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HADOOP-7333. Performance improvement in PureJavaCrc32. Contributed by Eric Caspole. 

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1128425 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Todd Lipcon 2011-05-27 18:58:14 +00:00
parent dec6fcdb00
commit 6891b254f4
2 changed files with 14 additions and 7 deletions
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3
CHANGES.txt
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@ -186,6 +186,9 @@ Trunk (unreleased changes)
(Harsh J Chouraria via todd)
OPTIMIZATIONS
HADOOP-7333. Performance improvement in PureJavaCrc32. (Eric Caspole
via todd)
BUG FIXES

18
src/java/org/apache/hadoop/util/PureJavaCrc32.java
View File

@ -57,23 +57,27 @@ public class PureJavaCrc32 implements Checksum {
/** {@inheritDoc} */
public void update(byte[] b, int off, int len) {
int localCrc = crc;
while(len > 7) {
int c0 = b[off++] ^ crc;
int c1 = b[off++] ^ (crc >>>= 8);
int c2 = b[off++] ^ (crc >>>= 8);
int c3 = b[off++] ^ (crc >>>= 8);
crc = (T8_7[c0 & 0xff] ^ T8_6[c1 & 0xff])
int c0 = b[off++] ^ localCrc;
int c1 = b[off++] ^ (localCrc >>>= 8);
int c2 = b[off++] ^ (localCrc >>>= 8);
int c3 = b[off++] ^ (localCrc >>>= 8);
localCrc = (T8_7[c0 & 0xff] ^ T8_6[c1 & 0xff])
^ (T8_5[c2 & 0xff] ^ T8_4[c3 & 0xff]);
crc ^= (T8_3[b[off++] & 0xff] ^ T8_2[b[off++] & 0xff])
localCrc ^= (T8_3[b[off++] & 0xff] ^ T8_2[b[off++] & 0xff])
^ (T8_1[b[off++] & 0xff] ^ T8_0[b[off++] & 0xff]);
len -= 8;
}
while(len > 0) {
crc = (crc >>> 8) ^ T8_0[(crc ^ b[off++]) & 0xff];
localCrc = (localCrc >>> 8) ^ T8_0[(localCrc ^ b[off++]) & 0xff];
len--;
}
// Publish crc out to object
crc = localCrc;
}
/** {@inheritDoc} */