bad_allocator.cpp

/**
 * Copyright (c) 2012 MIT License by 6.172 Staff
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 **/

#include <stdio.h>
#include <cstdlib>
#include "./allocator_interface.h"
#include "./memlib.h"
#define BAD_SIZE 4101

namespace my {
// bad_init - Does nothing.
int bad_allocator::init() {
  return 0;
}

// bad_check - No checker.
int bad_allocator::check() {
  return 1;
}

// bad_malloc - Allocate a block by incrementing the brk pointer.
// Always allocate a block whose size is not a multiple of the alignment,
// and may not fit the requested allocation size.
void * bad_allocator::malloc(size_t size) {
  size = BAD_SIZE;  // Overrides input, and has bad alignent.
  void *p = mem_sbrk(size);

  if (p == (void *) -1) {
    // The heap is probably full, so return NULL.
    return NULL;
  } else {
    return p;
  }
}

// bad_free - Freeing a block does nothing.
void bad_allocator::free(void *ptr) {
  // Do nothing.
}

// bad_realloc - Implemented simply in terms of bad_malloc and bad_free, but lacks
// copy step.
void * bad_allocator::realloc(void *ptr, size_t size) {
  void *newptr;

  // Allocate a new chunk of memory, and fail if that allocation fails.
  newptr = malloc(size);

  if (NULL == newptr) {
    return NULL;
  }

  // Release the old block.
  free(ptr);

  // Return a pointer to the new block.
  return newptr;
}


// call mem_reset_brk.
void bad_allocator::reset_brk() {
  mem_reset_brk();
}

// call mem_heap_lo
void * bad_allocator::heap_lo() {
  return mem_heap_lo();
}

// call mem_heap_hi
void * bad_allocator::heap_hi() {
  return mem_heap_hi();
}
};