#include <u.h>#include <libc.h>#include <thread.h>#include "dat.h"#include "fns.h" intfcopy(int dfd, int sfd, vlong off, vlong len){	uchar buf[BUFSZ];	int n; 	while(len != 0){		n = BUFSZ;		if(len > 0 && n > len)			n = len;		if((n = pread(sfd, buf, n, off)) < 0)			return -1;		if(n == 0)			return len > 0 ? -1 : 0;		if(write(dfd, buf, n) != n)			return -1;		if(off >= 0)			off += n;		if(len > 0)			len -= n;	}	return 0;} static uchar patchmark[12] = {	0xff, 0xff, 0xff, 0xff,	0xff, 0xff, 0xff, 0xff,	0xff, 0xff, 0xff, 0xff,}; intfpatchmark(int pfd, char *){	if(write(pfd, patchmark, 12) != 12)		return -1;	return 0;} typedef struct Frag Frag;struct Frag{	Frag	*next;	int	fd;	vlong	len;	vlong	off;}; intfpatch(int ofd, int bfd, int pfd){	vlong off, fstart, fend, start, end, len;	int err, front, back;	Frag *h, *f, *p;	uchar buf[12]; 	h = nil;	err = -1; 	if(bfd >= 0){		h = malloc(sizeof(Frag));		if(h == nil)			goto errout;		h->next = nil;		h->off = 0;		h->fd = bfd;		h->len = seek(h->fd, 0, 2);		if(h->len < 0)			goto errout;	} 	off = 0;	while(pfd >= 0){		if(readn(pfd, buf, 12) != 12)			break; 		if(memcmp(buf, patchmark, 12) == 0){			off = 0;			continue;		} 		start = buf[0]<<24 | buf[1]<<16 | buf[2]<<8 | buf[3];		end = buf[4]<<24 | buf[5]<<16 | buf[6]<<8 | buf[7];		len = buf[8]<<24 | buf[9]<<16 | buf[10]<<8 | buf[11]; 		if(start > end){			werrstr("bad patch: start > end");			goto errout;		} 		start += off;		end += off;		off += start + len - end; 		fstart = 0;		for(f = h; f; f = f->next, fstart = fend){			fend = fstart + f->len;			if(fend <= start)				continue;			if(fstart >= end)				break; 			front = start > fstart;			back = end < fend;			if(front && back){				p = malloc(sizeof(Frag));				if(p == nil)					goto errout;				*p = *f;				f->next = p;				f->len = start - fstart;				p->off += end - fstart;				p->len -= end - fstart;				break;			} else if(back){				f->off += end - fstart;				f->len -= end - fstart;				break;			} else if(front){				f->len = start - fstart;			} else {				f->len = 0;			}		} 		fstart = 0;		for(p = nil, f = h; f && fstart < start; p = f, f = f->next)			fstart += f->len; 		f = malloc(sizeof(Frag));		if(f == nil)			goto errout;		f->fd = pfd;		f->len = len;		f->off = seek(f->fd, 0, 1); 		if(p){			f->next = p->next;			p->next = f;		} else {			f->next = h;			h = f;		} 		if(f->off < 0)			goto errout;		if(seek(pfd, f->len, 1) < 0)			goto errout;	} 	for(f = h; f; f = f->next)		if(fcopy(ofd, f->fd, f->off, f->len) < 0)			goto errout;	err = 0; errout:	while(f = h){		h = f->next;		free(f);	} 	return err;}