### JavaScript MD5 hash for air.FileStream

Nov 5 2010 · javascript

This is the MD5 file hash used in progTools.

You can copy and paste the code below or get it via. bitbucket.

The code builds upon Paul Johnston’s MD5 implementation and you’ll need to include his code first.

`<!-- Paul Johnston's MD5 implementation -->`

<script type="text/javascript" src="tools/md5/md5.js"></script>

<!-- Additional MD5 functions for working on air.FileStream; requires Paj's md5.js -->

<script type="text/javascript" src="tools/md5/md5_file.js"></script>

core_md5_ex() is a modified/hacked version of the original core_md5() to allow for progressively processing chunks of data, instead of doing it all in one go.

`// modified version of Paul Johnston's MD5 implementation`

function core_md5_ex(x, len, abcd_start, append_padding, total_len)

{

/* append padding */

if (append_padding) {

x[len >> 5] |= 0x80 << ((len) % 32);

x[(((len + 64) >>> 9) << 4) + 14] = total_len*8;

}

var a = abcd_start[0];

var b = abcd_start[1];

var c = abcd_start[2];

var d = abcd_start[3];

for(var i = 0; i < x.length; i += 16)

{

var olda = a;

var oldb = b;

var oldc = c;

var oldd = d;

a = md5_ff(a, b, c, d, x[i+ 0], 7 , -680876936);

d = md5_ff(d, a, b, c, x[i+ 1], 12, -389564586);

c = md5_ff(c, d, a, b, x[i+ 2], 17, 606105819);

b = md5_ff(b, c, d, a, x[i+ 3], 22, -1044525330);

a = md5_ff(a, b, c, d, x[i+ 4], 7 , -176418897);

d = md5_ff(d, a, b, c, x[i+ 5], 12, 1200080426);

c = md5_ff(c, d, a, b, x[i+ 6], 17, -1473231341);

b = md5_ff(b, c, d, a, x[i+ 7], 22, -45705983);

a = md5_ff(a, b, c, d, x[i+ 8], 7 , 1770035416);

d = md5_ff(d, a, b, c, x[i+ 9], 12, -1958414417);

c = md5_ff(c, d, a, b, x[i+10], 17, -42063);

b = md5_ff(b, c, d, a, x[i+11], 22, -1990404162);

a = md5_ff(a, b, c, d, x[i+12], 7 , 1804603682);

d = md5_ff(d, a, b, c, x[i+13], 12, -40341101);

c = md5_ff(c, d, a, b, x[i+14], 17, -1502002290);

b = md5_ff(b, c, d, a, x[i+15], 22, 1236535329);

a = md5_gg(a, b, c, d, x[i+ 1], 5 , -165796510);

d = md5_gg(d, a, b, c, x[i+ 6], 9 , -1069501632);

c = md5_gg(c, d, a, b, x[i+11], 14, 643717713);

b = md5_gg(b, c, d, a, x[i+ 0], 20, -373897302);

a = md5_gg(a, b, c, d, x[i+ 5], 5 , -701558691);

d = md5_gg(d, a, b, c, x[i+10], 9 , 38016083);

c = md5_gg(c, d, a, b, x[i+15], 14, -660478335);

b = md5_gg(b, c, d, a, x[i+ 4], 20, -405537848);

a = md5_gg(a, b, c, d, x[i+ 9], 5 , 568446438);

d = md5_gg(d, a, b, c, x[i+14], 9 , -1019803690);

c = md5_gg(c, d, a, b, x[i+ 3], 14, -187363961);

b = md5_gg(b, c, d, a, x[i+ 8], 20, 1163531501);

a = md5_gg(a, b, c, d, x[i+13], 5 , -1444681467);

d = md5_gg(d, a, b, c, x[i+ 2], 9 , -51403784);

c = md5_gg(c, d, a, b, x[i+ 7], 14, 1735328473);

b = md5_gg(b, c, d, a, x[i+12], 20, -1926607734);

a = md5_hh(a, b, c, d, x[i+ 5], 4 , -378558);

d = md5_hh(d, a, b, c, x[i+ 8], 11, -2022574463);

c = md5_hh(c, d, a, b, x[i+11], 16, 1839030562);

