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committedSep 13, 2023
8315789: Minor HexFormat performance improvements
Reviewed-by: rriggs
1 parent ce93d27 commit 92ad4a2

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2 files changed

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‎src/java.base/share/classes/java/util/HexFormat.java

+45-28
Original file line numberDiff line numberDiff line change
@@ -140,14 +140,6 @@ public final class HexFormat {
140140
// Access to create strings from a byte array.
141141
private static final JavaLangAccess jla = SharedSecrets.getJavaLangAccess();
142142

143-
private static final byte[] UPPERCASE_DIGITS = {
144-
'0', '1', '2', '3', '4', '5', '6', '7',
145-
'8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
146-
};
147-
private static final byte[] LOWERCASE_DIGITS = {
148-
'0', '1', '2', '3', '4', '5', '6', '7',
149-
'8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
150-
};
151143
// Analysis has shown that generating the whole array allows the JIT to generate
152144
// better code compared to a slimmed down array, such as one cutting off after 'f'
153145
private static final byte[] DIGITS = {
@@ -173,29 +165,37 @@ public final class HexFormat {
173165
* The hexadecimal characters are from lowercase alpha digits.
174166
*/
175167
private static final HexFormat HEX_FORMAT =
176-
new HexFormat("", "", "", LOWERCASE_DIGITS);
168+
new HexFormat("", "", "", Case.LOWERCASE);
169+
170+
private static final HexFormat HEX_UPPER_FORMAT =
171+
new HexFormat("", "", "", Case.UPPERCASE);
177172

178173
private static final byte[] EMPTY_BYTES = {};
179174

180175
private final String delimiter;
181176
private final String prefix;
182177
private final String suffix;
183-
private final byte[] digits;
178+
private final Case digitCase;
179+
180+
private enum Case {
181+
LOWERCASE,
182+
UPPERCASE
183+
}
184184

185185
/**
186186
* Returns a HexFormat with a delimiter, prefix, suffix, and array of digits.
187187
*
188188
* @param delimiter a delimiter, non-null
189189
* @param prefix a prefix, non-null
190190
* @param suffix a suffix, non-null
191-
* @param digits byte array of digits indexed by low nibble, non-null
191+
* @param digitCase enum indicating how to case digits
192192
* @throws NullPointerException if any argument is null
193193
*/
194-
private HexFormat(String delimiter, String prefix, String suffix, byte[] digits) {
194+
private HexFormat(String delimiter, String prefix, String suffix, Case digitCase) {
195195
this.delimiter = Objects.requireNonNull(delimiter, "delimiter");
196196
this.prefix = Objects.requireNonNull(prefix, "prefix");
197197
this.suffix = Objects.requireNonNull(suffix, "suffix");
198-
this.digits = digits;
198+
this.digitCase = digitCase;
199199
}
200200

201201
/**
@@ -224,7 +224,7 @@ public static HexFormat of() {
224224
* @return a {@link HexFormat} with the delimiter and lowercase characters
225225
*/
226226
public static HexFormat ofDelimiter(String delimiter) {
227-
return new HexFormat(delimiter, "", "", LOWERCASE_DIGITS);
227+
return new HexFormat(delimiter, "", "", Case.LOWERCASE);
228228
}
229229

230230
/**
@@ -233,7 +233,7 @@ public static HexFormat ofDelimiter(String delimiter) {
233233
* @return a copy of this {@code HexFormat} with the delimiter
234234
*/
235235
public HexFormat withDelimiter(String delimiter) {
236-
return new HexFormat(delimiter, this.prefix, this.suffix, this.digits);
236+
return new HexFormat(delimiter, this.prefix, this.suffix, this.digitCase);
237237
}
238238

239239
/**
@@ -243,7 +243,7 @@ public HexFormat withDelimiter(String delimiter) {
243243
* @return a copy of this {@code HexFormat} with the prefix
244244
*/
245245
public HexFormat withPrefix(String prefix) {
246-
return new HexFormat(this.delimiter, prefix, this.suffix, this.digits);
246+
return new HexFormat(this.delimiter, prefix, this.suffix, this.digitCase);
247247
}
248248

249249
/**
@@ -253,7 +253,7 @@ public HexFormat withPrefix(String prefix) {
253253
* @return a copy of this {@code HexFormat} with the suffix
254254
*/
255255
public HexFormat withSuffix(String suffix) {
256-
return new HexFormat(this.delimiter, this.prefix, suffix, this.digits);
256+
return new HexFormat(this.delimiter, this.prefix, suffix, this.digitCase);
257257
}
258258

259259
/**
@@ -263,7 +263,9 @@ public HexFormat withSuffix(String suffix) {
263263
* @return a copy of this {@code HexFormat} with uppercase hexadecimal characters
264264
*/
265265
public HexFormat withUpperCase() {
266-
return new HexFormat(this.delimiter, this.prefix, this.suffix, UPPERCASE_DIGITS);
266+
if (this == HEX_FORMAT)
267+
return HEX_UPPER_FORMAT;
268+
return new HexFormat(this.delimiter, this.prefix, this.suffix, Case.UPPERCASE);
267269
}
268270

