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namespace Xmpp.Util {
/**
* Parse a number from a hexadecimal representation.
*
* Skips any whitespace at the start of the string, parses as many valid
* characters as hexadecimal digits as possible (possibly zero) and returns
* them as an integer value.
*
* ```
* // 0xa
* print("0x%lx\n", from_hex("A quick brown fox jumps over the lazy dog."));
* ```
*/
public long from_hex(string numeral) {
long result = 0;
bool skipping_whitespace = true;
foreach (uint8 byte in numeral.data) {
char c = (char)byte;
if (skipping_whitespace && c.isspace()) {
continue;
}
skipping_whitespace = false;
int digit;
if ('0' <= c && c <= '9') {
digit = c - '0';
} else if ('A' <= c && c <= 'F') {
digit = c - 'A' + 10;
} else if ('a' <= c && c <= 'f') {
digit = c - 'a' + 10;
} else {
break;
}
result = (result << 4) | digit;
}
return result;
}
}
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