feat(range-coder): re-import @thi.ng/range-coder package from MB2010

packages/range-coder/.npmignore

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+bench/*
+build/*
+dev/*
+node_modules
+src*
+test*
+bundle.*
+tsconfig.json
+webpack.config.js
+*.html
+*.tgz
+!doc/*
+!*.d.ts
+!*.js

packages/range-coder/README.md

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+# @thi.ng/range-coder
+
+[![npm (scoped)](https://img.shields.io/npm/v/@thi.ng/range-coder.svg)](https://www.npmjs.com/package/@thi.ng/range-coder)
+
+This project is part of the
+[@thi.ng/umbrella](https://github.com/thi-ng/umbrella/) monorepo.
+
+## About
+
+Range encoder / decoder for binary data, based on [Java implementation
+by Joe Halliwell](https://www.winterwell.com/software/compressor.php).
+
+## Installation
+
+```bash
+yarn add @thi.ng/range-coder
+```
+
+## Dependencies
+
+- [@thi.ng/bitstream](https://github.com/thi-ng/umbrella/tree/master/packages/bitstream)
+
+## API
+
+```ts
+import * as rc "@thi.ng/range-coder";
+```
+
+```ts
+// prepare dummy data
+src = new Uint8Array(1024);
+src.set([1,1,1,1,1,2,2,2,2,3,3,3,4,4,5,4,4,3,3,3,2,2,2,2,1,1,1,1,1], 512);
+
+// pack data
+packed = rc.encodeBytes(src);
+
+packed.length
+// 146
+
+packed.length/src.length
+// 0.142578125
+
+// unpack
+dest = rc.decodeBytes(packed);
+```
+
+## Authors
+
+- Karsten Schmidt
+
+## License
+
+© 2017 Karsten Schmidt // Apache Software License 2.0

packages/range-coder/package.json

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+{
+    "name": "@thi.ng/range-coder",
+    "version": "0.0.1",
+    "description": "Binary data range encoder / decoder",
+    "main": "./index.js",
+    "typings": "./index.d.ts",
+    "repository": {
+        "type": "git",
+        "url": "https://github.com/thi-ng/umbrella.git"
+    },
+    "homepage": "https://github.com/thi-ng/umbrella/tree/master/packages/rstream",
+    "author": "Karsten Schmidt <[email protected]>",
+    "license": "Apache-2.0",
+    "scripts": {
+        "build": "yarn clean && tsc --declaration",
+        "clean": "rm -rf *.js *.d.ts .nyc_output build coverage doc",
+        "cover": "yarn test && nyc report --reporter=lcov",
+        "doc": "node_modules/.bin/typedoc --mode modules --out doc src",
+        "pub": "yarn build && yarn publish --access public",
+        "test": "rm -rf build && tsc -p test && nyc mocha build/test/*.js"
+    },
+    "devDependencies": {
+        "@thi.ng/transducers": "1.14.1",
+        "@types/mocha": "^5.2.0",
+        "@types/node": "^10.0.6",
+        "mocha": "^5.1.1",
+        "nyc": "^11.7.1",
+        "typedoc": "^0.11.1",
+        "typescript": "^2.8.3"
+    },
+    "dependencies": {
+        "@thi.ng/bitstream": "0.4.14"
+    },
+    "keywords": [
+        "ES6",
+        "binary",
+        "entropy",
+        "packer",
+        "range encoding",
+        "typescript"
+    ],
+    "publishConfig": {
+        "access": "public"
+    }
+}

