/** Memory allocators.
 *
 * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
 * @copyright 2016, Institute for Automation of Complex Power Systems, EONERC
 */

#include <stdlib.h>
#include <sys/mman.h>

/* Required to allocate hugepages on Apple OS X */
#ifdef __MACH__
  #include <mach/vm_statistics.h>
#elif defined(__linux__)
  #include "kernel/kernel.h"
#endif

#include "log.h"
#include "memory.h"

int memory_init()
{
#ifdef __linux__
	int nr = kernel_get_nr_hugepages();
	
	debug(DBG_MEM | 2, "System has %d reserved hugepages", nr);
	
	if (nr < DEFAULT_NR_HUGEPAGES)
		kernel_set_nr_hugepages(DEFAULT_NR_HUGEPAGES);
#endif
	return 0;
}

void * memory_alloc(struct memtype *m, size_t len)
{
	void *ptr = m->alloc(m, len, sizeof(void *));
		
	debug(DBG_MEM | 2, "Allocated %#zx bytes of %s memory: %p", len, m->name, ptr);

	return ptr;
}

void * memory_alloc_aligned(struct memtype *m, size_t len, size_t alignment)
{
	void *ptr = m->alloc(m, len, alignment);
	
	debug(DBG_MEM | 2, "Allocated %#zx bytes of %#zx-byte-aligned %s memory: %p", len, alignment, m->name, ptr);
	
	return ptr;
}

int memory_free(struct memtype *m, void *ptr, size_t len)
{
	debug(DBG_MEM | 2, "Releasing %#zx bytes of %s memory", len, m->name);
	return m->free(m, ptr, len);
}

static void * memory_heap_alloc(struct memtype *m, size_t len, size_t alignment)
{
	void *ptr;
	int ret;
	
	if (alignment < sizeof(void *))
		alignment = sizeof(void *);
	
	ret = posix_memalign(&ptr, alignment, len);
	
	return ret ? NULL : ptr;
}

int memory_heap_free(struct memtype *m, void *ptr, size_t len)
{
	free(ptr);
	
	return 0;
}

/** Allocate memory backed by hugepages with malloc() like interface */
static void * memory_hugepage_alloc(struct memtype *m, size_t len, size_t alignment)
{
	int prot = PROT_READ | PROT_WRITE;
	int flags = MAP_PRIVATE | MAP_ANONYMOUS;
	
#ifdef __MACH__
	flags |= VM_FLAGS_SUPERPAGE_SIZE_2MB;
#elif defined(__linux__)
	flags |= MAP_HUGETLB | MAP_LOCKED;
#endif
	
	void *ret = mmap(NULL, len, prot, flags, -1, 0);
	
	if (ret == MAP_FAILED) {
		info("Failed to allocate huge pages: Check https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt");
		return NULL;
	}
	
	return ret;
}

static int memory_hugepage_free(struct memtype *m, void *ptr, size_t len)
{
	len = ALIGN(len, HUGEPAGESIZE); /* ugly see: https://lkml.org/lkml/2015/3/27/171 */

	return munmap(ptr, len);
}

void* memory_managed_alloc(struct memtype *m, size_t len, size_t alignment)
{
    /* Simple first-fit allocation */
	struct memblock *first = (struct memblock*) m->_vd;
	struct memblock *block;
	for (block = first; block != NULL; block = block->next) {
		if (block->flags & MEMBLOCK_USED)
			continue;
		char* cptr = (char*) block + sizeof(struct memblock);
		size_t avail = block->len;
		uintptr_t uptr = (uintptr_t) cptr;
		/* check alignment first; leave a gap at start of block to assure
		 * alignment if necessary */
		uintptr_t rem = uptr % alignment;
		uintptr_t gap = 0;
		if (rem != 0) {
			gap = alignment - rem;
			if (gap > avail)
				/* next aligned address isn't in this block anymore */
				continue;
			cptr += gap;
			avail -= gap;
		}
		if (avail >= len) {
			if (gap > sizeof(struct memblock)) {
				/* The alignment gap is big enough to fit another block.
				 * The original block descriptor is already at the correct
				 * position, so we just change its len and create a new block
				 * descriptor for the actual block we're handling. */
				block->len = gap - sizeof(struct memblock);
				struct memblock *newblock = (struct memblock*) (cptr - sizeof(struct memblock));
				newblock->prev = block;
				newblock->next = block->next;
				block->next = newblock;
				newblock->flags = 0;
				newblock->len = len;
				block = newblock;
			} else {
				/* The gap is too small to fit another block descriptor, so we
				 * must account for the gap length in the block length. */
				block->len = len + gap;
			}
			if (avail > len + sizeof(struct memblock)) {
				/* imperfect fit, so create another block for the remaining part */
				struct memblock *newblock = (struct memblock*) (cptr + len);
				newblock->prev = block;
				newblock->next = block->next;
				block->next = newblock;
				if (newblock->next)
					newblock->next->prev = newblock;
				newblock->flags = 0;
				newblock->len = avail - len - sizeof(struct memblock);
			} else {
				/* if this block was larger than the requested length, but only
				 * by less than sizeof(struct memblock), we may have wasted
				 * memory by previous assignments to block->len. */
				block->len = avail;
			}
			block->flags |= MEMBLOCK_USED;
			return (void*) cptr;
		}
	}
	/* no suitable block found */
	return NULL;
}

