Added 'Extract Files' operation and 'Forensics' category.

src/core/lib/Stream.mjs

@@ -0,0 +1,164 @@
+/**
+ * Stream class for parsing binary protocols.
+ *
+ * @author n1474335 [n1474335@gmail.com]
+ * @author tlwr [toby@toby.codes]
+ * @copyright Crown Copyright 2018
+ * @license Apache-2.0
+ *
+ */
+
+/**
+ * A Stream can be used to traverse a binary blob, interpreting sections of it
+ * as various data types.
+ *
+ * @param {Uint8Array} bytes
+ * @param {Object} fileDetail
+ * @param {string} fileDetail.mime
+ * @param {string} fileDetail.ext
+ * @param {number} fileDetail.offset
+ * @returns {File}
+ */
+export default class Stream {
+
+    /**
+     * Stream constructor.
+     *
+     * @param {Uint8Array} input
+     */
+    constructor(input) {
+        this.bytes = input;
+        this.position = 0;
+    }
+
+    /**
+     * Get a number of bytes from the current position.
+     *
+     * @param {number} numBytes
+     * @returns {Uint8Array}
+     */
+    getBytes(numBytes) {
+        const newPosition = this.position + numBytes;
+        const bytes = this.bytes.slice(this.position, newPosition);
+        this.position = newPosition;
+        return bytes;
+    }
+
+    /**
+     * Interpret the following bytes as a string, stopping at the next null byte or
+     * the supplied limit.
+     *
+     * @param {number} numBytes
+     * @returns {string}
+     */
+    readString(numBytes) {
+        let result = "";
+        for (let i = this.position; i < this.position + numBytes; i++) {
+            const currentByte = this.bytes[i];
+            if (currentByte === 0) break;
+            result += String.fromCharCode(currentByte);
+        }
+        this.position += numBytes;
+        return result;
+    }
+
+    /**
+     * Interpret the following bytes as an integer in big or little endian.
+     *
+     * @param {number} numBytes
+     * @param {string} [endianness="be"]
+     * @returns {number}
+     */
+    readInt(numBytes, endianness="be") {
+        let val = 0;
+        if (endianness === "be") {
+            for (let i = this.position; i < this.position + numBytes; i++) {
+                val = val << 8;
+                val |= this.bytes[i];
+            }
+        } else {
+            for (let i = this.position + numBytes - 1; i >= this.position; i--) {
+                val = val << 8;
+                val |= this.bytes[i];
+            }
+        }
+        this.position += numBytes;
+        return val;
+    }
+
+    /**
+     * Consume the stream until we reach the specified byte or sequence of bytes.
+     *
+     * @param {number|List<number>} val
+     */
+    continueUntil(val) {
+        if (typeof val === "number") {
+            while (++this.position < this.bytes.length && this.bytes[this.position] !== val) {
+                continue;
+            }
+            return;
+        }
+
+        // val is an array
+        let found = false;
+        while (!found && this.position < this.bytes.length) {
+            while (++this.position < this.bytes.length && this.bytes[this.position] !== val[0]) {
+                continue;
+            }
+            found = true;
+            for (let i = 1; i < val.length; i++) {
+                if (this.position + i > this.bytes.length || this.bytes[this.position + i] !== val[i])
+                    found = false;
+            }
+        }
+    }
+
+    /**
+     * Consume the next byte if it matches the supplied value.
+     *
+     * @param {number} val
+     */
+    consumeIf(val) {
+        if (this.bytes[this.position] === val)
+            this.position++;
+    }
+
+    /**
+     * Move forwards through the stream by the specified number of bytes.
+     *
+     * @param {number} numBytes
+     */
+    moveForwardsBy(numBytes) {
+        this.position += numBytes;
+    }
+
+    /**
+     * Move to a specified position in the stream.
+     *
+     * @param {number} pos
+     */
+    moveTo(pos) {
+        if (pos < 0 || pos > this.bytes.length - 1)
+            throw new Error("Cannot move to position " + pos + " in stream. Out of bounds.");
+        this.position = pos;
+    }
+
+    /**
+     * Returns true if there are more bytes left in the stream.
+     *
+     * @returns {boolean}
+     */
+    hasMore() {
+        return this.position < this.bytes.length;
+    }
+
+    /**
+     * Returns a slice of the stream up to the current position.
+     *
+     * @returns {Uint8Array}
+     */
+    carve() {
+        return this.bytes.slice(0, this.position);
+    }
+
+}