system_call_expand/linux-0.11-lab/cur/linux/fs/pipe.c

/*
 *  linux/fs/pipe.c
 *
 *  (C) 1991  Linus Torvalds
 */

#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)
{
	int chars, size, read = 0;

	while (count > 0)
	{
		while (!(size = PIPE_SIZE(*inode)))
		{
			wake_up(&inode->i_wait);
			if (inode->i_count != 2) /* are there any writers? */
				return read;
			sleep_on(&inode->i_wait);
		}
		chars = PAGE_SIZE - PIPE_TAIL(*inode);
		if (chars > count)
			chars = count;
		if (chars > size)
			chars = size;
		count -= chars;
		read += chars;
		size = PIPE_TAIL(*inode);
		PIPE_TAIL(*inode) += chars;
		PIPE_TAIL(*inode) &= (PAGE_SIZE - 1);
		while (chars-- > 0)
			put_fs_byte(((char *)inode->i_size)[size++], buf++);
	}
	wake_up(&inode->i_wait);
	return read;
}

int write_pipe(struct m_inode *inode, char *buf, int count)
{
	int chars, size, written = 0;

	while (count > 0)
	{
		while (!(size = (PAGE_SIZE - 1) - PIPE_SIZE(*inode)))
		{
			wake_up(&inode->i_wait);
			if (inode->i_count != 2)
			{ /* no readers */
				current->signal |= (1 << (SIGPIPE - 1));
				return written ? written : -1;
			}
			sleep_on(&inode->i_wait);
		}
		chars = PAGE_SIZE - PIPE_HEAD(*inode);
		if (chars > count)
			chars = count;
		if (chars > size)
			chars = size;
		count -= chars;
		written += chars;
		size = PIPE_HEAD(*inode);
		PIPE_HEAD(*inode) += chars;
		PIPE_HEAD(*inode) &= (PAGE_SIZE - 1);
		while (chars-- > 0)
			((char *)inode->i_size)[size++] = get_fs_byte(buf++);
	}
	wake_up(&inode->i_wait);
	return written;
}

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;
}

int sys_pipe2(int fd[2], int flags)
{
	if (flags == 0)
	{
		sys_pipe(fd);
	}
	return 0;
}