Add some utility functions that are now only used here

littlefs.js

@@ -84,6 +84,17 @@ function toHex(value, size=2) {
     return "0x" + value.toString(16).toUpperCase().padStart(size, "0");
 }
 
+function toByteArray(str) {
+    let byteArray = [];
+    for (let i = 0; i < str.length; i++) {
+      let charcode = str.charCodeAt(i);
+      if (charcode <= 0xFF) {
+        byteArray.push(charcode);
+      }
+    }
+    return byteArray;
+  }
+
 class LittleFS {
   constructor(config) {
     this.rcache = new Cache();
@@ -3340,4 +3351,97 @@ class LfsFile {
   }
 };
 
+class struct {
+    static lut = {
+      "b": {u: DataView.prototype.getInt8, p: DataView.prototype.setInt8, bytes: 1},
+      "B": {u: DataView.prototype.getUint8, p: DataView.prototype.setUint8, bytes: 1},
+      "h": {u: DataView.prototype.getInt16, p: DataView.prototype.setInt16, bytes: 2},
+      "H": {u: DataView.prototype.getUint16, p: DataView.prototype.setUint16, bytes: 2},
+      "i": {u: DataView.prototype.getInt32, p: DataView.prototype.setInt32, bytes: 4},
+      "I": {u: DataView.prototype.getUint32, p: DataView.prototype.setUint32, bytes: 4},
+      "q": {u: DataView.prototype.getInt64, p: DataView.prototype.setInt64, bytes: 8},
+      "Q": {u: DataView.prototype.getUint64, p: DataView.prototype.setUint64, bytes: 8},
+    }
+
+    static pack(...args) {
+        let format = args[0];
+        let pointer = 0;
+        let data = args.slice(1);
+        if (format.replace(/[<>]/, '').length != data.length) {
+            throw("Pack format to Argument count mismatch");
+            return;
+        }
+        let bytes = [];
+        let littleEndian = true;
+        for (let i = 0; i < format.length; i++) {
+            if (format[i] == "<") {
+                littleEndian = true;
+            } else if (format[i] == ">") {
+                littleEndian = false;
+            } else {
+                pushBytes(format[i], data[pointer]);
+                pointer++;
+            }
+        }
+
+        function pushBytes(formatChar, value) {
+            if (!(formatChar in struct.lut)) {
+                throw("Unhandled character '" + formatChar + "' in pack format");
+            }
+            let dataSize = struct.lut[formatChar].bytes;
+            let view = new DataView(new ArrayBuffer(dataSize));
+            let dataViewFn = struct.lut[formatChar].p.bind(view);
+            dataViewFn(0, value, littleEndian);
+            for (let i = 0; i < dataSize; i++) {
+                bytes.push(view.getUint8(i));
+            }
+        }
+
+        return bytes;
+    };
+
+    static unpack(format, bytes) {
+        let pointer = 0;
+        let data = [];
+        let littleEndian = true;
+
+        for (let c of format) {
+            if (c == "<") {
+                littleEndian = true;
+            } else if (c == ">") {
+                littleEndian = false;
+            } else {
+                pushData(c);
+            }
+        }
+
+        function pushData(formatChar) {
+            if (!(formatChar in struct.lut)) {
+                throw("Unhandled character '" + formatChar + "' in unpack format");
+            }
+            let dataSize = struct.lut[formatChar].bytes;
+            let view = new DataView(new ArrayBuffer(dataSize));
+            for (let i = 0; i < dataSize; i++) {
+              view.setUint8(i, bytes[pointer + i] & 0xFF);
+            }
+            let dataViewFn = struct.lut[formatChar].u.bind(view);
+            data.push(dataViewFn(0, littleEndian));
+            pointer += dataSize;
+        }
+
+        return data;
+    };
+
+    static calcsize(format) {
+        let size = 0;
+        for (let i = 0; i < format.length; i++) {
+            if (format[i] != "<" && format[i] != ">") {
+                size += struct.lut[format[i]].bytes;
+            }
+        }
+
+        return size;
+    }
+}
+
 export { LittleFS, LfsConfig, LfsFile, LFS_O_RDONLY, LFS_O_WRONLY, LFS_O_RDWR, LFS_O_CREAT, LFS_O_EXCL, LFS_O_TRUNC, LFS_O_APPEND };