Add EPK decompiler

todo: SHA1 checks for decompiling old format EPK

ayunEPKDecompiler.js

@@ -0,0 +1,244 @@
+window.decompileEPK = function () {
+	let currentOffset = 0;
+
+	let numFiles = 0;
+
+	function detectOldHeader(epkData) {
+		const oldHeader = "EAGPKG!!";
+		for (let i = 0; i < oldHeader.length; i++) {
+			if (epkData[i] != oldHeader.charCodeAt(i)) return false;
+		}
+		return true;
+	}
+
+	function readASCII(epkData) {
+		const len = read(epkData);
+		let str = "";
+		for (let i = 0; i < len; i++) {
+			str += String.fromCharCode(read(epkData));
+		}
+		return str;
+	}
+
+	function read(epkData) {
+		return epkData[currentOffset++];
+	}
+
+	function skip(num) {
+		currentOffset += num;
+	}
+
+	function loadShort(epkData) {
+		return (read(epkData) << 8) | read(epkData);
+	}
+
+	function loadInt(epkData) {
+		return (read(epkData) << 24) | (read(epkData) << 16) | (read(epkData) << 8) | read(epkData);
+	}
+
+	function readUTF(epkData) {
+		const len = loadShort(epkData);
+		let str = "";
+		for (let i = 0; i < len; i++) {
+			str += String.fromCharCode(read(epkData));
+		}
+		return str;
+	}
+
+	// https://stackoverflow.com/a/18639903/6917520
+
+	const crc32 = (function() {
+		let table = new Uint32Array(256);
+
+		for (let i = 256; i--;) {
+			let tmp = i;
+
+			for (let k = 8; k--;) {
+				tmp = tmp & 1 ? 3988292384 ^ tmp >>> 1 : tmp >>> 1;
+			}
+
+			table[i] = tmp;
+		}
+
+		return function(data) {
+			let crc = -1;
+
+			for (let i = 0, l = data.length; i < l; i++) {
+				crc = crc >>> 8 ^ table[crc & 255 ^ data[i]];
+			}
+
+			return (crc ^ -1) >>> 0;
+		};
+	})();
+
+	function decompileOld(epkData) {
+		readUTF(epkData);
+
+		try {
+			let zData = pako.inflate(epkData.slice(currentOffset));
+			currentOffset = 0;
+			return readFilesOld(zData);
+		} catch (err) {
+			return null;
+		}
+	}
+
+	function decompileNew(epkData) {
+		const vers = readASCII(epkData);
+		
+		if (!vers.startsWith("ver2.")) {
+			return null;
+		}
+
+		skip(read(epkData));
+		skip(loadShort(epkData));
+		skip(8);
+
+		numFiles = loadInt(epkData);
+
+		const compressionType = String.fromCharCode(read(epkData));
+
+		let zData = epkData.slice(currentOffset);
+		
+		if (compressionType == "Z" || compressionType == "G") {
+			try {
+				zData = pako.inflate(zData);
+			} catch (err) {
+				return null;
+			}
+		} else if (compressionType == "0") {
+			// do nothing
+		} else {
+			return null;
+		}
+
+		currentOffset = 0;
+
+		return readFilesNew(zData);
+	}
+
+	function readFilesOld(data) {
+		let files = [];
+
+		let file;
+		while ((file = readFileOld(data)) != null) {
+			if (file == -1) return null;
+			files.push(file);
+		}
+
+		return files;
+	}
+
+	function readFileOld(data) {
+		const s = readUTF(data);
+		if (s == " end") {
+			return null;
+		} else if (s != "<file>") {
+			return -1;
+		}
+
+		const path = readUTF(data);
+
+		skip(20);
+
+		const len = loadInt(data);
+		const blob = new Blob([data.slice(currentOffset, currentOffset + len)]);
+		skip(len);
+		if (readUTF(data) != "</file>") {
+			return -1;
+		}
+
+		return {
+			type: "FILE",
+			name: path,
+			data: blob
+		};
+	}
+
+	function readFilesNew(data) {
+		let files = [];
+
+		let file;
+		while ((file = readFileNew(data)) != null) {
+			if (file == -1) return null;
+			files.push(file);
+		}
+
+		return files;
+	}
+
+	function readFileNew(data) {
+		const type = String.fromCharCode(read(data), read(data), read(data), read(data));
+
+		if (numFiles == 0) {
+			if (type != "END$") {
+				return -1;
+			}
+			return null;
+		}
+
+		if (type == "END$") {
+			return -1;
+		}
+
+		const name = readASCII(data);
+		const len = loadInt(data);
+		let blob = null;
+
+		if (type == "FILE") {
+			if (len < 5) {
+				return -1;
+			}
+
+			const crc = loadInt(data);
+			const blobBuffer = data.slice(currentOffset, currentOffset + len - 5);
+			skip(len - 5);
+			blob = new Blob([blobBuffer]);
+
+			if (crc != (crc32(blobBuffer) | 0)) {
+				return -1;
+			}
+
+			if (read(data) != 58) {
+				return -1;
+			}
+		} else {
+			blob = new Blob([data.slice(currentOffset, currentOffset + len)]);
+			skip(len);
+		}
+
+		if (read(data) != 62) {
+			return -1;
+		}
+
+		numFiles--;
+
+		return {
+			type: type,
+			name: name,
+			data: blob
+		};
+	}
+
+	return async function(rawBuffer) {
+		let epkData = new Uint8Array(rawBuffer);
+
+		if (detectOldHeader(epkData)) {
+			epkData = epkData.slice(8);
+			return decompileOld(epkData);
+		}
+
+		const header = "EAGPKG$$";
+		for (let i = 0; i < header.length; i++) {
+			if (epkData[i] != header.charCodeAt(i)) return null;
+		}
+
+		const endCode = ":::YEE:>";
+		for (let i = 0; i < endCode.length; i++) {
+			if (epkData[epkData.length - 8 + i] != endCode.charCodeAt(i)) return null;
+		}
+
+		epkData = epkData.slice(8, -8);
+		return decompileNew(epkData);
+	};
+};

