fs/bcachefs/printbuf.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /* Copyright (C) 2022 Kent Overstreet */
   3
   4 #ifndef _BCACHEFS_PRINTBUF_H
   5 #define _BCACHEFS_PRINTBUF_H
   6
   7 /*
   8  * Printbufs: Simple strings for printing to, with optional heap allocation
   9  *
  10  * This code has provisions for use in userspace, to aid in making other code
  11  * portable between kernelspace and userspace.
  12  *
  13  * Basic example:
  14  *   struct printbuf buf = PRINTBUF;
  15  *
  16  *   prt_printf(&buf, "foo=");
  17  *   foo_to_text(&buf, foo);
  18  *   printk("%s", buf.buf);
  19  *   printbuf_exit(&buf);
  20  *
  21  * Or
  22  *   struct printbuf buf = PRINTBUF_EXTERN(char_buf, char_buf_size)
  23  *
  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.
  27  *
  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.
  31  *
  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.
  34  *
  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
  37  * the end.
  38  *
  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.
  43  *
  44  * Indenting, tabstops:
  45  *
  46  * To aid is writing multi-line pretty printers spread across multiple
  47  * functions, printbufs track the current indent level.
  48  *
  49  * printbuf_indent_push() and printbuf_indent_pop() increase and decrease the current indent
  50  * level, respectively.
  51  *
  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.
  57  *
  58  * Make sure you use prt_newline() instead of \n in the format string for indent
  59  * level and tabstops to work corretly.
  60  *
  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.
  64  */
  65
  66 #include <linux/kernel.h>
  67 #include <linux/string.h>
  68
  69 enum printbuf_si {
  70         PRINTBUF_UNITS_2,       /* use binary powers of 2^10 */
  71         PRINTBUF_UNITS_10,      /* use powers of 10^3 (standard SI) */
  72 };
  73
  74 #define PRINTBUF_INLINE_TABSTOPS        6
  75
  76 struct printbuf {
  77         char                    *buf;
  78         unsigned                size;
  79         unsigned                pos;
  80         unsigned                last_newline;
  81         unsigned                last_field;
  82         unsigned                indent;
  83         /*
  84          * If nonzero, allocations will be done with GFP_ATOMIC:
  85          */
  86         u8                      atomic;
  87         bool                    allocation_failure:1;
  88         bool                    heap_allocated:1;
  89         bool                    overflow:1;
  90         enum printbuf_si        si_units:1;
  91         bool                    human_readable_units:1;
  92         bool                    has_indent_or_tabstops:1;
  93         bool                    suppress_indent_tabstop_handling:1;
  94         u8                      nr_tabstops;
  95
  96         /*
  97          * Do not modify directly: use printbuf_tabstop_add(),
  98          * printbuf_tabstop_get()
  99          */
 100         u8                      cur_tabstop;
 101         u8                      _tabstops[PRINTBUF_INLINE_TABSTOPS];
 102 };
 103
 104 int bch2_printbuf_make_room(struct printbuf *, unsigned);
 105 __printf(2, 3) void bch2_prt_printf(struct printbuf *out, const char *fmt, ...);
 106 __printf(2, 0) void bch2_prt_vprintf(struct printbuf *out, const char *fmt, va_list);
 107 const char *bch2_printbuf_str(const struct printbuf *);
 108 void bch2_printbuf_exit(struct printbuf *);
 109
 110 void bch2_printbuf_tabstops_reset(struct printbuf *);
 111 void bch2_printbuf_tabstop_pop(struct printbuf *);
 112 int bch2_printbuf_tabstop_push(struct printbuf *, unsigned);
 113
 114 void bch2_printbuf_indent_add(struct printbuf *, unsigned);
 115 void bch2_printbuf_indent_sub(struct printbuf *, unsigned);
 116
 117 void bch2_prt_newline(struct printbuf *);
 118 void bch2_printbuf_strip_trailing_newline(struct printbuf *);
 119 void bch2_prt_tab(struct printbuf *);
 120 void bch2_prt_tab_rjust(struct printbuf *);
 121
 122 void bch2_prt_bytes_indented(struct printbuf *, const char *, unsigned);
 123 void bch2_prt_human_readable_u64(struct printbuf *, u64);
 124 void bch2_prt_human_readable_s64(struct printbuf *, s64);
 125 void bch2_prt_units_u64(struct printbuf *, u64);
 126 void bch2_prt_units_s64(struct printbuf *, s64);
 127 void bch2_prt_string_option(struct printbuf *, const char * const[], size_t);
 128 void bch2_prt_bitflags(struct printbuf *, const char * const[], u64);
 129 void bch2_prt_bitflags_vector(struct printbuf *, const char * const[],
 130                               unsigned long *, unsigned);
 131
 132 /* Initializer for a heap allocated printbuf: */
 133 #define PRINTBUF ((struct printbuf) { .heap_allocated = true })
 134
 135 /* Initializer a printbuf that points to an external buffer: */
 136 #define PRINTBUF_EXTERN(_buf, _size)                    \
 137 ((struct printbuf) {                                    \
 138         .buf    = _buf,                                 \
 139         .size   = _size,                                \
 140 })
 141
 142 /*
 143  * Returns size remaining of output buffer:
 144  */
 145 static inline unsigned printbuf_remaining_size(struct printbuf *out)
 146 {
 147         if (WARN_ON(out->size && out->pos >= out->size))
 148                 out->pos = out->size - 1;
 149         return out->size - out->pos;
 150 }
 151
 152 /*
 153  * Returns number of characters we can print to the output buffer - i.e.
