libgfortran/io/fbuf.c

   1 /* Copyright (C) 2008-2015 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 int
 175 fbuf_seek (gfc_unit * u, int off, int whence)
 176 {
 177   if (!u->fbuf)
 178     return -1;
 179
 180   switch (whence)
 181     {
 182     case SEEK_SET:
 183       break;
 184     case SEEK_CUR:
 185       off += u->fbuf->pos;
 186       break;
 187     case SEEK_END:
 188       off += u->fbuf->act;
 189       break;
 190     default:
 191       return -1;
 192     }
 193
 194   fbuf_debug (u, "fbuf_seek, off %d ", off);
 195   /* The start of the buffer is always equal to the left tab
 196      limit. Moving to the left past the buffer is illegal in C and
 197      would also imply moving past the left tab limit, which is never
 198      allowed in Fortran. Similarly, seeking past the end of the buffer
 199      is not possible, in that case the user must make sure to allocate
 200      space with fbuf_alloc().  So return error if that is
 201      attempted.  */
 202   if (off < 0 || off > u->fbuf->act)
 203     return -1;
 204   u->fbuf->pos = off;
 205   return off;
 206 }
 207
 208
 209 /* Fill the buffer with bytes for reading.  Returns a pointer to start
 210    reading from. If we hit EOF, returns a short read count. If any
 211    other error occurs, return NULL.  After reading, the caller is
 212    expected to call fbuf_seek to update the position with the number
 213    of bytes actually processed. */
 214
 215 char *
 216 fbuf_read (gfc_unit * u, int * len)
 217 {
 218   char *ptr;
 219   int oldact, oldpos;
 220   int readlen = 0;
 221
 222   fbuf_debug (u, "fbuf_read, len %d: ", *len);
 223   oldact = u->fbuf->act;
 224   oldpos = u->fbuf->pos;
 225   ptr = fbuf_alloc (u, *len);
 226   u->fbuf->pos = oldpos;
 227   if (oldpos + *len > oldact)
 228     {
 229       fbuf_debug (u, "reading %d bytes starting at %d ",
 230                   oldpos + *len - oldact, oldact);
 231       readlen = sread (u->s, u->fbuf->buf + oldact, oldpos + *len - oldact);
 232       if (readlen < 0)
 233         return NULL;
 234       *len = oldact - oldpos + readlen;
 235     }
 236   u->fbuf->act = oldact + readlen;
 237   fbuf_debug (u, "fbuf_read done: ");
 238   return ptr;
 239 }
 240
 241
 242 /* When the fbuf_getc() inline function runs out of buffer space, it
 243    calls this function to fill the buffer with bytes for
 244    reading. Never call this function directly.  */
 245
 246 int
 247 fbuf_getc_refill (gfc_unit * u)
 248 {
 249   int nread;
 250   char *p;
 251
 252   fbuf_debug (u, "fbuf_getc_refill ");
 253
 254   /* Read 80 bytes (average line length?).  This is a compromise
 255      between not needing to call the read() syscall all the time and
 256      not having to memmove unnecessary stuff when switching to the
 257      next record.  */
 258   nread = 80;
 259
 260   p = fbuf_read (u, &nread);
 261
 262   if (p && nread > 0)
 263     return (unsigned char) u->fbuf->buf[u->fbuf->pos++];
 264   else
 265     return EOF;
 266 }