mapleFU commented on code in PR #40915:
URL: https://github.com/apache/arrow/pull/40915#discussion_r1545721595
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cpp/src/arrow/util/bit_util.h:
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@@ -366,5 +367,18 @@ void PackBits(const uint32_t* values, uint8_t* out) {
}
}
+/// Determine if a word has a zero byte
+/// The subexpression (v - 0x01010101UL), evaluates to a high bit set in any
byte whenever
+/// the corresponding byte in v is zero or greater than 0x80. The
sub-expression ~v &
+/// 0x80808080UL evaluates to high bits set in bytes where the byte of v
doesn't have its
+/// high bit set (so the byte was less than 0x80). Finally, by ANDing these two
+/// sub-expressions the result is the high bits set where the bytes in v were
zero, since
+/// the high bits set due to a value greater than 0x80 in the first
sub-expression are
+/// masked off by the second.
+uint64_t HasZeroByte(uint64_t value) {
Review Comment:
Since it's a "has" return `bool`?
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