Added and updated some strict overflow checks.

src/io/nayuki/fastqrcodegen/BitBuffer.java

@@ -92,7 +92,7 @@ final class BitBuffer {
 	public void appendBits(int val, int len) {
 		if (len < 0 || len > 31 || val >>> len != 0)
 			throw new IllegalArgumentException("Value out of range");
-		if (Integer.MAX_VALUE - bitLength < len)
+		if (len > Integer.MAX_VALUE - bitLength)
 			throw new IllegalStateException("Maximum length reached");
 		
 		if (bitLength + len + 1 > data.length << 5)
@@ -118,12 +118,14 @@ final class BitBuffer {
 		Objects.requireNonNull(vals);
 		if (len == 0)
 			return;
-		if (len < 0 || len > vals.length * 32)
+		if (len < 0 || len > vals.length * 32L)
 			throw new IllegalArgumentException("Value out of range");
 		int wholeWords = len / 32;
 		int tailBits = len % 32;
 		if (tailBits > 0 && vals[wholeWords] << tailBits != 0)
 			throw new IllegalArgumentException("Last word must have low bits clear");
+		if (len > Integer.MAX_VALUE - bitLength)
+			throw new IllegalStateException("Maximum length reached");
 		
 		while (bitLength + len > data.length * 32)
 			data = Arrays.copyOf(data, data.length * 2);

src/io/nayuki/fastqrcodegen/QrSegment.java

@@ -57,6 +57,8 @@ public final class QrSegment {
 	 */
 	public static QrSegment makeBytes(byte[] data) {
 		Objects.requireNonNull(data);
+		if (data.length * 8L > Integer.MAX_VALUE)
+			throw new IllegalArgumentException("Data too long");
 		int[] bits = new int[(data.length + 3) / 4];
 		for (int i = 0; i < data.length; i++)
 			bits[i >>> 2] |= (data[i] & 0xFF) << (~i << 3);
@@ -243,7 +245,7 @@ public final class QrSegment {
 	public QrSegment(Mode md, int numCh, int[] data, int bitLen) {
 		mode = Objects.requireNonNull(md);
 		this.data = Objects.requireNonNull(data);
-		if (numCh < 0 || bitLen < 0 || bitLen > data.length * 32)
+		if (numCh < 0 || bitLen < 0 || bitLen > data.length * 32L)
 			throw new IllegalArgumentException("Invalid value");
 		numChars = numCh;
 		bitLength = bitLen;