lib/printfrr.h

   1 /*
   2  * Copyright (c) 2019  David Lamparter, for NetDEF, Inc.
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16
  17 #ifndef _FRR_PRINTFRR_H
  18 #define _FRR_PRINTFRR_H
  19
  20 #include <stddef.h>
  21 #include <stdarg.h>
  22 #include <stdint.h>
  23
  24 #include "compiler.h"
  25 #include "memory.h"
  26
  27 #ifdef __cplusplus
  28 extern "C" {
  29 #endif
  30
  31 struct fmt_outpos {
  32         unsigned int off_start, off_end;
  33 };
  34
  35 struct fbuf {
  36         char *buf;
  37         char *pos;
  38         size_t len;
  39
  40         struct fmt_outpos *outpos;
  41         size_t outpos_n, outpos_i;
  42 };
  43
  44 #define at(a, b) PRINTFRR(a, b)
  45 #define atn(a, b) \
  46         at(a, b) __attribute__((nonnull(1) _RET_NONNULL))
  47 #define atm(a, b) \
  48         atn(a, b) __attribute__((malloc))
  49
  50 /* return value is length needed for the full string (excluding \0) in all
  51  * cases.  The functions write as much as they can, but continue regardless,
  52  * so the return value is independent of buffer length.  Both bprintfrr and
  53  * snprintf also accept NULL as output buffer.
  54  */
  55
  56 /* bprintfrr does NOT null terminate! use sparingly (only provided since it's
  57  * the most direct interface) - useful for incrementally building long text
  58  * (call bprintfrr repeatedly with the same buffer)
  59  */
  60 ssize_t vbprintfrr(struct fbuf *out, const char *fmt, va_list) at(2, 0);
  61 ssize_t  bprintfrr(struct fbuf *out, const char *fmt, ...)     at(2, 3);
  62
  63 /* these do null terminate like their snprintf cousins */
  64 ssize_t vsnprintfrr(char *out, size_t sz, const char *fmt, va_list) at(3, 0);
  65 ssize_t  snprintfrr(char *out, size_t sz, const char *fmt, ...)     at(3, 4);
  66
  67 /* c = continue / concatenate (append at the end of the string)
  68  * return value is would-be string length (regardless of buffer length),
  69  * i.e. includes already written chars */
  70 ssize_t vcsnprintfrr(char *out, size_t sz, const char *fmt, va_list) at(3, 0);
  71 ssize_t  csnprintfrr(char *out, size_t sz, const char *fmt, ...)     at(3, 4);
  72
  73 /* memory allocations don't fail in FRR, so you always get something here.
  74  * (in case of error, returns a strdup of the format string) */
  75 char *vasprintfrr(struct memtype *mt, const char *fmt, va_list) atm(2, 0);
  76 char  *asprintfrr(struct memtype *mt, const char *fmt, ...)     atm(2, 3);
  77
  78 /* try to use provided buffer (presumably from stack), allocate if it's too
  79  * short.  Must call XFREE(mt, return value) if return value != out.
  80  */
  81 char *vasnprintfrr(struct memtype *mt, char *out, size_t sz,
  82                    const char *fmt, va_list) atn(4, 0);
  83 char  *asnprintfrr(struct memtype *mt, char *out, size_t sz,
  84                    const char *fmt, ...)     atn(4, 5);
  85
  86 #define printfrr(fmt, ...)                                                     \
  87         do {                                                                   \
  88                 char buf[256], *out;                                           \
  89                 out = asnprintfrr(MTYPE_TMP, buf, sizeof(buf), fmt,            \
  90                                   ##__VA_ARGS__);                              \
  91                 fputs(out, stdout);                                            \
  92                 if (out != buf)                                                \
  93                         XFREE(MTYPE_TMP, out);                                 \
  94         } while (0)
  95
  96 #undef at
  97 #undef atm
  98 #undef atn
  99
 100 /* extension specs must start with a capital letter (this is a restriction
 101  * for both performance's and human understanding's sake.)