269271
/**
@@ -273,7 +275,7 @@ public HexFormat withUpperCase() {
273275
* @return a copy of this {@code HexFormat} with lowercase hexadecimal characters
274276
*/
275277
public HexFormat withLowerCase() {
276-
return new HexFormat(this.delimiter, this.prefix, this.suffix, LOWERCASE_DIGITS);
278+
return new HexFormat(this.delimiter, this.prefix, this.suffix, Case.LOWERCASE);
277279
}
278280

279281
/**
@@ -311,7 +313,7 @@ public String suffix() {
311313
* otherwise {@code false}
312314
*/
313315
public boolean isUpperCase() {
314-
return Arrays.equals(digits, UPPERCASE_DIGITS);
316+
return digitCase == Case.UPPERCASE;
315317
}
316318

317319
/**
@@ -401,16 +403,17 @@ public <A extends Appendable> A formatHex(A out, byte[] bytes, int fromIndex, in
401403
int length = toIndex - fromIndex;
402404
if (length > 0) {
403405
try {
404-
String between = suffix + delimiter + prefix;
405406
out.append(prefix);
406407
toHexDigits(out, bytes[fromIndex]);
407-
if (between.isEmpty()) {
408+
if (suffix.isEmpty() && delimiter.isEmpty() && prefix.isEmpty()) {
408409
for (int i = 1; i < length; i++) {
409410
toHexDigits(out, bytes[fromIndex + i]);
410411
}
411412
} else {
412413
for (int i = 1; i < length; i++) {
413-
out.append(between);
414+
out.append(suffix);
415+
out.append(delimiter);
416+
out.append(prefix);
414417
toHexDigits(out, bytes[fromIndex + i]);
415418
}
416419
}
@@ -631,7 +634,14 @@ private static String escapeNL(String string) {
631634
* @return the hexadecimal character for the low 4 bits {@code 0-3} of the value
632635
*/
633636
public char toLowHexDigit(int value) {
634-
return (char)digits[value & 0xf];
637+
value = value & 0xf;
638+
if (value < 10) {
639+
return (char)('0' + value);
640+
}
641+
if (digitCase == Case.LOWERCASE) {
642+
return (char)('a' - 10 + value);
643+
}
644+
return (char)('A' - 10 + value);
635645
}
636646

637647
/**
@@ -645,7 +655,14 @@ public char toLowHexDigit(int value) {
645655
* @return the hexadecimal character for the bits {@code 4-7} of the value
646656
*/
647657
public char toHighHexDigit(int value) {
648-
return (char)digits[(value >> 4) & 0xf];
658+
value = (value >> 4) & 0xf;
659+
if (value < 10) {
660+
return (char)('0' + value);
661+
}
662+
if (digitCase == Case.LOWERCASE) {
663+
return (char)('a' - 10 + value);
664+
}
665+
return (char)('A' - 10 + value);
649666
}
650667

651668
/**
@@ -1052,7 +1069,7 @@ public boolean equals(Object o) {
10521069
if (o == null || getClass() != o.getClass())
10531070
return false;
10541071
HexFormat otherHex = (HexFormat) o;
1055-
return Arrays.equals(digits, otherHex.digits) &&
1072+
return digitCase == otherHex.digitCase &&
10561073
delimiter.equals(otherHex.delimiter) &&
10571074
prefix.equals(otherHex.prefix) &&
10581075
suffix.equals(otherHex.suffix);
@@ -1066,7 +1083,7 @@ public boolean equals(Object o) {
10661083
@Override
10671084
public int hashCode() {
10681085
int result = Objects.hash(delimiter, prefix, suffix);
1069-
result = 31 * result + Boolean.hashCode(Arrays.equals(digits, UPPERCASE_DIGITS));
1086+
result = 31 * result + Boolean.hashCode(digitCase == Case.UPPERCASE);
10701087
return result;
10711088
}
10721089

@@ -1078,7 +1095,7 @@ public int hashCode() {
10781095
*/
10791096
@Override
10801097
public String toString() {
1081-
return escapeNL("uppercase: " + Arrays.equals(digits, UPPERCASE_DIGITS) +
1098+
return escapeNL("uppercase: " + (digitCase == Case.UPPERCASE) +
10821099
", delimiter: \"" + delimiter +
10831100
"\", prefix: \"" + prefix +
10841101
"\", suffix: \"" + suffix + "\"");

