malloc.c

/*
** malloc.c for  in /home/jacqui_p/rendu/PSU_2016_malloc/
**
** Made by Pierre-Emmanuel Jacquier
** Login   <jacqui_p@epitech.eu>
**
** Started on  Mon Jan 30 10:57:50 2017 Pierre-Emmanuel Jacquier
** Last update Sat Feb 11 22:35:05 2017 Pierre-Emmanuel Jacquier
*/

#include <stdint.h>
#include "malloc.h"

t_memblock      *g_head = NULL;

void            *check_block(t_memblock *head, size_t size)
{
  t_memblock    *tmp;

  if (!head)
    return (NULL);
  tmp = head;
  while (tmp)
    {
      if (tmp->memsize >= size && tmp->isfree)
        return (tmp);
      tmp = tmp->next;
    }
  return (NULL);
}

void            split_block(t_memblock *block, size_t size)
{
  char          *new_data_block;
  size_t        old_size;

  if (block->memsize == size || (block->memsize - size) <= META_DATA_SIZE)
    {
      block->isfree = 0;
      return ;
    }
  old_size = block->memsize;
  new_data_block = (char *)block;
  new_data_block += (size + META_DATA_SIZE);
  ((t_memblock *)new_data_block)->next = block->next;
  ((t_memblock *)new_data_block)->prev = block;
  block->isfree = 0;
  block->next = (t_memblock *)new_data_block;
  block->next->isfree = 1;
  block->memsize = size;
  block->next->memsize = old_size - size - META_DATA_SIZE;
  if (block->next->next)
    block->next->next->prev = block->next;
}

void            *add_block(t_memblock *head, size_t size)
{
  t_memblock    *tmp;

  tmp = head;
  if (!tmp)
    {
      tmp = sbrk(0);
      if (sbrk(META_DATA_SIZE + size) == SBRK_ERROR)
        return (NULL);
      tmp->next = NULL;
      tmp->prev = NULL;
      tmp->memsize = size;
      tmp->isfree = 0;
      return (tmp);
    }
  while (tmp->next)
    tmp = tmp->next;
  tmp->next = sbrk(0);
  if (sbrk(META_DATA_SIZE + size) == SBRK_ERROR)
    return (NULL);
  tmp->next->prev = tmp;
  tmp->next->next = NULL;
  tmp->next->memsize = size;
  tmp->next->isfree = 0;
  return (tmp->next);
}

void            *malloc(size_t size)
{
  t_memblock    *block;
  size_t        alloc_size;

  if (!size)
    return (NULL);
  if (size == SIZE_MAX)
    return (NULL);
  size = ALIGN_BLOCK(size);
  alloc_size = ALIGN_TO_PAGESIZE(size);
  block = NULL;
  if (!g_head)
    {
      block = add_block(g_head, alloc_size);
      split_block(block, size);
      g_head = block;
      return (block + 1);
    }
  if ((block = check_block(g_head, size)))
    {
      split_block(block, size);
      return (block + 1);
    }
  block = add_block(g_head, alloc_size);
  split_block(block, size);
  return (block + 1);
}