Initial commit

.eslintrc

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+{
+	"extends": "@joepie91/eslint-config"
+}

.gitignore

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+node_modules

example.js

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+"use strict";
+
+const Promise = require("bluebird");
+const path = require("path");
+const errorChain = require("error-chain");
+
+const pipe = require("@promistream/pipe");
+const fromNodeStream = require("@promistream/from-node-stream");
+const map = require("@promistream/map");
+const join = require("@promistream/join");
+const splitLines = require("@promistream/split-lines");
+const decodeString = require("@promistream/decode-string");
+const readFile = require("./");
+
+return Promise.try(() => {
+	return pipe([
+		readFile(path.join(__dirname, "example.js")),
+		decodeString("utf8"),
+		splitLines(),
+		map((line) => line.trim()),
+		join("\n"),
+		fromNodeStream(process.stdout)
+	]).read();
+}).then(() => {
+	console.log("Done!");
+}).catch((error) => {
+	console.error(errorChain.render(error));
+});

index.js

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+"use strict";
+
+const Promise = require("bluebird");
+const fs = require("fs").promises;
+
+const pipe = require("@promistream/pipe");
+const simpleSource = require("@promistream/simple-source");
+const sequentialize = require("@promistream/sequentialize");
+const EndOfStream = require("@promistream/end-of-stream");
+
+const { validateArguments } = require("@validatem/core");
+const required = require("@validatem/required");
+const isString = require("@validatem/is-string");
+const isNumber = require("@validatem/is-number");
+const isInteger = require("@validatem/is-integer");
+const defaultTo = require("@validatem/default-to");
+const either = require("@validatem/either");
+const oneOf = require("@validatem/one-of");
+
+// NOTE: Below read size is derived from the high water mark in core lib/internal/fs/streams.js
+let defaultChunkSize = 64 * 1024;
+
+function doRead(handle, length) {
+	// TODO: Can we safely switch to `allocUnsafe` here?
+	let buffer = Buffer.alloc(length);
+
+	return Promise.try(() => {
+		return handle.read(buffer, 0, length);
+	}).then((result) => {
+		if (result.bytesRead === 0) {
+			// Not documented; https://github.com/nodejs/node/issues/35363
+			throw new EndOfStream();
+		} else if (result.bytesRead === length) {
+			return buffer;
+		} else if (result.bytesRead < length) {
+			// TODO: For possible future performance optimization, consider reusing the remaining Buffer allocation for a next read, if possible. Need more data on how often this case occurs first, though, to justify the added complexity.
+			return buffer.slice(0, length);
+		} else {
+			throw new Error(`Read more bytes (${result.bytesRead}) than the specified 'length' (${length}); this should never happen!`);
+		}
+	});
+}
+
+module.exports = function createReadFileStream(_path, _options) {
+	let [ path, options ] = validateArguments(arguments, [
+		[ "path", required, isString ],
+		[ "options", defaultTo({}), {
+			chunkSize: [ isInteger, defaultTo(defaultChunkSize) ],
+			flag: [ defaultTo("r"), oneOf([ "a", "ax", "a+", "ax+", "as", "as+", "r", "r+", "rs+", "w", "wx", "w+", "wx+" ]) ],
+			mode: [ either([ isString, isNumber ]) ] // FIXME: Stricter validation
+			// TODO: start/end
+		}]
+	]);
+	
+	let handlePromise = fs.open(path, options.flag, options.mode);
+
+	// TODO: Metadata, including stream label and file size/type/path
+	return pipe([
+		simpleSource({
+			onRequest: () => {
+				return Promise.try(() => {
+					// TODO: Can we optimize this by separately tracking when the open has completed, and replacing the Promise with the actual handle in that case?
+					return handlePromise;
+				}).then((handle) => {
+					return doRead(handle, options.chunkSize);
+				});
+			},
+			onAbort: (_reason) => {
+				return Promise.try(() => {
+					return handlePromise;
+				}).then((handle) => {
+					return handle.close();
+				});
+			}
+		}),
+		sequentialize()
+	]);
+};

package.json

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+{
+  "name": "@promistream/read-file",
+  "version": "0.1.0",
+  "main": "index.js",
+  "keywords": [
+    "promistream"
+  ],
+  "repository": "http://git.cryto.net/promistream/read-file.git",
+  "author": "Sven Slootweg <admin@cryto.net>",
+  "license": "WTFPL OR CC0-1.0",
+  "dependencies": {
+    "@promistream/end-of-stream": "^0.1.0",
+    "@promistream/pipe": "^0.1.1",
+    "@promistream/sequentialize": "^0.1.0",
+    "@promistream/simple-source": "^0.1.1",
+    "@validatem/core": "^0.3.11",
+    "@validatem/default-to": "^0.1.0",
+    "@validatem/either": "^0.1.9",
+    "@validatem/error": "^1.1.0",
+    "@validatem/is-integer": "^0.1.0",
+    "@validatem/is-number": "^0.1.3",
+    "@validatem/is-string": "^0.1.1",
+    "@validatem/one-of": "^0.1.1",
+    "@validatem/required": "^0.1.1",
+    "bluebird": "^3.7.2",
+    "default-value": "^1.0.0",
+    "validatem": "^0.2.1"
+  },
+  "devDependencies": {
+    "@joepie91/eslint-config": "^1.1.0",
+    "@promistream/decode-string": "^0.1.0",
+    "@promistream/from-node-stream": "^0.1.1",
+    "@promistream/join": "^0.1.0",
+    "@promistream/map": "^0.1.0",
+    "@promistream/split-lines": "^0.1.0",
+    "error-chain": "^0.1.0",
+    "eslint": "^6.8.0"
+  }
+}