/* - | Copyright | ------------------------------------------------------------
	 Copyright (c) 2026 Randy Jordan

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

 * --------------------------------------------------------------------------*/
#include "../include/platform/mem/ci2_arena.h"
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

/* Initialize an Arena with an existing buffer  */
void
ci2_arena_back(struct CI2_Arena* a, char* buf, ptrdiff_t len)
{
	assert(a != NULL);
	assert(buf != NULL);
	a->beg = buf;
	a->end = buf + len;
}

/* Allocate a new Arena */
struct CI2_Arena
ci2_arena_new(ptrdiff_t cap)
{
	struct Arena a = { 0 };
	a.beg = malloc(cap);
	a.end = a.beg ? a.beg + cap : 0;
	return a;
}

/* Get the current capacity of an Arena */
ptrdiff_t
ci2_arena_capacity(struct CI2_Arena a)
{
	ptrdiff_t res = a.end - a.beg;
	return res;
}

/* Make an allocation from an Arena and do not zero.*/
void*
ci2_arena_calloc(struct CI2_Arena* a,
								 ptrdiff_t size,
								 ptrdiff_t align,
								 ptrdiff_t count)
{
	ptrdiff_t padding = -(uintptr_t)a->beg & (align - 1);
	ptrdiff_t available = a->end - a->beg - padding;
	if (available < 0 || count > available / size) {
		return NULL;
	}
	ptrdiff_t total = padding + count * size;
	void* p = a->beg + total;
	a->beg += total;
	return memset(p, 0, total);
}

/* Make an allocation from an Arena and zero.*/
void*
ci2_arena_malloc(struct CI2_Arena* a,
								 ptrdiff_t size,
								 ptrdiff_t align,
								 ptrdiff_t count)
{
	ptrdiff_t padding = -(uintptr_t)a->beg & (align - 1);
	ptrdiff_t available = a->end - a->beg - padding;
	if (available < 0 || count > available / size) {
		return NULL;
	}
	ptrdiff_t total = padding + count * size;
	void* p = a->beg + total;
	a->beg += total;
	return p;
}
