Update varint processing to use a tagged array instead of a sequence.

digitalbazaar · Oct 16, 2024 · b5aae56 · b5aae56
1 parent 39ef6e3
commit b5aae56
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Showing 4 changed files with 11 additions and 7 deletions.
diff --git a/lib/decode.js b/lib/decode.js
@@ -138,8 +138,11 @@ function _getSuffix({cborldBytes}) {
   let index = 3;
   if(isModern && tagValue >= 128) {
     // FIXME: this assumes tag length <= 31 bytes; throw error if not
-    const varintArrayLength = cborldBytes[index] % 32;
-    index += varintArrayLength + 1;
+    // cborldBytes[index + 1] is the header byte for the varint bytestring
+    const varintArrayLength = cborldBytes[index + 1] % 32;
+    // This sets `index` to the index of the first byte of the second
+    // array element in `cborldBytes`
+    index += varintArrayLength + 2;
   }
   const {buffer, byteOffset, length} = cborldBytes;
   const suffix = new Uint8Array(buffer, byteOffset + index, length - index);

diff --git a/lib/encode.js b/lib/encode.js
@@ -149,7 +149,8 @@ function _getPrefix({isLegacy, compressionMode, registryEntryId}) {
     varintTagValue, varintByteValue
   } = _getVarintStructure(registryEntryId);
   if(varintByteValue) {
-    return [...varintTagValue, ...varintByteValue];
+    // define varintByteValue as first element in 2 element array
+    return [...varintTagValue, ...new Uint8Array([0x82]), ...varintByteValue];
   }
   return varintTagValue;
 

diff --git a/tests/decode.spec.js b/tests/decode.spec.js
@@ -30,15 +30,15 @@ describe('cborld decode', () => {
   it('should decode empty JSON-LD document bytes with varint >1 byte',
     async () => {
       const cborldBytes = new Uint8Array(
-        [0xd9, 0x06, 0x80, 0x81, 0x01, 0xa0]);
+        [0xd9, 0x06, 0x80, 0x82, 0x41, 0x01, 0xa0]);
       const jsonldDocument = await decode({cborldBytes});
       expect(jsonldDocument).deep.equal({});
     });
 
   it('should decode an empty JSON-LD document with multiple byte varint',
     async () => {
       const cborldBytes = new Uint8Array(
-        [0xd9, 0x06, 0x80, 0x44, 0x94, 0xeb, 0xdc, 0x03, 0xa0]);
+        [0xd9, 0x06, 0x80, 0x82, 0x44, 0x94, 0xeb, 0xdc, 0x03, 0xa0]);
       const jsonldDocument = await decode({cborldBytes});
       expect(jsonldDocument).deep.equal({});
     });

diff --git a/tests/encode.spec.js b/tests/encode.spec.js
@@ -46,7 +46,7 @@ describe('cborld encode', () => {
         registryEntryId
       });
       expect(cborldBytes).instanceof(Uint8Array);
-      expect(cborldBytes).equalBytes('d906804101a0');
+      expect(cborldBytes).equalBytes('d90680824101a0');
     });
 
   it('should encode an empty JSON-LD document with multiple byte varint',
@@ -58,7 +58,7 @@ describe('cborld encode', () => {
         registryEntryId
       });
       expect(cborldBytes).instanceof(Uint8Array);
-      expect(cborldBytes).equalBytes('d906804494ebdc03a0');
+      expect(cborldBytes).equalBytes('d90680824494ebdc03a0');
     });
 
   it('should encode xsd dateTime when using a prefix', async () => {