, fmt, ap);	va_end(ap);	/* If the result was too large, allocate a buffer on the heap. */	while (length < 0 || length >= fmtbuff_length) {		if (length >= fmtbuff_length)			fmtbuff_length = length+1;		else if (fmtbuff_length < 8192)			fmtbuff_length *= 2;		else if (fmtbuff_length < 1000000)			fmtbuff_length += fmtbuff_length / 4;		else {			length = fmtbuff_length;			fmtbuff_heap[length-1] = '/0';			break;		}		free(fmtbuff_heap);		fmtbuff_heap = malloc(fmtbuff_length);		/* Reformat the result into the heap buffer if we can. */		if (fmtbuff_heap != NULL) {			fmtbuff = fmtbuff_heap;			va_start(ap, fmt);			length = vsnprintf(fmtbuff, fmtbuff_length, fmt, ap);			va_end(ap);		} else {			/* Leave fmtbuff pointing to the truncated			 * string in fmtbuff_stack. */			length = sizeof(fmtbuff_stack) - 1;			break;		}	}	/* Note: mbrtowc() has a cleaner API, but mbtowc() seems a bit	 * more portable, so we use that here instead. */	if (mbtowc(NULL, NULL, 1) == -1) { /* Reset the shift state. */		/* mbtowc() should never fail in practice, but		 * handle the theoretical error anyway. */		free(fmtbuff_heap);		return;	}	/* Write data, expanding unprintable characters. */	p = fmtbuff;	i = 0;	try_wc = 1;	while (*p != '/0') {		/* Convert to wide char, test if the wide		 * char is printable in the current locale. */		if (try_wc && (n = mbtowc(&wc, p, length)) != -1) {			length -= n;			if (iswprint(wc) && wc != L'//') {				/* Printable, copy the bytes through. */				while (n-- > 0)					outbuff[i++] = *p++;			} else {				/* Not printable, format the bytes. */				while (n-- > 0)					i += (unsigned)bsdtar_expand_char(					    outbuff, i, *p++);			}		} else {			/* After any conversion failure, don't bother			 * trying to convert the rest. */			i += (unsigned)bsdtar_expand_char(outbuff, i, *p++);			try_wc = 0;		}		/* If our output buffer is full, dump it and keep going. */		if (i > (sizeof(outbuff) - 20)) {			outbuff[i] = '/0';			fprintf(f, "%s", outbuff);			i = 0;		}	}	outbuff[i] = '/0';	fprintf(f, "%s", outbuff);//.........这里部分代码省略.........

/* *	Log the message to the logfile. Include the severity and *	a time stamp. */int vradlog(int lvl, const char *fmt, va_list ap){	struct main_config_t *myconfig = &mainconfig;	unsigned char *p;	char buffer[8192];	int len;	/*	 *	NOT debugging, and trying to log debug messages.	 *	 *	Throw the message away.	 */	if (!debug_flag && (lvl == L_DBG)) {		return 0;	}	/*	 *	If we don't want any messages, then	 *	throw them away.	 */	if (myconfig->radlog_dest == RADLOG_NULL) {		return 0;	}	*buffer = '/0';	len = 0;	/*	 *	Don't print timestamps to syslog, it does that for us.	 *	Don't print timestamps for low levels of debugging.	 *	 *	Print timestamps for non-debugging, and for high levels	 *	of debugging.	 */	if ((myconfig->radlog_dest != RADLOG_SYSLOG) &&	    (debug_flag != 1) && (debug_flag != 2)) {		const char *s;		time_t timeval;		timeval = time(NULL);		CTIME_R(&timeval, buffer + len, sizeof(buffer) - len - 1);		s = fr_int2str(levels, (lvl & ~L_CONS), ": ");		strcat(buffer, s);		len = strlen(buffer);	}	vsnprintf(buffer + len, sizeof(buffer) - len - 1, fmt, ap);	/*	 *	Filter out characters not in Latin-1.	 */	for (p = (unsigned char *)buffer; *p != '/0'; p++) {		if (*p == '/r' || *p == '/n')			*p = ' ';		else if (*p == '/t') continue;		else if (*p < 32 || (*p >= 128 && *p <= 160))			*p = '?';	}	strcat(buffer, "/n");	switch (myconfig->radlog_dest) {#ifdef HAVE_SYSLOG_H	case RADLOG_SYSLOG:		switch(lvl & ~L_CONS) {			case L_DBG:				lvl = LOG_DEBUG;				break;			case L_AUTH:				lvl = LOG_NOTICE;				break;			case L_PROXY:				lvl = LOG_NOTICE;				break;			case L_ACCT:				lvl = LOG_NOTICE;				break;			case L_INFO:				lvl = LOG_INFO;				break;			case L_ERR:				lvl = LOG_ERR;				break;		}		syslog(lvl, "%s", buffer);		break;#endif	case RADLOG_FILES:	case RADLOG_STDOUT:	case RADLOG_STDERR:		write(myconfig->radlog_fd, buffer, strlen(buffer));		break;//.........这里部分代码省略.........

