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_eargs;
 116
 117 struct printfrr_ext {
 118         /* embedded string to minimize cache line pollution */
 119         char match[8];
 120
 121         /* both can be given, if not the code continues searching
 122          * (you can do %pX and %dX in 2 different entries)
 123          *
 124          * return value: number of bytes that would be printed if the buffer
 125          * was large enough.  be careful about not under-reporting this;
 126          * otherwise asnprintf() & co. will get broken.  Returning -1 means
 127          * something went wrong & default %p/%d handling should be executed.
 128          *
 129          * to consume extra input flags after %pXY, increment *fmt.  It points
 130          * at the first character after %pXY at entry.  Convention is to make
 131          * those flags lowercase letters or numbers.
 132          */
 133         ssize_t (*print_ptr)(struct fbuf *buf, struct printfrr_eargs *info,
 134                              const void *);
 135         ssize_t (*print_int)(struct fbuf *buf, struct printfrr_eargs *info,
 136                              uintmax_t);
 137 };
 138
 139 /* additional information passed to extended formatters */
 140
 141 struct printfrr_eargs {
 142         /* position in the format string.  Points to directly after the
 143          * extension specifier.  Increment when consuming extra "flag
 144          * characters".
 145          */
 146         const char *fmt;
 147
 148         /* %.1234x / %.*x
 149          * not POSIX compatible when used with %p, will cause warnings from
 150          * GCC & clang.  Usable with %d.  Not used by the printfrr() itself
 151          * for extension specifiers, so essentially available as a "free"
 152          * parameter.  -1 if not specified.  Value in the format string
 153          * cannot be negative, but negative values can be passed with %.*x
 154          */
 155         int precision;
 156
 157         /* %1234x / %*x
 158          * regular width specification.  Internally handled by printfrr(), set
 159          * to 0 if consumed by the extension in order to suppress standard
 160          * width/padding behavior.  0 if not specified.
 161          *
 162          * NB: always positive, even if a negative value is passed in with
 163          * %*x.  (The sign is used for the - flag.)
 164          */
 165         int width;
 166
 167         /* %#x
 168          * "alternate representation" flag, not POSIX compatible when used
 169          * with %p or %d, will cause warnings from GCC & clang.  Not used by
 170          * printfrr() itself for extension specifiers.
 171          */
 172         bool alt_repr;
 173
 174         /* %-x
 175          * left-pad flag.  Internally handled by printfrr() if width is
 176          * nonzero.  Only use if the extension sets width to 0.
 177          */
 178         bool leftadj;
 179 };
 180
 181 /* no locking - must be called when single threaded (e.g. at startup.)
 182  * this restriction hopefully won't be a huge bother considering normal usage
 183  * scenarios...
 184  */
 185 void printfrr_ext_reg(const struct printfrr_ext *);
 186
 187 #define printfrr_ext_autoreg_p(matchs, print_fn)                               \
 188         static ssize_t print_fn(struct fbuf *, struct printfrr_eargs *,        \
 189                                 const void *);                                 \
 190         static const struct printfrr_ext _printext_##print_fn = {              \
 191                 .match = matchs,                                               \
 192                 .print_ptr = print_fn,                                         \
 193         };                                                                     \
 194         static void _printreg_##print_fn(void) __attribute__((constructor));   \
 195         static void _printreg_##print_fn(void) {                               \
 196                 printfrr_ext_reg(&_printext_##print_fn);                       \
 197         }                                                                      \
 198         /* end */
 199
 200 #define printfrr_ext_autoreg_i(matchs, print_fn)                               \
 201         static ssize_t print_fn(struct fbuf *, struct printfrr_eargs *,        \
 202                                 uintmax_t);                                    \
 203         static const struct printfrr_ext _printext_##print_fn = {              \
 204                 .match = matchs,                                               \
 205                 .print_int = print_fn,                                         \
 206         };                                                                     \
 207         static void _printreg_##print_fn(void) __attribute__((constructor));   \
 208         static void _printreg_##print_fn(void) {                               \
 209                 printfrr_ext_reg(&_printext_##print_fn);                       \
 210         }                                                                      \
 211         /* end */
 212
 213 /* fbuf helper functions */
 214
 215 static inline ssize_t bputs(struct fbuf *buf, const char *str)
 216 {
 217         size_t len = strlen(str);
 218         size_t ncopy;
 219
 220         if (!buf)
 221                 return len;
 222
 223         ncopy = MIN(len, (size_t)(buf->buf + buf->len - buf->pos));
 224         memcpy(buf->pos, str, ncopy);
 225         buf->pos += ncopy;
 226
 227         return len;
 228 }
 229
 230 static inline ssize_t bputch(struct fbuf *buf, char ch)
 231 {
 232         if (buf && buf->pos < buf->buf + buf->len)
 233                 *buf->pos++ = ch;
 234         return 1;
 235 }
 236
 237 #ifdef __cplusplus
 238 }
 239 #endif
 240
 241 #endif