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Do UTF-8 encoding natively.

For strings consisting exclusively of ASCII characters, this is slightly
faster on the desktop JVM:

    length     benchmark  ns linear runtime
        64 NativeEncoder 103 ===
        64      GetBytes 113 ===
      1024 NativeEncoder 894 ============================
      1024      GetBytes 933 ==============================
    vm: java

It's substantially faster on dalvikvm:

    length     benchmark    us linear runtime
        64      GetBytes  6.46 ===========
        64 NativeEncoder  1.47 ==
      1024      GetBytes 16.20 ==============================
      1024 NativeEncoder 13.58 =========================
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swankjesse committed Nov 30, 2014
1 parent 35bbfb7 commit b2d19a9faee2e006339cf5a3e0a31378711e7f5f
Showing with 166 additions and 2 deletions.
  1. +65 −2 okio/src/main/java/okio/Buffer.java
  2. +101 −0 okio/src/test/java/okio/Utf8Test.java
@@ -557,13 +557,76 @@ public void clear() {
@Override public Buffer writeUtf8(String string) {
if (string == null) throw new IllegalArgumentException("string == null");
// TODO: inline UTF-8 encoding to save allocating a byte[]?
return writeString(string, Util.UTF_8);
// Transcode a UTF-16 Java String to UTF-8 bytes.
for (int i = 0, length = string.length(); i < length;) {
int c = string.charAt(i);
if (c < 0x80) {
Segment tail = writableSegment(1);
byte[] data = tail.data;
int segmentOffset = tail.limit - i;
int runLimit = Math.min(length, Segment.SIZE - segmentOffset);
// Emit a 7-bit character with 1 byte.
data[segmentOffset + i++] = (byte) c; // 0xxxxxxx
// Fast-path contiguous runs of ASCII characters. This is ugly, but yields a ~4x performance
// improvement over independent calls to writeByte().
while (i < runLimit) {
c = string.charAt(i);
if (c >= 0x80) break;
data[segmentOffset + i++] = (byte) c; // 0xxxxxxx
}
int runSize = i + segmentOffset - tail.limit; // Equivalent to i - (previous i).
tail.limit += runSize;
size += runSize;
} else if (c < 0x800) {
// Emit a 11-bit character with 2 bytes.
writeByte(c >> 6 | 0xc0); // 110xxxxx
writeByte(c & 0x3f | 0x80); // 10xxxxxx
i++;
} else if (c < 0xd800 || c > 0xdfff) {
// Emit a 16-bit character with 3 bytes.
writeByte(c >> 12 | 0xe0); // 1110xxxx
writeByte(c >> 6 & 0x3f | 0x80); // 10xxxxxx
writeByte(c & 0x3f | 0x80); // 10xxxxxx
i++;
} else {
// c is a surrogate. Make sure it is a high surrogate & that its successor is a low
// surrogate. If not, the UTF-16 is invalid, in which case we emit a replacement character.
int low = i + 1 < length ? string.charAt(i + 1) : 0;
if (c > 0xdbff || low < 0xdc00 || low > 0xdfff) {
writeByte('?');
i++;
continue;
}
// UTF-16 high surrogate: 110110xxxxxxxxxx (10 bits)
// UTF-16 low surrogate: 110111yyyyyyyyyy (10 bits)
// Unicode code point: 00010000000000000000 + xxxxxxxxxxyyyyyyyyyy (21 bits)
int codePoint = 0x010000 + ((c & ~0xd800) << 10 | low & ~0xdc00);
// Emit a 21-bit character with 4 bytes.
writeByte(codePoint >> 18 | 0xf0); // 11110xxx
writeByte(codePoint >> 12 & 0x3f | 0x80); // 10xxxxxx
writeByte(codePoint >> 6 & 0x3f | 0x80); // 10xxyyyy
writeByte(codePoint & 0x3f | 0x80); // 10yyyyyy
i += 2;
}
}
return this;
}
@Override public Buffer writeString(String string, Charset charset) {
if (string == null) throw new IllegalArgumentException("string == null");
