POC for decode(). Will be removed once we decide in final implementation

elements/lisk-codec/src/pocs/decode.js

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+/*
+ * Copyright © 2020 Lisk Foundation
+ *
+ * See the LICENSE file at the top-level directory of this distribution
+ * for licensing information.
+ *
+ * Unless otherwise agreed in a custom licensing agreement with the Lisk Foundation,
+ * no part of this software, including this file, may be copied, modified,
+ * propagated, or distributed except according to the terms contained in the
+ * LICENSE file.
+ *
+ * Removal or modification of this copyright notice is prohibited.
+ */
+
+
+ /*
+	THIS IS ONE POSSIBLE APPROACH FOR DECODING LISK BINARY MESSAGES. IT'S NOT RECURSIVE BUT IT SHOWS PART OF THE LOGIC
+	OF WALKING THE BUFFER AND BY THE FACT THAT BINARY MESSAGES ARE KEY/VALUE PAIRS SOME ASSUMPTIONS CAN BE MADE
+	LIKE ALL MESSAGES START WITH A VARINT ENCODED KEY FOLLWOED BY A SIZE OF WIRE TYPE IS 2
+ */
+
+const varint = require('varint');
+
+const binaryMsgHexString = '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';
+
+const msgBuffer = Buffer.from(binaryMsgHexString, 'hex');
+
+console.log(msgBuffer)
+console.log();
+
+const sortedOptimizedSchema = [
+  { fieldNumber: 1, name: 'address', type: 'bytes'},
+  { fieldNumber: 2, name: 'balance', type: 'uint64'},
+  { fieldNumber: 3, name: 'publicKey', type: 'bytes'},
+  { fieldNumber: 4, name: 'nonce', type: 'uint64'},
+  { fieldNumber: 5, name: 'keys', type: 'object'},
+  { fieldNumber: 6, name: 'asset', type: 'object'},
+]
+
+const WIRE_TYPE_TWO = 2; // Strings, bytes.....
+const WIRE_TYPE_ZERO = 0; // the rest that is not 2
+
+const keepReading = byte => (byte & 128) === 128 ? true : false;
+
+const getFieldNumber = bytes => varint.decode(bytes) >>> 3;
+
+const getWireType = byte => (byte & WIRE_TYPE_TWO) === WIRE_TYPE_TWO ? 2 : 0;
+
+const getChunk = (buffer, startPosition) => {
+  let i = startPosition;
+  const bytesToDecode = [];
+
+  while(keepReading(buffer[i])){
+    bytesToDecode.push(buffer[i]);
+    i++;
+  }
+  // If the encoded varint is 1 byte we need to push it as it would not have entered the loop
+  bytesToDecode.push(buffer[i]);
+  i++;
+  return { value: bytesToDecode, bytesRead: i - startPosition, };
+};
+
+const readers = {
+  bytes: (buffer, start, end, object) => {
+    console.log(`Decoding bytes from buffer from "${start}" to "${end}"`);
+    console.log(buffer.slice(start, start+end)); // buf.slice() uses indexes not length!
+    return buffer.slice(start, start+end);
+  }
+}
+
+
+const decode = (buffer, object = {}) => {
+  console.time('decoding');
+
+  for(let bufferIndex=0; bufferIndex < buffer.length; bufferIndex++) {
+    // Read key
+    const key = getChunk(buffer, bufferIndex);
+    const fieldNumber = getFieldNumber(key.value);
+    const wireType = getWireType(key.value)
+    bufferIndex = bufferIndex + key.bytesRead;
+
+    // Based on key figure out how to read following bytes
+    if(wireType === 2) {
+      console.log('wire type is string/bytes need to read lenght');
+      const byteSize = getChunk(buffer, bufferIndex); // In next byte(s) we have the size of string/bytes that follow
+      const byteSizeAsNumber = varint.decode(byteSize.value);
+      bufferIndex = bufferIndex + byteSize.bytesRead;
+      console.log('byteSize', byteSize, byteSizeAsNumber);
+      const byteContent = readers['bytes'](buffer, bufferIndex, byteSizeAsNumber, object); // 'bytes' should come from schema
+      // Move the loop counter so it starts on next key after reaging a binary key/value pair
+      bufferIndex = bufferIndex + byteSizeAsNumber - 1;
+      console.log();
+
+      // Write reesult to object
+      object[sortedOptimizedSchema[fieldNumber-1].name] = byteContent.toString('hex');
+
+      continue;
+    }
+
+    if(wireType === 0) {
+      console.log('WE HAVE A NUMBER');
+      // We have read the key so move the pointer forward
+      // Decode number
+      const res = getChunk(buffer, bufferIndex);
+
+      bufferIndex = bufferIndex + res.bytesRead - 1;
+      object[sortedOptimizedSchema[fieldNumber-1].name] = varint.decode(res.value);
+      console.log();
+      continue;
+    }
+    //console.log('bufferIndex:', bufferIndex);
+
+  }
+  console.timeEnd('decoding');
+}
+
+
+
+const obj = {};
+decode(msgBuffer, obj);
+
+console.log(obj);