#include <string.h>

#include "mem.h"

struct mem {
  mem_size_t next, prev;
#if MEM_ALIGNMENT == 1
  u8_t used;
#elif MEM_ALIGNMENT == 2
  u16_t used;
#elif MEM_ALIGNMENT == 4
  u32_t used;
#elif MEM_ALIGNMENT == 8
  u64_t used;
//#else
//#error "unhandled MEM_ALIGNMENT size"
#endif /* MEM_ALIGNMENT */
}; 

static struct mem *ram_end;
static u8_t ram[MEM_SIZE + sizeof(struct mem) + MEM_ALIGNMENT];

#define MIN_SIZE 12
#if 0 /* this one does not align correctly for some, resulting in crashes */
#define SIZEOF_STRUCT_MEM (unsigned int)MEM_ALIGN_SIZE(sizeof(struct mem))
#else
#define SIZEOF_STRUCT_MEM (sizeof(struct mem) + \
                          (((sizeof(struct mem) % MEM_ALIGNMENT) == 0)? 0 : \
                          (4 - (sizeof(struct mem) % MEM_ALIGNMENT))))
#endif

static struct mem *lfree;   /* pointer to the lowest free block */

static u8_t mem_sem;

static void
plug_holes(struct mem *mem)
{
  struct mem *nmem;
  struct mem *pmem;

//  LWIP_ASSERT("plug_holes: mem >= ram", (u8_t *)mem >= ram);
//  LWIP_ASSERT("plug_holes: mem < ram_end", (u8_t *)mem < (u8_t *)ram_end);
//  LWIP_ASSERT("plug_holes: mem->used == 0", mem->used == 0);
  
  /* plug hole forward */
//  LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE", mem->next <= MEM_SIZE);
  
  nmem = (struct mem *)&ram[mem->next];
  if (mem != nmem && nmem->used == 0 && (u8_t *)nmem != (u8_t *)ram_end) {
    if (lfree == nmem) {
      lfree = mem;
    }
    mem->next = nmem->next;
    ((struct mem *)&ram[nmem->next])->prev = (u8_t *)mem - ram;
  }

  /* plug hole backward */
  pmem = (struct mem *)&ram[mem->prev];
  if (pmem != mem && pmem->used == 0) 
  {
    if (lfree == mem) 
    {
      lfree = pmem;
    }
    pmem->next = mem->next;
    ((struct mem *)&ram[mem->next])->prev = (u8_t *)pmem - ram;
  }

}
void mem_init(void)
{
  struct mem *mem;

  memset(ram, 0, MEM_SIZE);
  mem = (struct mem *)ram;
  mem->next = MEM_SIZE;
  mem->prev = 0;
  mem->used = 0;
  ram_end = (struct mem *)&ram[MEM_SIZE];
  ram_end->used = 1;
  ram_end->next = MEM_SIZE;
  ram_end->prev = MEM_SIZE;

//  mem_sem = sys_sem_new(1);

  lfree = (struct mem *)ram;

#if MEM_STATS
  lwip_stats.mem.avail = MEM_SIZE;
#endif /* MEM_STATS */
}

void mem_free(void *rmem)
{
  struct mem *mem;

  if (rmem == NULL) {
//    LWIP_DEBUGF(MEM_DEBUG | DBG_TRACE | 2, ("mem_free(p == NULL) was called.\n"));
    return;
  }
  
//  sys_sem_wait(mem_sem);

//  LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
 //   (u8_t *)rmem < (u8_t *)ram_end);
  
  if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
//    LWIP_DEBUGF(MEM_DEBUG | 3, ("mem_free: illegal memory\n"));
#if MEM_STATS
    ++lwip_stats.mem.err;
#endif /* MEM_STATS */
//    sys_sem_signal(mem_sem);
    return;
  }
  mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);

//  LWIP_ASSERT("mem_free: mem->used", mem->used);
  
  mem->used = 0;

  if (mem < lfree) 
  {
	    lfree = mem;
  }
  
#if MEM_STATS
  lwip_stats.mem.used -= mem->next - ((u8_t *)mem - ram);
  
