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/* $Id: pushback.c,v 1.1.1.1 2007/08/18 13:57:14 jeunes2 Exp $

   $Log: pushback.c,v $

   Revision 1.1.1.1  2007/08/18 13:57:14  jeunes2

   Initial Revision.

   Revision 1.2  2000/12/14 18:45:35  ghazi

   Warning fixes:

        * compress.c: Include stdlib.h and compress.h.

        (rcsid): Delete.

        (report_str_error): Make static.

        (ez_inflate_str): Delete unused variable.  Add parens in if-stmt.

        (hrd_inflate_str): Likewise.

        * compress.h (init_compression, end_compression, init_inflation,

        end_inflation): Prototype void arguments.

        * dostime.c (rcsid): Delete.

        * jargrep.c: Include ctype.h, stdlib.h, zlib.h and compress.h.

        Make functions static.  Cast ctype function argument to `unsigned

        char'.  Add parens in if-stmts.  Constify.

        (Usage): Change into a macro.

        (jargrep): Remove unused parameter.

        * jartool.c: Constify.  Add parens in if-stmts.  Align

        signed/unsigned char pointers in functions calls using casts.

        (rcsid): Delete.

        (list_jar): Fix printf format specifier.

        (usage): Chop long string into bits.  Reformat.

        * pushback.c (rcsid): Delete.

   Revision 1.1  2000/12/09 03:08:23  apbianco

   2000-12-08  Alexandre Petit-Bianco  <apbianco@cygnus.com>

           * fastjar: Imported.

   Revision 1.2  2000/08/23 19:42:17  cory

   Added support for more Unix platforms.  The following code has been hacked

   to work on AIX, Solaris, True 64, and HP-UX.

   Added bigendian check.  Probably works on most big and little endian platforms

   now.

   Revision 1.1.1.1  1999/12/06 03:09:13  toast

   initial checkin..

   Revision 1.1  1999/05/10 08:32:37  burnsbr

   Initial revision

*/

/*

  pushback.c - code for a pushback buffer to handle file I/O

  Copyright (C) 1999  Bryan Burns

  This program is free software; you can redistribute it and/or

  modify it under the terms of the GNU General Public License

  as published by the Free Software Foundation; either version 2

  of the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,

  but WITHOUT ANY WARRANTY; without even the implied warranty of

  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License

  along with this program; if not, write to the Free Software

  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

 */

#include <unistd.h>

#include <string.h>

#include <stdio.h>

#include "jartool.h"

#include "pushback.h"

void pb_init(pb_file *pbf, int fd){

  pbf->fd = fd;

  pbf->next = pbf->pb_buff;

  pbf->buff_amt = 0;

}

int pb_push(pb_file *pbf, void *buff, int amt){

  int in_amt;

  int wrap = 0;

#ifdef DEBUG

  printf("%d bytes being pushed back to the buffer\n", amt);

#endif

  /* determine how much we can take */

  if((int)(RDSZ - pbf->buff_amt) < amt)

    in_amt = RDSZ - pbf->buff_amt;

  else

    in_amt = amt;

  if(in_amt == 0)

    return 0;

  /* figure out if we need to wrap around, and if so, by how much */

  if(((pbf->pb_buff + RDSZ) - pbf->next) < in_amt)

    wrap = in_amt - ((pbf->pb_buff + RDSZ) - pbf->next);

  /* write everything up til the end of the buffer */

  memcpy(pbf->next, buff, (in_amt - wrap));

  /* finish writing what's wrapped around */

  memcpy(pbf->pb_buff, ((char *)buff + (in_amt - wrap)), wrap);

  /* update the buff_amt field */

  pbf->buff_amt += in_amt;

#ifdef DEBUG

  printf("%d bytes we can't accept\n", (amt - in_amt));

#endif

  return in_amt;

}

int pb_read(pb_file *pbf, void *buff, int amt){

  int out_amt = 0;

  int wrap = 0;

  void *bp = buff;

  int tmp;

#ifdef DEBUG

  printf("%d bytes requested from us\n", amt);

#endif

  while(out_amt < amt){

    /* if our push-back buffer contains some data */

    if(pbf->buff_amt > 0){

#ifdef DEBUG

      printf("giving data from buffer\n");

#endif

      /* calculate how much we can actually give the caller */

      if( (amt - out_amt) < (int)pbf->buff_amt )

        tmp = (amt - out_amt);

      else

        tmp = pbf->buff_amt;

      /* Determine if we're going to need to wrap around the buffer */

      if(tmp > ((pbf->pb_buff + RDSZ) - pbf->next))

        wrap = tmp - ((pbf->pb_buff + RDSZ) - pbf->next);

      memcpy(bp, pbf->next, (tmp - wrap));

      bp = &(((char *)bp)[tmp - wrap]);

      /* If we need to wrap, read from the start of the buffer */

      if(wrap > 0){

        memcpy(bp, pbf->pb_buff, wrap);

        bp = &(((char *)bp)[wrap]);

      }

      /* update the buff_amt field */

      pbf->buff_amt -= tmp;

      pbf->next += tmp;

#ifdef DEBUG

      printf("%d bytes remaining in buffer\n", pbf->buff_amt);

#endif

      /* if the buffer is empty, reset the next header to the front of the

         buffer so subsequent pushbacks/reads won't have to wrap */

      if(pbf->buff_amt == 0)

        pbf->next = pbf->pb_buff;

      out_amt += tmp;

    } else {

#ifdef DEBUG

      printf("Reading from file..\n");

#endif

      /* The pushback buffer was empty, so we just need to read from the file */

      tmp = read(pbf->fd, bp, (amt - out_amt));

      if(tmp == 0)

        break;

      else

        out_amt += tmp;

      bp = &(((char *)bp)[tmp]);

    }

  }

#ifdef DEBUG

  printf("managed to read %d bytes\n", out_amt);

#endif

  return out_amt;

}