1 files changed, 102 insertions, 0 deletions
diff --git a/src/zmlib.js b/src/zmlib.js
new file mode 100644
index 0000000..f86070d
--- /dev/null
+++ b/src/zmlib.js
@@ -0,0 +1,102 @@
+"use strict";
+
+var Zmodem = module.exports;
+
+const
+    ZDLE = 0x18,
+    XON = 0x11,
+    XOFF = 0x13,
+    XON_HIGH = 0x80 | XON,
+    XOFF_HIGH = 0x80 | XOFF,
+    CAN = 0x18     //NB: same character as ZDLE
+;
+
+/**
+ * Tools and constants that are useful for ZMODEM.
+ *
+ * @exports ZMLIB
+ */
+Zmodem.ZMLIB = {
+
+    /**
+     * @property {number} The ZDLE constant, which ZMODEM uses for escaping
+     */
+    ZDLE: ZDLE,
+
+    /**
+     * @property {number} XON - ASCII XON
+     */
+    XON: XON,
+
+    /**
+     * @property {number} XOFF - ASCII XOFF
+     */
+    XOFF: XOFF,
+
+    /**
+     * @property {number[]} ABORT_SEQUENCE - ZMODEM’s abort sequence
+     */
+    ABORT_SEQUENCE: [ CAN, CAN, CAN, CAN, CAN ],
+
+    /**
+     * Remove octet values from the given array that ZMODEM always ignores.
+     * This will mutate the given array.
+     *
+     * @param {number[]} octets - The octet values to transform.
+     *      Each array member should be an 8-bit unsigned integer (0-255).
+     *      This object is mutated in the function.
+     *
+     * @returns {number[]} The passed-in array. This is the same object that is
+     *      passed in.
+     */
+    strip_ignored_bytes: function strip_ignored_bytes(octets) {
+        for (var o=octets.length-1; o>=0; o--) {
+            switch (octets[o]) {
+                case XON:
+                case XON_HIGH:
+                case XOFF:
+                case XOFF_HIGH:
+                    octets.splice(o, 1);
+                    continue;
+            }
+        }
+
+        return octets;
+    },
+
+    /**
+     * Like Array.prototype.indexOf, but searches for a subarray
+     * rather than just a particular value.
+     *
+     * @param {Array} haystack - The array to search, i.e., the bigger.
+     *
+     * @param {Array} needle - The array whose values to find,
+     *      i.e., the smaller.
+     *
+     * @returns {number} The position in “haystack” where “needle”
+     *      first appears—or, -1 if “needle” doesn’t appear anywhere
+     *      in “haystack”.
+     */
+    find_subarray: function find_subarray(haystack, needle) {
+        var h=0, n;
+
+        var start = Date.now();
+
+        HAYSTACK:
+        while (h !== -1) {
+            h = haystack.indexOf( needle[0], h );
+            if (h === -1) break HAYSTACK;
+
+            for (n=1; n<needle.length; n++) {
+                if (haystack[h + n] !== needle[n]) {
+                    h++;
+                    continue HAYSTACK;
+                }
+            }
+
+            return h;
+        }
+
+        return -1;
+    },
+};