1 /* SPDX-License-Identifier: LGPL-2.1+ */
2 /* Copyright (C) 2022 Kent Overstreet */
4 #ifndef _BCACHEFS_PRINTBUF_H
5 #define _BCACHEFS_PRINTBUF_H
8 * Printbufs: Simple strings for printing to, with optional heap allocation
10 * This code has provisions for use in userspace, to aid in making other code
11 * portable between kernelspace and userspace.
14 * struct printbuf buf = PRINTBUF;
16 * prt_printf(&buf, "foo=");
17 * foo_to_text(&buf, foo);
18 * printk("%s", buf.buf);
19 * printbuf_exit(&buf);
22 * struct printbuf buf = PRINTBUF_EXTERN(char_buf, char_buf_size)
24 * We can now write pretty printers instead of writing code that dumps
25 * everything to the kernel log buffer, and then those pretty-printers can be
26 * used by other code that outputs to kernel log, sysfs, debugfs, etc.
28 * Memory allocation: Outputing to a printbuf may allocate memory. This
29 * allocation is done with GFP_KERNEL, by default: use the newer
30 * memalloc_*_(save|restore) functions as needed.
32 * Since no equivalent yet exists for GFP_ATOMIC/GFP_NOWAIT, memory allocations
33 * will be done with GFP_NOWAIT if printbuf->atomic is nonzero.
35 * It's allowed to grab the output buffer and free it later with kfree() instead
36 * of using printbuf_exit(), if the user just needs a heap allocated string at
39 * Memory allocation failures: We don't return errors directly, because on
40 * memory allocation failure we usually don't want to bail out and unwind - we
41 * want to print what we've got, on a best-effort basis. But code that does want
42 * to return -ENOMEM may check printbuf.allocation_failure.
44 * Indenting, tabstops:
46 * To aid is writing multi-line pretty printers spread across multiple
47 * functions, printbufs track the current indent level.
49 * printbuf_indent_push() and printbuf_indent_pop() increase and decrease the current indent
50 * level, respectively.
52 * To use tabstops, set printbuf->tabstops[]; they are in units of spaces, from
53 * start of line. Once set, prt_tab() will output spaces up to the next tabstop.
54 * prt_tab_rjust() will also advance the current line of text up to the next
55 * tabstop, but it does so by shifting text since the previous tabstop up to the
56 * next tabstop - right justifying it.
58 * Make sure you use prt_newline() instead of \n in the format string for indent
59 * level and tabstops to work corretly.
61 * Output units: printbuf->units exists to tell pretty-printers how to output
62 * numbers: a raw value (e.g. directly from a superblock field), as bytes, or as
63 * human readable bytes. prt_units() obeys it.
66 #include <linux/kernel.h>
67 #include <linux/string.h>
70 PRINTBUF_UNITS_2, /* use binary powers of 2^10 */
71 PRINTBUF_UNITS_10, /* use powers of 10^3 (standard SI) */
74 #define PRINTBUF_INLINE_TABSTOPS 6
80 unsigned last_newline;
84 * If nonzero, allocations will be done with GFP_ATOMIC:
87 bool allocation_failure:1;
88 bool heap_allocated:1;
89 enum printbuf_si si_units:1;
90 bool human_readable_units:1;
91 bool has_indent_or_tabstops:1;
92 bool suppress_indent_tabstop_handling:1;
96 * Do not modify directly: use printbuf_tabstop_add(),
97 * printbuf_tabstop_get()
100 u8 _tabstops[PRINTBUF_INLINE_TABSTOPS];
103 int bch2_printbuf_make_room(struct printbuf *, unsigned);
104 __printf(2, 3) void bch2_prt_printf(struct printbuf *out, const char *fmt, ...);
105 __printf(2, 0) void bch2_prt_vprintf(struct printbuf *out, const char *fmt, va_list);
106 const char *bch2_printbuf_str(const struct printbuf *);
107 void bch2_printbuf_exit(struct printbuf *);
109 void bch2_printbuf_tabstops_reset(struct printbuf *);
110 void bch2_printbuf_tabstop_pop(struct printbuf *);
111 int bch2_printbuf_tabstop_push(struct printbuf *, unsigned);
113 void bch2_printbuf_indent_add(struct printbuf *, unsigned);
114 void bch2_printbuf_indent_sub(struct printbuf *, unsigned);
116 void bch2_prt_newline(struct printbuf *);
117 void bch2_prt_tab(struct printbuf *);
118 void bch2_prt_tab_rjust(struct printbuf *);
120 void bch2_prt_bytes_indented(struct printbuf *, const char *, unsigned);
121 void bch2_prt_human_readable_u64(struct printbuf *, u64);
122 void bch2_prt_human_readable_s64(struct printbuf *, s64);
123 void bch2_prt_units_u64(struct printbuf *, u64);
124 void bch2_prt_units_s64(struct printbuf *, s64);
125 void bch2_prt_string_option(struct printbuf *, const char * const[], size_t);
126 void bch2_prt_bitflags(struct printbuf *, const char * const[], u64);
127 void bch2_prt_bitflags_vector(struct printbuf *, const char * const[],
128 unsigned long *, unsigned);
130 /* Initializer for a heap allocated printbuf: */
131 #define PRINTBUF ((struct printbuf) { .heap_allocated = true })
133 /* Initializer a printbuf that points to an external buffer: */
134 #define PRINTBUF_EXTERN(_buf, _size) \
135 ((struct printbuf) { \
141 * Returns size remaining of output buffer:
143 static inline unsigned printbuf_remaining_size(struct printbuf *out)
145 return out->pos < out->size ? out->size - out->pos : 0;
149 * Returns number of characters we can print to the output buffer - i.e.