packages/range-coder/src/index.ts

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+import { BitInputStream, BitOutputStream } from "@thi.ng/bitstream";
+
+const HIGH = 0x7fffff;
+const HALF = 0x400000;
+const QUARTER = 0x200000;
+const THREE_QUARTER = 0x600000;
+const INITIAL_READ = 23;
+const FREQ = 257;
+
+export const encodeBytes = (src: Uint8Array) => {
+    const freq = new Uint32Array(FREQ).fill(1);
+    const out = new BitOutputStream(Math.max(src.length >> 1, 1));
+    const len = src.length;
+    let total = FREQ;
+    let lo = 0;
+    let hi = HIGH;
+    let _lo = lo;
+    let _hi = hi;
+    let step;
+    let scale = 0;
+    let curr = 0;
+    let i, j;
+
+    for (i = 0; i <= len; i++) {
+        if (i === len) {
+            lo = total - 1;
+            hi = total;
+        } else {
+            curr = src[i];
+            lo = 0;
+            for (j = 0; j < curr; j++) {
+                lo += freq[j];
+            }
+            hi = lo + freq[curr];
+        }
+
+        step = ((_hi - _lo + 1) / total) >>> 0;
+        _hi = _lo + step * hi - 1;
+        _lo += step * lo;
+
+        while (true) {
+            if (_hi < HALF) {
+                out.writeBit(0);
+                _lo <<= 1;
+                _hi = (_hi << 1) + 1;
+                scale && out.write(HIGH, scale);
+            } else if (_lo >= HALF) {
+                out.writeBit(1);
+                _lo = (_lo - HALF) << 1;
+                _hi = ((_hi - HALF) << 1) + 1;
+                scale && out.write(0, scale);
+            } else {
+                break;
+            }
+            scale = 0;
+        }
+
+        while (_lo > QUARTER && _hi < THREE_QUARTER) {
+            scale++;
+            _lo = (_lo - QUARTER) << 1;
+            _hi = ((_hi - QUARTER) << 1) + 1;
+        }
+
+        freq[curr]++;
+        total++;
+    }
+    if (_lo < QUARTER) {
+        out.writeBit(0);
+        out.write(HIGH, scale + 1);
+    } else {
+        out.writeBit(1);
+    }
+    return out.bytes();
+};
+
+export const decodeBytes = (src: Uint8Array) => {
+    const freq = new Uint32Array(FREQ).fill(1);
+    const input = new BitInputStream(src)
+    const nbits = input.length
+    const out = []
+    let total = FREQ
+    let current = 0
+    let lo = 0
+    let hi = HIGH
+    let _lo = lo
+    let _hi = hi
+    let step = 0
+    let buf = input.read(INITIAL_READ)
+    let val;
+
+    const read = () => input.position < nbits ? input.readBit() : 0;
+
+    while (true) {
+        step = ((_hi - _lo + 1) / total) >>> 0;
+        val = ((buf - _lo) / step) >>> 0;
+        lo = 0;
+        for (current = 0; current < 256 && lo + freq[current] <= val; current++) {
+            lo += freq[current];
+        }
+        if (current === 256) break;
+
+        out.push(current);
+        hi = lo + freq[current];
+
+        _hi = _lo + step * hi - 1;
+        _lo += step * lo;
+
+        while (true) {
+            if (_hi < HALF) {
+                buf <<= 1;
+                _lo <<= 1;
+                _hi = (_hi << 1) + 1;
+            } else if (_lo >= HALF) {
+                buf = (buf - HALF) << 1;
+                _lo = (_lo - HALF) << 1;
+                _hi = ((_hi - HALF) << 1) + 1;
+            } else {
+                break;
+            }
+            buf += read();
+        }
+
+        while (_lo > QUARTER && _hi < THREE_QUARTER) {
+            _lo = (_lo - QUARTER) << 1;
+            _hi = ((_hi - QUARTER) << 1) + 1;
+            buf = (buf - QUARTER) << 1;
+            buf += read();
+        }
+
+        freq[current]++;
+        total++;
+    }
+
+    return new Uint8Array(out);
+};

packages/range-coder/test/index.ts

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+import { repeat, repeatedly } from "@thi.ng/transducers";
+import * as assert from "assert";
+import { decodeBytes, encodeBytes } from "../src";
+
+describe("range-coder", () => {
+
+    it("fixed", () => {
+        const src = new Uint8Array([10, 20, 30, 10, 10, 10]);
+        const dest = encodeBytes(src);
+        assert.deepEqual(dest, [10, 10, 224, 160, 49, 91, 88]);
+        assert.deepEqual(src, decodeBytes(dest));
+    });
+
+    it("fuzz", () => {
+        for (let i = 0; i < 10; i++) {
+            const src = randomArray(640, 1024);
+            const dest = encodeBytes(src);
+            console.log(`${(dest.length / src.length * 100).toFixed(2)}%`);
+            assert.deepEqual(src, decodeBytes(dest));
+        }
+    });
+});
+
+function randomArray(n: number, len: number) {
+    return new Uint8Array([...repeatedly(() => ~~(Math.random() * 256), n), ...repeat(0, len - n)]);
+}

packages/range-coder/test/tsconfig.json

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+{
+    "extends": "../../../tsconfig.json",
+    "compilerOptions": {
+        "outDir": "../build"
+    },
+    "include": [
+        "./**/*.ts",
+        "../src/**/*.ts"
+    ]
+}

packages/range-coder/tsconfig.json

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+{
+    "extends": "../../tsconfig.json",
+    "compilerOptions": {
+        "outDir": "."
+    },
+    "include": [
+        "./src/**/*.ts",
+    ]
+}