You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: exportdata.go
    path of file: ./repos/sealer/vendor/golang.org/x/tools/internal/gcimporter
    
    the code of the file until where you have to start completion: // Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file is a copy of $GOROOT/src/go/internal/gcimporter/exportdata.go.

// This file implements FindExportData.

package gcimporter

import (
	"bufio"
	"fmt"
	"io"
	"strconv"
	"strings"
)

func readGopackHeader(r *bufio.Reader) (name string, size
    
func FindExportData(r *bufio.Reader) (hdr string, size int64, err error) {
	// Read first line to make sure this is an object file.
	line, err := r.ReadSlice('\n')
	if err != nil {
		err = fmt.Errorf("can't find export data (%v)", err)
		return
	}

	if string(line) == "!<arch>\n" {
		// Archive file. Scan to __.PKGDEF.
		var name string
		if name, size, err = readGopackHeader(r); err != nil {
			return
		}

		// First entry should be __.PKGDEF.
		if name != "__.PKGDEF" {
			err = fmt.Errorf("go archive is missing __.PKGDEF")
			return
		}

		// Read first line of __.PKGDEF data, so that line
		// is once again the first line of the input.
		if line, err = r.ReadSlice('\n'); err != nil {
			err = fmt.Errorf("can't find export data (%v)", err)
			return
		}
		size -= int64(len(line))
	}

	// Now at __.PKGDEF in archive or still at beginning of file.
	// Either way, line should begin with "go object ".
	if !strings.HasPrefix(string(line), "go object ") {
		err = fmt.Errorf("not a Go object file")
		return
	}

	// Skip over object header to export data.
	// Begins after first line starting with $$.
	for line[0] != '$' {
		if line, err = r.ReadSlice('\n'); err != nil {
			err = fmt.Errorf("can't find export data (%v)", err)
			return
		}
		size -= int64(len(line))
	}
	hdr = string(line)
	if size < 0 {
		size = -1
	}

	return
}