FrameDescriptionEntry

pub const FrameDescriptionEntry = struct {
    pc_begin: u64,
    pc_range: u64,
    instructions: []const u8,

    /// This function expects to read the FDE starting at the PC Begin field.
    /// The returned struct references memory backed by `fde_bytes`.
    fn parse(
        /// The virtual address of the FDE we're parsing, *excluding* its entry header (i.e. the
        /// address is after the header). If `fde_bytes` is backed by the memory of a loaded
        /// module's `.eh_frame` section, this will equal `fde_bytes.ptr`.
        fde_vaddr: u64,
        fde_bytes: []const u8,
        cie: *const CommonInformationEntry,
        endian: Endian,
    ) !FrameDescriptionEntry {
        if (cie.segment_selector_size != 0) return error.UnsupportedAddrSize;

        var r: Reader = .fixed(fde_bytes);

        const pc_begin = try readEhPointer(&r, cie.fde_pointer_enc, cie.addr_size_bytes, .{
            .pc_rel_base = fde_vaddr,
        }, endian);

        // I swear I'm not kidding when I say that PC Range is encoded with `cie.fde_pointer_enc`, but ignoring `rel`.
        const pc_range = switch (try readEhPointerAbs(&r, cie.fde_pointer_enc.type, cie.addr_size_bytes, endian)) {
            .unsigned => |x| x,
            .signed => |x| cast(u64, x) orelse return bad(),
        };

        switch (cie.augmentation_kind) {
            .none, .gcc_eh => {},
            .lsb_z => {
                // There is augmentation data, but it's irrelevant to us -- it
                // only contains the LSDA pointer, which we don't care about.
                const aug_data_len = try r.takeLeb128(usize);
                _ = try r.discardAll(aug_data_len);
            },
        }

        return .{
            .pc_begin = pc_begin,
            .pc_range = pc_range,
            .instructions = r.buffered(),
        };
    }
}