/* If we know we'll reuse small elements often, we'll just preallocate a buffer, then fall back to malloc */
// TODO: Replace free status check with bitmask+CLZ

#ifndef AFL_PREALLOC_H
#define AFL_PREALLOC_H

#include <stdio.h>
#include <stdbool.h>
#include <string.h>

#include "debug.h"

typedef enum prealloc_status {
  PRE_STATUS_UNUSED = 0,/* free in buf */
  PRE_STATUS_USED,      /* used in buf */
  PRE_STATUS_MALLOC     /* system malloc */
} pre_status_t;


/* Adds the entry used for prealloc bookkeeping to this struct */

#define PREALLOCABLE ;pre_status_t pre_status; /* prealloc status of this instance */


/* allocate an element of type *el_ptr, to this variable.
    Uses (and reuses) the given prealloc_buf before hitting libc's malloc.
    prealloc_buf must be the pointer to an array with type `type`.
    `type` must be a struct with uses PREALLOCABLE (a pre_status_t pre_status member).
    prealloc_size must be the array size.
    prealloc_counter must be a variable initialized with 0 (of any name). 
    */

#define PRE_ALLOC(el_ptr, prealloc_buf, prealloc_size, prealloc_counter) do {   \
                                                                                \
  if ((prealloc_counter) >= (prealloc_size)) {                                  \
                                                                                \
    el_ptr = malloc(sizeof(*el_ptr));                                           \
    el_ptr->pre_status = PRE_STATUS_MALLOC;                                     \
                                                                                \
  } else {                                                                      \
                                                                                \
    /* Find one of our preallocated elements */                                 \
    u32 i;                                                                      \
    for (i = 0; i < (prealloc_size); i++) {                                     \
                                                                                \
      el_ptr = &((prealloc_buf)[i]);                                            \
      if (el_ptr->pre_status == PRE_STATUS_UNUSED) {                            \
                                                                                \
        (prealloc_counter)++;                                                   \
        el_ptr->pre_status = PRE_STATUS_USED;                                   \
        break;                                                                  \
                                                                                \
      }                                                                         \
    }                                                                           \
  }                                                                             \
                                                                                \
  if(!el_ptr) {                                                                 \
    FATAL("BUG in list.h -> no element found or allocated!");                   \
  }                                                                             \
} while(0);


/* Take a chosen (free) element from the prealloc_buf directly */

#define PRE_ALLOC_FORCE(el_ptr, prealloc_counter) do {  \
  if ((el_ptr)->pre_status != PRE_STATUS_UNUSED) {      \
    FATAL("PRE_ALLOC_FORCE element already allocated"); \
  }                                                     \
  (el_ptr)->pre_status = PRE_STATUS_USED;               \
  (prealloc_counter)++;                                 \
} while(0);


/* free an preallocated element */

#define PRE_FREE(el_ptr, prealloc_counter) do {     \
                                                    \
  switch ((el_ptr)->pre_status) {                   \
                                                    \
    case PRE_STATUS_USED: {                         \
      (el_ptr)->pre_status = PRE_STATUS_UNUSED;     \
      (prealloc_counter)--;                         \
      if ((prealloc_counter) < 0) {                 \
        FATAL("Inconsistent data in PRE_FREE");     \
      }                                             \
      break;                                        \
    }                                               \
    case PRE_STATUS_MALLOC: {                       \
      (el_ptr)->pre_status = PRE_STATUS_UNUSED;     \
      free((el_ptr));                               \
      break;                                        \
    }                                               \
    default: {                                      \
      FATAL("Double Free Detected");                \
      break;                                        \
    }                                               \
                                                    \
  }                                                 \
} while(0);

#endif