org.glassfish.grizzly.http2.hpack.IntegerReader Maven / Gradle / Ivy
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package org.glassfish.grizzly.http2.hpack;
import org.glassfish.grizzly.Buffer;
import java.util.Arrays;
import static java.lang.String.format;
final class IntegerReader {
private static final byte NEW = 0x0;
private static final byte CONFIGURED = 0x1;
private static final byte FIRST_BYTE_READ = 0x2;
private static final byte DONE = 0x4;
private byte state = NEW;
private int N;
private int maxValue;
private int value;
private long r;
private long b = 1;
public IntegerReader configure(int N) {
return configure(N, Integer.MAX_VALUE);
}
//
// Why is it important to configure 'maxValue' here. After all we can wait
// for the integer to be fully read and then check it. Can't we?
//
// Two reasons.
//
// 1. Value wraps around long won't be unnoticed.
// 2. It can spit out an exception as soon as it becomes clear there's
// an overflow. Therefore, no need to wait for the value to be fully read.
//
public IntegerReader configure(int N, int maxValue) {
if (state != NEW) {
throw new IllegalStateException("Already configured");
}
checkPrefix(N);
if (maxValue < 0) {
throw new IllegalArgumentException(
"maxValue >= 0: maxValue=" + maxValue);
}
this.maxValue = maxValue;
this.N = N;
state = CONFIGURED;
return this;
}
public boolean read(Buffer input) {
if (state == NEW) {
throw new IllegalStateException("Configure first");
}
if (state == DONE) {
return true;
}
if (!input.hasRemaining()) {
return false;
}
if (state == CONFIGURED) {
int max = (2 << (N - 1)) - 1;
int n = input.get() & max;
if (n != max) {
value = n;
state = DONE;
return true;
} else {
r = max;
}
state = FIRST_BYTE_READ;
}
if (state == FIRST_BYTE_READ) {
// variable-length quantity (VLQ)
byte i;
do {
if (!input.hasRemaining()) {
return false;
}
i = input.get();
long increment = b * (i & 127);
if (r + increment > maxValue) {
throw new IllegalArgumentException(format(
"Integer overflow: maxValue=%,d, value=%,d",
maxValue, r + increment));
}
r += increment;
b *= 128;
} while ((128 & i) == 128);
value = (int) r;
state = DONE;
return true;
}
throw new InternalError(Arrays.toString(
new Object[]{state, N, maxValue, value, r, b}));
}
public int get() throws IllegalStateException {
if (state != DONE) {
throw new IllegalStateException("Has not been fully read yet");
}
return value;
}
private static void checkPrefix(int N) {
if (N < 1 || N > 8) {
throw new IllegalArgumentException("1 <= N <= 8: N= " + N);
}
}
public IntegerReader reset() {
b = 1;
state = NEW;
return this;
}
}
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