vmalloc.c

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/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/
 
#include <vmalloc/vmalloc.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
 
static bool make_space(Vmalloc_t *vm) {
 
  if (vm->size == vm->capacity) {
 
    // expand our allocation storage
    size_t c = vm->capacity == 0 ? 1 : vm->capacity * 2;
    void **p = realloc(vm->allocated, sizeof(vm->allocated[0]) * c);
    if (p == NULL) {
      return false;
    }
 
    // save the new array
    vm->allocated = p;
    vm->capacity = c;
  }
 
  return true;
}
 
void *vmalloc(Vmalloc_t *vm, size_t size) {
 
  if (!make_space(vm)) {
    return NULL;
  }
 
  void *p = malloc(size);
  if (p == NULL) {
    return NULL;
  }
 
  vm->allocated[vm->size] = p;
  ++vm->size;
 
  return p;
}
 
void vmfree(Vmalloc_t *vm, void *data) {
 
  if (!data) { // ANSI-ism
    return;
  }
 
  // find the pointer we previously allocated
  for (size_t i = 0; i < vm->size; ++i) {
    if (vm->allocated[i] == data) {
 
      // clear this slot
      size_t extent = sizeof(vm->allocated[0]) * (vm->size - i - 1);
      memmove(vm->allocated + i, vm->allocated + i + 1, extent);
      --vm->size;
 
      // give this back to the underlying allocator
      free(data);
 
      return;
    }
  }
 
  // we did not find this pointer; free() of something we did not allocate
}