next

pub fn next(bc: *BitcodeReader) !?Item {
    while (true) {
        const record = (try bc.nextRecord()) orelse
            return if (bc.stack.items.len > 1) error.EndOfStream else null;
        switch (record.id) {
            else => return .{ .record = record },
            Abbrev.Builtin.end_block.toRecordId() => {
                const block_id = bc.stack.items[bc.stack.items.len - 1].block_id.?;
                try bc.endBlock();
                return .{ .end_block = .{
                    .name = if (bc.block_info.get(block_id)) |block_info|
                        block_info.block_name
                    else
                        &.{},
                    .id = block_id,
                    .len = 0,
                } };
            },
            Abbrev.Builtin.enter_subblock.toRecordId() => {
                const block_id: u32 = @intCast(record.operands[0]);
                switch (block_id) {
                    Block.block_info => {
                        try bc.startBlock(Block.block_info, @intCast(record.operands[1]));
                        try bc.parseBlockInfoBlock();
                        try bc.endBlock();
                    },
                    Block.first_reserved...Block.last_standard => return error.UnsupportedBlockId,
                    else => {
                        try bc.startBlock(block_id, @intCast(record.operands[1]));
                        return .{ .start_block = .{
                            .name = if (bc.block_info.get(block_id)) |block_info|
                                block_info.block_name
                            else
                                &.{},
                            .id = block_id,
                            .len = @intCast(record.operands[2]),
                        } };
                    },
                }
            },
            Abbrev.Builtin.define_abbrev.toRecordId() => try bc.stack.items[bc.stack.items.len - 1]
                .abbrevs.addOwnedAbbrev(bc.allocator, try record.toOwnedAbbrev(bc.allocator)),
        }
    }
}