 102  *
 103  * Note that the entire thing mostly works because a letter directly following
 104  * a %p print specifier is extremely unlikely to occur (why would you want to
 105  * print "0x12345678HELLO"?)  Normally, you'd expect spacing or punctuation
 106  * after a placeholder.  That also means that neither of those works well for
 107  * extension purposes, e.g. "%p{foo}" is reasonable to see actually used.
 108  *
 109  * TODO: would be nice to support a "%pF%dF" specifier that consumes 2
 110  * arguments, e.g. to pass an integer + a list of known values...  can be
 111  * done, but a bit tricky.
 112  */
 113 #define printfrr_ext_char(ch) ((ch) >= 'A' && (ch) <= 'Z')
 114
 115 struct printfrr_ext {
 116         /* embedded string to minimize cache line pollution */
 117         char match[8];
 118
 119         /* both can be given, if not the code continues searching
 120          * (you can do %pX and %dX in 2 different entries)
 121          *
 122          * return value: number of bytes that would be printed if the buffer
 123          * was large enough.  be careful about not under-reporting this;
 124          * otherwise asnprintf() & co. will get broken.  Returning -1 means
 125          * something went wrong & default %p/%d handling should be executed.
 126          *
 127          * to consume extra input flags after %pXY, increment *fmt.  It points
 128          * at the first character after %pXY at entry.  Convention is to make
 129          * those flags lowercase letters or numbers.
 130          *
 131          * prec is the precision specifier (the 999 in "%.999p")  -1 means
 132          * none given (value in the format string cannot be negative)
 133          */
 134         ssize_t (*print_ptr)(struct fbuf *buf, const char **fmt, int prec,
 135                         const void *);
 136         ssize_t (*print_int)(struct fbuf *buf, const char **fmt, int prec,
 137                         uintmax_t);
 138 };
 139
 140 /* no locking - must be called when single threaded (e.g. at startup.)
 141  * this restriction hopefully won't be a huge bother considering normal usage
 142  * scenarios...
 143  */
 144 void printfrr_ext_reg(const struct printfrr_ext *);
 145
 146 #define printfrr_ext_autoreg_p(matchs, print_fn)                               \
 147         static ssize_t print_fn(struct fbuf *, const char **, int,             \
 148                                 const void *);                                 \
 149         static const struct printfrr_ext _printext_##print_fn = {              \
 150                 .match = matchs,                                               \
 151                 .print_ptr = print_fn,                                         \
 152         };                                                                     \
 153         static void _printreg_##print_fn(void) __attribute__((constructor));   \
 154         static void _printreg_##print_fn(void) {                               \
 155                 printfrr_ext_reg(&_printext_##print_fn);                       \
 156         }                                                                      \
 157         /* end */
 158
 159 #define printfrr_ext_autoreg_i(matchs, print_fn)                               \
 160         static ssize_t print_fn(struct fbuf *, const char **, int, uintmax_t); \
 161         static const struct printfrr_ext _printext_##print_fn = {              \
 162                 .match = matchs,                                               \
 163                 .print_int = print_fn,                                         \
 164         };                                                                     \
 165         static void _printreg_##print_fn(void) __attribute__((constructor));   \
 166         static void _printreg_##print_fn(void) {                               \
 167                 printfrr_ext_reg(&_printext_##print_fn);                       \
 168         }                                                                      \
 169         /* end */
 170
 171 /* fbuf helper functions */
 172
 173 static inline ssize_t bputs(struct fbuf *buf, const char *str)
 174 {
 175         size_t len = strlen(str);
 176         size_t ncopy;
 177
 178         if (!buf)
 179                 return len;
 180
 181         ncopy = MIN(len, (size_t)(buf->buf + buf->len - buf->pos));
 182         memcpy(buf->pos, str, ncopy);
 183         buf->pos += ncopy;
 184
 185         return len;
 186 }
 187
 188 static inline ssize_t bputch(struct fbuf *buf, char ch)
 189 {
 190         if (buf && buf->pos < buf->buf + buf->len)
 191                 *buf->pos++ = ch;
 192         return 1;
 193 }
 194
 195 #ifdef __cplusplus
 196 }
 197 #endif
 198
 199 #endif