StdLib/LibC/Stdio/fseeko.c

   1 /*  $NetBSD: fseeko.c,v 1.5 2005/03/04 16:04:58 dsl Exp $ */
   2
   3 /*-
   4  * Copyright (c) 1990, 1993
   5  *  The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Chris Torek.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34 //#include <Uefi.h>               // REMOVE, For DEBUG only
  35 //#include <Library/UefiLib.h>    // REMOVE, For DEBUG only
  36
  37 #include  <LibConfig.h>
  38 #include <sys/EfiCdefs.h>
  39 #if defined(LIBC_SCCS) && !defined(lint)
  40 __RCSID("$NetBSD: fseeko.c,v 1.5 2005/03/04 16:04:58 dsl Exp $");
  41 #endif /* LIBC_SCCS and not lint */
  42
  43 #include "namespace.h"
  44 #include <sys/types.h>
  45 #include <sys/stat.h>
  46
  47 #include <assert.h>
  48 #include <errno.h>
  49 #include <fcntl.h>
  50 #include <stdio.h>
  51 #include <stdlib.h>
  52 #include "reentrant.h"
  53 #include "local.h"
  54
  55 #ifdef __weak_alias
  56 __weak_alias(fseeko, _fseeko)
  57 #endif
  58
  59 #define POS_ERR (-(fpos_t)1)
  60
  61 /*
  62  * Seek the given file to the given offset.
  63  * `Whence' must be one of the three SEEK_* macros.
  64  */
  65 int
  66 fseeko(FILE *fp, off_t offset, int whence)
  67 {
  68   fpos_t (*seekfn)(void *, fpos_t, int);
  69   fpos_t target, curoff;
  70   size_t n;
  71   struct stat st;
  72   int havepos;
  73
  74   _DIAGASSERT(fp != NULL);
  75
  76 #ifdef __GNUC__
  77   /* This outrageous construct just to shut up a GCC warning. */
  78   (void) &curoff;
  79 #endif
  80
  81   /* make sure stdio is set up */
  82   if (!__sdidinit)
  83     __sinit();
  84
  85 //Print(L"%a( %d, %Ld, %d)\n", __func__, fp->_file, offset, whence);
  86   FLOCKFILE(fp);
  87
  88   /*
  89    * Have to be able to seek.
  90    */
  91   if ((seekfn = fp->_seek) == NULL) {
  92     errno = ESPIPE;     /* historic practice */
  93     FUNLOCKFILE(fp);
  94 //Print(L"%a: %d\n", __func__, __LINE__);
  95     return (-1);
  96   }
  97
  98   /*
  99    * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
 100    * After this, whence is either SEEK_SET or SEEK_END.
 101    */
 102   switch (whence) {
 103
 104   case SEEK_CUR:
 105     /*
 106      * In order to seek relative to the current stream offset,
 107      * we have to first find the current stream offset a la
 108      * ftell (see ftell for details).
 109      */
 110     __sflush(fp); /* may adjust seek offset on append stream */
 111     if (fp->_flags & __SOFF)
 112       curoff = fp->_offset;
 113     else {
 114       curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR);
 115       if (curoff == POS_ERR) {
 116         FUNLOCKFILE(fp);
 117 //Print(L"%a: %d\n", __func__, __LINE__);
 118         return (-1);
 119       }
 120     }
 121     if (fp->_flags & __SRD) {
 122       curoff -= fp->_r;
 123       if (HASUB(fp))
 124         curoff -= fp->_ur;
 125     } else if (fp->_flags & __SWR && fp->_p != NULL)
 126       curoff += fp->_p - fp->_bf._base;
 127
 128     offset += curoff;
 129     whence = SEEK_SET;
 130     havepos = 1;
 131     break;
 132
 133   case SEEK_SET:
 134   case SEEK_END:
 135     curoff = 0;   /* XXX just to keep gcc quiet */
 136     havepos = 0;
 137     break;
 138
 139   default:
 140     errno = EINVAL;
 141     FUNLOCKFILE(fp);
 142 //Print(L"%a: %d\n", __func__, __LINE__);
 143     return (-1);
 144   }
 145
 146   /*
 147    * Can only optimise if:
 148    *  reading (and not reading-and-writing);
 149    *  not unbuffered; and
 150    *  this is a `regular' Unix file (and hence seekfn==__sseek).
 151    * We must check __NBF first, because it is possible to have __NBF
 152    * and __SOPT both set.
 153    */
 154   if (fp->_bf._base == NULL)
 155     __smakebuf(fp);
 156   if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT))
 157     goto dumb;
 158   if ((fp->_flags & __SOPT) == 0) {
 159     if (seekfn != __sseek ||
 160         fp->_file < 0 || fstat(fp->_file, &st) ||
 161         !S_ISREG(st.st_mode)) {
 162       fp->_flags |= __SNPT;
 163       goto dumb;
 164     }
 165     fp->_blksize = st.st_blksize;
 166     fp->_flags |= __SOPT;
 167   }
 168
 169   /*
 170    * We are reading; we can try to optimise.
