谁能给出sprintf函数的原型（可变参数）

[me5438]

RT,想自己模仿sprintf函数写一个格式化函数

不胜感激！

[战在春秋]

楼主是想询问sprintf的源代码吧？它的实现还是比较麻烦的。
可参考http://www.koders.com/c/fid63ECD67500436C41E614C92397D8EF845AF52977.aspx?s=cdefs#L40
其中vsnprintf函数的实现可参考http://www.koders.com/c/fid94C6E23788EAD1A51D0662A43C50B1B543CAFB34.aspx?s=cdefs#L40
最左侧列表可查询其它函数实现。

[Eleven]

/*** 
*sprintf.c   -   print   formatted   to   string 
* 
*               Copyright   (c)   1985-1997,   Microsoft   Corporation.   All   rights   reserved. 
* 
*Purpose: 
*               defines   sprintf()   and   _snprintf()   -   print   formatted   data   to   string 
* 
*******************************************************************************/ 

#include   <cruntime.h> 
#include   <stdio.h> 
#include   <dbgint.h> 
#include   <stdarg.h> 
#include   <internal.h> 
#include   <limits.h> 
#include   <mtdll.h> 

#define   MAXSTR   INT_MAX 


/*** 
*ifndef   _COUNT_ 
*int   sprintf(string,   format,   ...)   -   print   formatted   data   to   string 
*else 
*int   _snprintf(string,   cnt,   format,   ...)   -   print   formatted   data   to   string 
*endif 
* 
*Purpose: 
*               Prints   formatted   data   to   the   using   the   format   string   to 
*               format   data   and   getting   as   many   arguments   as   called   for 
*               Sets   up   a   FILE   so   file   i/o   operations   can   be   used,   make 
*               string   look   like   a   huge   buffer   to   it,   but   _flsbuf   will 
*               refuse   to   flush   it   if   it   fills   up.     Appends   '\0 '   to   make 
*               it   a   true   string.   _output   does   the   real   work   here 
* 
*               Allocate   the   'fake '   _iob[]   entry   statically   instead   of   on 
*               the   stack   so   that   other   routines   can   assume   that   _iob[] 
*               entries   are   in   are   in   DGROUP   and,   thus,   are   near. 
* 
*ifdef   _COUNT_ 
*               The   _snprintf()   flavor   takes   a   count   argument   that   is 
*               the   max   number   of   bytes   that   should   be   written   to   the 
*               user 's   buffer. 
*endif 
* 
*               Multi-thread:   (1)   Since   there   is   no   stream,   this   routine   must 
*               never   try   to   get   the   stream   lock   (i.e.,   there   is   no   stream 
*               lock   either).   (2)   Also,   since   there   is   only   one   statically 
*               allocated   'fake '   iob,   we   must   lock/unlock   to   prevent   collisions. 
* 
*Entry: 
*               char   *string   -   pointer   to   place   to   put   output 
*ifdef   _COUNT_ 
*               size_t   count   -   max   number   of   bytes   to   put   in   buffer 
*endif 
*               char   *format   -   format   string   to   control   data   format/number 
*               of   arguments   followed   by   list   of   arguments,   number   and   type 
*               controlled   by   format   string 
* 
*Exit: 
*               returns   number   of   characters   printed 
* 
*Exceptions: 
* 
*******************************************************************************/ 

#ifndef   _COUNT_ 

int   __cdecl   sprintf   ( 
                char   *string, 
                const   char   *format, 
                ... 
                ) 
#else     /*   _COUNT_   */ 

int   __cdecl   _snprintf   ( 
                char   *string, 
                size_t   count, 
                const   char   *format, 
                ... 
                ) 
#endif     /*   _COUNT_   */ 

{ 
                FILE   str; 
                REG1   FILE   *outfile   =   &str; 
                va_list   arglist; 
                REG2   int   retval; 

                va_start(arglist,   format); 

                _ASSERTE(string   !=   NULL); 
                _ASSERTE(format   !=   NULL); 

                outfile-> _flag   =   _IOWRT|_IOSTRG; 
                outfile-> _ptr   =   outfile-> _base   =   string; 
#ifndef   _COUNT_ 
                outfile-> _cnt   =   MAXSTR; 
#else     /*   _COUNT_   */ 
                outfile-> _cnt   =   count; 
#endif     /*   _COUNT_   */ 

                retval   =   _output(outfile,format,arglist); 

