/*
   * seq_buf.c
   *
   * Copyright (C) 2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
   *
   * The seq_buf is a handy tool that allows you to pass a descriptor around
   * to a buffer that other functions can write to. It is similar to the
   * seq_file functionality but has some differences.
   *
   * To use it, the seq_buf must be initialized with seq_buf_init().
   * This will set up the counters within the descriptor. You can call
   * seq_buf_init() more than once to reset the seq_buf to start
   * from scratch.
   */
  #include <linux/uaccess.h>
  #include <linux/seq_file.h>
  #include <linux/seq_buf.h>

  /**

   * seq_buf_can_fit - can the new data fit in the current buffer?
   * @s: the seq_buf descriptor
   * @len: The length to see if it can fit in the current buffer
   *
   * Returns true if there's enough unused space in the seq_buf buffer
   * to fit the amount of new data according to @len.
   */
  static bool seq_buf_can_fit(struct seq_buf *s, size_t len)
  {

  	return s->len + len <= s->size;

  }
  
  /**

   * seq_buf_print_seq - move the contents of seq_buf into a seq_file
   * @m: the seq_file descriptor that is the destination
   * @s: the seq_buf descriptor that is the source.
   *
   * Returns zero on success, non zero otherwise
   */
  int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s)
  {

  	unsigned int len = seq_buf_used(s);

  
  	return seq_write(m, s->buffer, len);
  }
  
  /**
   * seq_buf_vprintf - sequence printing of information.
   * @s: seq_buf descriptor
   * @fmt: printf format string
   * @args: va_list of arguments from a printf() type function
   *
   * Writes a vnprintf() format into the sequencce buffer.
   *
   * Returns zero on success, -1 on overflow.
   */
  int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args)
  {
  	int len;
  
  	WARN_ON(s->size == 0);
  
  	if (s->len < s->size) {
  		len = vsnprintf(s->buffer + s->len, s->size - s->len, fmt, args);

  		if (s->len + len < s->size) {

  			s->len += len;
  			return 0;
  		}
  	}
  	seq_buf_set_overflow(s);
  	return -1;
  }
  
  /**
   * seq_buf_printf - sequence printing of information
   * @s: seq_buf descriptor
   * @fmt: printf format string
   *
   * Writes a printf() format into the sequence buffer.
   *
   * Returns zero on success, -1 on overflow.
   */
  int seq_buf_printf(struct seq_buf *s, const char *fmt, ...)
  {
  	va_list ap;
  	int ret;
  
  	va_start(ap, fmt);
  	ret = seq_buf_vprintf(s, fmt, ap);
  	va_end(ap);
  
  	return ret;
  }

  #ifdef CONFIG_BINARY_PRINTF

  /**
   * seq_buf_bprintf - Write the printf string from binary arguments
   * @s: seq_buf descriptor
   * @fmt: The format string for the @binary arguments
   * @binary: The binary arguments for @fmt.
   *
   * When recording in a fast path, a printf may be recorded with just
   * saving the format and the arguments as they were passed to the
   * function, instead of wasting cycles converting the arguments into
   * ASCII characters. Instead, the arguments are saved in a 32 bit
   * word array that is defined by the format string constraints.
   *
   * This function will take the format and the binary array and finish
   * the conversion into the ASCII string within the buffer.
   *
   * Returns zero on success, -1 on overflow.
   */
  int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)
  {
  	unsigned int len = seq_buf_buffer_left(s);
  	int ret;
  
  	WARN_ON(s->size == 0);
  
  	if (s->len < s->size) {
  		ret = bstr_printf(s->buffer + s->len, len, fmt, binary);

  		if (s->len + ret < s->size) {

  			s->len += ret;
  			return 0;
  		}
  	}
  	seq_buf_set_overflow(s);
  	return -1;
  }

  #endif /* CONFIG_BINARY_PRINTF */

  
  /**
   * seq_buf_puts - sequence printing of simple string
   * @s: seq_buf descriptor
   * @str: simple string to record
   *
   * Copy a simple string into the sequence buffer.
   *
   * Returns zero on success, -1 on overflow
   */
  int seq_buf_puts(struct seq_buf *s, const char *str)
  {
  	unsigned int len = strlen(str);
  
  	WARN_ON(s->size == 0);

  	if (seq_buf_can_fit(s, len)) {

  		memcpy(s->buffer + s->len, str, len);
  		s->len += len;
  		return 0;
  	}
  	seq_buf_set_overflow(s);
  	return -1;
  }
  
