/*
 * Copyright 2019 The Hafnium Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "hf/std.h"

#include "hf/panic.h"

/* Declare unsafe functions locally so they are not available globally. */
void *memset(void *s, int c, size_t n);
void *memcpy(void *dst, const void *src, size_t n);
void *memmove(void *dst, const void *src, size_t n);

void memset_s(void *dest, rsize_t destsz, int ch, rsize_t count)
{
	if (dest == NULL) {
		goto fail;
	}

	if (destsz > RSIZE_MAX || count > RSIZE_MAX) {
		goto fail;
	}

	if (count > destsz) {
		goto fail;
	}

	memset(dest, ch, count);
	return;

fail:
	panic("memset_s failure");
}

void memcpy_s(void *dest, rsize_t destsz, const void *src, rsize_t count)
{
	uintptr_t d = (uintptr_t)dest;
	uintptr_t s = (uintptr_t)src;

	if (dest == NULL || src == NULL) {
		goto fail;
	}

	if (destsz > RSIZE_MAX || count > RSIZE_MAX) {
		goto fail;
	}

	if (count > destsz) {
		goto fail;
	}

	/* Destination overlaps the end of source. */
	if (d > s && d < (s + count)) {
		goto fail;
	}

	/* Source overlaps the end of destination. */
	if (s > d && s < (d + destsz)) {
		goto fail;
	}

	/* TODO: consider wrapping? */

	memcpy(dest, src, count);
	return;

fail:
	panic("memcpy_s failure");
}

void memmove_s(void *dest, rsize_t destsz, const void *src, rsize_t count)
{
	if (dest == NULL || src == NULL) {
		goto fail;
	}

	if (destsz > RSIZE_MAX || count > RSIZE_MAX) {
		goto fail;
	}

	if (count > destsz) {
		goto fail;
	}

	memmove(dest, src, count);
	return;

fail:
	panic("memmove_s failure");
}

size_t strnlen_s(const char *str, size_t strsz)
{
	const char *p = str;

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

	while (*p && strsz--) {
		p++;
	}

	return p - str;
}