b = md5_hh(b, c, d, a, x[i+14], 23, -35309556);

a = md5_hh(a, b, c, d, x[i+ 1], 4 , -1530992060);

d = md5_hh(d, a, b, c, x[i+ 4], 11, 1272893353);

c = md5_hh(c, d, a, b, x[i+ 7], 16, -155497632);

b = md5_hh(b, c, d, a, x[i+10], 23, -1094730640);

a = md5_hh(a, b, c, d, x[i+13], 4 , 681279174);

d = md5_hh(d, a, b, c, x[i+ 0], 11, -358537222);

c = md5_hh(c, d, a, b, x[i+ 3], 16, -722521979);

b = md5_hh(b, c, d, a, x[i+ 6], 23, 76029189);

a = md5_hh(a, b, c, d, x[i+ 9], 4 , -640364487);

d = md5_hh(d, a, b, c, x[i+12], 11, -421815835);

c = md5_hh(c, d, a, b, x[i+15], 16, 530742520);

b = md5_hh(b, c, d, a, x[i+ 2], 23, -995338651);

a = md5_ii(a, b, c, d, x[i+ 0], 6 , -198630844);

d = md5_ii(d, a, b, c, x[i+ 7], 10, 1126891415);

c = md5_ii(c, d, a, b, x[i+14], 15, -1416354905);

b = md5_ii(b, c, d, a, x[i+ 5], 21, -57434055);

a = md5_ii(a, b, c, d, x[i+12], 6 , 1700485571);

d = md5_ii(d, a, b, c, x[i+ 3], 10, -1894986606);

c = md5_ii(c, d, a, b, x[i+10], 15, -1051523);

b = md5_ii(b, c, d, a, x[i+ 1], 21, -2054922799);

a = md5_ii(a, b, c, d, x[i+ 8], 6 , 1873313359);

d = md5_ii(d, a, b, c, x[i+15], 10, -30611744);

c = md5_ii(c, d, a, b, x[i+ 6], 15, -1560198380);

b = md5_ii(b, c, d, a, x[i+13], 21, 1309151649);

a = md5_ii(a, b, c, d, x[i+ 4], 6 , -145523070);

d = md5_ii(d, a, b, c, x[i+11], 10, -1120210379);

c = md5_ii(c, d, a, b, x[i+ 2], 15, 718787259);

b = md5_ii(b, c, d, a, x[i+ 9], 21, -343485551);

a = safe_add(a, olda);

b = safe_add(b, oldb);

c = safe_add(c, oldc);

d = safe_add(d, oldd);

}

return Array(a, b, c, d);

}

What’s changed is:

- We pass in the starting values (which is the current hash on the data thus far, minus the necessary padding)
- We use a variable to determine whether or not to append padding to the input; this is only done when processing the last block on data read from the stream.

hex_md5_stream() is the function which processes the stream: reading in chunks, transforming the bytes in inBytes into an array 4-byte WORDs, and calling core_md5_ex() with the necessary data.

`function hex_md5_stream(inStream)`

{

var abcd_start = new Array();

abcd_start.push(1732584193);

abcd_start.push(-271733879);

abcd_start.push(-1732584194);

abcd_start.push(271733878);

var inBytes = new air.ByteArray();

var appendPaddingToBlock = false;

var totalLen = 0;

while (inStream.bytesAvailable > 0)

{

inStream.readBytes(inBytes, 0, Math.min(8192, inStream.bytesAvailable));

if(inBytes.length < 8192)

{

appendPaddingToBlock = true;

}

totalLen += inBytes.length;

bin = new Array();

for(var i = 0; i < inBytes.length * 8; i+=8)

bin[i>>5] |= (inBytes[i>>3] & 0xff) << (i%32);

abcd_start = core_md5_ex(bin, inBytes.length*8, abcd_start, appendPaddingToBlock, totalLen);

inBytes.clear();

}

return binl2hex(abcd_start);

}

Here’s the top-level view of how it works:

`var inStream = new air.FileStream(); `

var file = new air.File();

file.url = "file:///" + filename;

inStream.open(file, air.FileMode.READ);

var md5result = hex_md5_stream(inStream);

inStream.close();