The Annoyance Filter.pdf - Fourmilab

§105 ANNOYANCE-FILTER FLASH STREAM DECODER 85
105. Flash files are a little schizophrenic when it comes to the definition of strings. Sometimes they’re
stored with a leading count byte followed by the given number of bytes of text, while in other places
they’re stored C style, with a zero terminator byte marking the end of the string. The getString method
handles both kinds. If called with no length argument, it reads a zero terminated string, otherwise it
reads a string of n characters. It’s up to the caller to first read the length and pass it as the n argument,
〈 Class implementations 11 〉 +≡
void flashStream ::getString (string &s, int n)
{
s = "";
}
char ch ;
if (n ≡ −1) {
while ((ch = get8 ( )) ≠ 0) {
s += ch ;
}
}
else {
while (n > 0) {
ch = get8 ( );
s += ch ;
n−−;
}
}
106. A rectangle is stored as a 5 bit field which specifies the number of bits in the extent fields which
follow, which are sign extended when extracted.
〈 Class implementations 11 〉 +≡
void flashStream ::getRect (rect ∗ r)
{
initBits ( );
}
int nBits = static cast〈int〉(getBits (5));
r ⃗ xMin = getSignedBits (nBits );
r ⃗ xMax = getSignedBits (nBits );
r ⃗ yMin = getSignedBits (nBits );
r ⃗ yMax = getSignedBits (nBits );