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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Cannot use reusable encoders/decoders in custom codecs","articleBody":"When using reusable encoders/decoders, decoding fails when using the reused `decode()` function in the custom decoding function.\r\n\r\nThe following example works if `USE_REUSABLE_CODING` is set to `false`, meaning the whole logic uses the global `encode`/`decode` function exported by msgpack, but when set to `true`, `encode` and `decode` are reusable instances of `Encode`/`Decore` correspondibly. It fails with `RangeError: Extra 18 of 21 byte(s) found at buffer[3]`.\r\n\r\nDoes reusable encoders/decoders not work with custom codecs?\r\n\r\nExample:\r\n\r\n```ts\r\nimport {\r\n\tEncoder,\r\n\tDecoder,\r\n\tExtensionCodec,\r\n\tencode as _encode,\r\n\tdecode as _decode,\r\n} from \"@msgpack/msgpack\"\r\n\r\n\r\nconst USE_REUSABLE_CODING = true;\r\n\r\nexport class MsgPackContext\r\n{\r\n\treadonly context = this;\r\n\treadonly encode: ( value: unknown ) =\u003e Uint8Array;\r\n\treadonly decode: ( buffer: BufferSource | ArrayLike\u003c number \u003e ) =\u003e unknown;\r\n\treadonly extensionCodec = new ExtensionCodec\u003c MsgPackContext \u003e( );\r\n\r\n\tconstructor( )\r\n\t{\r\n\t\tconst encoder = new Encoder( this.extensionCodec, this );\r\n\t\tconst decoder = new Decoder( this.extensionCodec, this );\r\n\r\n\t\tthis.encode = encoder.encode.bind( encoder );\r\n\t\tthis.decode = decoder.decode.bind( decoder );\r\n\r\n\t\tregisterCodecs( this );\r\n\t}\r\n}\r\n\r\nconst MSGPACK_EXT_TYPE_BIGINT = 0;\r\nconst MSGPACK_EXT_TYPE_MAP = 1;\r\n\r\nexport function registerCodecs( context: MsgPackContext )\r\n{\r\n\tconst { extensionCodec, encode, decode } = context;\r\n\r\n\textensionCodec.register( {\r\n\t\ttype: MSGPACK_EXT_TYPE_BIGINT,\r\n\t\tencode: value =\u003e\r\n\t\t\t( typeof value === 'bigint' || value instanceof BigInt )\r\n\t\t\t?\r\n\t\t\t\tUSE_REUSABLE_CODING\r\n\t\t\t\t? encode( value.toString( ) )\r\n\t\t\t\t: _encode( value.toString( ), context )\r\n\t\t\t: null,\r\n\t\tdecode: data =\u003e\r\n\t\t\tUSE_REUSABLE_CODING\r\n\t\t\t? BigInt( decode( data ) as string )\r\n\t\t\t: BigInt( _decode( data, context ) as string ),\r\n\t} );\r\n\r\n\textensionCodec.register( {\r\n\t\ttype: MSGPACK_EXT_TYPE_MAP,\r\n\t\tencode: value =\u003e\r\n\t\t\tvalue instanceof Map\r\n\t\t\t?\r\n\t\t\t\tUSE_REUSABLE_CODING\r\n\t\t\t\t? encode( [ ...value.entries( ) ] )\r\n\t\t\t\t: _encode( [ ...value.entries( ) ], context )\r\n\t\t\t: null,\r\n\t\tdecode: data =\u003e\r\n\t\t\tUSE_REUSABLE_CODING\r\n\t\t\t? new Map( decode( data ) as Array\u003cany\u003e )\r\n\t\t\t: new Map( _decode( data, context ) as Array\u003cany\u003e ),\r\n\t} );\r\n}\r\n\r\nconst context = new MsgPackContext( );\r\nif ( USE_REUSABLE_CODING )\r\n{\r\n\tconst buf = context.encode( { m: new Map( [ [ 'big', BigInt( 42 ) ] ] ) } );\r\n\tconst data = context.decode( buf );\r\n\tconsole.log( data );\r\n}\r\nelse\r\n{\r\n\tconst buf = _encode( { m: new Map( [ [ 'big', BigInt( 42 ) ] ] ) }, context );\r\n\tconst data = _decode( buf, context );\r\n\tconsole.log( data );\r\n}\r\n```\r\n\r\nJust to be clear, the following is the same code without global `encode`/`decode` usage (`USE_REUSABLE_CODING` being `false`). This code _should_ work, and could be a regression unit test ☺️:\r\n\r\n```ts\r\nimport {\r\n\tEncoder,\r\n\tDecoder,\r\n\tExtensionCodec,\r\n} from \"@msgpack/msgpack\"\r\n\r\n\r\nexport class MsgPackContext\r\n{\r\n\treadonly encode: ( value: unknown ) =\u003e Uint8Array;\r\n\treadonly decode: ( buffer: BufferSource | ArrayLike\u003c number \u003e ) =\u003e unknown;\r\n\treadonly extensionCodec = new ExtensionCodec\u003c MsgPackContext \u003e( );\r\n\r\n\tconstructor( )\r\n\t{\r\n\t\tconst encoder = new Encoder( this.extensionCodec, this );\r\n\t\tconst decoder = new Decoder( this.extensionCodec, this );\r\n\r\n\t\tthis.encode = encoder.encode.bind( encoder );\r\n\t\tthis.decode = decoder.decode.bind( decoder );\r\n\r\n\t\tregisterCodecs( this );\r\n\t}\r\n}\r\n\r\nconst MSGPACK_EXT_TYPE_BIGINT = 0;\r\nconst MSGPACK_EXT_TYPE_MAP = 1;\r\n\r\nexport function registerCodecs( context: MsgPackContext )\r\n{\r\n\tconst { extensionCodec, encode, decode } = context;\r\n\r\n\textensionCodec.register( {\r\n\t\ttype: MSGPACK_EXT_TYPE_BIGINT,\r\n\t\tencode: value =\u003e\r\n\t\t\t( typeof value === 'bigint' || value instanceof BigInt )\r\n\t\t\t? encode( value.toString( ) )\r\n\t\t\t: null,\r\n\t\tdecode: data =\u003e\r\n\t\t\tBigInt( decode( data ) as string ),\r\n\t} );\r\n\r\n\textensionCodec.register( {\r\n\t\ttype: MSGPACK_EXT_TYPE_MAP,\r\n\t\tencode: value =\u003e\r\n\t\t\tvalue instanceof Map\r\n\t\t\t? encode( [ ...value.entries( ) ] )\r\n\t\t\t: null,\r\n\t\tdecode: data =\u003e\r\n\t\t\tnew Map( decode( data ) as Array\u003cany\u003e ),\r\n\t} );\r\n}\r\n\r\nconst context = new MsgPackContext( );\r\nconst buf = context.encode( { m: new Map( [ [ 'big', BigInt( 42 ) ] ] ) } );\r\nconst data = context.decode( buf );\r\nconsole.log( data );\r\n```","author":{"url":"https://github.com/grantila","@type":"Person","name":"grantila"},"datePublished":"2021-10-23T19:09:50.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/195/msgpack-javascript/issues/195"}