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LICENSE

@@ -0,0 +1,57 @@
+GNU LESSER GENERAL PUBLIC LICENSE
+Version 3, 29 June 2007
+
+Copyright © 2007 Free Software Foundation, Inc. <https://fsf.org/>
+
+Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
+
+This version of the GNU Lesser General Public License incorporates the terms and conditions of version 3 of the GNU General Public License, supplemented by the additional permissions listed below.
+
+0. Additional Definitions.
+As used herein, “this License” refers to version 3 of the GNU Lesser General Public License, and the “GNU GPL” refers to version 3 of the GNU General Public License.
+
+“The Library” refers to a covered work governed by this License, other than an Application or a Combined Work as defined below.
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README.md

@@ -1,4 +1,4 @@
-# Range-based set reconciliation
+# range_reconcile
 
 A module for the efficient reconciliation of sets. This is a TypeScript
 implementation of range-based set reconciliation as described in
@@ -10,14 +10,14 @@ totally ordered set.
 When two ranges from different peers hold the same items, they produce the same
 fingerprint.
 
-But when two ranges from different peers are different from one another, they
-produce different fingeprints. The two peers then subdivide non-matching ranges,
-generating and comparing fingerprints until the ranges are whittled down to the
-disjoint elements, which are then exchanged.
+But when two ranges are different from one another, they produce different
+fingeprints. The two peers then subdivide non-matching ranges, generating and
+comparing fingerprints until the ranges are whittled down to the disjoint
+elements, which are then exchanged.
 
 ## About this implementation
 
-This implementation of this implementation has the following features:
+This implementation has the following features:
 
 - A reasonably fast self-balancing `FingerprintTree` built upon Deno's std
   `RedBlackTree`. This is used to hold your set's values and generate
@@ -33,7 +33,7 @@ This implementation of this implementation has the following features:
   method which takes and returns an encoded message, which you then transport to
   the other peer in whichever way you prefer.
 
-One caveat: the `FingerprintTree` provided by this module can only persist its
+One caveat: the `FingerprintTree` provided by this module can only store its
 values in memory.
 
 ## Using this moudule
@@ -49,24 +49,39 @@ At the broadest level:
 
 ### Detailed usage
 
+### Importing
+
+```js
+import {
+  FingerprintTree,
+  RangeMessenger,
+} from "https://deno.land/x/range_reconcile/mod.ts";
+```
+
+NPM distribution coming soon!
+
 #### FingerprintTree
 
 The `FingerprintTree` is used as the representation of a set you wish to
 reconcile. Instantiation requires a 'lifting monoid' to be provided, and
 optionally a function with which to compare inserted values.
 
-The lifting monoid must satisfy the following criteria:
+This lifting monoid is important because it is used to generate the fingerprints
+which peers exchange and compare their own fingerprints to.
+
+Therefore the lifting monoid **must** satisfy the following criteria:
 
-1. The lift method should create a unique value within the universe of the set,
-   where each possible value of the set has a unique lifted value (must ask
-   aljoscha to get this right, I know this isn't)
+1. The lift method must map every item that could possibly occur in a set to a
+   value from the monoid, that is, to a value that can be combined with other
+   such values according to the next two rules. `lift(item)` is the fingerprint
+   of the set that contains only item. For larger sets, the fingerprint is
+   computed by `combine`ing the results of `lift(item)` of all the individual
+   items in the larger set.
 2. The combine method must be associative — i.e.
    `combine(a, combine(b, c)) === combine(combine(a, b), c)`
-3. The neutral method is a constant value which does not affect the outcome of
-   the combine method (ask... aljoscha...)
-
-If no comparison function is provided, `FingerprintTree` will use JavaScript's
-built in comparison instead. You have been warned!
+3. The neutral value must be a value from the monoid that leaves other (monoid)
+   values unaffected when combining them with it: combine(a, neutral) === a and
+   combine(neutral, a) === a.
 
 #### RangeMessenger
 
@@ -77,13 +92,13 @@ peer.
 This `RangeMessenger` requires a configuration which describes how to decode and
 encode messages from and to the other peer respectively.
 
-Once instantiated, the initial messages to send the other peer can be generated
-with the `initialMessages` method.
+Once instantiated, the initial messages to send to the other peer can be
+generated with the `initialMessages` method.
 
 Upon receiving a message, it should be passed to `RangeMessenger.respond`, which
 returns the response to be sent back in turn.
 
-How messages are sent and received are up to you. Just make sure that whichever
+How messages are sent and received is up to you. Just make sure that whichever
 system you choose sends and processes the messages in order (i.e. first-in,
 first-out).
 
@@ -92,15 +107,21 @@ first-out).
 This module uses Deno as its development runtime.
 [Installation instructions can be found here](https://deno.land/#installation).
 
-Documentation can be viewed with `deno doc mod.ts`.
+API documentation can be viewed with `deno doc mod.ts`.
 
 Tests can be run with `deno task test`.
 
 Benchmarks can be run with `deno task bench`.
 
