Fixed #50

Author: calebsander

README.md

@@ -83,7 +83,7 @@ const tribeType = new sb.StructType({
 	money: new sb.MapType(personType, new sb.FloatType)
 });
 ````
-### Converting types and values to `Buffer`s
+### Converting types and values to binary data
 ````javascript
 const sb = require('structure-bytes');
 
@@ -97,9 +97,9 @@ const tribeType = new sb.StructType({
 	members: new sb.SetType(personType),
 	money: new sb.MapType(personType, new sb.FloatType)
 });
-let typeBuffer = tribeType.toBuffer(); //ArrayBuffer { byteLength: 49 }
+let typeBuffer = tribeType.toBuffer(); //ArrayBuffer { byteLength: 47 }
 console.log(Buffer.from(typeBuffer));
-//<Buffer 51 03 06 6c 65 61 64 65 72 51 03 03 64 6f 62 15 02 69 64 12 04 6e 61 6d 65 41 07 6d 65 6d 62 65 72 73 53 ff 00 1b 05 6d 6f 6e 65 79 54 ff 00 25 20>
+//<Buffer 51 03 06 6c 65 61 64 65 72 51 03 03 64 6f 62 1a 02 69 64 12 04 6e 61 6d 65 41 07 6d 65 6d 62 65 72 73 53 ff 1b 05 6d 6f 6e 65 79 54 ff 24 20>
 
 let louis = {
 	dob: new Date(1437592284193),
@@ -120,16 +120,16 @@ let value = {
 	members: new Set().add(louis).add(garfield),
 	money: new Map().set(louis, 23.05).set(garfield, -10.07)
 };
-let valueBuffer = tribeType.valueBuffer(value); //ArrayBuffer { byteLength: 100 }
+let valueBuffer = tribeType.valueBuffer(value); //ArrayBuffer { byteLength: 94 }
 console.log(Buffer.from(valueBuffer));
-//<Buffer 00 00 01 4e b7 2d 6c 20 00 0a 4a 6f 65 00 00 00 00 02 00 00 01 4e b7 2d 6c 21 00 09 4c 6f 75 69 73 00 00 00 01 4e b7 2d 6c 22 00 11 47 61 72 66 69 65 ... >
+//<Buffer 00 00 01 4e b7 2d 6c 20 00 0a 4a 6f 65 00 02 00 00 01 4e b7 2d 6c 21 00 09 4c 6f 75 69 73 00 00 00 01 4e b7 2d 6c 22 00 11 47 61 72 66 69 65 6c 64 00 ... >
 ````
-### Reading from type and value `Buffer`s
+### Reading from type and value buffers
 ````javascript
 const sb = require('structure-bytes');
 
 //Buffer obtained somehow
-let tribeBuffer = new Uint8Array([0x51, 0x03, 0x06, 0x6c, 0x65, 0x61, 0x64, 0x65, 0x72, 0x51, 0x03, 0x03, 0x64, 0x6f, 0x62, 0x15, 0x02, 0x69, 0x64, 0x12, 0x04, 0x6e, 0x61, 0x6d, 0x65, 0x41, 0x07, 0x6d, 0x65, 0x6d, 0x62, 0x65, 0x72, 0x73, 0x53, 0xff, 0x00, 0x1b, 0x05, 0x6d, 0x6f, 0x6e, 0x65, 0x79, 0x54, 0xff, 0x00, 0x25, 0x20]);
+let tribeBuffer = new Uint8Array([0x51, 0x03, 0x06, 0x6c, 0x65, 0x61, 0x64, 0x65, 0x72, 0x51, 0x03, 0x03, 0x64, 0x6f, 0x62, 0x1a, 0x02, 0x69, 0x64, 0x12, 0x04, 0x6e, 0x61, 0x6d, 0x65, 0x41, 0x07, 0x6d, 0x65, 0x6d, 0x62, 0x65, 0x72, 0x73, 0x53, 0xff, 0x1b, 0x05, 0x6d, 0x6f, 0x6e, 0x65, 0x79, 0x54, 0xff, 0x24, 0x20]);
 let type = sb.r.type(tribeBuffer.buffer);
 console.log(type);
 /*
@@ -141,8 +141,8 @@ StructType {
 */
 
