text: #ifndef _LINUX_SEQ_FILE_H
  #define _LINUX_SEQ_FILE_H
  
  #include <linux/types.h>
  #include <linux/string.h>
  #include <linux/mutex.h>
  #include <linux/cpumask.h>
  #include <linux/nodemask.h>
  
  struct seq_operations;
  struct file;
  struct path;
  struct inode;
  struct dentry;
  
  struct seq_file {
  	char *buf;
  	size_t size;
  	size_t from;
  	size_t count;
  	loff_t index;
  	loff_t read_pos;
  	u64 version;
  	struct mutex lock;
  	const struct seq_operations *op;
  	int poll_event;
  	void *private;
  };
  
  struct seq_operations {
  	void * (*start) (struct seq_file *m, loff_t *pos);
  	void (*stop) (struct seq_file *m, void *v);
  	void * (*next) (struct seq_file *m, void *v, loff_t *pos);
  	int (*show) (struct seq_file *m, void *v);
  };
  
  #define SEQ_SKIP 1
  
  /**
   * seq_get_buf - get buffer to write arbitrary data to
   * @m: the seq_file handle
   * @bufp: the beginning of the buffer is stored here
   *
   * Return the number of bytes available in the buffer, or zero if
   * there's no space.
   */
  static inline size_t seq_get_buf(struct seq_file *m, char **bufp)
  {
  	BUG_ON(m->count > m->size);
  	if (m->count < m->size)
  		*bufp = m->buf + m->count;
  	else
  		*bufp = NULL;
  
  	return m->size - m->count;
  }
  
  /**
   * seq_commit - commit data to the buffer
   * @m: the seq_file handle
   * @num: the number of bytes to commit
   *
   * Commit @num bytes of data written to a buffer previously acquired
   * by seq_buf_get.  To signal an error condition, or that the data
   * didn't fit in the available space, pass a negative @num value.
   */
  static inline void seq_commit(struct seq_file *m, int num)
  {
  	if (num < 0) {
  		m->count = m->size;
  	} else {
  		BUG_ON(m->count + num > m->size);
  		m->count += num;
  	}
  }
  
  char *mangle_path(char *s, const char *p, const char *esc);
  int seq_open(struct file *, const struct seq_operations *);
  ssize_t seq_read(struct file *, char __user *, size_t, loff_t *);
  loff_t seq_lseek(struct file *, loff_t, int);
  int seq_release(struct inode *, struct file *);
  int seq_escape(struct seq_file *, const char *, const char *);
  int seq_putc(struct seq_file *m, char c);
  int seq_puts(struct seq_file *m, const char *s);
  int seq_write(struct seq_file *seq, const void *data, size_t len);
  
  __printf(2, 3) int seq_printf(struct seq_file *, const char *, ...);
  
  int seq_path(struct seq_file *, const struct path *, const char *);
  int seq_dentry(struct seq_file *, struct dentry *, const char *);
  int seq_path_root(struct seq_file *m, const struct path *path,
  		  const struct path *root, const char *esc);
  int seq_bitmap(struct seq_file *m, const unsigned long *bits,
  				   unsigned int nr_bits);
  static inline int seq_cpumask(struct seq_file *m, const struct cpumask *mask)
  {
  	return seq_bitmap(m, cpumask_bits(mask), nr_cpu_ids);
  }
  
  static inline int seq_nodemask(struct seq_file *m, nodemask_t *mask)
  {
  	return seq_bitmap(m, mask->bits, MAX_NUMNODES);
  }
  
  int seq_bitmap_list(struct seq_file *m, const unsigned long *bits,
  		unsigned int nr_bits);
  
  static inline int seq_cpumask_list(struct seq_file *m,
  				   const struct cpumask *mask)
  {
  	return seq_bitmap_list(m, cpumask_bits(mask), nr_cpu_ids);
  }
  
  static inline int seq_nodemask_list(struct seq_file *m, nodemask_t *mask)
  {
  	return seq_bitmap_list(m, mask->bits, MAX_NUMNODES);
  }
  
  int single_open(struct file *, int (*)(struct seq_file *, void *), void *);
  int single_release(struct inode *, struct file *);
  void *__seq_open_private(struct file *, const struct seq_operations *, int);
  int seq_open_private(struct file *, const struct seq_operations *, int);
  int seq_release_private(struct inode *, struct file *);
  
  #define SEQ_START_TOKEN ((void *)1)
  
  /*
   * Helpers for iteration over list_head-s in seq_files
   */
  
  extern struct list_head *seq_list_start(struct list_head *head,
  		loff_t pos);
  extern struct list_head *seq_list_start_head(struct list_head *head,
  		loff_t pos);
  extern struct list_head *seq_list_next(void *v, struct list_head *head,
  		loff_t *ppos);
  
  /*
   * Helpers for iteration over hlist_head-s in seq_files
   */
  
  extern struct hlist_node *seq_hlist_start(struct hlist_head *head,
  					  loff_t pos);
  extern struct hlist_node *seq_hlist_start_head(struct hlist_head *head,
  					       loff_t pos);
  extern struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
  					 loff_t *ppos);
  
  extern struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
  					      loff_t pos);
  extern struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
  						   loff_t pos);
  extern struct hlist_node *seq_hlist_next_rcu(void *v,
  						   struct hlist_head *head,
  						   loff_t *ppos);
  #endif
  