nobug_ringbuffer.c

   1 /*
   2     nobug_ringbuffer.c - a small debugging library
   3
   4   Copyright (C) 2007, Christian Thaeter <ct@pipapo.org>
   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 version 2 as
   8   published by the Free Software Foundation.
   9
  10   This program is distributed in the hope that it will be useful,
  11   but WITHOUT ANY WARRANTY; without even the implied warranty of
  12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13   GNU General Public License for more details.
  14
  15   You should have received a copy of the GNU General Public License
  16   along with this program; if not, contact me.
  17
  18 */
  19 #include <fcntl.h>
  20 #include <errno.h>
  21 #include <unistd.h>
  22 #include <stdarg.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 void
  32 nobug_ringbuffer_init (struct nobug_ringbuffer* self, size_t size, const char * name, enum nobug_ringbuffer_flags 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   munmap(start, size+2*self->maxmsg);
  88
  89   /* map the backing file */
  90   self->start = mmap(start+self->maxmsg, size, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, fd, 0);
  91   /* map beginning after the end */
  92   mmap(start+self->maxmsg+size, self->maxmsg, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, fd, 0);
  93   /* map end before beginning */
  94   mmap(start, self->maxmsg, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, fd, size-self->maxmsg);
  95
  96   close (fd);
  97
  98   if (flags & NOBUG_RINGBUFFER_APPEND)
  99     {
 100       start = memchr(self->start, ~0, size);
 101       if (!start)
 102         /* new file, can't append */
 103         goto init;
 104       self->pos = start-1;
 105       if (self->pos < self->start)
 106         self->pos += size;
 107     }
 108   else
 109     {
 110     init:
 111       /* set pos to the end of the file, then new writes will start at the beginning */
 112       self->pos = self->start+size-1;
 113       /* ~0 is used as marker for the turnaround point */
 114       self->pos[1] = ~0;
 115     }
 116 }
 117
 118 void
 119 nobug_ringbuffer_destroy (struct nobug_ringbuffer* self)
 120 {
 121   if (self->name[0])
 122     unlink(self->name);
 123   munmap(self->start-self->maxmsg, self->size + 2 * self->maxmsg);
 124 }
 125
 126
 127 int
 128 nobug_ringbuffer_printf (struct nobug_ringbuffer* self, const char* fmt, ...)
 129 {
 130   va_list ap;
 131   va_start (ap, fmt);
 132   int written = vsnprintf (self->pos + 1, self->maxmsg-2, fmt, ap);
 133   va_end(ap);
 134   self->pos += (written + 1);
 135
 136   if (self->pos > self->start+self->size)
 137     self->pos -= self->size;
 138
 139   self->pos[1] = ~0;
 140
 141   return written;
 142 }
 143
 144 char*
 145 nobug_ringbuffer_prev (struct nobug_ringbuffer* self, char* pos)
 146 {
 147   if (!pos)
 148     pos = self->pos;
 149   else
 150     --pos;
 151
 152   while(!*--pos);
 153   while(*--pos);
 154   if (pos < self->start)
 155     pos += self->size;
 156
 157   if (pos[1] == ~0)
 158     return NULL;
 159
 160   return pos+1;
 161 }
 162
 163 char*
 164 nobug_ringbuffer_next (struct nobug_ringbuffer* self, char* pos)
 165 {
 166   if (!pos)
 167     pos = self->pos+1;
 168
 169   while (*++pos);
 170   while (!*++pos);
 171   if (pos > self->start+self->size)
 172     pos -= self->size;
 173
 174   if (*pos == ~0)
 175     return NULL;
 176
 177   return pos;
 178 }
 179
 180 int
 181 nobug_ringbuffer_save (struct nobug_ringbuffer* self, FILE* out)
 182 {
 183   int ret = 0;
 184   int cnt;
 185   char* next;
 186
 187   for (next = nobug_ringbuffer_next(self,NULL); next; next = nobug_ringbuffer_next(self, next))
 188     {
 189       cnt = fprintf (out,"%s\n", next);
 190       if (cnt < 0)
 191         return -ret-1;
 192       else
 193         ret += cnt;
 194     }
 195   return ret;
 196 }
 197
 198 int
 199 nobug_ringbuffer_load (struct nobug_ringbuffer* self, FILE* in)
 200 {
 201   int ret = 0;
 202   char buf[NOBUG_RINGBUFFER_MAX_MSG];
 203
 204   while (fgets(buf, self->maxmsg, in))
 205     {
 206       size_t l = strlen(buf);
 207       if (buf[l-1] == '\n')
 208         buf[l-1] = '\0';
 209       ret += nobug_ringbuffer_printf (self, "%s", buf);
 210     }
 211   return ret;
 212 }
 213
 214 char*
 215 nobug_ringbuffer_pos (struct nobug_ringbuffer* self)
 216 {
 217   return self->pos+1;
 218 }
 219
 220 void
 221 nobug_ringbuffer_pop (struct nobug_ringbuffer* self)
 222 {
 223   self->pos[0] = '\n';  /* clear the \0 */
 224   self->pos[1] = ' ';   /* clear the ~0 */
 225
 226   self->pos = strrchr(self->pos, 0);
 227   if (self->pos < self->start)
 228     self->pos += self->size;
 229
 230   self->pos[1] = ~0;
 231 }