fastjar/pushback.c

   1 /* $Id: pushback.c,v 1.1 2000/12/09 03:08:23 apbianco Exp $
   2
   3    $Log: pushback.c,v $
   4    Revision 1.1  2000/12/09 03:08:23  apbianco
   5    2000-12-08  Alexandre Petit-Bianco  <apbianco@cygnus.com>
   6
   7            * fastjar: Imported.
   8
   9    Revision 1.2  2000/08/23 19:42:17  cory
  10    Added support for more Unix platforms.  The following code has been hacked
  11    to work on AIX, Solaris, True 64, and HP-UX.
  12    Added bigendian check.  Probably works on most big and little endian platforms
  13    now.
  14
  15    Revision 1.1.1.1  1999/12/06 03:09:13  toast
  16    initial checkin..
  17
  18
  19
  20    Revision 1.1  1999/05/10 08:32:37  burnsbr
  21    Initial revision
  22
  23 */
  24
  25 /*
  26   pushback.c - code for a pushback buffer to handle file I/O
  27   Copyright (C) 1999  Bryan Burns
  28
  29   This program is free software; you can redistribute it and/or
  30   modify it under the terms of the GNU General Public License
  31   as published by the Free Software Foundation; either version 2
  32   of the License, or (at your option) any later version.
  33
  34   This program is distributed in the hope that it will be useful,
  35   but WITHOUT ANY WARRANTY; without even the implied warranty of
  36   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  37   GNU General Public License for more details.
  38
  39   You should have received a copy of the GNU General Public License
  40   along with this program; if not, write to the Free Software
  41   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  42  */
  43
  44 #include <unistd.h>
  45 #include <string.h>
  46 #include <stdio.h>
  47
  48 #include "jartool.h"
  49 #include "pushback.h"
  50
  51 void pb_init(pb_file *pbf, int fd){
  52   pbf->fd = fd;
  53   pbf->next = pbf->pb_buff;
  54   pbf->buff_amt = 0;
  55 }
  56
  57 int pb_push(pb_file *pbf, void *buff, int amt){
  58   int in_amt;
  59   int wrap = 0;
  60
  61 #ifdef DEBUG
  62   printf("%d bytes being pushed back to the buffer\n", amt);
  63 #endif
  64
  65   /* determine how much we can take */
  66   if((RDSZ - pbf->buff_amt) < amt)
  67     in_amt = RDSZ - pbf->buff_amt;
  68   else
  69     in_amt = amt;
  70
  71   if(in_amt == 0)
  72     return 0;
  73
  74   /* figure out if we need to wrap around, and if so, by how much */
  75   if(((pbf->pb_buff + RDSZ) - pbf->next) < in_amt)
  76     wrap = in_amt - ((pbf->pb_buff + RDSZ) - pbf->next);
  77
  78   /* write everything up til the end of the buffer */
  79   memcpy(pbf->next, buff, (in_amt - wrap));
  80
  81   /* finish writing what's wrapped around */
  82   memcpy(pbf->pb_buff, ((char *)buff + (in_amt - wrap)), wrap);
  83
  84   /* update the buff_amt field */
  85   pbf->buff_amt += in_amt;
  86
  87 #ifdef DEBUG
  88   printf("%d bytes we can't accept\n", (amt - in_amt));
  89 #endif
  90
  91   return in_amt;
  92 }
  93
  94
  95 int pb_read(pb_file *pbf, void *buff, int amt){
  96   int out_amt = 0;
  97   int wrap = 0;
  98   void *bp = buff;
  99   int tmp;
 100
 101 #ifdef DEBUG
 102   printf("%d bytes requested from us\n", amt);
 103 #endif
 104   while(out_amt < amt){
 105     /* if our push-back buffer contains some data */
 106     if(pbf->buff_amt > 0){
 107
 108 #ifdef DEBUG
 109       printf("giving data from buffer\n");
 110 #endif
 111
 112       /* calculate how much we can actually give the caller */
 113       if( (amt - out_amt) < pbf->buff_amt )
 114         tmp = (amt - out_amt);
 115       else
 116         tmp = pbf->buff_amt;
 117
 118       /* Determine if we're going to need to wrap around the buffer */
 119       if(tmp > ((pbf->pb_buff + RDSZ) - pbf->next))
 120         wrap = tmp - ((pbf->pb_buff + RDSZ) - pbf->next);
 121
 122       memcpy(bp, pbf->next, (tmp - wrap));
 123       bp = &(((char *)bp)[tmp - wrap]);
 124
 125       /* If we need to wrap, read from the start of the buffer */
 126       if(wrap > 0){
 127         memcpy(bp, pbf->pb_buff, wrap);
 128         bp = &(((char *)bp)[wrap]);
 129       }
 130
 131       /* update the buff_amt field */
 132       pbf->buff_amt -= tmp;
 133       pbf->next += tmp;
 134
 135 #ifdef DEBUG
 136       printf("%d bytes remaining in buffer\n", pbf->buff_amt);
 137 #endif
 138
 139       /* if the buffer is empty, reset the next header to the front of the
 140          buffer so subsequent pushbacks/reads won't have to wrap */
 141       if(pbf->buff_amt == 0)
 142         pbf->next = pbf->pb_buff;
 143
 144       out_amt += tmp;
 145
 146     } else {
 147 #ifdef DEBUG
 148       printf("Reading from file..\n");
 149 #endif
 150
 151       /* The pushback buffer was empty, so we just need to read from the file */
 152       tmp = read(pbf->fd, bp, (amt - out_amt));
 153       if(tmp == 0)
 154         break;
 155       else
 156         out_amt += tmp;
 157
 158       bp = &(((char *)bp)[tmp]);
 159     }
 160   }
 161
 162 #ifdef DEBUG
 163   printf("managed to read %d bytes\n", out_amt);
 164 #endif
 165   return out_amt;
 166 }