This is traditionally not possible with JavaScript, but it may be if the W3 File Upload spec ever catches on.
A variant is available in Firefox 3:
var content= input.files[0].getAsBinary();
For other browsers you would have to fall back to Flash and/or server-side hashing.
Here's a bonus JS implementation of SHA-1 for you:
function sha_hexdigest(bytes) {
var digest= sha_bytes(sha_calculate(sha_ints(bytes), bytes.length*8));
var digits= '0123456789abcdef';
var hex= '';
for (var i= 0; i<digest.length; i++) {
var c= digest.charCodeAt(i);
hex+= digits.charAt((c>>4)&0xF) + digits.charAt(c&0xF);
}
return hex;
}
function sha_ints(bytes) {
while (bytes.length%4!=0)
bytes+= '\x00';
var ints= new Array();
for (var i= 0; i<bytes.length; i+= 4) {
ints[ints.length]= (
(bytes.charCodeAt(i)&0xFF)<<24 | (bytes.charCodeAt(i+1)&0xFF)<<16 |
(bytes.charCodeAt(i+2)&0xFF)<<8 | (bytes.charCodeAt(i+3)&0xFF)
); }
return ints;
}
function sha_bytes(ints) {
var bytes= '';
for (var i= 0; i<ints.length; i++)
bytes+= String.fromCharCode((ints[i]>>24)&0xFF, (ints[i]>>16)&0xFF, (ints[i]>>8)&0xFF, ints[i]&0xFF)
return bytes;
}
function sha_calculate(ints, bitn) {
while (ints.length*32<=bitn) ints[ints.length]= 0;
ints[ints.length-1]|= 1<<(31-bitn%32)
while (ints.length%16!=14) ints[ints.length]= 0;
ints[ints.length]= Math.floor(bitn/0x100000000);
ints[ints.length]= bitn&0xFFFFFFFF;
var h0= 1732584193, h1= -271733879, h2= -1732584194, h3= 271733878, h4= -1009589776;
var a, b, c, d, e, f, k, temp, w= new Array(80);
for(var inti= 0; inti<ints.length; inti+= 16) {
a= h0; b= h1; c= h2; d= h3; e= h4;
for (var i= 0; i<16; i++) w[i]= ints[inti+i];
for (; i<80; i++) w[i]= sha_rol(w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16], 1);
for(var i= 0; i<80; i++) {
switch (Math.floor(i/20)) {
case 0: f= sha_add(1518500249, (b & c) | ((~b) & d)); break;
case 1: f= sha_add(1859775393, b ^ c ^ d); break;
case 2: f= sha_add(-1894007588, (b & c) | (b & d) | (c & d)); break;
case 3: f= sha_add(-899497514, b ^ c ^ d); break;
}
temp= sha_add( sha_add(sha_rol(a, 5), w[i]), sha_add(e, f) );
e= d; d= c; c= b; b= a; a= temp;
c= sha_rol(c, 30);
}
h0= sha_add(h0, a); h1= sha_add(h1, b); h2= sha_add(h2, c); h3= sha_add(h3, d); h4= sha_add(h4, e);
}
return new Array(h0, h1, h2, h3, h4);
}
function sha_add(a, b) {
var lsw= (a&0xFFFF) + (b&0xFFFF);
var msw= (a>>16) + (b>>16) + (lsw>>16);
return (msw<<16) | (lsw&0xFFFF);
}
function sha_rol(n, bits) {
return (n<<bits) | (n>>>(32-bits));
}