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HDFS-10656. Optimize conversion of byte arrays back to path string. Contributed by Daryn Sharp. 

(cherry picked from commit bebf10d245)
This commit is contained in:
Kihwal Lee 2016-08-03 11:54:51 -05:00
parent dd21d242eb
commit ab7072838f
1 changed files with 30 additions and 18 deletions
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48
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSUtil.java
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@ -85,7 +85,6 @@ import org.apache.hadoop.security.authorize.AccessControlList;
import org.apache.hadoop.util.ToolRunner;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Charsets;
import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
@ -268,27 +267,40 @@ public class DFSUtil {
/**
* Given a list of path components returns a path as a UTF8 String
*/
public static String byteArray2PathString(byte[][] pathComponents,
int offset, int length) {
if (pathComponents.length == 0) {
public static String byteArray2PathString(final byte[][] components,
final int offset, final int length) {
// specifically not using StringBuilder to more efficiently build
// string w/o excessive byte[] copies and charset conversions.
final int range = offset + length;
Preconditions.checkPositionIndexes(offset, range, components.length);
if (length == 0) {
return "";
}
Preconditions.checkArgument(offset >= 0 && offset < pathComponents.length);
Preconditions.checkArgument(length >= 0 && offset + length <=
pathComponents.length);
if (offset == 0 && length == 1
&& (pathComponents[0] == null || pathComponents[0].length == 0)) {
return Path.SEPARATOR;
// absolute paths start with either null or empty byte[]
byte[] firstComponent = components[offset];
boolean isAbsolute = (offset == 0 &&
(firstComponent == null || firstComponent.length == 0));
if (offset == 0 && length == 1) {
return isAbsolute ? Path.SEPARATOR : bytes2String(firstComponent);
}
StringBuilder result = new StringBuilder();
int lastIndex = offset + length - 1;
for (int i = offset; i <= lastIndex; i++) {
result.append(new String(pathComponents[i], Charsets.UTF_8));
if (i < lastIndex) {
result.append(Path.SEPARATOR_CHAR);
}
// compute length of full byte[], seed with 1st component and delimiters
int pos = isAbsolute ? 0 : firstComponent.length;
int size = pos + length - 1;
for (int i=offset + 1; i < range; i++) {
size += components[i].length;
}
return result.toString();
final byte[] result = new byte[size];
if (!isAbsolute) {
System.arraycopy(firstComponent, 0, result, 0, firstComponent.length);
}
// append remaining components as "/component".
for (int i=offset + 1; i < range; i++) {
result[pos++] = (byte)Path.SEPARATOR_CHAR;
int len = components[i].length;
System.arraycopy(components[i], 0, result, pos, len);
pos += len;
}
return bytes2String(result);
}
public static String byteArray2PathString(byte[][] pathComponents) {