ber: Test the encoding/decoding of the Length on a BER string

BERTLVStream.st

@@ -178,3 +178,44 @@ Object subclass: BERTag [
         ^ Array with: self classType with: self isConstructed with: self tagValue.
     ]
 ]
+
+Object subclass: BERLength [
+    <category: 'osmo-asn1'>
+    <comment: 'I can handle the length for definite and indefinite length. I wonder
+of myself if I should be class or instance based or even be a SmallInteger or an
+extension to a SmallInteger. Should I have a method called isIndefinite. Time will tell.'>
+
+    BERLength class >> new [
+        ^ self error: 'Only use the class helper functions'
+    ]
+
+    BERLength class >> parseMultiOctet: len from: aStream [
+        "I should handle paragraph 8.1.3.5. But I don't."
+        <category: 'private-decoding'>
+        ^ self error: 'Decoding multi octet length is not implemented'.
+    ]
+
+    BERLength class >> parseFrom: aStream [
+        | len |
+        <category: 'decoding'>
+
+        len := aStream next.
+        ^ (len bitAnd: 16r80) > 0
+            ifTrue:  [self parseMultiOctet: len from: aStream]
+            ifFalse: [len].
+    ]
+
+    BERLength class >> writeMultiOctet: aLength on: aStream [
+        <category: 'private-encoding'>
+        ^ self error: 'Multi octet writing is not implemented yet'.
+    ]
+
+    BERLength class >> writeLength: aLength on: aStream [
+        <category: 'encoding'>
+
+        ^ aLength > 16r7F
+            ifTrue:  [self writeMultiOctet: aLength on: aStream]
+            ifFalse: [aStream nextPut: aLength].
+    ]
+]
+

BERTLVStreamTest.st

@@ -41,3 +41,37 @@ TestCase subclass: BERTagTest [
         self assert: stream contents = #(16rA1) asByteArray
     ]
 ]
+
+TestCase subclass: BERLengthTest [
+    testSimpleLengthRead [
+        | read |
+        read := BERLength parseFrom: #(10) asByteArray readStream.
+        self assert: read = 10.
+    ]
+
+    testSimpleLenghWrite [
+        | write stream |
+        stream := WriteStream on: (ByteArray new: 1).
+        write := BERLength writeLength: 10 on: stream.
+        self assert: stream contents = #(10) asByteArray
+    ]
+
+    testIndefiniteRead [
+        "I test that indefinite coding is not implemented"
+        self should: [BERLength parseFrom: #(16r80) asByteArray readStream] raise: Error
+    ]
+
+    testLongRead [
+        "I test that a multi octet length can not be read"
+        self should: [BERLength parseFrom: #(16r83 0 0 0) asByteArray readStream] raise: Error
+    ]
+
+    testLongWrite [
+        | stream | 
+
+        "I test that a multi octet length can not be written"
+        stream := WriteStream on: (ByteArray new: 1).
+        self should: [BERLength writeLength: 128 on: stream] raise: Error.
+    ]
+]
+

package.xml

@@ -9,6 +9,7 @@
         <sunit>Osmo.BERTest</sunit>
         <sunit>Osmo.BERTagTest</sunit>
         <sunit>Osmo.BERTLVStreamTest</sunit>
+        <sunit>Osmo.BERLengthTest</sunit>
         <filein>Tests.st</filein>
         <filein>BERTLVStreamTest.st</filein>
     </test>