 //Buffer obtained somehow
-let valueBuffer = new Uint8Array([0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x20, 0x00, 0x0a, 0x4a, 0x6f, 0x65, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x21, 0x00, 0x09, 0x4c, 0x6f, 0x75, 0x69, 0x73, 0x00, 0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x22, 0x00, 0x11, 0x47, 0x61, 0x72, 0x66, 0x69, 0x65, 0x6c, 0x64, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x21, 0x00, 0x09, 0x4c, 0x6f, 0x75, 0x69, 0x73, 0x00, 0x41, 0xb8, 0x66, 0x66, 0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x22, 0x00, 0x11, 0x47, 0x61, 0x72, 0x66, 0x69, 0x65, 0x6c, 0x64, 0x00, 0xc1, 0x21, 0x1e, 0xb8]);
-console.log(sb.r.value({type, buffer: valueBuffer.buffer}));
+let valueBuffer = new Uint8Array([0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x20, 0x00, 0x0a, 0x4a, 0x6f, 0x65, 0x00, 0x02, 0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x21, 0x00, 0x09, 0x4c, 0x6f, 0x75, 0x69, 0x73, 0x00, 0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x22, 0x00, 0x11, 0x47, 0x61, 0x72, 0x66, 0x69, 0x65, 0x6c, 0x64, 0x00, 0x02, 0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x21, 0x00, 0x09, 0x4c, 0x6f, 0x75, 0x69, 0x73, 0x00, 0x41, 0xb8, 0x66, 0x66, 0x00, 0x00, 0x01, 0x4e, 0xb7, 0x2d, 0x6c, 0x22, 0x00, 0x11, 0x47, 0x61, 0x72, 0x66, 0x69, 0x65, 0x6c, 0x64, 0x00, 0xc1, 0x21, 0x1e, 0xb8]);
+console.log(type.readValue(valueBuffer.buffer));
 /*
 { leader: { dob: 2015-07-22T19:11:24.192Z, id: 10, name: 'Joe' },
   members:
@@ -287,6 +287,11 @@ that it requires the value to be of type:
 */
 ````
 You can even add explicit `VALUE` generics to make the compiler check that your `Type` serializes the correct types of values.
+Many non-primitive types (e.g. `ArrayType`, `MapType`, `StructType`) can take either one or two generics.
+The first, `VALUE`, specifies the type of values the type can write.
+The second, `READ_VALUE`, specifies the type of values the type will read from written values and defaults to `VALUE` if omitted.
+Generally the two generics are the same, except in the case of numeric types (which write `number | string` but read `number`) and `OptionalType` (which writes `E | null | undefined` but reads `E | null`).
+`READ_VALUE` must be a subset of `VALUE`, so in most cases where you specify the generic it makes sense to restrict `VALUE` to the type of read values and let `READ_VALUE` default to `VALUE`.
 
 With `StructType`:
 ````typescript
@@ -328,10 +333,11 @@ let structType = new sb.StructType<SerializedCar>({
 
 With `ChoiceType` (and similarly for `NamedChoiceType`), you can let the type be inferred automatically if each of the possible types writes the same type of values:
 ````javascript
-let type = new sb.ChoiceType([ //Type<number | string>
+let type = new sb.ChoiceType([ //Type<number | string, number>
 	new sb.ByteType,
 	new sb.ShortType,
-	new sb.IntType
+	new sb.IntType,
+	new sb.DoubleType
 ])
 ````
 However, if the value types are not the same, TypeScript will complain about them not matching, and you should express the union type explicitly:

client-side/download.ts

@@ -65,7 +65,7 @@ export function download({name, url, options}: DownloadOptions): Promise<any> {
 			if (typeInCache && typeInCache.sig === sig) {
 				return response.arrayBuffer()
 					.then(buffer => {
-						const value = r.value({buffer, type: typeInCache.type})
+						const value = typeInCache.type.readValue(buffer)
 						return Promise.resolve(value)
 					})
 			}
@@ -74,7 +74,7 @@ export function download({name, url, options}: DownloadOptions): Promise<any> {
 					.then(buffer => {
 						const readType = r._consumeType(buffer, 0)
 						const type = readType.value
-						const value = r.value({buffer, offset: readType.length, type})
+						const value = type.readValue(buffer, readType.length)
 						typeCache[name] = {sig, type}
 						saveTypeCache()
 						return Promise.resolve(value)