Function read [src]

Reads a header for either an FDE or a CIE, then advances the fbr to the position after the trailing structure. fbr must be a FixedBufferReader backed by either the .eh_frame or .debug_frame sections.

Prototype

pub fn read( fbr: *FixedBufferReader, opt_ma: ?*MemoryAccessor, dwarf_section: Section.Id, ) !EntryHeader

Parameters

fbr: *FixedBufferReaderopt_ma: ?*MemoryAccessordwarf_section: Section.Id

Source

  pub fn read(
    fbr: *FixedBufferReader,
    opt_ma: ?*MemoryAccessor,
    dwarf_section: Section.Id,
) !EntryHeader {
    assert(dwarf_section == .eh_frame or dwarf_section == .debug_frame);

    const length_offset = fbr.pos;
    const unit_header = try readUnitHeader(fbr, opt_ma);
    const unit_length = cast(usize, unit_header.unit_length) orelse return bad();
    if (unit_length == 0) return .{
        .length_offset = length_offset,
        .format = unit_header.format,
        .type = .terminator,
        .entry_bytes = &.{},
    };
    const start_offset = fbr.pos;
    const end_offset = start_offset + unit_length;
    defer fbr.pos = end_offset;

    const id = try if (opt_ma) |ma|
        fbr.readAddressChecked(unit_header.format, ma)
    else
        fbr.readAddress(unit_header.format);
    const entry_bytes = fbr.buf[fbr.pos..end_offset];
    const cie_id: u64 = switch (dwarf_section) {
        .eh_frame => CommonInformationEntry.eh_id,
        .debug_frame => switch (unit_header.format) {
            .@"32" => CommonInformationEntry.dwarf32_id,
            .@"64" => CommonInformationEntry.dwarf64_id,
        },
        else => unreachable,
    };

    return .{
        .length_offset = length_offset,
        .format = unit_header.format,
        .type = if (id == cie_id) .cie else .{ .fde = switch (dwarf_section) {
            .eh_frame => try std.math.sub(u64, start_offset, id),
            .debug_frame => id,
            else => unreachable,
        } },
        .entry_bytes = entry_bytes,
    };
}  