WIP

implementations/javascript/src/annotations.js

@@ -0,0 +1,54 @@
+"use strict";
+// Preserves Annotations.
+
+if (require('./singletonmodule.js')('leastfixedpoint.com/preserves',
+                                    require('../package.json').version,
+                                    'annotations.js',
+                                    module)) return;
+
+const { Record, List, Map, Set } = require('./values.js');
+const { PreserveOn, AsPreserve } = require('./symbols.js');
+
+function Annotated(item) {
+  this.annotations = [];
+  this.item = item;
+}
+
+Annotated.prototype[AsPreserve] = function () {
+  return this;
+};
+
+Annotated.prototype[PreserveOn] = function (encoder) {
+  for (const a of this.annotations) {
+    encoder.header(0, 0, 5);
+    encoder.push(a);
+  }
+  encoder.push(this.item);
+};
+
+function stripAnnotations(v, depth) {
+  function step(v, depth) {
+    if (depth === 0) return v;
+    if (!(v instanceof Annotated)) return v;
+
+    const nextDepth = depth - 1;
+    function walk(v) { return step(v, nextDepth); }
+
+    if (v.item instanceof Record) {
+      return Record(walk(v.item.label), v.item.fields.map(walk));
+    } else if (List.isList(v.item)) {
+      return v.item.map(walk);
+    } else if (Set.isSet(v.item)) {
+      return v.item.map(walk);
+    } else if (Map.isMap(v.item)) {
+      return v.item.mapEntries((e) => [walk(e[0]), walk(e[1])]);
+    } else if (v.item instanceof Annotated) {
+      const e = new Error("Improper annotation structure");
+      e.irritant = v;
+      throw e;
+    } else {
+      return v.item;
+    }
+  }
+  step(v, (depth === void 0) ? Infinity : depth);
+}

implementations/javascript/src/codec.js

@@ -7,6 +7,7 @@ if (require('./singletonmodule.js')('leastfixedpoint.com/preserves',
                                     module)) return;
 
 const Values = require('./values.js');
+const Annotations = require('./annotations.js');
 const { List, Map, Set, Bytes, Record, Single, Double } = Values;
 
 const { PreserveOn } = require('./symbols.js');
@@ -27,7 +28,7 @@ class Decoder {
       ? (packet._view || packet) // strip off Bytes wrapper, if any
       : new Uint8Array(0);
     this.index = 0;
-    this.shortForms = options.shortForms || {};
+    this.includeAnnotations = options.includeAnnotations || false;
   }
 
   write(data) {
@@ -75,16 +76,15 @@ class Decoder {
     return [major, minor, arg];
   }
 
-  peekend(arg) {
-    const [a,i,r] = this.nextop();
-    const result = (a === 0) && (i === 3) && (r === arg);
+  peekend() {
+    const result = this.nextop() === 4;
     if (!result) this.index--;
     return result;
   }
 
-  binarystream(arg, minor) {
+  binarystream(minor) {
     const result = [];
-    while (!this.peekend(arg)) {
+    while (!this.peekend()) {
       const chunk = this.next();
       if (ArrayBuffer.isView(chunk)) {
         result.push(new Uint8Array(chunk.buffer, chunk.byteOffset, chunk.byteLength));
@@ -99,10 +99,10 @@ class Decoder {
     return this.decodebinary(minor, Bytes.concat(result));
   }
 
-  valuestream(arg, minor, decoder) {
+  valuestream(minor) {
     const result = [];
-    while (!this.peekend(arg)) result.push(this.next());
-    return decoder(minor, result);
+    while (!this.peekend()) result.push(this.next());
+    return this.decodecompound(minor, result);
   }
 
   decodeint(bs) {
@@ -123,23 +123,15 @@ class Decoder {
     }
   }
 
-  decoderecord(minor, vs) {
-    if (minor === 3) {
-      if (vs.length === 0) throw new DecodeError("Too few elements in encoded record");
-      return new Record(vs[0], vs.slice(1));
-    } else {
-      const label = this.shortForms[minor];
-      if (label === void 0) throw new DecodeError("Use of unconfigured short form " + minor);
-      return new Record(label, vs);
-    }
-  }
-
-  decodecollection(minor, vs) {
+  decodecompound(minor, vs) {
     switch (minor) {
-      case 0: return List(vs);
-      case 1: return Set(vs);
-      case 2: return this.mapFromArray(vs);
-      case 3: throw new DecodeError("Invalid collection type");
+      case 0: {
+        if (vs.length === 0) throw new DecodeError("Too few elements in encoded record");
+        return new Record(vs[0], vs.slice(1));
+      }
+      case 1: return List(vs);
+      case 2: return Set(vs);
+      case 3: return this.mapFromArray(vs);
     }
   }
 
