sfwrite.c   [plain text]

#include	"sfhdr.h"

/*	Write data out to the file system
**
**	Written by Kiem-Phong Vo.
*/

#if __STD_C
ssize_t sfwrite(reg Sfio_t* f, const Void_t* buf, reg size_t n)
#else
ssize_t sfwrite(f,buf,n)
reg Sfio_t*	f;	/* write to this stream. 	*/
Void_t*		buf;	/* buffer to be written.	*/
reg size_t	n;	/* number of bytes. 		*/
#endif
{
	reg uchar	*s, *begs, *next;
	reg ssize_t	w;
	reg int		local;

	SFMTXSTART(f, (ssize_t)(-1));

	GETLOCAL(f,local);

	if(!buf)
		SFMTXRETURN(f, (ssize_t)(-1));

	/* release peek lock */
	if(f->mode&SF_PEEK)
	{	if(!(f->mode&SF_WRITE) && (f->flags&SF_RDWR) != SF_RDWR)
			SFMTXRETURN(f, (ssize_t)(-1));

		if((uchar*)buf != f->next &&
		   (!f->rsrv || f->rsrv->data != (uchar*)buf) )
			SFMTXRETURN(f, (ssize_t)(-1));

		f->mode &= ~SF_PEEK;

		if(f->mode&SF_PKRD)
		{	/* read past peeked data */
			char		buf[16];
			reg ssize_t	r;

			for(w = n; w > 0; )
			{	if((r = w) > sizeof(buf))
					r = sizeof(buf);
				if((r = read(f->file,buf,r)) <= 0)
				{	n -= w;
					break;
				}
				else	w -= r;
			}

			f->mode &= ~SF_PKRD;
			f->endb = f->data + n;
			f->here += n;
		}

		if((f->mode&SF_READ) && f->proc)
			f->next += n;
	}

	s = begs = (uchar*)buf;
	for(;; f->mode &= ~SF_LOCK)
	{	/* check stream mode */
		if(SFMODE(f,local) != SF_WRITE && _sfmode(f,SF_WRITE,local) < 0 )
		{	w = s > begs ? s-begs : -1;
			SFMTXRETURN(f,w);
		}

		SFLOCK(f,local);

		w = f->endb - f->next;

		if(s == f->next) /* after sfreserve */
		{	if(w > (ssize_t)n)
				w = (ssize_t)n;
			f->next = (s += w);
			n -= w;
			break;
		}

		/* attempt to create space in buffer */
		if(w == 0 || ((f->flags&SF_WHOLE) && w < (ssize_t)n) )
		{	if(f->flags&SF_STRING) /* extend buffer */
			{	(void)SFWR(f, s, n-w, f->disc);
				if((w = f->endb - f->next) < (ssize_t)n)
					break;
			}
			else if(f->next > f->data)
			{	(void)SFFLSBUF(f, -1);
				if((w = f->endb - f->next) < (ssize_t)n &&
				   (f->flags&SF_WHOLE) && f->next > f->data )
					break;
			}
		}

		if(!(f->flags&SF_STRING) && f->next == f->data && SFDIRECT(f,n) )
		{	/* bypass buffering */
			if((w = SFWR(f,s,n,f->disc)) <= 0 )
				break;
		}
		else
		{	if(w > (ssize_t)n)
				w = (ssize_t)n;
			if(w <= 0) /* no forward progress possible */
				break;
			memcpy(f->next, s, w);
			f->next += w;
		}

		s += w;
		if((n -= w) <= 0)
			break;
	}

	/* always flush buffer for share streams */
	if(f->extent < 0 && (f->flags&SF_SHARE) && !(f->flags&SF_PUBLIC) )
		(void)SFFLSBUF(f,-1);

	/* check to see if buffer should be flushed */
	else if(n == 0 && (f->flags&SF_LINE) && !(f->flags&SF_STRING))
	{	if((ssize_t)(n = f->next-f->data) > (w = s-begs))
			n = w;
		if(n > 0 && n < HIFORLINE)
		{	for(next = f->next-1; n > 0; --n, --next)
			{	if(*next == '\n')
				{	n = HIFORLINE;
					break;
				}
			}
		}
		if(n >= HIFORLINE)
			(void)SFFLSBUF(f,-1);
	}

	SFOPEN(f,local);

	w = s-begs;
	SFMTXRETURN(f,w);
}