-## TODO
+## Acknowledgements
+
+- [Aljoscha Meyer](https://aljoscha-meyer.de), who not only designed this new
+  method, but also answered my many, many questions; spotted my errors;
+  suggested improvements; and been an all-round great friend and teacher.
+- [NLnet foundation](https://nlnet.nl), whose funding made it possible for me to
+  work on this.
+
+TODO:
 
-- [ ] Make b and k of MessageBroker configurable.
 - [ ] Create comparative benchmarks for syncing with changing b / k.
-- [ ] Add `onInsertedValue` callback subscriber to `RangeMessenger` (i.e. to
-      trigger Earthstar checking if it wants a doc thumbnail)
+- [ ] Create a NPM distribution and publish it.

src/fingerprint_tree/fingerprint_tree.bench.ts

@@ -19,7 +19,15 @@ const sizes = [1, 10, 100, 1000, 10000];
 for (const size of sizes) {
   const set = makeSet(size);
 
-  const tree = new FingerprintTree(concatMonoid);
+  const tree = new FingerprintTree(concatMonoid, (a, b) => {
+    if (a > b) {
+      return 1;
+    } else if (a < b) {
+      return -1;
+    } else {
+      return 0;
+    }
+  });
   const rbTree = new RedBlackTree();
 
   Deno.bench(`Insert into RedBlackTree (${size} items)`, {

src/fingerprint_tree/fingerprint_tree.test.ts

@@ -22,6 +22,15 @@ const rangeVectors: RangeVector[] = [
 Deno.test("FingerprintTree", () => {
   const tree = new FingerprintTree(
     concatMonoid,
+    (a, b) => {
+      if (a > b) {
+        return 1;
+      } else if (a < b) {
+        return -1;
+      } else {
+        return 0;
+      }
+    },
   );
 
   const set = ["a", "b", "c", "d", "e", "f", "g"];

src/fingerprint_tree/fingerprint_tree.ts

@@ -98,7 +98,7 @@ export class FingerprintTree<ValueType, LiftedType>
     /** The lifting monoid which is used to label nodes and derive fingerprints from ranges. */
     monoid: LiftingMonoid<ValueType, LiftedType>,
     /** A function to sort values by. Will use JavaScript's default comparison if not provided. */
-    compare?: (a: ValueType, b: ValueType) => number,
+    compare: (a: ValueType, b: ValueType) => number,
   ) {
     super(compare);
 

src/lifting_monoid.ts

@@ -1,5 +1,3 @@
-import { xxHash32 } from "https://raw.githubusercontent.com/gnlow/deno-xxhash/master/mod.ts";
-
 export type LiftingMonoid<ValueType, LiftedType> = {
   lift: (i: ValueType) => LiftedType;
   combine: (
@@ -46,21 +44,3 @@ export const sizeMonoid: LiftingMonoid<unknown, number> = {
   combine: (a: number, b: number) => a + b,
   neutral: 0,
 };
-
-/** A monoid which lifts using xxHash32, and combines the resulting hash using a bitwise XOR.*/
-export const xxHash32XorMonoid: LiftingMonoid<Uint8Array, Uint8Array> = {
-  lift: (v: Uint8Array) => {
-    const hash = xxHash32(v).toString(16);
-    return new TextEncoder().encode(hash);
-  },
-  combine: (a: Uint8Array, b: Uint8Array) => {
-    const xored = [];
-
-    for (let i = 0; i < a.length; i++) {
-      xored.push(a[i] ^ b[i]);
-    }
-
-    return new Uint8Array(xored);
-  },
-  neutral: new Uint8Array(8),
-};

src/range_messenger/range_messenger.bench.ts

@@ -22,32 +22,42 @@ function nativeEquals(a: string, b: string) {
   return a === b;
 }
 
+function compare<T>(a: T, b: T) {
+  if (a > b) {
+    return 1;
+  } else if (a < b) {
+    return -1;
+  } else {
+    return 0;
+  }
+}
+
 for (const size of sizes) {
   const setA = makeSet(size);
   const setB = makeSet(size);
 
   Deno.bench(`Instantiate two sets (size ${size})`, () => {
-    const treeA = new FingerprintTree(concatMonoid);
+    const treeA = new FingerprintTree(concatMonoid, compare);
 
     for (const item of setA) {
       treeA.insert(`${item}`);
     }
 
-    const treeB = new FingerprintTree(concatMonoid);
+    const treeB = new FingerprintTree(concatMonoid, compare);
 
     for (const item of setB) {
       treeB.insert(`${item}`);
     }
   });
 
   Deno.bench(`Instantiate and sync two sets (size ${size})`, async () => {
-    const treeA = new FingerprintTree(concatMonoid);
+    const treeA = new FingerprintTree(concatMonoid, compare);
 
     for (const item of setA) {
       treeA.insert(`${item}`);
     }
 
-    const treeB = new FingerprintTree(concatMonoid);
+    const treeB = new FingerprintTree(concatMonoid, compare);
 
     for (const item of setB) {
       treeB.insert(`${item}`);

src/range_messenger/range_messenger.test.ts

@@ -21,6 +21,16 @@ function multiplyElements(elements: string[], by: number): string[] {
 
 const elements = ["ape", "bee", "cat", "doe", "eel", "fox", "gnu", "hog"];
 
+function compare<T>(a: T, b: T) {
+  if (a > b) {
+    return 1;
+  } else if (a < b) {
+    return -1;
+  } else {
+    return 0;
+  }
+}
+
 function createTestSet() {
   const baseCount = Math.floor(Math.random() * 8);
 
@@ -45,7 +55,7 @@ function nativeEquals(a: string, b: string) {
 }
 
 async function createTestCase() {
-  const treeA = new FingerprintTree(concatMonoid);
+  const treeA = new FingerprintTree(concatMonoid, compare);
 
   const setA = createTestSet();
 
@@ -63,7 +73,7 @@ async function createTestCase() {
 
   // Other peer
 
-  const treeB = new FingerprintTree(concatMonoid);
+  const treeB = new FingerprintTree(concatMonoid, compare);
 
   const setB = createTestSet();