#endif /* MEM_STATS */
  plug_holes(mem);
//  sys_sem_signal(mem_sem);
}
void *mem_reallocm(void *rmem, mem_size_t newsize)
{
  void *nmem;
  nmem = mem_malloc(newsize);
  if (nmem == NULL) {
    return mem_realloc(rmem, newsize);
  }
  memcpy(nmem, rmem, newsize);
  mem_free(rmem);
  return nmem;
}

void *mem_realloc(void *rmem, mem_size_t newsize)
{
  mem_size_t size;
  mem_size_t ptr, ptr2;
  struct mem *mem, *mem2;

  /* Expand the size of the allocated memory region so that we can
     adjust for alignment. */
  if ((newsize % MEM_ALIGNMENT) != 0) {
   newsize += MEM_ALIGNMENT - ((newsize + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT);
  }
  
  if (newsize > MEM_SIZE) {
    return NULL;
  }
  
//  sys_sem_wait(mem_sem);
  
//  LWIP_ASSERT("mem_realloc: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
//   (u8_t *)rmem < (u8_t *)ram_end);
  
  if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
//   LWIP_DEBUGF(MEM_DEBUG | 3, ("mem_realloc: illegal memory\n"));
    return rmem;
  }
  mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);

  ptr = (u8_t *)mem - ram;

  size = mem->next - ptr - SIZEOF_STRUCT_MEM;
#if MEM_STATS
  lwip_stats.mem.used -= (size - newsize);
#endif /* MEM_STATS */
  
  if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE < size) {
    ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
    mem2 = (struct mem *)&ram[ptr2];
    mem2->used = 0;
    mem2->next = mem->next;
    mem2->prev = ptr;
    mem->next = ptr2;
    if (mem2->next != MEM_SIZE) {
      ((struct mem *)&ram[mem2->next])->prev = ptr2;
    }

    plug_holes(mem2);
  }
//  sys_sem_signal(mem_sem);  
  return rmem;
}
void *mem_malloc(mem_size_t size)
{
  mem_size_t ptr, ptr2;
  struct mem *mem, *mem2;

  if (size == 0) {
    return NULL;
  }

  /* Expand the size of the allocated memory region so that we can
     adjust for alignment. */
  if ((size % MEM_ALIGNMENT) != 0) 
  {
    size += MEM_ALIGNMENT - ((size + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT);
  }
  
  if (size > MEM_SIZE) 
  {
    return NULL;
  }
  
//  sys_sem_wait(mem_sem);

  for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE; ptr = ((struct mem *)&ram[ptr])->next) 
  {
    mem = (struct mem *)&ram[ptr];
    if (!mem->used &&
         mem->next - (ptr + SIZEOF_STRUCT_MEM) >= size + SIZEOF_STRUCT_MEM) 
    {
      ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
      mem2 = (struct mem *)&ram[ptr2];

      mem2->prev = ptr;      
      mem2->next = mem->next;
      mem->next = ptr2;      
      if (mem2->next != MEM_SIZE) 
      {
        ((struct mem *)&ram[mem2->next])->prev = ptr2;
      }
      
      mem2->used = 0;      
      mem->used = 1;
#if MEM_STATS
      lwip_stats.mem.used += (size + SIZEOF_STRUCT_MEM);
      /*      if (lwip_stats.mem.max < lwip_stats.mem.used) {
        lwip_stats.mem.max = lwip_stats.mem.used;
  } */
      if (lwip_stats.mem.max < ptr2) 
      {
        lwip_stats.mem.max = ptr2;
      }      
#endif /* MEM_STATS */

      if (mem == lfree) 
      {
  /* Find next free block after mem */
	        while (lfree->used && lfree != ram_end) 
	        {
	            lfree = (struct mem *)&ram[lfree->next];
	        }
//        LWIP_ASSERT("mem_malloc: !lfree->used", !lfree->used);
      }
//      sys_sem_signal(mem_sem);
//      LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.",
//       (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
//      LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
//       (unsigned long)((u8_t *)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
      return (u8_t *)mem + SIZEOF_STRUCT_MEM;
    }    
  }
//  LWIP_DEBUGF(MEM_DEBUG | 2, ("mem_malloc: could not allocate %d bytes\n", (int)size));
#if MEM_STATS
  ++lwip_stats.mem.err;
#endif /* MEM_STATS */  
  return NULL;
}