seq_buf.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_SEQ_BUF_H
  3#define _LINUX_SEQ_BUF_H
  4
  5#include <linux/bug.h>
  6#include <linux/minmax.h>
  7#include <linux/seq_file.h>
  8#include <linux/types.h>
  9
 10/*
 11 * Trace sequences are used to allow a function to call several other functions
 12 * to create a string of data to use.
 13 */
 14
 15/**
 16 * struct seq_buf - seq buffer structure
 17 * @buffer:	pointer to the buffer
 18 * @size:	size of the buffer
 19 * @len:	the amount of data inside the buffer
 20 */
 21struct seq_buf {
 22	char			*buffer;
 23	size_t			size;
 24	size_t			len;
 25};
 26
 27#define DECLARE_SEQ_BUF(NAME, SIZE)			\
 28	struct seq_buf NAME = {				\
 29		.buffer = (char[SIZE]) { 0 },		\
 30		.size = SIZE,				\
 31	}
 32
 33static inline void seq_buf_clear(struct seq_buf *s)
 34{
 35	s->len = 0;
 36	if (s->size)
 37		s->buffer[0] = '\0';
 38}
 39
 40static inline void
 41seq_buf_init(struct seq_buf *s, char *buf, unsigned int size)
 42{
 43	s->buffer = buf;
 44	s->size = size;
 45	seq_buf_clear(s);
 46}
 47
 48/*
 49 * seq_buf have a buffer that might overflow. When this happens
 50 * len is set to be greater than size.
 51 */
 52static inline bool
 53seq_buf_has_overflowed(struct seq_buf *s)
 54{
 55	return s->len > s->size;
 56}
 57
 58static inline void
 59seq_buf_set_overflow(struct seq_buf *s)
 60{
 61	s->len = s->size + 1;
 62}
 63
 64/*
 65 * How much buffer is left on the seq_buf?
 66 */
 67static inline unsigned int
 68seq_buf_buffer_left(struct seq_buf *s)
 69{
 70	if (seq_buf_has_overflowed(s))
 71		return 0;
 72
 73	return s->size - s->len;
 74}
 75
 76/* How much buffer was written? */
 77static inline unsigned int seq_buf_used(struct seq_buf *s)
 78{
 79	return min(s->len, s->size);
 80}
 81
 82/**
 83 * seq_buf_str - get NUL-terminated C string from seq_buf
 84 * @s: the seq_buf handle
 85 *
 86 * This makes sure that the buffer in @s is NUL-terminated and
 87 * safe to read as a string.
 88 *
 89 * Note, if this is called when the buffer has overflowed, then
 90 * the last byte of the buffer is zeroed, and the len will still
 91 * point passed it.
 92 *
 93 * After this function is called, s->buffer is safe to use
 94 * in string operations.
 95 *
 96 * Returns: @s->buf after making sure it is terminated.
 97 */
 98static inline const char *seq_buf_str(struct seq_buf *s)
 99{
100	if (WARN_ON(s->size == 0))
101		return "";
102
103	if (seq_buf_buffer_left(s))
104		s->buffer[s->len] = 0;
105	else
106		s->buffer[s->size - 1] = 0;
107
108	return s->buffer;
109}
110
111/**
112 * seq_buf_get_buf - get buffer to write arbitrary data to
113 * @s: the seq_buf handle
114 * @bufp: the beginning of the buffer is stored here
115 *
116 * Returns: the number of bytes available in the buffer, or zero if
117 * there's no space.
118 */
119static inline size_t seq_buf_get_buf(struct seq_buf *s, char **bufp)
120{
121	WARN_ON(s->len > s->size + 1);
122
123	if (s->len < s->size) {
124		*bufp = s->buffer + s->len;
125		return s->size - s->len;
126	}
127
128	*bufp = NULL;
129	return 0;
130}
131
132/**
133 * seq_buf_commit - commit data to the buffer
134 * @s: the seq_buf handle
135 * @num: the number of bytes to commit
136 *
137 * Commit @num bytes of data written to a buffer previously acquired
138 * by seq_buf_get_buf(). To signal an error condition, or that the data
139 * didn't fit in the available space, pass a negative @num value.
140 */
141static inline void seq_buf_commit(struct seq_buf *s, int num)
142{
143	if (num < 0) {
144		seq_buf_set_overflow(s);
145	} else {
146		/* num must be negative on overflow */
147		BUG_ON(s->len + num > s->size);
148		s->len += num;
149	}
150}
151
152/**
153 * seq_buf_pop - pop off the last written character
154 * @s: the seq_buf handle
155 *
156 * Removes the last written character to the seq_buf @s.
157 *
158 * Returns the last character or -1 if it is empty.
159 */
160static inline int seq_buf_pop(struct seq_buf *s)
161{
162	if (!s->len)
163		return -1;
164
165	s->len--;
166	return (unsigned int)s->buffer[s->len];
167}
168
169extern __printf(2, 3)
170int seq_buf_printf(struct seq_buf *s, const char *fmt, ...);
171extern __printf(2, 0)
172int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args);
173extern int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s);
174extern int seq_buf_to_user(struct seq_buf *s, char __user *ubuf,
175			   size_t start, int cnt);
176extern int seq_buf_puts(struct seq_buf *s, const char *str);
177extern int seq_buf_putc(struct seq_buf *s, unsigned char c);
178extern int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len);
179extern int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
180			      unsigned int len);
181extern int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc);
182extern int seq_buf_hex_dump(struct seq_buf *s, const char *prefix_str,
183			    int prefix_type, int rowsize, int groupsize,
184			    const void *buf, size_t len, bool ascii);
185
186#ifdef CONFIG_BINARY_PRINTF
187__printf(2, 0)
188int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary);
189#endif
190
191void seq_buf_do_printk(struct seq_buf *s, const char *lvl);
192
193#endif /* _LINUX_SEQ_BUF_H */