int memory_managed_free(struct memtype *m, void *ptr, size_t len)
{
	struct memblock *first = m->_vd;
	struct memblock *block;
	char* cptr = (char*) ptr;
	for (block = first; block != NULL; block = block->next) {
		if (!(block->flags & MEMBLOCK_USED))
			continue;
		/* since we may waste some memory at the start of a block to ensure
		 * alignment, ptr may not actually be the start of the block */
		if ((char*) block + sizeof(struct memblock) <= cptr &&
		    cptr < (char*) block + sizeof(struct memblock) + block->len) {
			/* try to merge it with neighbouring free blocks */
			if (block->prev && !(block->prev->flags & MEMBLOCK_USED) &&
			    block->next && !(block->next->flags & MEMBLOCK_USED)) {
				/* special case first: both previous and next block are unused */
				block->prev->len += block->len + block->next->len + 2 * sizeof(struct memblock);
				block->prev->next = block->next->next;
				if (block->next->next)
					block->next->next->prev = block->prev;
			} else if (block->prev && !(block->prev->flags & MEMBLOCK_USED)) {
				block->prev->len += block->len + sizeof(struct memblock);
				block->prev->next = block->next;
				if (block->next)
					block->next->prev = block->prev;
			} else if (block->next && !(block->next->flags & MEMBLOCK_USED)) {
				block->len += block->next->len + sizeof(struct memblock);
				block->next = block->next->next;
				if (block->next)
					block->next->prev = block;
			} else {
				/* no neighbouring free block, so just mark it as free */
				block->flags &= (~MEMBLOCK_USED);
			}
			return 0;
		}
	}
	return -1;
}

struct memtype* memtype_managed_init(void *ptr, size_t len)
{
	if (len < sizeof(struct memtype) + sizeof(struct memblock)) {
		info("memtype_managed_init: passed region too small");
		return NULL;
	}
	struct memtype *mt = (struct memtype*) ptr;
	mt->name = "managed";
	mt->flags = 0;
	mt->alloc = memory_managed_alloc;
	mt->free = memory_managed_free;
	mt->alignment = 1;

	char *cptr = (char*) ptr;
	cptr += ALIGN(sizeof(struct memtype), sizeof(void*));
	struct memblock *first = (struct memblock*) ((void*) cptr);
	first->prev = NULL;
	first->next = NULL;
	cptr += ALIGN(sizeof(struct memblock), sizeof(void*));
	first->len = len - (cptr - (char*) ptr);
	first->flags = 0;
	mt->_vd = (void*) first;

	return mt;
}

/* List of available memory types */
struct memtype memtype_heap = {
	.name = "heap",
	.flags = MEMORY_HEAP,
	.alloc = memory_heap_alloc,
	.free = memory_heap_free,
	.alignment = 1,
	._vd = NULL,
};

struct memtype memtype_hugepage = {
	.name = "mmap_hugepages",
	.flags = MEMORY_MMAP | MEMORY_HUGEPAGE,
	.alloc = memory_hugepage_alloc,
	.free = memory_hugepage_free,
	.alignment = 21,  /* 2 MiB hugepage */
	._vd = NULL,
};

/** @todo */
const struct memtype memtype_dma = {
	.name = "dma",
	.flags = MEMORY_DMA | MEMORY_MMAP,
	.alloc = NULL, .free = NULL,
	.alignment = 12
};