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: asn1.go
    path of file: ./repos/plumber/vendor/golang.org/x/crypto/cryptobyte
    
    the code of the file until where you have to start completion: // Copyright 2017 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.

package cryptobyte

import (
	encoding_asn1 "encoding/asn1"
	"fmt"
	"math/big"
	"reflect"
	"time"

	"golang.org/x/crypto/cryptobyte/asn1"
)

// This file contains ASN.1-related methods for String and Builder.

// Builder

// AddASN1Int64 appends a DER-encoded ASN.1 INTEGER.
func (b *
    
func (s *String) readASN1(out *String, outTag *asn1.Tag, skipHeader bool) bool {
	if len(*s) < 2 {
		return false
	}
	tag, lenByte := (*s)[0], (*s)[1]

	if tag&0x1f == 0x1f {
		// ITU-T X.690 section 8.1.2
		//
		// An identifier octet with a tag part of 0x1f indicates a high-tag-number
		// form identifier with two or more octets. We only support tags less than
		// 31 (i.e. low-tag-number form, single octet identifier).
		return false
	}

	if outTag != nil {
		*outTag = asn1.Tag(tag)
	}

	// ITU-T X.690 section 8.1.3
	//
	// Bit 8 of the first length byte indicates whether the length is short- or
	// long-form.
	var length, headerLen uint32 // length includes headerLen
	if lenByte&0x80 == 0 {
		// Short-form length (section 8.1.3.4), encoded in bits 1-7.
		length = uint32(lenByte) + 2
		headerLen = 2
	} else {
		// Long-form length (section 8.1.3.5). Bits 1-7 encode the number of octets
		// used to encode the length.
		lenLen := lenByte & 0x7f
		var len32 uint32

		if lenLen == 0 || lenLen > 4 || len(*s) < int(2+lenLen) {
			return false
		}

		lenBytes := String((*s)[2 : 2+lenLen])
		if !lenBytes.readUnsigned(&len32, int(lenLen)) {
			return false
		}

		// ITU-T X.690 section 10.1 (DER length forms) requires encoding the length
		// with the minimum number of octets.
		if len32 < 128 {
			// Length should have used short-form encoding.
			return false
		}
		if len32>>((lenLen-1)*8) == 0 {
			// Leading octet is 0. Length should have been at least one byte shorter.
			return false
		}

		headerLen = 2 + uint32(lenLen)
		if headerLen+len32 < len32 {
			// Overflow.
			return false
		}
		length = headerLen + len32
	}

	if int(length) < 0 || !s.ReadBytes((*[]byte)(out), int(length)) {
		return false
	}
	if skipHeader && !out.Skip(int(headerLen)) {
		panic("cryptobyte: internal error")
	}

	return true
}