ADD hex.compress and hex.decompress

README.md

@@ -16,7 +16,6 @@ In this tutorial we will sign data in javascript and validate the signature insi
 
 In this tutorial we will use the ethereum-identites and asymmetric cryptography to send a encrypted and signed message from alice to bob. [Encrypted Message](./tutorials/encrypted-message.md).
 
-
 ## Functions
 
 ### Install
@@ -185,3 +184,24 @@ const serializedTx = EthCrypto.signTransaction(
 );
 const receipt = await web3.eth.sendSignedTransaction(serializedTx);
 ```
+
+### hex compress/decompress
+
+Compress or decompress a hex-string to make it smaller. You can either compress to utf16 which reduces the size to about 1/4, or to base64 which reduces the size to about 4/5.
+
+```javascript
+const hexString = '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07';
+
+const utf16 = EthCrypto.hex.compress(hexString); // compress to utf16
+// > 'ၻ炞䆷襞ⶬ輦ꂩቊ쮷蛰ﴚ艡Řᨇ'
+
+const base64 = EthCrypto.hex.compress(hexString, true); // compress to base64
+// > 'EHvpRnCeQbeJXuqfLaz5mKCpEkrLt4bw/RqCYQFYGgc='
+
+EthCrypto.hex.decompress(utf16); // decompress from utf16
+// > '0x107be946709e41b7895eea9f2d...'
+
+EthCrypto.hex.decompress(base64, true); // decompress from utf16
+// > '0x107be946709e41b7895eea9f2d...'
+
+```

src/hex.js

@@ -0,0 +1,42 @@
+/**
+ * compress/decompress hex-strings to utf16 or base64
+ * thx @juvian
+ * @link https://stackoverflow.com/a/40471908/3443137
+ */
+
+import * as util from './util';
+
+export function compress(hex, base64 = false) {
+    hex = util.removeTrailing0x(hex);
+
+    // if base64:true, we use our own function because it results in a smaller output
+    if (base64 === true)
+        return new Buffer(hex, 'hex').toString('base64');
+
+    let string = '';
+    while (hex.length % 4 != 0) { // we need it to be multiple of 4
+        hex = '0' + hex;
+    }
+    for (let i = 0; i < hex.length; i += 4) {
+        // get char from ascii code which goes from 0 to 65536
+        string += String.fromCharCode(parseInt(hex.substring(i, i + 4), 16));
+    }
+    return string;
+}
+
+export function decompress(compressedString, base64 = false) {
+
+    // if base64:true, we use our own function because it results in a smaller output
+    if (base64 === true) {
+        const ret = new Buffer(compressedString, 'base64').toString('hex');
+        return util.addTrailing0x(ret);
+    }
+
+    let hex = '';
+    for (let i = 0; i < compressedString.length; i++) {
+        // get character ascii code and convert to hexa string, adding necessary 0s
+        hex += ((i == 0 ? '' : '000') + compressedString.charCodeAt(i).toString(16)).slice(-4);
+    }
+    hex = hex.toLowerCase();
+    return util.addTrailing0x(hex);
+}

src/index.js

@@ -8,6 +8,7 @@ import sign from './sign';
 import signTransaction from './sign-transaction';
 import txDataByCompiled from './tx-data-by-compiled';
 import * as hash from './hash';
+import * as hex from './hex';
 import * as vrs from './vrs';
 import * as util from './util';
 
@@ -22,6 +23,7 @@ export {
     signTransaction,
     txDataByCompiled,
     hash,
+    hex,
     vrs,
     util
 };
@@ -37,6 +39,7 @@ export default {
     signTransaction,
     txDataByCompiled,
     hash,
+    hex,
     vrs,
     util
 };

src/util.js

@@ -1,3 +1,16 @@
 import Web3 from 'web3';
 
 export const web3 = new Web3();
+
+
+export function removeTrailing0x(str) {
+    if (str.startsWith('0x'))
+        return str.substring(2);
+    else return str;
+}
+
+export function addTrailing0x(str) {
+    if (!str.startsWith('0x'))
+        return '0x' + str;
+    else return str;
+}

test/tutorials/encrypted-message.test.js

@@ -28,8 +28,8 @@ describe('encrypted-message.md', () => {
             bob.publicKey,
             JSON.stringify(payload)
         );
-        console.log('encrypted:');
-        console.dir(encrypted);
+        // console.log('encrypted:');
+        // console.dir(encrypted);
 
         // decrypt
         const decrypted = await EthCrypto.decryptWithPrivateKey(
@@ -38,8 +38,8 @@ describe('encrypted-message.md', () => {
         );
         const decryptedPayload = JSON.parse(decrypted);
         const senderAddress = EthCrypto.addressByPublicKey(decryptedPayload.sender);
-        console.log('decryptedPayload:');
-        console.dir(decryptedPayload);
+        // console.log('decryptedPayload:');
+        // console.dir(decryptedPayload);
 
         // check signature
         const signer = EthCrypto.recover(
@@ -49,13 +49,13 @@ describe('encrypted-message.md', () => {
         if (signer !== senderAddress)
             throw new Error('signature not valid');
 
-        console.log(
-            'Got message from ' +
-            senderAddress +
-            ': "' +
-            decryptedPayload.message + '"'
-        );
-
+        /*        console.log(
+                    'Got message from ' +
+                    senderAddress +
+                    ': "' +
+                    decryptedPayload.message + '"'
+                );
+        */
         assert.equal(decryptedPayload.message, secretMessage);
 
 

test/unit.test.js

@@ -8,6 +8,8 @@ const TEST_DATA = {
     privateKey: '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07',
     publicKey: 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06eceacf2b81dd326d278cd992d5e03b0df140f2df389ac9a1c2415a220a4a9e8c046'
 };
+const HEX_STRING = '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';
+
 
 describe('unit.test.js', () => {
     describe('.createIdentity()', () => {
@@ -163,7 +165,22 @@ describe('unit.test.js', () => {
             });
         });
     });
+    describe('hex', () => {
+        it('compress/decompress to utf16', () => {
+            const compressed = EthCrypto.hex.compress(HEX_STRING, false);
+            assert.ok(compressed.length < HEX_STRING.length);
+
+            const decompressed = EthCrypto.hex.decompress(compressed, false);
+            assert.equal(decompressed, HEX_STRING);
+        });
+        it('compress/decompress to base64', () => {
+            const compressed = EthCrypto.hex.compress(HEX_STRING, true);
+            assert.ok(compressed.length < HEX_STRING.length);
 
+            const decompressed = EthCrypto.hex.decompress(compressed, true);
+            assert.equal(decompressed, HEX_STRING);
+        });
+    });
     /*
         describe('.testBlock()', ()=> {
             describe('positive', ()=> {});

typings/index.d.ts

@@ -66,9 +66,17 @@ export type hash = {
 };
 
 export type util = {
-    web3: Web3
+    web3: Web3;
+    removeTrailing0x(str: string): string;
+    addTrailing0x(str: string): string;
 };
 
+export type hex = {
+    compress(hex: string, base64?: boolean): string;
+    decompress(str: string, base64?: boolean): string;
+};
+
+
 export function publicKeyToAddress(publicKey: string): string;
 
 declare const _default: {
@@ -82,6 +90,7 @@ declare const _default: {
     signTransaction,
     txDataByCompiled,
     hash,
+    hex,
     vrs,
     util
 };