lib/sh/zread.c

   1 /* Copyright (C) 1999 Free Software Foundation, Inc.
   2
   3    This file is part of GNU Bash, the Bourne Again SHell.
   4
   5    Bash is free software; you can redistribute it and/or modify it under
   6    the terms of the GNU General Public License as published by the Free
   7    Software Foundation; either version 2, or (at your option) any later
   8    version.
   9
  10    Bash is distributed in the hope that it will be useful, but WITHOUT ANY
  11    WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13    for more details.
  14
  15    You should have received a copy of the GNU General Public License along
  16    with Bash; see the file COPYING.  If not, write to the Free Software
  17    Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA. */
  18
  19 #include <config.h>
  20
  21 #include <sys/types.h>
  22
  23 #if defined (HAVE_UNISTD_H)
  24 #  include <unistd.h>
  25 #endif
  26
  27 #include <errno.h>
  28
  29 #if !defined (errno)
  30 extern int errno;
  31 #endif
  32
  33 #ifndef SEEK_CUR
  34 #  define SEEK_CUR 1
  35 #endif
  36
  37 /* Read LEN bytes from FD into BUF.  Retry the read on EINTR.  Any other
  38    error causes the loop to break. */
  39 int
  40 zread (fd, buf, len)
  41      int fd;
  42      char *buf;
  43      size_t len;
  44 {
  45   int r;
  46
  47   while ((r = read (fd, buf, len)) < 0 && errno == EINTR)
  48     ;
  49   return r;
  50 }
  51
  52 /* Read LEN bytes from FD into BUF.  Retry the read on EINTR, up to three
  53    interrupts.  Any other error causes the loop to break. */
  54
  55 #ifdef NUM_INTR
  56 #  undef NUM_INTR
  57 #endif
  58 #define NUM_INTR 3
  59
  60 int
  61 zread1 (fd, buf, len)
  62      int fd;
  63      char *buf;
  64      size_t len;
  65 {
  66   int r, nintr;
  67
  68   for (nintr = 0; ; )
  69     {
  70       r = read (fd, buf, len);
  71       if (r >= 0)
  72         return r;
  73       if (r == -1 && errno == EINTR)
  74         {
  75           if (++nintr > NUM_INTR)
  76             return -1;
  77           continue;
  78         }
  79       return r;
  80     }
  81 }
  82
  83 /* Read one character from FD and return it in CP.  Return values are as
  84    in read(2).  This does some local buffering to avoid many one-character
  85    calls to read(2), like those the `read' builtin performs. */
  86
  87 static unsigned char lbuf[128];
  88 static int lind, lused;
  89
  90 int
  91 zreadc (fd, cp)
  92      int fd;
  93      char *cp;
  94 {
  95   int r;
  96
  97   if (lind == lused || lused == 0)
  98     {
  99       lused = zread (fd, lbuf, sizeof (lbuf));
 100       lind = 0;
 101       if (lused <= 0)
 102         return (lused);
 103     }
 104   if (cp)
 105     *cp = (char)lbuf[lind++];
 106   return 1;
 107 }
 108
 109 void
 110 zreset ()
 111 {
 112   lind = lused = 0;
 113 }
 114
 115 /* Sync the seek pointer for FD so that the kernel's idea of the last char
 116    read is the last char returned by zreadc. */
 117 void
 118 zsyncfd (fd)
 119      int fd;
 120 {
 121   int off;
 122
 123   off = lused - lind;
 124   if (off > 0)
 125     lseek (fd, -off, SEEK_CUR);
 126   lused = lind = 0;
 127 }