Utility

The u module is exposed as:

import Neon, { u } from "@cityofzion/neon-js";
Neon.u.reverseHex(hexstring);

The utility module contains:

• Format manipulation methods
• Hashing methods
• Utility classes

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Classes

StringStream

StringStream is a simple stream object that allows us to read a hexstring byte by byte. It is not an actual stream but fakes the stream interface for better manipulation. It stores the whole string and a pointer to keep track of the current position on the string.

It is used in serializing and deserializing a transaction object. The ScriptBuilder class for smart contracts inherits from StringStream.

const ss = new Neon.u.StringStream("abcdefgh");
ss.read(1); // 'ab'
ss.read(2); // 'cdef'
ss.isEmpty(); // false
ss.read(1); // 'gh'
ss.isEmpty(); // true
ss.str; // 'abcdefgh'

Methods

Format

While most of the methods in Neon takes in strings and outputs strings, the underlying logic requires a lot of format conversions.

Neon.u.reverseHex(hexstring);
Neon.u.ab2str(arrayBuffer);

// Conversions to hex
Neon.u.str2hexstring("normalString"); // 6e6f726d616c537472696e67
Neon.u.int2hex(234); // EA
Neon.u.ab2hexstring(arrayBuffer);

// Conversion from hex
Neon.u.hexstring2str("6e6f726d616c537472696e67"); // normalString
Neon.u.hex2int("EA"); // 234
Neon.u.hexstring2ab(hexString);

The most common format is hex string. This is a string where every 2 characters represents a byte in an bytearray. neon-js intentionally works with hex strings because strings are easy to print and manipulate.

Hashing

These methods are convenient wrappers around the CryptoJS functions. They take in strings and return strings.

import Neon from "@cityofzion/neon-js";
// Performs a single SHA
Neon.u.sha256(item);
// Performs a SHA followed by a SHA
Neon.u.hash256(item);
// Performs a SHA followed by a RIPEMD160
Neon.u.hash160(item);