Initial commit

.gitignore

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+node_modules
+.nyc_output
+npm-debug.log
+package-lock.json
+yarn.lock

.travis.yml

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+language: node_js
+node_js:
+  - '8'
+script: npm test
+after_success: npm run coverage
+notifications:
+  email:
+    on_success: never

LICENSE

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+MIT License
+
+Copyright (c) 2018 Luke Childs
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# build-output-script
+
+> Builds a P2PKH Bitcoin transaction output script
+
+[![Build Status](https://travis-ci.org/lukechilds/build-output-script.svg?branch=master)](https://travis-ci.org/lukechilds/build-output-script)
+[![Coverage Status](https://coveralls.io/repos/github/lukechilds/build-output-script/badge.svg?branch=master)](https://coveralls.io/github/lukechilds/build-output-script?branch=master)
+[![npm](https://img.shields.io/npm/dm/build-output-script.svg)](https://www.npmjs.com/package/build-output-script)
+[![npm](https://img.shields.io/npm/v/build-output-script.svg)](https://www.npmjs.com/package/build-output-script)
+
+Builds a P2PKH Bitcoin transaction output script from an array of P2PKH addresses and amounts. Will also work with any Bitcoin derived cryptocurrencies with a single byte pubkey hash prefix.
+
+## Install
+
+```shell
+npm install build-output-script
+```
+
+## License
+
+MIT © Luke Childs

package.json

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+{
+  "name": "build-output-script",
+  "version": "0.0.0",
+  "description": "Builds a P2PKH Bitcoin transaction output script.",
+  "main": "src/index.js",
+  "engines": {
+    "node": ">=8"
+  },
+  "scripts": {
+    "test": "xo && nyc ava",
+    "coverage": "nyc report --reporter=text-lcov | coveralls"
+  },
+  "xo": {
+    "extends": "xo-lukechilds"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/lukechilds/build-output-script.git"
+  },
+  "keywords": [
+    "bitcoin",
+    "outputscript",
+    "output",
+    "script",
+    "build"
+  ],
+  "author": "Luke Childs <lukechilds123@gmail.com> (http://lukechilds.co.uk)",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/lukechilds/build-output-script/issues"
+  },
+  "homepage": "https://github.com/lukechilds/build-output-script#readme",
+  "devDependencies": {
+    "ava": "^0.25.0",
+    "coveralls": "^3.0.2",
+    "eslint-config-xo-lukechilds": "^1.0.1",
+    "nyc": "^13.1.0",
+    "xo": "^0.23.0"
+  },
+  "dependencies": {
+    "bitcoin-ops": "^1.4.1",
+    "bs58check": "^2.1.2",
+    "varuint-bitcoin": "^1.1.0"
+  }
+}

src/index.js

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+const bs58check = require('bs58check');
+const { encode: numberToCompactSizeUInt } = require('varuint-bitcoin');
+const { OP_DUP, OP_HASH160, OP_EQUALVERIFY, OP_CHECKSIG } = require('bitcoin-ops');
+
+const addressDecode = address => bs58check.decode(address).slice(1);
+
+const checkUInt53 = number => {
+	if (number < 0 || !Number.isSafeInteger(number)) {
+		throw new RangeError('value out of range');
+	}
+};
+
+const numberToUInt64 = number => {
+	checkUInt53(number);
+
+	const buffer = Buffer.alloc(8);
+
+	buffer.writeUInt32LE(number >>> 0);
+	buffer.writeUInt32LE((number / 0x100000000) | 0, 4);
+
+	return buffer;
+};
+
+const buildOutputScript = outputs => {
+	let outputScript = [...numberToCompactSizeUInt(outputs.length)];
+
+	for (const [address, value] of outputs) {
+		const pubkeyHash = addressDecode(address);
+
+		const scriptPubKey = [
+			OP_DUP,
+			OP_HASH160,
+			pubkeyHash.length,
+			...pubkeyHash,
+			OP_EQUALVERIFY,
+			OP_CHECKSIG
+		];
+
+		outputScript = [
+			...outputScript,
+			...numberToUInt64(value),
+			...numberToCompactSizeUInt(scriptPubKey.length),
+			...scriptPubKey
+		];
+	}
+
+	return Buffer.from(outputScript).toString('hex');
+};
+
+module.exports = buildOutputScript;

test/unit.js

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+import test from 'ava';
+import buildOutputScript from '..';