 171    * Figure out where we are going and where we are now.
 172    */
 173   if (whence == SEEK_SET)
 174     target = offset;
 175   else {
 176     if (fstat(fp->_file, &st))
 177     {
 178 //Print(L"%a: %d\n", __func__, __LINE__);
 179       goto dumb;
 180     }
 181     target = st.st_size + offset;
 182   }
 183
 184   if (!havepos) {
 185     if (fp->_flags & __SOFF)
 186       curoff = fp->_offset;
 187     else {
 188       curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR);
 189       if (curoff == POS_ERR)
 190       {
 191 //Print(L"%a: %d\n", __func__, __LINE__);
 192         goto dumb;
 193       }
 194     }
 195     curoff -= fp->_r;
 196     if (HASUB(fp))
 197       curoff -= fp->_ur;
 198   }
 199
 200   /*
 201    * Compute the number of bytes in the input buffer (pretending
 202    * that any ungetc() input has been discarded).  Adjust current
 203    * offset backwards by this count so that it represents the
 204    * file offset for the first byte in the current input buffer.
 205    */
 206   if (HASUB(fp)) {
 207     curoff += fp->_r; /* kill off ungetc */
 208     n = fp->_up - fp->_bf._base;
 209     curoff -= n;
 210     n += fp->_ur;
 211   } else {
 212     n = fp->_p - fp->_bf._base;
 213     curoff -= n;
 214     n += fp->_r;
 215   }
 216
 217   /*
 218    * If the target offset is within the current buffer,
 219    * simply adjust the pointers, clear EOF, undo ungetc(),
 220    * and return.  (If the buffer was modified, we have to
 221    * skip this; see fgetln.c.)
 222    */
 223   if ((fp->_flags & __SMOD) == 0 &&
 224       target >= curoff && target < (fpos_t)(curoff + n)) {
 225     int o = (int)(target - curoff);
 226
 227     fp->_p = fp->_bf._base + o;
 228     fp->_r = (int)(n - o);
 229     if (HASUB(fp))
 230       FREEUB(fp);
 231     fp->_flags &= ~__SEOF;
 232     FUNLOCKFILE(fp);
 233     return (0);
 234   }
 235
 236   /*
 237    * The place we want to get to is not within the current buffer,
 238    * but we can still be kind to the kernel copyout mechanism.
 239    * By aligning the file offset to a block boundary, we can let
 240    * the kernel use the VM hardware to map pages instead of
 241    * copying bytes laboriously.  Using a block boundary also
 242    * ensures that we only read one block, rather than two.
 243    */
 244   curoff = target & ~(fp->_blksize - 1);
 245   if ((*seekfn)(fp->_cookie, curoff, SEEK_SET) == POS_ERR)
 246   {
 247 //Print(L"%a: %d\n", __func__, __LINE__);
 248     goto dumb;
 249   }
 250   fp->_r = 0;
 251   fp->_p = fp->_bf._base;
 252   if (HASUB(fp))
 253     FREEUB(fp);
 254   fp->_flags &= ~__SEOF;
 255   n = (int)(target - curoff);
 256   if (n) {
 257     if (__srefill(fp) || fp->_r < (int)n)
 258     {
 259 //Print(L"%a: %d\n", __func__, __LINE__);
 260       goto dumb;
 261     }
 262     fp->_p += n;
 263     fp->_r -= (int)n;
 264   }
 265   FUNLOCKFILE(fp);
 266   return (0);
 267
 268   /*
 269    * We get here if we cannot optimise the seek ... just
 270    * do it.  Allow the seek function to change fp->_bf._base.
 271    */
 272 dumb:
 273 //Print(L"%a: %d\n", __func__, __LINE__);
 274   if (__sflush(fp) ||
 275       (*seekfn)(fp->_cookie, (fpos_t)offset, whence) == POS_ERR) {
 276     FUNLOCKFILE(fp);
 277 //Print(L"%a: %d\n", __func__, __LINE__);
 278     return (-1);
 279   }
 280   /* success: clear EOF indicator and discard ungetc() data */
 281   if (HASUB(fp))
 282     FREEUB(fp);
 283   fp->_p = fp->_bf._base;
 284   fp->_r = 0;
 285   /* fp->_w = 0; */ /* unnecessary (I think...) */
 286   fp->_flags &= ~__SEOF;
 287   FUNLOCKFILE(fp);
 288 //Print(L"%a: %d\n", __func__, __LINE__);
 289   return (0);
 290 }