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 4
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);
128 /* Initializer for a heap allocated printbuf: */
129 #define PRINTBUF ((struct printbuf) { .heap_allocated = true })
131 /* Initializer a printbuf that points to an external buffer: */
132 #define PRINTBUF_EXTERN(_buf, _size) \
133 ((struct printbuf) { \
139 * Returns size remaining of output buffer:
141 static inline unsigned printbuf_remaining_size(struct printbuf *out)
143 return out->pos < out->size ? out->size - out->pos : 0;
147 * Returns number of characters we can print to the output buffer - i.e.
148 * excluding the terminating nul:
150 static inline unsigned printbuf_remaining(struct printbuf *out)
152 return out->pos < out->size ? out->size - out->pos - 1 : 0;
155 static inline unsigned printbuf_written(struct printbuf *out)
157 return out->size ? min(out->pos, out->size - 1) : 0;
161 * Returns true if output was truncated:
163 static inline bool printbuf_overflowed(struct printbuf *out)
165 return out->pos >= out->size;
168 static inline void printbuf_nul_terminate(struct printbuf *out)
170 bch2_printbuf_make_room(out, 1);
172 if (out->pos < out->size)
173 out->buf[out->pos] = 0;
175 out->buf[out->size - 1] = 0;
178 /* Doesn't call bch2_printbuf_make_room(), doesn't nul terminate: */
179 static inline void __prt_char_reserved(struct printbuf *out, char c)
181 if (printbuf_remaining(out))
182 out->buf[out->pos] = c;
186 /* Doesn't nul terminate: */
187 static inline void __prt_char(struct printbuf *out, char c)
189 bch2_printbuf_make_room(out, 1);
190 __prt_char_reserved(out, c);
193 static inline void prt_char(struct printbuf *out, char c)
196 printbuf_nul_terminate(out);
199 static inline void __prt_chars_reserved(struct printbuf *out, char c, unsigned n)
201 unsigned i, can_print = min(n, printbuf_remaining(out));
203 for (i = 0; i < can_print; i++)
204 out->buf[out->pos++] = c;
205 out->pos += n - can_print;
208 static inline void prt_chars(struct printbuf *out, char c, unsigned n)
210 bch2_printbuf_make_room(out, n);
211 __prt_chars_reserved(out, c, n);
212 printbuf_nul_terminate(out);
215 static inline void prt_bytes(struct printbuf *out, const void *b, unsigned n)
217 unsigned i, can_print;
219 bch2_printbuf_make_room(out, n);
221 can_print = min(n, printbuf_remaining(out));
223 for (i = 0; i < can_print; i++)
224 out->buf[out->pos++] = ((char *) b)[i];
225 out->pos += n - can_print;
227 printbuf_nul_terminate(out);
230 static inline void prt_str(struct printbuf *out, const char *str)
232 prt_bytes(out, str, strlen(str));
235 static inline void prt_str_indented(struct printbuf *out, const char *str)
237 bch2_prt_bytes_indented(out, str, strlen(str));
240 static inline void prt_hex_byte(struct printbuf *out, u8 byte)
242 bch2_printbuf_make_room(out, 2);
243 __prt_char_reserved(out, hex_asc_hi(byte));
244 __prt_char_reserved(out, hex_asc_lo(byte));
245 printbuf_nul_terminate(out);
248 static inline void prt_hex_byte_upper(struct printbuf *out, u8 byte)
250 bch2_printbuf_make_room(out, 2);
251 __prt_char_reserved(out, hex_asc_upper_hi(byte));
252 __prt_char_reserved(out, hex_asc_upper_lo(byte));
253 printbuf_nul_terminate(out);
257 * printbuf_reset - re-use a printbuf without freeing and re-initializing it:
259 static inline void printbuf_reset(struct printbuf *buf)
262 buf->allocation_failure = 0;
264 buf->nr_tabstops = 0;
265 buf->cur_tabstop = 0;
269 * printbuf_atomic_inc - mark as entering an atomic section
271 static inline void printbuf_atomic_inc(struct printbuf *buf)
277 * printbuf_atomic_inc - mark as leaving an atomic section
279 static inline void printbuf_atomic_dec(struct printbuf *buf)
284 #endif /* _BCACHEFS_PRINTBUF_H */