add Ox.oshash

source/Ox/js/Hash.js

@@ -0,0 +1,94 @@
+'use strict';
+
+/*@
+Ox.oshash <f> compute oshahs for given File or Blob object (async)
+@*/
+Ox.oshash = function(file, callback) {
+    //needs to go via string to work for files > 2GB
+    var hash = fromString(file.size.toString());
+
+    read(0);
+
+    function add(A, B) {
+        var a, b, c, d; 
+        d = A[3] + B[3];
+        c = A[2] + B[2] + (d >> 16);
+        d &= 0xffff;
+        b = A[1] + B[1] + (c >> 16);
+        c &= 0xffff;
+        a = A[0] + B[0] + (b >> 16);
+        b &= 0xffff;
+        //cut of overflow
+        a &= 0xffff;
+        return [a, b, c ,d];
+    }
+    
+    function fromData(s, offset) {
+        offset = offset || 0;
+        return [
+            s.charCodeAt(offset+6) + (s.charCodeAt(offset+7) << 8),
+            s.charCodeAt(offset+4) + (s.charCodeAt(offset+5) << 8),
+            s.charCodeAt(offset+2) + (s.charCodeAt(offset+3) << 8),
+            s.charCodeAt(offset+0) + (s.charCodeAt(offset+1) << 8)
+        ];
+    }
+
+    function fromString(str) {
+        var base = 10,
+            blen = 1,
+            i,
+            num,
+            pos,
+            r = [0, 0, 0, 0];
+        for(pos=0;pos<str.length;pos++) {
+            num = parseInt(str.charAt(pos), base);
+            i = 0;
+            do {
+                while (i < blen) {
+                    num += r[3-i] * base;
+                    r[3-i++] = (num & 0xffff);
+                    num >>>= 16;
+                }
+                if (num) {
+                    blen++;
+                }
+            } while (num);
+        }
+        return r;
+    }
+
+    function hex(h) {
+        return (Ox.pad(h[0].toString(16), 4)
+            + Ox.pad(h[1].toString(16), 4)
+            + Ox.pad(h[2].toString(16), 4)
+            + Ox.pad(h[3].toString(16), 4)).toLowerCase();
+    }
+
+    function read(offset, last) {
+        var blob,
+            block = 65536,
+            length = 8,
+            reader = new FileReader();
+        reader.onload = function(data) {
+            var s = data.target.result,
+                s_length = s.length - length,
+                i;
+            for(i=0;i<=s_length; i+=length) {
+                hash = add(hash, fromData(s, i));
+            }
+            if(file.size < block || last) {
+                callback(hex(hash));
+            } else {
+                read(file.size - block, true);
+            }
+        };
+        if(file.mozSlice) {
+            blob = file.mozSlice(offset, offset+block);
+        } else if(file.webkitSlice) {
+            blob = file.webkitSlice(offset, offset+block);
+        } else {
+            blob = file.slice(offset, offset+block);
+        }
+        reader.readAsBinaryString(blob);
+    }
+};