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