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发信人: GyeaonWoo (柏林恋人), 信区: Linux
标  题: Linus's Linux--fs/pipe.c
发信站: 荔园晨风BBS站 (Mon Aug 25 20:05:19 2003), 站内信件

#include <signal.h>

#include <linux/sched.h>
#include <linux/mm.h>   /* for get_free_page */
#include <asm/segment.h>

int read_pipe(struct m_inode * inode, char * buf, int count)
{
        char * b=buf;

        while (PIPE_EMPTY(*inode)) {
                wake_up(&inode->i_wait);
                if (inode->i_count != 2) /* are there any writers left? */
                        return 0;
                sleep_on(&inode->i_wait);
        }
        while (count>0 && !(PIPE_EMPTY(*inode))) {
                count --;
                put_fs_byte(((char *)inode->i_size)[PIPE_TAIL(*inode)],b++);
                INC_PIPE( PIPE_TAIL(*inode) );
        }
        wake_up(&inode->i_wait);
        return b-buf;
}

int write_pipe(struct m_inode * inode, char * buf, int count)
{
        char * b=buf;

        wake_up(&inode->i_wait);
        if (inode->i_count != 2) { /* no readers */
                current->signal |= (1<<(SIGPIPE-1));
                return -1;
        }
        while (count-->0) {
                while (PIPE_FULL(*inode)) {
                        wake_up(&inode->i_wait);
                        if (inode->i_count != 2) {
                                current->signal |= (1<<(SIGPIPE-1));
                                return b-buf;
                        }
                        sleep_on(&inode->i_wait);
                }
                ((char *)inode->i_size)[PIPE_HEAD(*inode)] = get_fs_byte(b++);
                INC_PIPE( PIPE_HEAD(*inode) );
                wake_up(&inode->i_wait);
        }
        wake_up(&inode->i_wait);
        return b-buf;
}

int sys_pipe(unsigned long * fildes)
{
        struct m_inode * inode;
        struct file * f[2];
        int fd[2];
        int i,j;

        j=0;
        for(i=0;j<2 && i<NR_FILE;i++)
                if (!file_table[i].f_count)
                        (f[j++]=i+file_table)->f_count++;
        if (j==1)
                f[0]->f_count=0;
        if (j<2)
                return -1;
        j=0;
        for(i=0;j<2 && i<NR_OPEN;i++)
                if (!current->filp[i]) {
                        current->filp[ fd[j]=i ] = f[j];
                        j++;
                }
        if (j==1)
                current->filp[fd[0]]=NULL;
        if (j<2) {
                f[0]->f_count=f[1]->f_count=0;
                return -1;
        }
        if (!(inode=get_pipe_inode())) {
                current->filp[fd[0]] =
                        current->filp[fd[1]] = NULL;
                f[0]->f_count = f[1]->f_count = 0;
                return -1;
        }
        f[0]->f_inode = f[1]->f_inode = inode;
        f[0]->f_pos = f[1]->f_pos = 0;
        f[0]->f_mode = 1;               /* read */
        f[1]->f_mode = 2;               /* write */
        put_fs_long(fd[0],0+fildes);
        put_fs_long(fd[1],1+fildes);
        return 0;
}

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