Extract ascii2der into a library package

cmd/ascii2der/encoder.go → ascii2der/encoder.go

@@ -12,15 +12,45 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package ascii2der
 
 import (
  "errors"
  "fmt"
+ "unicode/utf16"
 
  "github.com/google/der-ascii/internal"
 )
 
+// appendUTF16 marshals r using UTF-16 and appends the result to dst, returning
+// the updated slice.
+//
+// This logic intentionally tolerates unpaired surrogates.
+func appendUTF16(dst []byte, r rune) []byte {
+ if r <= 0xffff {
+ return append(dst, byte(r>>8), byte(r))
+ }
+
+ r1, r2 := utf16.EncodeRune(r)
+ dst = append(dst, byte(r1>>8), byte(r1))
+ dst = append(dst, byte(r2>>8), byte(r2))
+ return dst
+}
+
+// appendUTF16 marshals r using UTF-32 and appends the result to dst, returning
+// the updated slice.
+//
+// In other words, this function writes r as an integer in big-endian order.
+func appendUTF32(dst []byte, r rune) []byte {
+ return append(dst, byte(r>>24), byte(r>>16), byte(r>>8), byte(r))
+}
+
+// appendBase128 marshals an integer in base 128, a varint format used by OIDs
+// and long-form tag numbers, and appends the result to dst, returning the
+// updated slice.
+//
+// This function is the same as appendBase128WithLength with length set to zero,
+// which cannot fail.
 func appendBase128(dst []byte, value uint32) []byte {
  dst, err := appendBase128WithLength(dst, value, 0)
  if err != nil {
@@ -30,6 +60,11 @@ func appendBase128(dst []byte, value uint32) []byte {
  return dst
 }
 
+// appendBase128 marshals an integer in base 128, a varint format used by OIDs
+// and long-form tag numbers, and appends the result to dst, returning the
+// updated slice.
+//
+// If length is zero, the minimal length is chosen.
 func appendBase128WithLength(dst []byte, value uint32, length int) ([]byte, error) {
  // Count how many bytes are needed.
  var l int
@@ -120,18 +155,25 @@ func appendInteger(dst []byte, value int64) []byte {
  return dst
 }
 
-func appendObjectIdentifier(dst []byte, value []uint32) ([]byte, bool) {
+// appendObjectIdentifier marshals the given array of integers as an OID.
+func appendObjectIdentifier(dst []byte, value []uint32) ([]byte, error) {
  // Validate the input before anything is written.
- if len(value) < 2 || value[0] > 2 || (value[0] < 2 && value[1] > 39) {
- return dst, false
+ if len(value) < 2 {
+ return dst, errors.New("OIDs must have at least two arcs")
+ }
+ if value[0] > 2 {
+ return dst, fmt.Errorf("first arc of an OID must be one of 0, 1, or 2; got %d", value[0])
+ }
+ if value[0] < 2 && value[1] > 39 {
+ return dst, fmt.Errorf("second arc of an OID must be at most 39; got %d", value[1])
  }
  if value[0]*40+value[1] < value[1] {
- return dst, false
+ return dst, errors.New("first two arcs overflowed")
  }
 
  dst = appendBase128(dst, value[0]*40+value[1])
  for _, v := range value[2:] {
  dst = appendBase128(dst, v)
  }
- return dst, true
+ return dst, nil
 }

cmd/ascii2der/encoder_test.go → ascii2der/encoder_test.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package main
+package ascii2der
 
 import (
  "bytes"
@@ -162,21 +162,21 @@ var appendObjectIdentifierTests = []struct {
 
 func TestAppendObjectIdentifier(t *testing.T) {
  for i, tt := range appendObjectIdentifierTests {
- dst, ok := appendObjectIdentifier(nil, tt.value)
+ dst, err := appendObjectIdentifier(nil, tt.value)
  if !tt.ok {
- if ok {
+ if err == nil {
  t.Errorf("%d. appendObjectIdentifier(nil, %v) unexpectedly suceeded.", i, tt.value)
  } else if len(dst) != 0 {
  t.Errorf("%d. appendObjectIdentifier did not preserve input.", i)
  }
  } else if !bytes.Equal(dst, tt.encoded) {
- t.Errorf("%d. appendObjectIdentifier(nil, %v) = %v, wanted %v.", i, tt.value, dst, tt.encoded)
+ t.Errorf("%d. appendObjectIdentifier(nil, %v) = %v, %v, wanted %v.", i, tt.value, dst, err, tt.encoded)
  }
 
  dst = []byte{0}
- dst, ok = appendObjectIdentifier(dst, tt.value)
+ dst, err = appendObjectIdentifier(dst, tt.value)
  if !tt.ok {
- if ok {
+ if err == nil {
  t.Errorf("%d. appendObjectIdentifier(nil, %v) unexpectedly suceeded.", i, tt.value)
  } else if !bytes.Equal(dst, []byte{0}) {
  t.Errorf("%d. appendObjectIdentifier did not preserve input.", i)

ascii2der/examples_test.go

@@ -0,0 +1,31 @@
+// Copyright 2015 The DER ASCII Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ascii2der
+
+import (
+ "fmt"
+)
+
+func Example() {
+ scanner := NewScanner(`
+ SEQUENCE {
+ INTEGER { "totally an integer" }
+ }
+`)
+
+ der, _ := scanner.Exec()
+ fmt.Printf("%x\n", der)
+ // Output: 30140212746f74616c6c7920616e20696e7465676572
+}