    const std = @import("../../../std.zig");

    pub const magic = 0xeb9f;
    pub const version = 1;

    pub const ext = @import("btf_ext.zig");

    /// All offsets are in bytes relative to the end of this header
    pub const Header = extern struct {
        magic: u16,
        version: u8,
        flags: u8,
        hdr_len: u32,

        /// offset of type section
        type_off: u32,

        /// length of type section
        type_len: u32,

        /// offset of string section
        str_off: u32,

        /// length of string section
        str_len: u32,
    };

    /// Max number of type identifiers
    pub const max_type = 0xfffff;

    /// Max offset into string section
    pub const max_name_offset = 0xffffff;

    /// Max number of struct/union/enum member of func args
    pub const max_vlen = 0xffff;

    pub const Type = extern struct {
        name_off: u32,
        info: packed struct(u32) {
            /// number of struct's members
            vlen: u16,

            unused_1: u8,
            kind: Kind,
            unused_2: u2,

            /// used by Struct, Union, and Fwd
            kind_flag: bool,
        },

        /// size is used by Int, Enum, Struct, Union, and DataSec, it tells the size
        /// of the type it is describing
        ///
        /// type is used by Ptr, Typedef, Volatile, Const, Restrict, Func,
        /// FuncProto, and Var. It is a type_id referring to another type
        size_type: extern union { size: u32, typ: u32 },
    };

    /// For some kinds, Type is immediately followed by extra data
    pub const Kind = enum(u5) {
        unknown,
        int,
        ptr,
        array,
        @"struct",
        @"union",
        @"enum",
        fwd,
        typedef,
        @"volatile",
        @"const",
        restrict,
        func,
        func_proto,
        @"var",
        datasec,
        float,
        decl_tag,
        type_tag,
        enum64,
    };

    /// int kind is followed by this struct
    pub const IntInfo = packed struct(u32) {
        bits: u8,
        unused: u8,
        offset: u8,
        encoding: enum(u4) {
            signed = 1 << 0,
            char = 1 << 1,
            boolean = 1 << 2,
        },
    };

    test "IntInfo is 32 bits" {
        try std.testing.expectEqual(@bitSizeOf(IntInfo), 32);
    }

    /// enum kind is followed by this struct
    pub const Enum = extern struct {
        name_off: u32,
        val: i32,
    };

    /// enum64 kind is followed by this struct
    pub const Enum64 = extern struct {
        name_off: u32,
        val_lo32: i32,
        val_hi32: i32,
    };

    /// array kind is followed by this struct
    pub const Array = extern struct {
        typ: u32,
        index_type: u32,
        nelems: u32,
    };

    /// struct and union kinds are followed by multiple Member structs. The exact
    /// number is stored in vlen
    pub const Member = extern struct {
        name_off: u32,
        typ: u32,

        /// if the kind_flag is set, offset contains both member bitfield size and
        /// bit offset, the bitfield size is set for bitfield members. If the type
        /// info kind_flag is not set, the offset contains only bit offset
        offset: packed struct(u32) {
            bit: u24,
            bitfield_size: u8,
        },
    };

    /// func_proto is followed by multiple Params, the exact number is stored in vlen
    pub const Param = extern struct {
        name_off: u32,
        typ: u32,
    };

    pub const VarLinkage = enum {
        static,
        global_allocated,
        global_extern,
    };

    pub const FuncLinkage = enum {
        static,
        global,
        external,
    };

    /// var kind is followed by a single Var struct to describe additional
    /// information related to the variable such as its linkage
    pub const Var = extern struct {
        linkage: u32,
    };

    /// datasec kind is followed by multiple VarSecInfo to describe all Var kind
    /// types it contains along with it's in-section offset as well as size.
    pub const VarSecInfo = extern struct {
        typ: u32,
        offset: u32,
        size: u32,
    };

    // decl_tag kind is followed by a single DeclTag struct to describe

    // additional information related to the tag applied location.

    // If component_idx == -1, the tag is applied to a struct, union,

    // variable or function. Otherwise, it is applied to a struct/union

    // member or a func argument, and component_idx indicates which member

    // or argument (0 ... vlen-1).

    pub const DeclTag = extern struct {
        component_idx: u32,
    };