libgfortran/io/fbuf.c

   1 /* Copyright (C) 2008-2016 Free Software Foundation, Inc.
   2    Contributed by Janne Blomqvist
   3
   4 This file is part of the GNU Fortran runtime library (libgfortran).
   5
   6 Libgfortran 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 3, or (at your option)
   9 any later version.
  10
  11 Libgfortran 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 Under Section 7 of GPL version 3, you are granted additional
  17 permissions described in the GCC Runtime Library Exception, version
  18 3.1, as published by the Free Software Foundation.
  19
  20 You should have received a copy of the GNU General Public License and
  21 a copy of the GCC Runtime Library Exception along with this program;
  22 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 <http://www.gnu.org/licenses/>.  */
  24
  25
  26 #include "io.h"
  27 #include "fbuf.h"
  28 #include "unix.h"
  29 #include <string.h>
  30 #include <stdlib.h>
  31
  32
  33 //#define FBUF_DEBUG
  34
  35
  36 void
  37 fbuf_init (gfc_unit * u, int len)
  38 {
  39   if (len == 0)
  40     len = 512;                  /* Default size.  */
  41
  42   u->fbuf = xmalloc (sizeof (struct fbuf));
  43   u->fbuf->buf = xmalloc (len);
  44   u->fbuf->len = len;
  45   u->fbuf->act = u->fbuf->pos = 0;
  46 }
  47
  48
  49 void
  50 fbuf_destroy (gfc_unit * u)
  51 {
  52   if (u->fbuf == NULL)
  53     return;
  54   free (u->fbuf->buf);
  55   free (u->fbuf);
  56   u->fbuf = NULL;
  57 }
  58
  59
  60 static void
  61 #ifdef FBUF_DEBUG
  62 fbuf_debug (gfc_unit * u, const char * format, ...)
  63 {
  64   va_list args;
  65   va_start(args, format);
  66   vfprintf(stderr, format, args);
  67   va_end(args);
  68   fprintf (stderr, "fbuf_debug pos: %d, act: %d, buf: ''",
  69            u->fbuf->pos, u->fbuf->act);
  70   for (int ii = 0; ii < u->fbuf->act; ii++)
  71     {
  72       putc (u->fbuf->buf[ii], stderr);
  73     }
  74   fprintf (stderr, "''\n");
  75 }
  76 #else
  77 fbuf_debug (gfc_unit * u __attribute__ ((unused)),
  78             const char * format __attribute__ ((unused)),
  79             ...) {}
  80 #endif
  81
  82
  83
  84 /* You should probably call this before doing a physical seek on the
  85    underlying device.  Returns how much the physical position was
  86    modified.  */
  87
  88 int
  89 fbuf_reset (gfc_unit * u)
  90 {
  91   int seekval = 0;
  92
  93   if (!u->fbuf)
  94     return 0;
  95
  96   fbuf_debug (u, "fbuf_reset: ");
  97   fbuf_flush (u, u->mode);
  98   /* If we read past the current position, seek the underlying device
  99      back.  */
 100   if (u->mode == READING && u->fbuf->act > u->fbuf->pos)
 101     {
 102       seekval = - (u->fbuf->act - u->fbuf->pos);
 103       fbuf_debug (u, "fbuf_reset seekval %d, ", seekval);
 104     }
 105   u->fbuf->act = u->fbuf->pos = 0;
 106   return seekval;
 107 }
 108
 109
 110 /* Return a pointer to the current position in the buffer, and increase
 111    the pointer by len. Makes sure that the buffer is big enough,
 112    reallocating if necessary.  */
 113
 114 char *
 115 fbuf_alloc (gfc_unit * u, int len)
 116 {
 117   int newlen;
 118   char *dest;
 119   fbuf_debug (u, "fbuf_alloc len %d, ", len);
 120   if (u->fbuf->pos + len > u->fbuf->len)
 121     {
 122       /* Round up to nearest multiple of the current buffer length.  */
 123       newlen = ((u->fbuf->pos + len) / u->fbuf->len + 1) * u->fbuf->len;
 124       u->fbuf->buf = xrealloc (u->fbuf->buf, newlen);
 125       u->fbuf->len = newlen;
 126     }
 127
 128   dest = u->fbuf->buf + u->fbuf->pos;
 129   u->fbuf->pos += len;
 130   if (u->fbuf->pos > u->fbuf->act)
 131     u->fbuf->act = u->fbuf->pos;
 132   return dest;
 133 }
 134
 135
 136 /* mode argument is WRITING for write mode and READING for read
 137    mode. Return value is 0 for success, -1 on failure.  */
 138
 139 int
 140 fbuf_flush (gfc_unit * u, unit_mode mode)
 141 {
 142   int nwritten;
 143
 144   if (!u->fbuf)
 145     return 0;
 146
 147   fbuf_debug (u, "fbuf_flush with mode %d: ", mode);
 148
 149   if (mode == WRITING)
 150     {
 151       if (u->fbuf->pos > 0)
 152         {
 153           nwritten = swrite (u->s, u->fbuf->buf, u->fbuf->pos);
 154           if (nwritten < 0)
 155             return -1;
 156         }
 157     }
 158   /* Salvage remaining bytes for both reading and writing. This
 159      happens with the combination of advance='no' and T edit
 160      descriptors leaving the final position somewhere not at the end
 161      of the record. For reading, this also happens if we sread() past
 162      the record boundary.  */
 163   if (u->fbuf->act > u->fbuf->pos && u->fbuf->pos > 0)
 164     memmove (u->fbuf->buf, u->fbuf->buf + u->fbuf->pos,
 165              u->fbuf->act - u->fbuf->pos);
 166
 167   u->fbuf->act -= u->fbuf->pos;
 168   u->fbuf->pos = 0;
 169
 170   return 0;
 171 }
 172
 173
 174 /* The mode argument is LIST_WRITING for write mode and LIST_READING for
 175    read.  This should only be used for list directed  I/O.
