// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/* Copyright (c) 2021 Facebook */
/* Copyright (c) 2024, Oracle and/or its affiliates. */

#ifdef __KERNEL__
#include <linux/bpf.h>
#include <linux/btf.h>

#define btf_var_secinfos(t)	(struct btf_var_secinfo *)btf_type_var_secinfo(t)

#else
#include "btf.h"
#include "libbpf_internal.h"
#endif

int btf_field_iter_init(struct btf_field_iter *it, struct btf_type *t,
			enum btf_field_iter_kind iter_kind)
{
	it->p = NULL;
	it->m_idx = -1;
	it->off_idx = 0;
	it->vlen = 0;

	switch (iter_kind) {
	case BTF_FIELD_ITER_IDS:
		switch (btf_kind(t)) {
		case BTF_KIND_UNKN:
		case BTF_KIND_INT:
		case BTF_KIND_FLOAT:
		case BTF_KIND_ENUM:
		case BTF_KIND_ENUM64:
			it->desc = (struct btf_field_desc) {};
			break;
		case BTF_KIND_FWD:
		case BTF_KIND_CONST:
		case BTF_KIND_VOLATILE:
		case BTF_KIND_RESTRICT:
		case BTF_KIND_PTR:
		case BTF_KIND_TYPEDEF:
		case BTF_KIND_FUNC:
		case BTF_KIND_VAR:
		case BTF_KIND_DECL_TAG:
		case BTF_KIND_TYPE_TAG:
			it->desc = (struct btf_field_desc) { 1, {offsetof(struct btf_type, type)} };
			break;
		case BTF_KIND_ARRAY:
			it->desc = (struct btf_field_desc) {
				2, {sizeof(struct btf_type) + offsetof(struct btf_array, type),
				sizeof(struct btf_type) + offsetof(struct btf_array, index_type)}
			};
			break;
		case BTF_KIND_STRUCT:
		case BTF_KIND_UNION:
			it->desc = (struct btf_field_desc) {
				0, {},
				sizeof(struct btf_member),
				1, {offsetof(struct btf_member, type)}
			};
			break;
		case BTF_KIND_FUNC_PROTO:
			it->desc = (struct btf_field_desc) {
				1, {offsetof(struct btf_type, type)},
				sizeof(struct btf_param),
				1, {offsetof(struct btf_param, type)}
			};
			break;
		case BTF_KIND_DATASEC:
			it->desc = (struct btf_field_desc) {
				0, {},
				sizeof(struct btf_var_secinfo),
				1, {offsetof(struct btf_var_secinfo, type)}
			};
			break;
		default:
			return -EINVAL;
		}
		break;
	case BTF_FIELD_ITER_STRS:
		switch (btf_kind(t)) {
		case BTF_KIND_UNKN:
			it->desc = (struct btf_field_desc) {};
			break;
		case BTF_KIND_INT:
		case BTF_KIND_FLOAT:
		case BTF_KIND_FWD:
		case BTF_KIND_ARRAY:
		case BTF_KIND_CONST:
		case BTF_KIND_VOLATILE:
		case BTF_KIND_RESTRICT:
		case BTF_KIND_PTR:
		case BTF_KIND_TYPEDEF:
		case BTF_KIND_FUNC:
		case BTF_KIND_VAR:
		case BTF_KIND_DECL_TAG:
		case BTF_KIND_TYPE_TAG:
		case BTF_KIND_DATASEC:
			it->desc = (struct btf_field_desc) {
				1, {offsetof(struct btf_type, name_off)}
			};
			break;
		case BTF_KIND_ENUM:
			it->desc = (struct btf_field_desc) {
				1, {offsetof(struct btf_type, name_off)},
				sizeof(struct btf_enum),
				1, {offsetof(struct btf_enum, name_off)}
			};
			break;
		case BTF_KIND_ENUM64:
			it->desc = (struct btf_field_desc) {
				1, {offsetof(struct btf_type, name_off)},
				sizeof(struct btf_enum64),
				1, {offsetof(struct btf_enum64, name_off)}
			};
			break;
		case BTF_KIND_STRUCT:
		case BTF_KIND_UNION:
			it->desc = (struct btf_field_desc) {
				1, {offsetof(struct btf_type, name_off)},
				sizeof(struct btf_member),
				1, {offsetof(struct btf_member, name_off)}
			};
			break;
		case BTF_KIND_FUNC_PROTO:
			it->desc = (struct btf_field_desc) {
				1, {offsetof(struct btf_type, name_off)},
				sizeof(struct btf_param),
				1, {offsetof(struct btf_param, name_off)}
			};
			break;
		default:
			return -EINVAL;
		}
		break;
	default:
		return -EINVAL;
	}

	if (it->desc.m_sz)
		it->vlen = btf_vlen(t);

	it->p = t;
	return 0;
}

__u32 *btf_field_iter_next(struct btf_field_iter *it)
{
	if (!it->p)
		return NULL;

	if (it->m_idx < 0) {
		if (it->off_idx < it->desc.t_off_cnt)
			return it->p + it->desc.t_offs[it->off_idx++];
		/* move to per-member iteration */
		it->m_idx = 0;
		it->p += sizeof(struct btf_type);
		it->off_idx = 0;
	}

	/* if type doesn't have members, stop */
	if (it->desc.m_sz == 0) {
		it->p = NULL;
		return NULL;
	}

	if (it->off_idx >= it->desc.m_off_cnt) {
		/* exhausted this member's fields, go to the next member */
		it->m_idx++;
		it->p += it->desc.m_sz;
		it->off_idx = 0;
	}

	if (it->m_idx < it->vlen)
		return it->p + it->desc.m_offs[it->off_idx++];

	it->p = NULL;
	return NULL;
}