src/nobug_ringbuffer.c

   1 /*
   2  This file is part of the NoBug debugging library.
   3
   4  Copyright (C) 2007, 2008, Christian Thaeter <chth@gmx.net>
   5
   6  This program is free software; you can redistribute it and/or modify
   7  it under the terms of the GNU General Public License as published by
   8  the Free Software Foundation; either version 2 of the License, or
   9  (at your option) any later version.
  10
  11  This program is distributed in the hope that it will be useful,
  12  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  GNU General Public License for more details.
  15
  16  You should have received a copy of the GNU General Public License
  17  along with this program; if not, contact Christian Thaeter <ct@pipapo.org>.
  18 */
  19 #include <fcntl.h>
  20 #include <errno.h>
  21 #include <unistd.h>
  22 #include <stdlib.h>
  23
  24 #include <sys/mman.h>
  25
  26 #define NOBUG_LIBNOBUG_C
  27 #include "nobug.h"
  28
  29 #define NOBUG_RINGBUFFER_MAX_MSG 4094
  30
  31 struct nobug_ringbuffer*
  32 nobug_ringbuffer_init (struct nobug_ringbuffer* self, size_t size, const char * name, int flags)
  33 {
  34   size_t pagesz = sysconf (_SC_PAGESIZE);
  35
  36   size = (size + pagesz-1) & ~(pagesz-1);
  37   self->maxmsg = (NOBUG_RINGBUFFER_MAX_MSG+2 + pagesz-1) & ~(pagesz-1);
  38
  39   self->name[255] = '\0';
  40   if (!name)
  41     {
  42       strcpy(self->name, "/tmp/nobug_ringbufferXXXXXX");
  43     }
  44   else
  45     {
  46       strncpy(self->name, name, 255);
  47     }
  48
  49   int fd = mkstemp(self->name);
  50
  51   int oflags = O_RDWR|O_CREAT;
  52   if (!(flags & NOBUG_RINGBUFFER_APPEND))
  53     oflags |= O_TRUNC;
  54
  55   if (fd == -1 && errno == EINVAL)
  56     fd = open(self->name, oflags, 0600);
  57
  58   if (fd == -1)
  59     {
  60       /* still error, exit here */
  61       fprintf(stderr, "nobug_ringbuffer: Failed to open nobug_ringbuffer %s: %s\n", self->name, strerror(errno));
  62       exit (EXIT_FAILURE);
  63     }
  64
  65   if (!name || flags & NOBUG_RINGBUFFER_TEMP)
  66     unlink (self->name);
  67
  68   if (!name || !(flags & NOBUG_RINGBUFFER_KEEP))
  69     {
  70       /* just in case we need the name later, store the first character at the end */
  71       self->name[255] = self->name[0];
  72       self->name[0] = 0;
  73     }
  74
  75   ftruncate(fd, size);
  76   self->size = size;
  77
  78   /* get contigous address range */
  79   char * start = mmap (0, size+2*self->maxmsg, PROT_NONE, MAP_SHARED|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0);
  80   if (!start)
  81     {
  82       fprintf(stderr, "nobug_ringbuffer: Failed to reserve %d bytes of address space: %s\n",
  83               size+2*self->maxmsg, strerror(errno));
  84       exit (EXIT_FAILURE);
  85     }
  86
  87   /* map the backing file */
  88   self->start = mmap (start+self->maxmsg, size, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, fd, 0);
  89   if (!self->start)
  90     {
  91       fprintf(stderr, "nobug_ringbuffer: Failed to mmap backing file, %s\n", strerror(errno));
  92       exit (EXIT_FAILURE);
  93     }
  94   /* map beginning after the end */
  95   if (!mmap (start+self->maxmsg+size, self->maxmsg, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, fd, 0))
  96     {
  97       fprintf(stderr, "nobug_ringbuffer: Failed to mmap trailing guard page, %s\n", strerror(errno));
  98       exit (EXIT_FAILURE);
  99     }
 100   /* map end before beginning */
 101   if (!mmap (start, self->maxmsg, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, fd, size-self->maxmsg))
 102     {
 103       fprintf(stderr, "nobug_ringbuffer: Failed to mmap leading guard page, %s\n", strerror(errno));
 104       exit (EXIT_FAILURE);
 105     }
 106
 107   close (fd);
 108
 109   if (flags & NOBUG_RINGBUFFER_APPEND)
 110     {
