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

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

#include <asm/uaccess.h>
#include <asm/page.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, const struct seq_operations *op)
{
        struct seq_file *p = file->private_data;

        if (!p) {
                p = kmalloc(sizeof(*p), GFP_KERNEL);
                if (!p)
                        return -ENOMEM;
                file->private_data = p;
        }
        memset(p, 0, sizeof(*p));
        mutex_init(&p->lock);
        p->op = op;

        /*
         * Wrappers around seq_open(e.g. swaps_open) need to be
         * aware of this. If they set f_version themselves, they
         * should call seq_open first and then set f_version.
         */
        file->f_version = 0;

        /* SEQ files support lseek, but not pread/pwrite */
        file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
        return 0;
}
EXPORT_SYMBOL(seq_open);

/**
 *      seq_read -      ->read() method for sequential files.
 *      @file: the file to read from
 *      @buf: the buffer to read to
 *      @size: the maximum number of bytes to read
 *      @ppos: the current position in the file
 *
 *      Ready-made ->f_op->read()
 */
ssize_t seq_read(struct file *file, char __user *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;

        mutex_lock(&m->lock);
        /*
         * seq_file->op->..m_start/m_stop/m_next may do special actions
         * or optimisations based on the file->f_version, so we want to
         * pass the file->f_version to those methods.
         *
         * seq_file->version is just copy of f_version, and seq_file
         * methods can treat it simply as file version.
         * It is copied in first and copied out after all operations.
         * It is convenient to have it as  part of structure to avoid the
         * need of passing another argument to all the seq_file methods.
         */
        m->version = file->f_version;
        /* 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->count = 0;
                m->version = 0;
        }
        m->op->stop(m, p);
        m->count = 0;
        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;
        file->f_version = m->version;
        mutex_unlock(&m->lock);
        return copied;
Enomem:
        err = -ENOMEM;
        goto Done;
Efault:
        err = -EFAULT;
        goto Done;
}
EXPORT_SYMBOL(seq_read);

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

        m->version = 0;
        index = 0;
        m->count = m->from = 0;
        if (!offset) {
                m->index = index;
                return 0;
        }
        if (!m->buf) {
                m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
                if (!m->buf)
                        return -ENOMEM;
        }
        p = m->op->start(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;
                        m->index = index;
                        break;
                }
                pos += m->count;
                m->count = 0;
                if (pos == offset) {
                        index++;
                        m->index = index;
                        break;
                }
                p = m->op->next(m, p, &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: the file in question
 *      @offset: new position
 *      @origin: 0 for absolute, 1 for relative position
 *
 *      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;

        mutex_lock(&m->lock);
        m->version = file->f_version;
        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 prejudice... */
                                        file->f_pos = 0;
                                        m->version = 0;
                                        m->index = 0;
                                        m->count = 0;
                                } else {
                                        retval = file->f_pos = offset;
                                }
                        }
        }
        file->f_version = m->version;
        mutex_unlock(&m->lock);
        return retval;
}
EXPORT_SYMBOL(seq_lseek);

/**
 *      seq_release -   free the structures associated with sequential file.
 *      @file: file in question
 *      @inode: file->f_path.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;
}
EXPORT_SYMBOL(seq_release);

/**
 *      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 occurrence 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;
}
EXPORT_SYMBOL(seq_escape);

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;
}
EXPORT_SYMBOL(seq_printf);

int seq_path(struct seq_file *m, struct path *path, char *esc)
{
        if (m->count < m->size) {
                char *s = m->buf + m->count;
                char *p = d_path(path, s, m->size - m->count);
                if (!IS_ERR(p)) {
                        while (s <= p) {
                                char c = *p++;
                                if (!c) {
                                        p = m->buf + m->count;
                                        m->count = s - m->buf;
                                        return s - p;
                                } else if (!strchr(esc, c)) {
                                        *s++ = c;
                                } else if (s + 4 > p) {
                                        break;
                                } else {
                                        *s++ = '\\';
                                        *s++ = '0' + ((c & 0300) >> 6);
                                        *s++ = '0' + ((c & 070) >> 3);
                                        *s++ = '0' + (c & 07);
                                }
                        }
                }
        }
        m->count = m->size;
        return -1;
}
EXPORT_SYMBOL(seq_path);

static void *single_start(struct seq_file *p, loff_t *pos)
{
        return NULL + (*pos == 0);
}

static void *single_next(struct seq_file *p, void *v, loff_t *pos)
{
        ++*pos;
        return NULL;
}

static void single_stop(struct seq_file *p, void *v)
{
}

int single_open(struct file *file, int (*show)(struct seq_file *, void *),
                void *data)
{
        struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
        int res = -ENOMEM;

        if (op) {
                op->start = single_start;
                op->next = single_next;
                op->stop = single_stop;
                op->show = show;
                res = seq_open(file, op);
                if (!res)
                        ((struct seq_file *)file->private_data)->private = data;
                else
                        kfree(op);
        }
        return res;
}
EXPORT_SYMBOL(single_open);

int single_release(struct inode *inode, struct file *file)
{
        const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
        int res = seq_release(inode, file);
        kfree(op);
        return res;
}
EXPORT_SYMBOL(single_release);

int seq_release_private(struct inode *inode, struct file *file)
{
        struct seq_file *seq = file->private_data;

        kfree(seq->private);
        seq->private = NULL;
        return seq_release(inode, file);
}
EXPORT_SYMBOL(seq_release_private);

void *__seq_open_private(struct file *f, const struct seq_operations *ops,
                int psize)
{
        int rc;
        void *private;
        struct seq_file *seq;

        private = kzalloc(psize, GFP_KERNEL);
        if (private == NULL)
                goto out;

        rc = seq_open(f, ops);
        if (rc < 0)
                goto out_free;

        seq = f->private_data;
        seq->private = private;
        return private;

out_free:
        kfree(private);
out:
        return NULL;
}
EXPORT_SYMBOL(__seq_open_private);

int seq_open_private(struct file *filp, const struct seq_operations *ops,
                int psize)
{
        return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
}
EXPORT_SYMBOL(seq_open_private);

int seq_putc(struct seq_file *m, char c)
{
        if (m->count < m->size) {
                m->buf[m->count++] = c;
                return 0;
        }
        return -1;
}
EXPORT_SYMBOL(seq_putc);

int seq_puts(struct seq_file *m, const char *s)
{
        int len = strlen(s);
        if (m->count + len < m->size) {
                memcpy(m->buf + m->count, s, len);
                m->count += len;
                return 0;
        }
        m->count = m->size;
        return -1;
}
EXPORT_SYMBOL(seq_puts);

struct list_head *seq_list_start(struct list_head *head, loff_t pos)
{
        struct list_head *lh;

        list_for_each(lh, head)
                if (pos-- == 0)
                        return lh;

        return NULL;
}

EXPORT_SYMBOL(seq_list_start);

struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
{
        if (!pos)
                return head;

        return seq_list_start(head, pos - 1);
}

EXPORT_SYMBOL(seq_list_start_head);

struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
{
        struct list_head *lh;

        lh = ((struct list_head *)v)->next;
        ++*ppos;
        return lh == head ? NULL : lh;
}

EXPORT_SYMBOL(seq_list_next);