/*
 * linux/fs/seq_file.c
 *
 * helper functions for making syntetic files from sequences of records.
 * initial implementation -- AV, Oct 2001.
 */

#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>

#include <asm/uaccess.h>

/**
 *      seq_open -      initialize sequential file
 *      @file: file we initialize
 *      @op: method table describing the sequence
 *
 *      seq_open() sets @file, associating it with a sequence described
 *      by @op.  @op->start() sets the iterator up and returns the first
 *      element of sequence. @op->stop() shuts it down.  @op->next()
 *      returns the next element of sequence.  @op->show() prints element
 *      into the buffer.  In case of error ->start() and ->next() return
 *      ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
 *      returns 0 in case of success and negative number in case of error.
 */
int seq_open(struct file *file, struct seq_operations *op)
{
        struct seq_file *p = kmalloc(sizeof(*p), GFP_KERNEL);
        if (!p)
                return -ENOMEM;
        memset(p, 0, sizeof(*p));
        sema_init(&p->sem, 1);
        p->op = op;
        file->private_data = p;
        return 0;
}

/**
 *      seq_read -      ->read() method for sequential files.
 *      @file, @buf, @size, @ppos: see file_operations method
 *
 *      Ready-made ->f_op->read()
 */
ssize_t seq_read(struct file *file, char *buf, size_t size, loff_t *ppos)
{
        struct seq_file *m = (struct seq_file *)file->private_data;
        size_t copied = 0;
        loff_t pos;
        size_t n;
        void *p;
        int err = 0;

        if (ppos != &file->f_pos)
                return -EPIPE;

        down(&m->sem);
        /* grab buffer if we didn't have one */
        if (!m->buf) {
                m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
                if (!m->buf)
                        goto Enomem;
        }
        /* if not empty - flush it first */
        if (m->count) {
                n = min(m->count, size);
                err = copy_to_user(buf, m->buf + m->from, n);
                if (err)
                        goto Efault;
                m->count -= n;
                m->from += n;
                size -= n;
                buf += n;
                copied += n;
                if (!m->count)
                        m->index++;
                if (!size)
                        goto Done;
        }
        /* we need at least one record in buffer */
        while (1) {
                pos = m->index;
                p = m->op->start(m, &pos);
                err = PTR_ERR(p);
                if (!p || IS_ERR(p))
                        break;
                err = m->op->show(m, p);
                if (err)
                        break;
                if (m->count < m->size)
                        goto Fill;
                m->op->stop(m, p);
                kfree(m->buf);
                m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
                if (!m->buf)
                        goto Enomem;
        }
        m->op->stop(m, p);
        goto Done;
Fill:
        /* they want more? let's try to get some more */
        while (m->count < size) {
                size_t offs = m->count;
                loff_t next = pos;
                p = m->op->next(m, p, &next);
                if (!p || IS_ERR(p)) {
                        err = PTR_ERR(p);
                        break;
                }
                err = m->op->show(m, p);
                if (err || m->count == m->size) {
                        m->count = offs;
                        break;
                }
                pos = next;
        }
        m->op->stop(m, p);
        n = min(m->count, size);
        err = copy_to_user(buf, m->buf, n);
        if (err)
                goto Efault;
        copied += n;
        m->count -= n;
        if (m->count)
                m->from = n;
        else
                pos++;
        m->index = pos;
Done:
        if (!copied)
                copied = err;
        else
                *ppos += copied;
        up(&m->sem);
        return copied;
Enomem:
        err = -ENOMEM;
        goto Done;
Efault:
        err = -EFAULT;
        goto Done;
}

static int traverse(struct seq_file *m, loff_t offset)
{
        loff_t pos = 0;
        int error = 0;
        void *p;

        m->index = 0;
        m->count = m->from = 0;
        if (!offset)
                return 0;
        if (!m->buf) {
                m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
                if (!m->buf)
                        return -ENOMEM;
        }
        p = m->op->start(m, &m->index);
        while (p) {
                error = PTR_ERR(p);
                if (IS_ERR(p))
                        break;
                error = m->op->show(m, p);
                if (error)
                        break;
                if (m->count == m->size)
                        goto Eoverflow;
                if (pos + m->count > offset) {
                        m->from = offset - pos;
                        m->count -= m->from;
                        break;
                }
                pos += m->count;
                m->count = 0;
                if (pos == offset) {
                        m->index++;
                        break;
                }
                p = m->op->next(m, p, &m->index);
        }
        m->op->stop(m, p);
        return error;

Eoverflow:
        m->op->stop(m, p);
        kfree(m->buf);
        m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
        return !m->buf ? -ENOMEM : -EAGAIN;
}

/**
 *      seq_lseek -     ->llseek() method for sequential files.
 *      @file, @offset, @origin: see file_operations method
 *
 *      Ready-made ->f_op->llseek()
 */
loff_t seq_lseek(struct file *file, loff_t offset, int origin)
{
        struct seq_file *m = (struct seq_file *)file->private_data;
        long long retval = -EINVAL;

        down(&m->sem);
        switch (origin) {
                case 1:
                        offset += file->f_pos;
                case 0:
                        if (offset < 0)
                                break;
                        retval = offset;
                        if (offset != file->f_pos) {
                                while ((retval=traverse(m, offset)) == -EAGAIN)
                                        ;
                                if (retval) {
                                        /* with extreme perjudice... */
                                        file->f_pos = 0;
                                        m->index = 0;
                                        m->count = 0;
                                } else {
                                        retval = file->f_pos = offset;
                                }
                        }
        }
        up(&m->sem);
        return retval;
}

/**
 *      seq_release -   free the structures associated with sequential file.
 *      @file: file in question
 *      @inode: file->f_dentry->d_inode
 *
 *      Frees the structures associated with sequential file; can be used
 *      as ->f_op->release() if you don't have private data to destroy.
 */
int seq_release(struct inode *inode, struct file *file)
{
        struct seq_file *m = (struct seq_file *)file->private_data;
        kfree(m->buf);
        kfree(m);
        return 0;
}

/**
 *      seq_escape -    print string into buffer, escaping some characters
 *      @m:     target buffer
 *      @s:     string
 *      @esc:   set of characters that need escaping
 *
 *      Puts string into buffer, replacing each occurence of character from
 *      @esc with usual octal escape.  Returns 0 in case of success, -1 - in
 *      case of overflow.
 */
int seq_escape(struct seq_file *m, const char *s, const char *esc)
{
        char *end = m->buf + m->size;
        char *p;
        char c;

        for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
                if (!strchr(esc, c)) {
                        *p++ = c;
                        continue;
                }
                if (p + 3 < end) {
                        *p++ = '\\';
                        *p++ = '0' + ((c & 0300) >> 6);
                        *p++ = '0' + ((c & 070) >> 3);
                        *p++ = '0' + (c & 07);
                        continue;
                }
                m->count = m->size;
                return -1;
        }
        m->count = p - m->buf;
        return 0;
}

int seq_printf(struct seq_file *m, const char *f, ...)
{
        va_list args;
        int len;

        if (m->count < m->size) {
                va_start(args, f);
                len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
                va_end(args);
                if (m->count + len < m->size) {
                        m->count += len;
                        return 0;
                }
        }
        m->count = m->size;
        return -1;
}