##include "../param.h"#include "../systm.h"#include "../user.h"#include "../reg.h"#include "../file.h"#include "../inode.h"/* * read system call */read(){	rdwr(FREAD);}/* * write system call */write(){	rdwr(FWRITE);}/* * common code for read and write calls: * check permissions, set base, count, and offset, * and switch out to readi, writei, or pipe code. */rdwr(mode){	register *fp, m;	m = mode;	fp = getf(u.u_ar0[R0]);	if(fp == NULL)		return;	if((fp->f_flag&m) == 0) {		u.u_error = EBADF;		return;	}	u.u_base = u.u_arg[0];	u.u_count = u.u_arg[1];	u.u_segflg = 0;	if(fp->f_flag&FPIPE) {		if(m==FREAD)			readp(fp); else			writep(fp);	} else {		u.u_offset[1] = fp->f_offset[1];		u.u_offset[0] = fp->f_offset[0];		if(m==FREAD)			readi(fp->f_inode); else			writei(fp->f_inode);		dpadd(fp->f_offset, u.u_arg[1]-u.u_count);	}	u.u_ar0[R0] = u.u_arg[1]-u.u_count;}/* * open system call */open(){	register *ip;	extern uchar;	ip = namei(&uchar, 0);	if(ip == NULL)		return;	u.u_arg[1]++;	open1(ip, u.u_arg[1], 0);}/* * creat system call */creat(){	register *ip;	extern uchar;	ip = namei(&uchar, 1);	if(ip == NULL) {		if(u.u_error)			return;		ip = maknode(u.u_arg[1]&07777&(~ISVTX));		if (ip==NULL)			return;		open1(ip, FWRITE, 2);	} else		open1(ip, FWRITE, 1);}/* * common code for open and creat. * Check permissions, allocate an open file structure, * and call the device open routine if any. */open1(ip, mode, trf)int *ip;{	register struct file *fp;	register *rip, m;	int i;	rip = ip;	m = mode;	if(trf != 2) {		if(m&FREAD)			access(rip, IREAD);		if(m&FWRITE) {			access(rip, IWRITE);			if((rip->i_mode&IFMT) == IFDIR)				u.u_error = EISDIR;		}	}	if(u.u_error)		goto out;	if(trf)		itrunc(rip);	prele(rip);	if ((fp = falloc()) == NULL)		goto out;	fp->f_flag = m&(FREAD|FWRITE);	fp->f_inode = rip;	i = u.u_ar0[R0];	openi(rip, m&FWRITE);	if(u.u_error == 0)		return;	u.u_ofile[i] = NULL;	fp->f_count--;out:	iput(rip);}/* * close system call */close(){	register *fp;	fp = getf(u.u_ar0[R0]);	if(fp == NULL)		return;	u.u_ofile[u.u_ar0[R0]] = NULL;	closef(fp);}/* * seek system call */seek(){	int n[2];	register *fp, t;	fp = getf(u.u_ar0[R0]);	if(fp == NULL)		return;	if(fp->f_flag&FPIPE) {		u.u_error = ESPIPE;		return;	}	t = u.u_arg[1];	if(t > 2) {		n[1] = u.u_arg[0]<<9;		n[0] = u.u_arg[0]>>7;		if(t == 3)			n[0] =& 0777;	} else {		n[1] = u.u_arg[0];		n[0] = 0;		if(t!=0 && n[1]<0)			n[0] = -1;	}	switch(t) {	case 1:	case 4:		n[0] =+ fp->f_offset[0];		dpadd(n, fp->f_offset[1]);		break;	default:		n[0] =+ fp->f_inode->i_size0&0377;		dpadd(n, fp->f_inode->i_size1);	case 0:	case 3:		;	}	fp->f_offset[1] = n[1];	fp->f_offset[0] = n[0];}/* * link system call */link(){	register *ip, *xp;	extern uchar;	ip = namei(&uchar, 0);	if(ip == NULL)		return;	if(ip->i_nlink >= 127) {		u.u_error = EMLINK;		goto out;	}	if((ip->i_mode&IFMT)==IFDIR && !suser())		goto out;	/*	 * unlock to avoid possibly hanging the namei	 */	ip->i_flag =& ~ILOCK;	u.u_dirp = u.u_arg[1];	xp = namei(&uchar, 1);	if(xp != NULL) {		u.u_error = EEXIST;		iput(xp);	}	if(u.u_error)		goto out;	if(u.u_pdir->i_dev != ip->i_dev) {		iput(u.u_pdir);		u.u_error = EXDEV;		goto out;	}	wdir(ip);	ip->i_nlink++;	ip->i_flag =| IUPD;out:	iput(ip);}/* * mknod system call */mknod(){	register *ip;	extern uchar;	if(suser()) {		ip = namei(&uchar, 1);		if(ip != NULL) {			u.u_error = EEXIST;			goto out;		}	}	if(u.u_error)		return;	ip = maknode(u.u_arg[1]);	if (ip==NULL)		return;	ip->i_addr[0] = u.u_arg[2];out:	iput(ip);}/* * sleep system call * not to be confused with the sleep internal routine. */sslep(){	char *d[2];	spl7();	d[0] = time[0];	d[1] = time[1];	dpadd(d, u.u_ar0[R0]);	while(dpcmp(d[0], d[1], time[0], time[1]) > 0) {		if(dpcmp(tout[0], tout[1], time[0], time[1]) <= 0 ||		   dpcmp(tout[0], tout[1], d[0], d[1]) > 0) {			tout[0] = d[0];			tout[1] = d[1];		}		sleep(tout, PSLEP);	}	spl0();}