 111       start = memchr (self->start, ~0, size);
 112       if (!start)
 113         /* new file, can't append */
 114         goto init;
 115       self->pos = start-1;
 116       if (self->pos < self->start)
 117         self->pos += size;
 118     }
 119   else
 120     {
 121     init:
 122       /* set pos to the end of the file, then new writes will start at the beginning */
 123       self->pos = self->start+size-1;
 124       /* ~0 is used as marker for the turnaround point */
 125       self->pos[1] = ~0;
 126     }
 127   return self;
 128 }
 129
 130
 131 struct nobug_ringbuffer*
 132 nobug_ringbuffer_new (size_t size, const char * name, int flags)
 133 {
 134   struct nobug_ringbuffer* self = malloc (sizeof (struct nobug_ringbuffer));
 135   if (!self)
 136     return NULL;
 137   return nobug_ringbuffer_init (self, size, name, flags);
 138 }
 139
 140
 141 struct nobug_ringbuffer*
 142 nobug_ringbuffer_destroy (struct nobug_ringbuffer* self)
 143 {
 144   if (self->name[0])
 145     unlink(self->name);
 146   munmap(self->start-self->maxmsg, self->size + 2 * self->maxmsg);
 147   return self;
 148 }
 149
 150
 151 void
 152 nobug_ringbuffer_delete (struct nobug_ringbuffer* self)
 153 {
 154   free (nobug_ringbuffer_destroy (self));
 155 }
 156
 157
 158 int
 159 nobug_ringbuffer_vprintf (struct nobug_ringbuffer* self, const char* fmt, va_list ap)
 160 {
 161   int written = vsnprintf (self->pos + 1, self->maxmsg-2, fmt, ap);
 162   self->pos += (written + 1);
 163
 164   if (self->pos > self->start+self->size)
 165     self->pos -= self->size;
 166
 167   self->pos[1] = ~0;
 168
 169   return written;
 170 }
 171
 172
 173 int
 174 nobug_ringbuffer_printf (struct nobug_ringbuffer* self, const char* fmt, ...)
 175 {
 176   va_list ap;
 177   va_start (ap, fmt);
 178   int written = nobug_ringbuffer_vprintf (self, fmt, ap);
 179   va_end(ap);
 180   return written;
 181 }
 182
 183
 184 char*
 185 nobug_ringbuffer_prev (struct nobug_ringbuffer* self, char* pos)
 186 {
 187   if (!pos)
 188     pos = self->pos;
 189   else
 190     --pos;
 191
 192   while(!*--pos);
 193   while(*--pos);
 194   if (pos < self->start)
 195     pos += self->size;
 196
 197   if (pos[1] == ~0)
 198     return NULL;
 199
 200   return pos+1;
 201 }
 202
 203 char*
 204 nobug_ringbuffer_next (struct nobug_ringbuffer* self, char* pos)
 205 {
 206   if (!pos)
 207     pos = self->pos+1;
 208
 209   while (*++pos);
 210   while (!*++pos);
 211   if (pos > self->start+self->size)
 212     pos -= self->size;
 213
 214   if (*pos == ~0)
 215     return NULL;
 216
 217   return pos;
 218 }
 219
 220 int
 221 nobug_ringbuffer_save (struct nobug_ringbuffer* self, FILE* out)
 222 {
 223   int ret = 0;
 224   int cnt;
 225   char* next;
 226
 227   for (next = nobug_ringbuffer_next (self, NULL); next; next = nobug_ringbuffer_next(self, next))
 228     {
 229       cnt = fprintf (out,"%s\n", next);
 230       if (cnt < 0)
 231         return -ret-1;
 232       else
 233         ret += cnt;
 234     }
 235   return ret;
 236 }
 237
 238 int
 239 nobug_ringbuffer_load (struct nobug_ringbuffer* self, FILE* in)
 240 {
 241   int ret = 0;
 242   char buf[NOBUG_RINGBUFFER_MAX_MSG];
 243
 244   while (fgets(buf, self->maxmsg, in))
 245     {
 246       size_t l = strlen(buf);
 247       if (buf[l-1] == '\n')
 248         buf[l-1] = '\0';
 249       ret += nobug_ringbuffer_printf (self, "%s", buf);
 250     }
 251   return ret;
 252 }
 253
 254 char*
 255 nobug_ringbuffer_pos (struct nobug_ringbuffer* self)
 256 {
 257   return self->pos+1;
 258 }
 259
 260 void
 261 nobug_ringbuffer_pop (struct nobug_ringbuffer* self)
 262 {
 263   self->pos[0] = '\n';  /* clear the \0 */
 264   self->pos[1] = ' ';   /* clear the ~0 */
 265
 266   self->pos = strrchr(self->pos, 0);
 267   if (self->pos < self->start)
 268     self->pos += self->size;
 269
 270   self->pos[1] = ~0;
 271 }