‎test/micro/org/openjdk/bench/java/util/HexFormatBench.java

+156
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,156 @@
1+
/*
2+
* Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
3+
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4+
*
5+
* This code is free software; you can redistribute it and/or modify it
6+
* under the terms of the GNU General Public License version 2 only, as
7+
* published by the Free Software Foundation.
8+
*
9+
* This code is distributed in the hope that it will be useful, but WITHOUT
10+
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11+
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12+
* version 2 for more details (a copy is included in the LICENSE file that
13+
* accompanied this code).
14+
*
15+
* You should have received a copy of the GNU General Public License version
16+
* 2 along with this work; if not, write to the Free Software Foundation,
17+
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18+
*
19+
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20+
* or visit www.oracle.com if you need additional information or have any
21+
* questions.
22+
*/
23+
package org.openjdk.bench.java.util;
24+
25+
import org.openjdk.jmh.annotations.Benchmark;
26+
import org.openjdk.jmh.annotations.BenchmarkMode;
27+
import org.openjdk.jmh.annotations.Fork;
28+
import org.openjdk.jmh.annotations.Measurement;
29+
import org.openjdk.jmh.annotations.Mode;
30+
import org.openjdk.jmh.annotations.OutputTimeUnit;
31+
import org.openjdk.jmh.annotations.Param;
32+
import org.openjdk.jmh.annotations.Scope;
33+
import org.openjdk.jmh.annotations.Setup;
34+
import org.openjdk.jmh.annotations.State;
35+
import org.openjdk.jmh.annotations.Warmup;
36+
import org.openjdk.jmh.infra.Blackhole;
37+
38+
import java.util.HexFormat;
39+
import java.util.Random;
40+
import java.util.concurrent.TimeUnit;
41+
42+
/**
43+
* Tests java.net.URLEncoder.encode and Decoder.decode.
44+
*/
45+
@BenchmarkMode(Mode.AverageTime)
46+
@OutputTimeUnit(TimeUnit.MICROSECONDS)
47+
@State(Scope.Thread)
48+
@Warmup(iterations = 5, time = 1)
49+
@Measurement(iterations = 5, time = 1)
50+
@Fork(value = 3)
51+
public class HexFormatBench {
52+
53+
@Param({"512"})
54+
public int size;
55+
56+
public byte[] bytes;
57+
58+
public StringBuilder builder = new StringBuilder(size * 2);
59+
60+
HexFormat LOWER_FORMATTER = HexFormat.of();
61+
HexFormat UPPER_FORMATTER = HexFormat.of().withUpperCase();
62+
63+
@Setup
64+
public void setupStrings() {
65+
Random random = new Random(3);
66+
bytes = new byte[size];
67+
for (int i = 0; i < size; i++) {
68+
bytes[i] = (byte)random.nextInt(16);
69+
}
70+
}
71+
72+
@Benchmark
73+
public StringBuilder appenderLower() {
74+
builder.setLength(0);
75+
return HexFormat.of().formatHex(builder, bytes);
76+
}
77+
78+
@Benchmark
79+
public StringBuilder appenderUpper() {
80+
builder.setLength(0);
81+
return HexFormat.of().withUpperCase().formatHex(builder, bytes);
82+
}
83+
84+
@Benchmark
85+
public StringBuilder appenderLowerCached() {
86+
builder.setLength(0);
87+
return LOWER_FORMATTER.formatHex(builder, bytes);
88+
}
89+
90+
@Benchmark
91+
public StringBuilder appenderUpperCached() {
92+
builder.setLength(0);
93+
return UPPER_FORMATTER.formatHex(builder, bytes);
94+
}
95+
96+
97+
@Benchmark
98+
public void toHexLower(Blackhole bh) {
99+
for (byte b : bytes) {
100+
bh.consume(HexFormat.of().toHighHexDigit(b));
101+
bh.consume(HexFormat.of().toLowHexDigit(b));
102+
}
103+
}
104+
105+
@Benchmark
106+
public void toHexUpper(Blackhole bh) {
107+
for (byte b : bytes) {
108+
bh.consume(HexFormat.of().withUpperCase().toHighHexDigit(b));
109+
bh.consume(HexFormat.of().withUpperCase().toLowHexDigit(b));
110+
}
111+
}
112+
113+
@Benchmark
114+
public void toHexLowerCached(Blackhole bh) {
115+
for (byte b : bytes) {
116+
bh.consume(LOWER_FORMATTER.toHighHexDigit(b));
117+
bh.consume(LOWER_FORMATTER.toLowHexDigit(b));
118+
}
119+
}
120+
121+
@Benchmark
122+
public void toHexUpperCached(Blackhole bh) {
123+
for (byte b : bytes) {
124+
bh.consume(UPPER_FORMATTER.toHighHexDigit(b));
125+
bh.consume(UPPER_FORMATTER.toLowHexDigit(b));
126+
}
127+
}
128+
129+
@Benchmark
130+
public void toHexDigitsByte(Blackhole bh) {
131+
for (byte b : bytes) {
132+
bh.consume(LOWER_FORMATTER.toHexDigits(b));
133+
}
134+
}
135+
136+
@Benchmark
137+
public void toHexDigitsShort(Blackhole bh) {
138+
for (short b : bytes) {
139+
bh.consume(LOWER_FORMATTER.toHexDigits(b));
140+
}
141+
}
142+
143+
@Benchmark
144+
public void toHexDigitsInt(Blackhole bh) {
145+
for (int b : bytes) {
146+
bh.consume(LOWER_FORMATTER.toHexDigits(b));
147+
}
148+
}
149+
150+
@Benchmark
151+
public void toHexDigitsLong(Blackhole bh) {
152+
for (long b : bytes) {
153+
bh.consume(LOWER_FORMATTER.toHexDigits(b));
154+
}
155+
}
156+
}

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