decompile.html

@@ -0,0 +1,109 @@
+<!DOCTYPE html>
+<html>
+	<head>
+		<script async src="https://arc.io/widget.min.js#HEPCFa3K"></script>
+		<meta charset="utf-8"/>
+		<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
+		<title>ayunWebEPK</title>
+		<script type="text/javascript" src="jszip.min.js"></script>
+		<script type="text/javascript" src="pako_inflate.min.js"></script>
+		<script type="text/javascript" src="ayunEPKDecompiler.js"></script>
+		<link rel="preconnect" href="https://fonts.googleapis.com"/>
+		<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin/>
+		<link href="https://fonts.googleapis.com/css2?family=Nunito&display=swap" rel="stylesheet"/>
+		<style>
+			a:not([href]) {
+				display: none;
+			}
+			*, ::file-selector-button {
+				font-family: 'Nunito', sans-serif;
+			}
+			body {
+				background-color: #111111;
+				color: #dddddd;
+			}
+			input[disabled] {
+				opacity: 0.8;
+			}
+			::file-selector-button, progress {
+				background-color: #343434;
+				color: #eeeeee;
+				border: 1px solid #eeeeee;
+				border-radius: 4px;
+			}
+			a, input[type=file] {
+				color: #dddddd;
+			}
+			progress {
+				height: 1em;
+			}
+			progress, ::-webkit-file-upload-button {
+				-webkit-appearance: none;
+        		-moz-appearance: none;
+        		appearance: none;
+			}
+			progress[value="0"][max="1"] {
+				display: none;
+			}
+			::-moz-progress-bar {
+				background-color: #eeeeee;
+			}
+			::-webkit-progress-value {
+				background-color: #eeeeee;
+			}
+			::-webkit-progress-bar {
+				background-color: #343434;
+				border-radius: 4px;
+			}
+		</style>
+	</head>
+	<body>
+		<sub><a href="..">Want to compile one instead?</a></sub>
+		<h1>ayunWebEPK</h1>
+		<p>Decompile EPK files in your browser!</p>
+		Select .EPK file: <input type="file" onchange="selectFile(this);" accept=".epk"/>
+		<br/>
+		<progress value="0" max="1"></progress>
+		<a download="my-cool.zip">Download as a ZIP!</a>
+		<script>
+			const downloadLink = document.querySelectorAll('a')[1];
+			const progressBar = document.querySelector('progress');
+
+			function selectFile(fileElem) {
+				downloadLink.removeAttribute('href');
+				fileElem.disabled = true;
+				if (fileElem.files.length > 0) {
+					const epkFile = fileElem.files[0];
+					const reader = new FileReader();
+					reader.onload = function(e) {
+						window.decompileEPK()(e.target.result).then(function(fileList) {
+							if (fileList == null) {
+								alert("Invalid EPK!");
+								fileElem.removeAttribute('disabled');
+								return;
+							}
+							const zip = new JSZip();
+							progressBar.max = fileList.length;
+							for (const file of fileList) {
+								progressBar.value++;
+								if (file.type != 'FILE') continue;
+								zip.file(file.name, file.data); // todo: check if it'll accept a blob as input
+							}
+							
+							zip.generateAsync({type: 'blob'}).then(function(content) {
+								downloadLink.href = window.URL.createObjectURL(content);
+								fileElem.value = '';
+								progressBar.value = 0;
+								progressBar.max = 1;
+								fileElem.removeAttribute('disabled')
+							});
+						});
+					};
+					reader.readAsArrayBuffer(epkFile);
+				} else {
+					fileElem.removeAttribute('disabled');
+				}
+			}
+		</script>
+	</body>
+</html>

index.html

@@ -102,6 +102,7 @@
 		</style>
 	</head>
 	<body>
+		<sub><a href="decompile.html">Want to decompile one instead?</a></sub>
 		<h1>ayunWebEPK</h1>
 		<p>Compile EPK files in your browser!</p>
 		Use legacy format: <input type="checkbox"/>
@@ -142,7 +143,7 @@
 				};
 			})();
 
-			const downloadLink = document.querySelector('a');
+			const downloadLink = document.querySelectorAll('a')[1];
 			const progressBar = document.querySelector('progress');
 			const fileElems = document.querySelectorAll('input[type=file]');
 			const oldBox = document.querySelector('input[type=checkbox]');