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Reject non-ASCII digit look-alikes in AsciiEncoding SWAR fast paths #367

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Reject non-ASCII digit look-alikes in AsciiEncoding SWAR fast paths #367

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40 changes: 28 additions & 12 deletions agrona/src/main/java/org/agrona/AsciiEncoding.java
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Original file line number Diff line number Diff line change
Expand Up @@ -595,21 +595,37 @@ private static void throwParseLongOverflowError(final CharSequence cs, final int

private static int readFourBytesLittleEndian(final CharSequence cs, final int index)
{
return cs.charAt(index + 3) << 24 |
cs.charAt(index + 2) << 16 |
cs.charAt(index + 1) << 8 |
cs.charAt(index);
final int c0 = cs.charAt(index);
final int c1 = cs.charAt(index + 1);
final int c2 = cs.charAt(index + 2);
final int c3 = cs.charAt(index + 3);
// A char above 0xFF is not ASCII; its high byte would otherwise be shifted
// out of the packed word (leaving a digit look-alike), so force the digit
// check to fail here instead.
final int nonAscii = ((c0 | c1 | c2 | c3) & 0xFF00) != 0 ? 0xFFFFFFFF : 0;
return nonAscii | c3 << 24 | c2 << 16 | c1 << 8 | c0;
}

private static long readEightBytesLittleEndian(final CharSequence cs, final int index)
{
return (long)cs.charAt(index + 7) << 56 |
(long)cs.charAt(index + 6) << 48 |
(long)cs.charAt(index + 5) << 40 |
(long)cs.charAt(index + 4) << 32 |
(long)cs.charAt(index + 3) << 24 |
(long)cs.charAt(index + 2) << 16 |
cs.charAt(index + 1) << 8 |
cs.charAt(index);
final int c0 = cs.charAt(index);
final int c1 = cs.charAt(index + 1);
final int c2 = cs.charAt(index + 2);
final int c3 = cs.charAt(index + 3);
final int c4 = cs.charAt(index + 4);
final int c5 = cs.charAt(index + 5);
final int c6 = cs.charAt(index + 6);
final int c7 = cs.charAt(index + 7);
// See readFourBytesLittleEndian: reject a non-ASCII char whose high byte
// would be shifted out of the packed word.
final long nonAscii = ((c0 | c1 | c2 | c3 | c4 | c5 | c6 | c7) & 0xFF00) != 0 ? -1L : 0L;
return nonAscii | (long)c7 << 56 |
(long)c6 << 48 |
(long)c5 << 40 |
(long)c4 << 32 |
(long)c3 << 24 |
(long)c2 << 16 |
c1 << 8 |
c0;
}
}
5 changes: 5 additions & 0 deletions agrona/src/test/java/org/agrona/AsciiEncodingTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -116,6 +116,11 @@ void shouldRejectNonAsciiCharsWhoseLowByteLooksLikeADigit()
assertThrows(AsciiNumberFormatException.class, () -> parseIntAscii("123456789İ", 0, 10));
assertThrows(
AsciiNumberFormatException.class, () -> parseLongAscii("123456789012345678İ", 0, 19));

// A look-alike in the top lane of a 4-/8-char SWAR window: its high byte
// shifts out of the word, leaving only the digit-looking low byte.
assertThrows(AsciiNumberFormatException.class, () -> parseIntAscii("123İ", 0, 4));
assertThrows(AsciiNumberFormatException.class, () -> parseLongAscii("1234567İ", 0, 8));
}

@Test
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