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var BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF];
// returns a function that reads bits.
// takes a buffer iterator as input
module.exports = function bitIterator(nextBuffer) {
var bit = 0, byte = 0;
var bytes = nextBuffer();
var f = function(n) {
if (n === null && bit != 0) { // align to byte boundary
bit = 0
byte++;
return;
}
var result = 0;
while(n > 0) {
if (byte >= bytes.length) {
byte = 0;
bytes = nextBuffer();
}
var left = 8 - bit;
if (bit === 0 && n > 0)
f.bytesRead++;
if (n >= left) {
result <<= left;
result |= (BITMASK[left] & bytes[byte++]);
bit = 0;
n -= left;
} else {
result <<= n;
result |= ((bytes[byte] & (BITMASK[n] << (8 - n - bit))) >> (8 - n - bit));
bit += n;
n = 0;
}
}
return result;
};
f.bytesRead = 0;
return f;
};
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