                _putc_lk( '\0 ',outfile);   /*   no-lock   version   */ 

                return(retval); 
}

[ouyh12345]

int sprintf(char *str, const char *fmt,...);

[我才是心翼]

int sprintf( char *buffer, const char *format [, argument] ... );

int swprintf( wchar_t *buffer, const wchar_t *format [, argument] ... );

/* SPRINTF.C: This program uses sprintf to format various
 * data and place them in the string named buffer.
 */

#include <stdio.h>

void main( void )
{
   char  buffer[200], s[] = "computer", c = 'l';
   int   i = 35, j;
   float fp = 1.7320534f;

   /* Format and print various data: */
   j  = sprintf( buffer,     "\tString:    %s\n", s );
   j += sprintf( buffer + j, "\tCharacter: %c\n", c );
   j += sprintf( buffer + j, "\tInteger:   %d\n", i );
   j += sprintf( buffer + j, "\tReal:      %f\n", fp );

   printf( "Output:\n%s\ncharacter count = %d\n", buffer, j );
}

Output

Output:
String: computer
Character: l
Integer: 35
Real: 1.732053

character count = 71

[buyong]

可以看看sprintf的源代码
[Quote=引用楼主 me5438 的回复:]
RT,想自己模仿sprintf函数写一个格式化函数

不胜感激！
[/Quote]

[d00107916]

int __cdecl sprintf_s (
char *string,
size_t sizeInBytes,
const char *format,
...
)
{
va_list arglist;
va_start(arglist, format);
return _vsprintf_s_l(string, sizeInBytes, format, NULL, arglist);
}

[me5438]

随便写了个，但隐含存在的问题还是有的，望大家指教：
MyCString& MyCString::format(const char *fmt,...)
{
va_list ap;
int i = 0;

char *tmp = new char[strlen(fmt)+50];
memset(tmp,0,sizeof(tmp));

delete myData;
myData = tmp;

va_start(ap, fmt);

char *Pvalue1 = NULL;
char *Pvalue2 = NULL;
int Ivalue = 0;
double Dvalue = 0;

char *pFmt = (char *)fmt;
while(*pFmt)
{
while( *pFmt != '%' )
{
*tmp++ = *pFmt++; //循环完之后*pFmt = '%'
}
++pFmt;
switch (*pFmt)
{
case 's':
Pvalue1 = va_arg(ap, char *);
//while((*tmp++ = *Pvalue1++) != '\0');
strncpy(tmp,Pvalue1,strlen(Pvalue1));
*(tmp+strlen(Pvalue1)) = '\0';
tmp += strlen(Pvalue1); //移动当前指针到末尾
break;

case 'd':
Ivalue = va_arg(ap, int);
if( Ivalue < 0 )
{
*tmp++ = '-';
Ivalue = -Ivalue;
}
i = (int)log10((float)Ivalue)+1; //i表示正整数Ivalue的位数
Pvalue2 = new char[i+1];
itoa(Ivalue,Pvalue2,10);

strncpy(tmp,Pvalue2,i);
*(tmp+i) = '\0';
tmp += i; //移动当前指针到末尾
delete Pvalue2;
Pvalue2 = NULL;
break;

case 'f':
Dvalue = va_arg(ap,double);
if(Dvalue < 0)
{
*tmp++ = '-';
Dvalue = -Dvalue;
}
Pvalue2 = new char[20];

sprintf(Pvalue2,"%f",Dvalue);
strncpy(tmp,Pvalue2,strlen(Pvalue2));
*(tmp + strlen(Pvalue2)) = '\0';
tmp += strlen(Pvalue2);
delete Pvalue2;
Pvalue2 = NULL;
break;

}
++pFmt;
//continue;
}

va_end (ap);

return *this;
}

[Binzo]

void test(char *szTemplate,char *szData1, char *szData2) {
char buf[BUFFER_SIZE];
sprintf(buf,szTemplate,szData1,szData2);
}

int sprintf( char *buffer, const char *format [, argument] ... );

Parameters
buffer
Storage location for output.
format
Format-control string.
argument
Optional arguments.