150 * excluding the terminating nul:
152 static inline unsigned printbuf_remaining(struct printbuf *out)
154 return out->pos < out->size ? out->size - out->pos - 1 : 0;
157 static inline unsigned printbuf_written(struct printbuf *out)
159 return out->size ? min(out->pos, out->size - 1) : 0;
163 * Returns true if output was truncated:
165 static inline bool printbuf_overflowed(struct printbuf *out)
167 return out->pos >= out->size;
170 static inline void printbuf_nul_terminate(struct printbuf *out)
172 bch2_printbuf_make_room(out, 1);
174 if (out->pos < out->size)
175 out->buf[out->pos] = 0;
177 out->buf[out->size - 1] = 0;
180 /* Doesn't call bch2_printbuf_make_room(), doesn't nul terminate: */
181 static inline void __prt_char_reserved(struct printbuf *out, char c)
183 if (printbuf_remaining(out))
184 out->buf[out->pos] = c;
188 /* Doesn't nul terminate: */
189 static inline void __prt_char(struct printbuf *out, char c)
191 bch2_printbuf_make_room(out, 1);
192 __prt_char_reserved(out, c);
195 static inline void prt_char(struct printbuf *out, char c)
198 printbuf_nul_terminate(out);
201 static inline void __prt_chars_reserved(struct printbuf *out, char c, unsigned n)
203 unsigned i, can_print = min(n, printbuf_remaining(out));
205 for (i = 0; i < can_print; i++)
206 out->buf[out->pos++] = c;
207 out->pos += n - can_print;
210 static inline void prt_chars(struct printbuf *out, char c, unsigned n)
212 bch2_printbuf_make_room(out, n);
213 __prt_chars_reserved(out, c, n);
214 printbuf_nul_terminate(out);
217 static inline void prt_bytes(struct printbuf *out, const void *b, unsigned n)
219 unsigned i, can_print;
221 bch2_printbuf_make_room(out, n);
223 can_print = min(n, printbuf_remaining(out));
225 for (i = 0; i < can_print; i++)
226 out->buf[out->pos++] = ((char *) b)[i];
227 out->pos += n - can_print;
229 printbuf_nul_terminate(out);
232 static inline void prt_str(struct printbuf *out, const char *str)
234 prt_bytes(out, str, strlen(str));
237 static inline void prt_str_indented(struct printbuf *out, const char *str)
239 bch2_prt_bytes_indented(out, str, strlen(str));
242 static inline void prt_hex_byte(struct printbuf *out, u8 byte)
244 bch2_printbuf_make_room(out, 2);
245 __prt_char_reserved(out, hex_asc_hi(byte));
246 __prt_char_reserved(out, hex_asc_lo(byte));
247 printbuf_nul_terminate(out);
250 static inline void prt_hex_byte_upper(struct printbuf *out, u8 byte)
252 bch2_printbuf_make_room(out, 2);
253 __prt_char_reserved(out, hex_asc_upper_hi(byte));
254 __prt_char_reserved(out, hex_asc_upper_lo(byte));
255 printbuf_nul_terminate(out);
259 * printbuf_reset - re-use a printbuf without freeing and re-initializing it:
261 static inline void printbuf_reset(struct printbuf *buf)
264 buf->allocation_failure = 0;
266 buf->nr_tabstops = 0;
267 buf->cur_tabstop = 0;
271 * printbuf_atomic_inc - mark as entering an atomic section
273 static inline void printbuf_atomic_inc(struct printbuf *buf)
279 * printbuf_atomic_inc - mark as leaving an atomic section
281 static inline void printbuf_atomic_dec(struct printbuf *buf)
286 #endif /* _BCACHEFS_PRINTBUF_H */