voidsetproctitle(const char *fmt, ...){	static struct ps_strings *ps_strings;	static char *buf = NULL;	static char *obuf = NULL;	static char **oargv, *kbuf;	static int oargc = -1;	static char *nargv[2] = { NULL, NULL };	char **nargvp;	int nargc;	int i;	va_list ap;	size_t len;	unsigned long ul_ps_strings;	int oid[4];	if (buf == NULL) {		buf = malloc(SPT_BUFSIZE);		if (buf == NULL) 			return;		nargv[0] = buf;	}	if (obuf == NULL ) {		obuf = malloc(SPT_BUFSIZE);		if (obuf == NULL)			return;		*obuf = '/0';	}	va_start(ap, fmt);	if (fmt) {		buf[SPT_BUFSIZE - 1] = '/0';		if (fmt[0] == '-') {			/* skip program name prefix */			fmt++;			len = 0;		} else {			/* print program name heading for grep */			(void)snprintf(buf, SPT_BUFSIZE, "%s: ", _getprogname());			len = strlen(buf);		}		/* print the argument string */		(void) vsnprintf(buf + len, SPT_BUFSIZE - len, fmt, ap);		nargvp = nargv;		nargc = 1;		kbuf = buf;	} else if (*obuf != '/0') {  		/* Idea from NetBSD - reset the title on fmt == NULL */		nargvp = oargv;		nargc = oargc;		kbuf = obuf;	} else		/* Nothing to restore */		return;	va_end(ap);	/* Set the title into the kernel cached command line */	oid[0] = CTL_KERN;	oid[1] = KERN_PROC;	oid[2] = KERN_PROC_ARGS;	oid[3] = getpid();	sysctl(oid, 4, 0, 0, kbuf, strlen(kbuf) + 1);	if (ps_strings == NULL) {		len = sizeof(ul_ps_strings);		if (sysctlbyname("kern.ps_strings", &ul_ps_strings, &len, NULL,		    0) == -1)			ul_ps_strings = PS_STRINGS;		ps_strings = (struct ps_strings *)ul_ps_strings;	}	/* PS_STRINGS points to zeroed memory on a style #2 kernel */	if (ps_strings->ps_argvstr) {		/* style #3 */		if (oargc == -1) {			/* Record our original args */			oargc = ps_strings->ps_nargvstr;			oargv = ps_strings->ps_argvstr;			for (i = len = 0; i < oargc; i++) {				/*				 * The program may have scribbled into its				 * argv array, e.g., to remove some arguments.				 * If that has happened, break out before				 * trying to call strlen on a NULL pointer.				 */				if (oargv[i] == NULL) {					oargc = i;					break;				}				snprintf(obuf + len, SPT_BUFSIZE - len, "%s%s",				    len ? " " : "", oargv[i]);				if (len)					len++;//.........这里部分代码省略.........

intMtrace(char *fmt,...){	static	int inMtraceNow;	int len;	char *eolp;	va_list argp;		/* Mtrace not configured or disabled, so just return.	 */	if (!Mip || Mip->off)		return(0);	/* This may be called from interrupt and/or non-interrupt space of	 * an application, so we must deal with possible reentrancy here.	 */	if (inMtraceNow) {		Mip->reentered++;		return(0);		}	inMtraceNow = 1;	Mip->ptr += snprintf(Mip->ptr,MAXLINSIZE,"/n<%04d> ",Mip->sno++);	va_start(argp,fmt);	len = vsnprintf(Mip->ptr,MAXLINSIZE,fmt,argp);	va_end(argp);	/* Strip all CR/LFs from the incoming string.	 * The incoming string can have CR/LFs in it; however, they are stripped	 * so that the format of the dump is stable (one line per Mtrace call).	 * Notice that the top line of this function inserts a newline ahead	 * of the sequence number; hence, additional CR/LFs in the text would	 * just confuse the output.	 */	eolp = Mip->ptr;	while(*eolp) {		if ((*eolp == '/r') || (*eolp == '/n')) {			strcpy(eolp,eolp+1);			len--;		}		else			eolp++;	}	/* If print flag is set, then dump to the console...	 */	if (Mip->mode & MODE_PRINT) {		int	i;		for(i=0;i<len;i++)			putchar(*Mip->ptr++);		putchar('/n');	}	else		Mip->ptr += len;	if (Mip->ptr >= Mip->end) {		Mip->ptr = Mip->base;		if (Mip->mode & MODE_NOWRAP)			Mip->off = 1;		else			Mip->wrap++;	}	/* Flush the d-cache of the mtrace buffer and Mip structure after each	 * transfer...	 * This is important because if this is being accessed from an	 * application that has d-cache enabled, then the hardware is reset,	 * there is a chance that the data written was in cache and would be	 * lost.	 */	flushDcache((char *)Mip,sizeof(struct mtInfo));	flushDcache((char *)Mip->base,Mip->end - Mip->base);	inMtraceNow = 0;	return(len);}

/* Copyright (C) 2004       Manuel Novoa III    <[email
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