 176    Return value is 0 for success, -1 on failure.  */
 177
 178 int
 179 fbuf_flush_list (gfc_unit * u, unit_mode mode)
 180 {
 181   int nwritten;
 182
 183   if (!u->fbuf)
 184     return 0;
 185
 186   if (u->fbuf->pos < 524288) /* Upper limit for list writing.  */
 187     return 0;
 188
 189   fbuf_debug (u, "fbuf_flush_list with mode %d: ", mode);
 190
 191   if (mode == LIST_WRITING)
 192     {
 193       nwritten = swrite (u->s, u->fbuf->buf, u->fbuf->pos);
 194       if (nwritten < 0)
 195         return -1;
 196     }
 197
 198   /* Salvage remaining bytes for both reading and writing.  */
 199   if (u->fbuf->act > u->fbuf->pos)
 200     memmove (u->fbuf->buf, u->fbuf->buf + u->fbuf->pos,
 201              u->fbuf->act - u->fbuf->pos);
 202
 203   u->fbuf->act -= u->fbuf->pos;
 204   u->fbuf->pos = 0;
 205
 206   return 0;
 207 }
 208
 209
 210 int
 211 fbuf_seek (gfc_unit * u, int off, int whence)
 212 {
 213   if (!u->fbuf)
 214     return -1;
 215
 216   switch (whence)
 217     {
 218     case SEEK_SET:
 219       break;
 220     case SEEK_CUR:
 221       off += u->fbuf->pos;
 222       break;
 223     case SEEK_END:
 224       off += u->fbuf->act;
 225       break;
 226     default:
 227       return -1;
 228     }
 229
 230   fbuf_debug (u, "fbuf_seek, off %d ", off);
 231   /* The start of the buffer is always equal to the left tab
 232      limit. Moving to the left past the buffer is illegal in C and
 233      would also imply moving past the left tab limit, which is never
 234      allowed in Fortran. Similarly, seeking past the end of the buffer
 235      is not possible, in that case the user must make sure to allocate
 236      space with fbuf_alloc().  So return error if that is
 237      attempted.  */
 238   if (off < 0 || off > u->fbuf->act)
 239     return -1;
 240   u->fbuf->pos = off;
 241   return off;
 242 }
 243
 244
 245 /* Fill the buffer with bytes for reading.  Returns a pointer to start
 246    reading from. If we hit EOF, returns a short read count. If any
 247    other error occurs, return NULL.  After reading, the caller is
 248    expected to call fbuf_seek to update the position with the number
 249    of bytes actually processed. */
 250
 251 char *
 252 fbuf_read (gfc_unit * u, int * len)
 253 {
 254   char *ptr;
 255   int oldact, oldpos;
 256   int readlen = 0;
 257
 258   fbuf_debug (u, "fbuf_read, len %d: ", *len);
 259   oldact = u->fbuf->act;
 260   oldpos = u->fbuf->pos;
 261   ptr = fbuf_alloc (u, *len);
 262   u->fbuf->pos = oldpos;
 263   if (oldpos + *len > oldact)
 264     {
 265       fbuf_debug (u, "reading %d bytes starting at %d ",
 266                   oldpos + *len - oldact, oldact);
 267       readlen = sread (u->s, u->fbuf->buf + oldact, oldpos + *len - oldact);
 268       if (readlen < 0)
 269         return NULL;
 270       *len = oldact - oldpos + readlen;
 271     }
 272   u->fbuf->act = oldact + readlen;
 273   fbuf_debug (u, "fbuf_read done: ");
 274   return ptr;
 275 }
 276
 277
 278 /* When the fbuf_getc() inline function runs out of buffer space, it
 279    calls this function to fill the buffer with bytes for
 280    reading. Never call this function directly.  */
 281
 282 int
 283 fbuf_getc_refill (gfc_unit * u)
 284 {
 285   int nread;
 286   char *p;
 287
 288   fbuf_debug (u, "fbuf_getc_refill ");
 289
 290   /* Read 80 bytes (average line length?).  This is a compromise
 291      between not needing to call the read() syscall all the time and
 292      not having to memmove unnecessary stuff when switching to the
 293      next record.  */
 294   nread = 80;
 295
 296   p = fbuf_read (u, &nread);
 297
 298   if (p && nread > 0)
 299     return (unsigned char) u->fbuf->buf[u->fbuf->pos++];
 300   else
 301     return EOF;
 302 }