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[SPARK-9483] Fix UTF8String.getPrefix for big-endian. #7902

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mtbrandy wants to merge 2 commits into from
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[SPARK-9483] Fix UTF8String.getPrefix for big-endian. #7902

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[SPARK-9483] Fix UTF8String.getPrefix for big-endian.
mtbrandy Jul 31, 2015
ec31df8
[SPARK-9483] Changes from review comments.
mtbrandy Aug 3, 2015
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14 changes: 11 additions & 3 deletions unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
import javax.annotation.Nonnull;
import java.io.Serializable;
import java.io.UnsupportedEncodingException;
import java.nio.ByteOrder;
import java.util.Arrays;

import org.apache.spark.unsafe.PlatformDependent;
Expand Down Expand Up @@ -161,18 +162,25 @@ public long getPrefix() {
// If size is greater than 4, assume we have at least 8 bytes of data to fetch.
// After getting the data, we use a mask to mask out data that is not part of the string.
long p;
long mask = 0;
if (numBytes >= 8) {
p = PlatformDependent.UNSAFE.getLong(base, offset);

@rxin rxin Aug 3, 2015

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don't we need something for this branch also?

@rxin rxin Aug 3, 2015

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ah nvm u don't need it since the reversebytes was done later.

I think it's not that big of a deal to duplicate code here, and the nested ifs really make it harder to read.

@mtbrandy mtbrandy Aug 3, 2015

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The mask represents the characters that need to be cleared. p needs no modification (and thus mask of zero is correct) when numBytes is equal to zero or greater than 8.

} else if (numBytes > 4) {
mask = (1L << (8 - numBytes) * 8) - 1;
p = PlatformDependent.UNSAFE.getLong(base, offset);
p = p & ((1L << numBytes * 8) - 1);
} else if (numBytes > 0) {
mask = (1L << (8 - numBytes) * 8) - 1;
p = (long) PlatformDependent.UNSAFE.getInt(base, offset);
p = p & ((1L << numBytes * 8) - 1);
if (ByteOrder.nativeOrder() == ByteOrder.BIG_ENDIAN) {

@rxin rxin Aug 3, 2015

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can we move the result of ByteOrder.nativeOrder into a static variable?

@mtbrandy mtbrandy Aug 3, 2015

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Will do

p <<= 32;
}
} else {
p = 0;
}
p = java.lang.Long.reverseBytes(p);
if (ByteOrder.nativeOrder() == ByteOrder.LITTLE_ENDIAN) {
p = java.lang.Long.reverseBytes(p);
}
p &= ~mask;
return p;
}

Expand Down