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- // 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_test
- import (
- "encoding/asn1"
- "fmt"
- "golang.org/x/crypto/cryptobyte"
- )
- func ExampleString_lengthPrefixed() {
- // This is an example of parsing length-prefixed data (as found in, for
- // example, TLS). Imagine a 16-bit prefixed series of 8-bit prefixed
- // strings.
- input := cryptobyte.String([]byte{0, 12, 5, 'h', 'e', 'l', 'l', 'o', 5, 'w', 'o', 'r', 'l', 'd'})
- var result []string
- var values cryptobyte.String
- if !input.ReadUint16LengthPrefixed(&values) ||
- !input.Empty() {
- panic("bad format")
- }
- for !values.Empty() {
- var value cryptobyte.String
- if !values.ReadUint8LengthPrefixed(&value) {
- panic("bad format")
- }
- result = append(result, string(value))
- }
- // Output: []string{"hello", "world"}
- fmt.Printf("%#v\n", result)
- }
- func ExampleString_asn1() {
- // This is an example of parsing ASN.1 data that looks like:
- // Foo ::= SEQUENCE {
- // version [6] INTEGER DEFAULT 0
- // data OCTET STRING
- // }
- input := cryptobyte.String([]byte{0x30, 12, 0xa6, 3, 2, 1, 2, 4, 5, 'h', 'e', 'l', 'l', 'o'})
- var (
- version int64
- data, inner, versionBytes cryptobyte.String
- haveVersion bool
- )
- if !input.ReadASN1(&inner, cryptobyte.Tag(asn1.TagSequence).Constructed()) ||
- !input.Empty() ||
- !inner.ReadOptionalASN1(&versionBytes, &haveVersion, cryptobyte.Tag(6).Constructed().ContextSpecific()) ||
- (haveVersion && !versionBytes.ReadASN1Integer(&version)) ||
- (haveVersion && !versionBytes.Empty()) ||
- !inner.ReadASN1(&data, asn1.TagOctetString) ||
- !inner.Empty() {
- panic("bad format")
- }
- // Output: haveVersion: true, version: 2, data: hello
- fmt.Printf("haveVersion: %t, version: %d, data: %s\n", haveVersion, version, string(data))
- }
- func ExampleBuilder_asn1() {
- // This is an example of building ASN.1 data that looks like:
- // Foo ::= SEQUENCE {
- // version [6] INTEGER DEFAULT 0
- // data OCTET STRING
- // }
- version := int64(2)
- data := []byte("hello")
- const defaultVersion = 0
- var b cryptobyte.Builder
- b.AddASN1(cryptobyte.Tag(asn1.TagSequence).Constructed(), func(b *cryptobyte.Builder) {
- if version != defaultVersion {
- b.AddASN1(cryptobyte.Tag(6).Constructed().ContextSpecific(), func(b *cryptobyte.Builder) {
- b.AddASN1Int64(version)
- })
- }
- b.AddASN1OctetString(data)
- })
- result, err := b.Bytes()
- if err != nil {
- panic(err)
- }
- // Output: 300ca603020102040568656c6c6f
- fmt.Printf("%x\n", result)
- }
- func ExampleBuilder_lengthPrefixed() {
- // This is an example of building length-prefixed data (as found in,
- // for example, TLS). Imagine a 16-bit prefixed series of 8-bit
- // prefixed strings.
- input := []string{"hello", "world"}
- var b cryptobyte.Builder
- b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
- for _, value := range input {
- b.AddUint8LengthPrefixed(func(b *cryptobyte.Builder) {
- b.AddBytes([]byte(value))
- })
- }
- })
- result, err := b.Bytes()
- if err != nil {
- panic(err)
- }
- // Output: 000c0568656c6c6f05776f726c64
- fmt.Printf("%x\n", result)
- }
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