  /**
   * seq_buf_putc - sequence printing of simple character
   * @s: seq_buf descriptor
   * @c: simple character to record
   *
   * Copy a single character into the sequence buffer.
   *
   * Returns zero on success, -1 on overflow
   */
  int seq_buf_putc(struct seq_buf *s, unsigned char c)
  {
  	WARN_ON(s->size == 0);

  	if (seq_buf_can_fit(s, 1)) {

  		s->buffer[s->len++] = c;
  		return 0;
  	}
  	seq_buf_set_overflow(s);
  	return -1;
  }
  
  /**
   * seq_buf_putmem - write raw data into the sequenc buffer
   * @s: seq_buf descriptor
   * @mem: The raw memory to copy into the buffer
   * @len: The length of the raw memory to copy (in bytes)
   *
   * There may be cases where raw memory needs to be written into the
   * buffer and a strcpy() would not work. Using this function allows
   * for such cases.
   *
   * Returns zero on success, -1 on overflow
   */
  int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
  {
  	WARN_ON(s->size == 0);

  	if (seq_buf_can_fit(s, len)) {

  		memcpy(s->buffer + s->len, mem, len);
  		s->len += len;
  		return 0;
  	}
  	seq_buf_set_overflow(s);
  	return -1;
  }
  
  #define MAX_MEMHEX_BYTES	8U
  #define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1)
  
  /**
   * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
   * @s: seq_buf descriptor
   * @mem: The raw memory to write its hex ASCII representation of
   * @len: The length of the raw memory to copy (in bytes)
   *
   * This is similar to seq_buf_putmem() except instead of just copying the
   * raw memory into the buffer it writes its ASCII representation of it
   * in hex characters.
   *
   * Returns zero on success, -1 on overflow
   */
  int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
  		       unsigned int len)
  {
  	unsigned char hex[HEX_CHARS];
  	const unsigned char *data = mem;
  	unsigned int start_len;
  	int i, j;
  
  	WARN_ON(s->size == 0);
  
  	while (len) {
  		start_len = min(len, HEX_CHARS - 1);
  #ifdef __BIG_ENDIAN
  		for (i = 0, j = 0; i < start_len; i++) {
  #else
  		for (i = start_len-1, j = 0; i >= 0; i--) {
  #endif
  			hex[j++] = hex_asc_hi(data[i]);
  			hex[j++] = hex_asc_lo(data[i]);
  		}
  		if (WARN_ON_ONCE(j == 0 || j/2 > len))
  			break;
  
  		/* j increments twice per loop */
  		len -= j / 2;
  		hex[j++] = ' ';
  
  		seq_buf_putmem(s, hex, j);
  		if (seq_buf_has_overflowed(s))
  			return -1;
  	}
  	return 0;
  }
  
  /**
   * seq_buf_path - copy a path into the sequence buffer
   * @s: seq_buf descriptor
   * @path: path to write into the sequence buffer.

   * @esc: set of characters to escape in the output

   *
   * Write a path name into the sequence buffer.
   *

   * Returns the number of written bytes on success, -1 on overflow

   */

  int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)

  {

  	char *buf;
  	size_t size = seq_buf_get_buf(s, &buf);

  	int res = -1;

  
  	WARN_ON(s->size == 0);

  	if (size) {
  		char *p = d_path(path, buf, size);
  		if (!IS_ERR(p)) {
  			char *end = mangle_path(buf, p, esc);
  			if (end)
  				res = end - buf;

  		}
  	}

  	seq_buf_commit(s, res);

  
  	return res;

  }
  
  /**
   * seq_buf_to_user - copy the squence buffer to user space
   * @s: seq_buf descriptor
   * @ubuf: The userspace memory location to copy to
   * @cnt: The amount to copy
   *
   * Copies the sequence buffer into the userspace memory pointed to
   * by @ubuf. It starts from the last read position (@s->readpos)
   * and writes up to @cnt characters or till it reaches the end of
   * the content in the buffer (@s->len), which ever comes first.
   *
   * On success, it returns a positive number of the number of bytes
   * it copied.
   *
   * On failure it returns -EBUSY if all of the content in the
   * sequence has been already read, which includes nothing in the
   * sequence (@s->len == @s->readpos).
   *
   * Returns -EFAULT if the copy to userspace fails.
   */
  int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
  {
  	int len;
  	int ret;
  
  	if (!cnt)
  		return 0;

  	len = seq_buf_used(s);
  
  	if (len <= s->readpos)

  		return -EBUSY;

  	len -= s->readpos;

  	if (cnt > len)
  		cnt = len;
  	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
  	if (ret == cnt)
  		return -EFAULT;
  
  	cnt -= ret;
  
  	s->readpos += cnt;
  	return cnt;
  }