/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ /* * Buffered I/O on block devices. * Write buffering ignores offset. */ #include <u.h>#include <libc.h>#include <disk.h>#include "dat.h"#include "fns.h" Buf*bopen(long (*fn)(Buf*, void*, long, ulong), int omode, int bs, int nblock){	Buf *b; 	assert(omode == OREAD || OWRITE);	assert(bs > 0 && nblock > 0);	assert(fn != nil); 	b = emalloc(sizeof(*b));	b->data = emalloc(bs*nblock);	b->ndata = 0;	b->nblock = nblock;	b->bs = bs;	b->omode = omode;	b->fn = fn;		/* function to read or write bs-byte blocks */ 	return b;} longbread(Buf *b, void *v, long n, vlong off){	long m;	vlong noff; 	assert(b->omode == OREAD); 	/* Refill buffer */	if(b->off > off || off >= b->off+b->ndata) {		noff = off - off % b->bs;		if(vflag > 1)			fprint(2, "try refill at %lld...", noff);		if((m = b->fn(b, b->data, b->nblock, noff/b->bs)) <= 0) {			if (vflag)				fprint(2, "read failed: %r\n");			return m;		}		b->ndata = b->bs * m;		b->off = noff;		if(vflag > 1)			fprint(2, "got %ld\n", b->ndata);	} //	fprint(2, "read %ld at %ld\n", n, off);	/* Satisfy request from buffer */	off -= b->off;	if(n > b->ndata - off)		n = b->ndata - off;	memmove(v, b->data+off, n);	return n;} longbwrite(Buf *b, void *v, long n){	long on, m, mdata;	uchar *p; 	p = v;	on = n; 	/* Fill buffer */	mdata = b->bs*b->nblock;	m = mdata - b->ndata;	if(m > n)		m = n;	memmove(b->data+b->ndata, p, m);	p += m;	n -= m;	b->ndata += m; 	/* Flush buffer */	if(b->ndata == mdata) {		if(b->fn(b, b->data, b->nblock, 0) < 0) {			if(vflag)				fprint(2, "write fails: %r\n");			return -1;		}		b->ndata = 0;	} 	/* For now, don't worry about big writes; 9P only does 8k */	assert(n < mdata); 	/* Add remainder to buffer */	if(n) {		memmove(b->data, p, n);		b->ndata = n;	} 	return on;} voidbterm(Buf *b){	/* DVD & BD prefer full ecc blocks (tracks), but can cope with less */	if(b->omode == OWRITE && b->ndata)		b->fn(b, b->data, (b->ndata + b->bs - 1)/b->bs, 0);  	free(b->data);	free(b);}