source: trunk/athena/bin/delete/stack.c @ 10977

/*
 * $Source: /afs/dev.mit.edu/source/repository/athena/bin/delete/stack.c,v $
 * $Author: danw $
 *
 * This program is part of a package including delete, undelete,
 * lsdel, expunge and purge.  The software suite is meant as a
 * replacement for rm which allows for file recovery.
 * 
 * Copyright (c) 1989 by the Massachusetts Institute of Technology.
 * For copying and distribution information, see the file "mit-copying.h."
 */

#if (!defined(lint) && !defined(SABER))
     static char rcsid_stack_c[] = "$Header: /afs/dev.mit.edu/source/repository/athena/bin/delete/stack.c,v 1.11 1997-12-31 22:36:01 danw Exp $";
#endif

#include <sys/types.h>
#include <stdio.h>
#include <errno.h>
#include "stack.h"
#include "delete_errs.h"
#include "errors.h"
#include "mit-copying.h"
#include "util.h"

#define STACK_INC       25



int dostack(data, op, bytes)
caddr_t data;
int op, bytes;
{
     static caddr_t stack = (caddr_t) NULL;
     static int size = 0, count = 0;
     
     switch (op) {
     case EMPTY_STACK:
          if (size) {
               free(stack);
               stack = (caddr_t) NULL;
               size = count = 0;
          }
#ifdef STACK_DEBUG
          fprintf(stderr, "dostack: return 1 (EMPTY_STACK).\n");
#endif
          return 0;
     case STACK_PUSH:
          if (bytes == 0) {
#ifdef STACK_DEBUG
               fprintf(stderr, "Pushing 0 bytes at %d offset.\n", count);
               fprintf(stderr, "dostack: return 2 (STACK_PUSH).\n");
#endif
               return 0;
          }
          if (size - count < bytes) {
               do
                    size += STACK_INC;
               while (size - count < bytes);
               stack = (caddr_t) (stack ? realloc((char *) stack,
                                                  (unsigned) size) :
                                  Malloc((unsigned) size));
#ifdef MALLOC_0_RETURNS_NULL
               if ((! stack) && size)
#else
               if (! stack)
#endif
               {
                    size = count = 0;
                    set_error(errno);
                    error("Malloc");
#ifdef STACK_DEBUG
                    fprintf(stderr, "dostack: return 3 (STACK_PUSH).\n");
#endif
                    return error_code;
               }
          }
#ifdef STACK_DEBUG
          fprintf(stderr, "Pushing %d bytes at %d offset.\n", bytes, count);
#endif
          memcpy(stack + count, data, bytes);
          count += bytes;
#ifdef STACK_DEBUG
          fprintf(stderr, "dostack: return 4 (STACK_PUSH).\n");
#endif
          return 0;
     case STACK_POP:
          if (bytes == 0) {
#ifdef STACK_DEBUG
               fprintf(stderr, "Popping 0 bytes at %d offset.\n", count);
               fprintf(stderr, "dostack: return 5 (STACK_POP).\n");
#endif
               return 0;
          }
          if (count == 0) {
               set_status(STACK_EMPTY);
#ifdef STACK_DEBUG
               fprintf(stderr, "dostack: return 6 (STACK_POP).\n");
#endif
               return error_code;
          }
          else {
               int newblocks, newsize;

               count -= bytes;
#ifdef STACK_DEBUG
               fprintf(stderr, "Popping %d bytes at %d offset.\n", bytes,
                       count);
#endif
               memcpy(data, stack + count, bytes);
               newblocks = count / STACK_INC + ((count % STACK_INC) ? 1 : 0);
               newsize = newblocks * STACK_INC;
               if (newsize < size) {
                    size = newsize;
                    stack = (caddr_t) realloc((char *) stack, (unsigned) size);
#ifdef MALLOC_0_RETURNS_NULL
                    if ((! stack) && size)
#else
                    if (! stack)
#endif
                    {
                         set_error(errno);
                         error("realloc");
#ifdef STACK_DEBUG
                         fprintf(stderr, "dostack: return 7 (STACK_POP).\n");
#endif
                         return error_code;
                    }
               }
#ifdef STACK_DEBUG
               fprintf(stderr, "dostack: return 8 (STACK_POP).\n");
#endif
               return 0;
          }
     default:
          set_error(STACK_BAD_OP);
#ifdef STACK_DEBUG
          fprintf(stderr, "dostack: return 9.\n");
#endif
          return error_code;
     }
}