 154  * excluding the terminating nul:
 155  */
 156 static inline unsigned printbuf_remaining(struct printbuf *out)
 157 {
 158         return out->size ? printbuf_remaining_size(out) - 1 : 0;
 159 }
 160
 161 static inline unsigned printbuf_written(struct printbuf *out)
 162 {
 163         return out->size ? min(out->pos, out->size - 1) : 0;
 164 }
 165
 166 static inline void printbuf_nul_terminate_reserved(struct printbuf *out)
 167 {
 168         if (WARN_ON(out->size && out->pos >= out->size))
 169                 out->pos = out->size - 1;
 170         if (out->size)
 171                 out->buf[out->pos] = 0;
 172 }
 173
 174 static inline void printbuf_nul_terminate(struct printbuf *out)
 175 {
 176         bch2_printbuf_make_room(out, 1);
 177         printbuf_nul_terminate_reserved(out);
 178 }
 179
 180 /* Doesn't call bch2_printbuf_make_room(), doesn't nul terminate: */
 181 static inline void __prt_char_reserved(struct printbuf *out, char c)
 182 {
 183         if (printbuf_remaining(out))
 184                 out->buf[out->pos++] = c;
 185 }
 186
 187 /* Doesn't nul terminate: */
 188 static inline void __prt_char(struct printbuf *out, char c)
 189 {
 190         bch2_printbuf_make_room(out, 1);
 191         __prt_char_reserved(out, c);
 192 }
 193
 194 static inline void prt_char(struct printbuf *out, char c)
 195 {
 196         bch2_printbuf_make_room(out, 2);
 197         __prt_char_reserved(out, c);
 198         printbuf_nul_terminate_reserved(out);
 199 }
 200
 201 static inline void __prt_chars_reserved(struct printbuf *out, char c, unsigned n)
 202 {
 203         unsigned can_print = min(n, printbuf_remaining(out));
 204
 205         for (unsigned i = 0; i < can_print; i++)
 206                 out->buf[out->pos++] = c;
 207 }
 208
 209 static inline void prt_chars(struct printbuf *out, char c, unsigned n)
 210 {
 211         bch2_printbuf_make_room(out, n);
 212         __prt_chars_reserved(out, c, n);
 213         printbuf_nul_terminate_reserved(out);
 214 }
 215
 216 static inline void prt_bytes(struct printbuf *out, const void *b, unsigned n)
 217 {
 218         bch2_printbuf_make_room(out, n);
 219
 220         unsigned can_print = min(n, printbuf_remaining(out));
 221
 222         for (unsigned i = 0; i < can_print; i++)
 223                 out->buf[out->pos++] = ((char *) b)[i];
 224
 225         printbuf_nul_terminate(out);
 226 }
 227
 228 static inline void prt_str(struct printbuf *out, const char *str)
 229 {
 230         prt_bytes(out, str, strlen(str));
 231 }
 232
 233 static inline void prt_str_indented(struct printbuf *out, const char *str)
 234 {
 235         bch2_prt_bytes_indented(out, str, strlen(str));
 236 }
 237
 238 static inline void prt_hex_byte(struct printbuf *out, u8 byte)
 239 {
 240         bch2_printbuf_make_room(out, 3);
 241         __prt_char_reserved(out, hex_asc_hi(byte));
 242         __prt_char_reserved(out, hex_asc_lo(byte));
 243         printbuf_nul_terminate_reserved(out);
 244 }
 245
 246 static inline void prt_hex_byte_upper(struct printbuf *out, u8 byte)
 247 {
 248         bch2_printbuf_make_room(out, 3);
 249         __prt_char_reserved(out, hex_asc_upper_hi(byte));
 250         __prt_char_reserved(out, hex_asc_upper_lo(byte));
 251         printbuf_nul_terminate_reserved(out);
 252 }
 253
 254 /**
 255  * printbuf_reset - re-use a printbuf without freeing and re-initializing it:
 256  */
 257 static inline void printbuf_reset(struct printbuf *buf)
 258 {
 259         buf->pos                = 0;
 260         buf->allocation_failure = 0;
 261         buf->indent             = 0;
 262         buf->nr_tabstops        = 0;
 263         buf->cur_tabstop        = 0;
 264 }
 265
 266 /**
 267  * printbuf_atomic_inc - mark as entering an atomic section
 268  */
 269 static inline void printbuf_atomic_inc(struct printbuf *buf)
 270 {
 271         buf->atomic++;
 272 }
 273
 274 /**
 275  * printbuf_atomic_inc - mark as leaving an atomic section
 276  */
 277 static inline void printbuf_atomic_dec(struct printbuf *buf)
 278 {
 279         buf->atomic--;
 280 }
 281
 282 #endif /* _BCACHEFS_PRINTBUF_H */