if (charset == null) throw new IllegalArgumentException("charset == null");
if (charset.equals(Util.UTF_8)) return writeUtf8(string);
byte[] data = string.getBytes(charset);
return write(data, 0, data.length);
}
@@ -0,0 +1,101 @@
/*
* Copyright (C) 2014 Square, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package okio;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public final class Utf8Test {
@Test public void oneByteCharacters() throws Exception {
assertEncoded("00", 0x00); // Smallest 1-byte character.
assertEncoded("20", ' ');
assertEncoded("7e", '~');
assertEncoded("7f", 0x7f); // Largest 1-byte character.
}
@Test public void twoByteCharacters() throws Exception {
assertEncoded("c280", 0x0080); // Smallest 2-byte character.
assertEncoded("c3bf", 0x00ff);
assertEncoded("c480", 0x0100);
assertEncoded("dfbf", 0x07ff); // Largest 2-byte character.
}
@Test public void threeByteCharacters() throws Exception {
assertEncoded("e0a080", 0x0800); // Smallest 3-byte character.
assertEncoded("e0bfbf", 0x0fff);
assertEncoded("e18080", 0x1000);
assertEncoded("e1bfbf", 0x1fff);
assertEncoded("ed8080", 0xd000);
assertEncoded("ed9fbf", 0xd7ff); // Largest character lower than the min surrogate.
assertEncoded("ee8080", 0xe000); // Smallest character greater than the max surrogate.
assertEncoded("eebfbf", 0xefff);
assertEncoded("ef8080", 0xf000);
assertEncoded("efbfbf", 0xffff); // Largest 3-byte character.
}
@Test public void fourByteCharacters() throws Exception {
assertEncoded("f0908080", 0x010000); // Smallest surrogate pair.
assertEncoded("f48fbfbf", 0x10ffff); // Largest code point expressible by UTF-16.
}
@Test public void danglingHighSurrogate() throws Exception {
assertEncoded("3f", "\ud800"); // "?"
}
@Test public void lowSurrogateWithoutHighSurrogate() throws Exception {
assertEncoded("3f", "\udc00"); // "?"
}
@Test public void highSurrogateFollowedByNonSurrogate() throws Exception {
assertEncoded("3f61", "\ud800\u0061"); // "?a": Following character is too low.
assertEncoded("3fee8080", "\ud800\ue000"); // "?\ue000": Following character is too high.
}
@Test public void multipleSegmentString() throws Exception {
String a = TestUtil.repeat('a', Segment.SIZE + Segment.SIZE + 1);
Buffer encoded = new Buffer().writeUtf8(a);
Buffer expected = new Buffer().write(a.getBytes(Util.UTF_8));
assertEquals(expected, encoded);
}
@Test public void stringSpansSegments() throws Exception {
Buffer buffer = new Buffer();
String a = TestUtil.repeat('a', Segment.SIZE - 1);
String b = "bb";
String c = TestUtil.repeat('c', Segment.SIZE - 1);
buffer.writeUtf8(a);
buffer.writeUtf8(b);
buffer.writeUtf8(c);
assertEquals(a + b + c, buffer.readUtf8());
}
private void assertEncoded(String hex, int... codePoints) throws Exception {
assertEncoded(hex, new String(codePoints, 0, codePoints.length));
}
private void assertEncoded(String hex, String string) throws Exception {
ByteString expectedUtf8 = ByteString.decodeHex(hex);
// Confirm our expectations are consistent with the platform.
ByteString platformUtf8 = ByteString.of(string.getBytes("UTF-8"));
assertEquals(expectedUtf8, platformUtf8);
// Confirm our implementation matches those expectations.
ByteString actualUtf8 = new Buffer().writeUtf8(string).readByteString();
assertEquals(expectedUtf8, actualUtf8);
}
}

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