@@ -162,28 +154,31 @@ class Decoder {
               case 1: return true;
               case 2: return Single(this.nextbytes(4).getFloat32(0, false));
               case 3: return Double(this.nextbytes(8).getFloat64(0, false));
+              case 4: throw new DecodeError("Unexpected end-of-stream marker");
+              case 5: ...annotation...;
+              default: throw new DecodeError("Illegal format A lead byte");
             }
           case 1:
-            return (arg > 12) ? arg - 16 : arg;
+            ...placeholder...;
           case 2: {
             const t = arg >> 2;
             const n = arg & 3;
             switch (t) {
-              case 0: throw new DecodeError("Invalid format C start byte");
-              case 1: return this.binarystream(arg, n);
-              case 2: return this.valuestream(arg, n, this.decoderecord.bind(this));
-              case 3: return this.valuestream(arg, n, this.decodecollection.bind(this));
+              case 0: throw new DecodeError("Invalid format C start byte (0)");
+              case 1: return this.binarystream(n);
+              case 2: return this.valuestream(n);
+              case 3: throw new DecodeError("Invalid format C start byte (3)");
             }
           }
           case 3:
-            throw new DecodeError("Invalid format C end byte");
+            return (arg > 12) ? arg - 16 : arg;
         }
       case 1:
         return this.decodebinary(minor, Bytes.from(this.nextbytes(this.wirelength(arg))));
       case 2:
-        return this.decoderecord(minor, this.nextvalues(this.wirelength(arg)));
+        return this.decodecompound(minor, this.nextvalues(this.wirelength(arg)));
       case 3:
-        return this.decodecollection(minor, this.nextvalues(this.wirelength(arg)));
+        throw new DecodeError("Invalid lead byte (major 3)");
     }
   }
 
@@ -207,7 +202,6 @@ class Encoder {
     this.chunks = [];
     this.view = new DataView(new ArrayBuffer(256));
     this.index = 0;
-    this.shortForms = options.shortForms || {};
   }
 
   contents() {
@@ -275,7 +269,7 @@ class Encoder {
   }
 
   encodecollection(minor, items) {
-    this.header(3, minor, items.size);
+    this.header(2, minor, items.size);
     for (const item of items) { this.push(item); }
   }
 
@@ -283,10 +277,11 @@ class Encoder {
     const tn = ((t & 3) << 2) | (n & 3);
     this.header(0, 2, tn);
     for (const item of items) { this.push(item); }
-    this.header(0, 3, tn);
+    this.header(0, 0, 4);
   }
 
   push(v) {
+    ...placeholder...;
     if (typeof v === 'object' && v !== null && typeof v[PreserveOn] === 'function') {
       v[PreserveOn](this);
     }
@@ -295,7 +290,7 @@ class Encoder {
     }
     else if (typeof v === 'number') {
       if (v >= -3 && v <= 12) {
-        this.leadbyte(0, 1, v >= 0 ? v : v + 16);
+        this.leadbyte(0, 3, v >= 0 ? v : v + 16);
       } else {
         this.encodeint(v);
       }
@@ -323,18 +318,18 @@ class Encoder {
       }
     }
     else if (List.isList(v)) {
-      this.encodecollection(0, v);
-    }
-    else if (Set.isSet(v)) {
       this.encodecollection(1, v);
     }
+    else if (Set.isSet(v)) {
+      this.encodecollection(2, v);
+    }
     else if (Map.isMap(v)) {
-      this.encodecollection(2, List().withMutations((l) => {
+      this.encodecollection(3, List().withMutations((l) => {
         v.forEach((val, key) => { l.push(key).push(val); });
       }));
     }
     else if (typeof v === 'object' && v !== null && typeof v[Symbol.iterator] === 'function') {
-      this.encodestream(3, 0, v);
+      this.encodestream(2, 0, v);
     }
     else {
       throw new EncodeError("Cannot encode", v);

implementations/javascript/src/index.js

@@ -8,3 +8,4 @@ if (require('./singletonmodule.js')('leastfixedpoint.com/preserves',
 Object.assign(module.exports, require('./symbols.js'));
 Object.assign(module.exports, require('./codec.js'));
 Object.assign(module.exports, require('./values.js'));
+Object.assign(module.exports, require('./annotations.js'));

implementations/javascript/src/values.js

@@ -10,7 +10,7 @@ if (require('./singletonmodule.js')('leastfixedpoint.com/preserves',
 const util = require('util');
 
 const Immutable = require('immutable');
-const { List, isList, Map, Set, is } = Immutable;
+const { List, Map, Set, is } = Immutable;
 
 const { PreserveOn, AsPreserve } = require('./symbols.js');
 
@@ -341,16 +341,8 @@ Record.prototype.set = function (index, newValue) {
 };
 
 Record.prototype[PreserveOn] = function (encoder) {
-  if (is(encoder.shortForms[0], this.label)) {
-    encoder.header(2, 0, this.fields.size);
-  } else if (is(encoder.shortForms[1], this.label)) {
-    encoder.header(2, 1, this.fields.size);
-  } else if (is(encoder.shortForms[2], this.label)) {
-    encoder.header(2, 2, this.fields.size);
-  } else {
-    encoder.header(2, 3, this.fields.size + 1);
-    encoder.push(this.label);
-  }
+  encoder.header(2, 0, this.fields.size + 1);
+  encoder.push(this.label);
   for (const field of this.fields) { encoder.push(field); }
 };