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1 // Protocol Buffers - Google's data interchange format | 1 // Protocol Buffers - Google's data interchange format |
2 // Copyright 2008 Google Inc. All rights reserved. | 2 // Copyright 2008 Google Inc. All rights reserved. |
3 // https://developers.google.com/protocol-buffers/ | 3 // https://developers.google.com/protocol-buffers/ |
4 // | 4 // |
5 // Redistribution and use in source and binary forms, with or without | 5 // Redistribution and use in source and binary forms, with or without |
6 // modification, are permitted provided that the following conditions are | 6 // modification, are permitted provided that the following conditions are |
7 // met: | 7 // met: |
8 // | 8 // |
9 // * Redistributions of source code must retain the above copyright | 9 // * Redistributions of source code must retain the above copyright |
10 // notice, this list of conditions and the following disclaimer. | 10 // notice, this list of conditions and the following disclaimer. |
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26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | 26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | 27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | 28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | 29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
30 | 30 |
31 package com.google.protobuf; | 31 package com.google.protobuf; |
32 | 32 |
33 import static java.lang.Math.max; | 33 import static java.lang.Math.max; |
34 import static java.lang.Math.min; | 34 import static java.lang.Math.min; |
35 | 35 |
| 36 import java.io.FileOutputStream; |
36 import java.io.IOException; | 37 import java.io.IOException; |
37 import java.io.OutputStream; | 38 import java.io.OutputStream; |
38 import java.lang.ref.SoftReference; | 39 import java.lang.ref.SoftReference; |
39 import java.lang.reflect.Field; | |
40 import java.nio.ByteBuffer; | 40 import java.nio.ByteBuffer; |
41 import java.nio.channels.WritableByteChannel; | |
42 | 41 |
43 /** | 42 /** |
44 * Utility class to provide efficient writing of {@link ByteBuffer}s to {@link O
utputStream}s. | 43 * Utility class to provide efficient writing of {@link ByteBuffer}s to {@link O
utputStream}s. |
45 */ | 44 */ |
46 final class ByteBufferWriter { | 45 final class ByteBufferWriter { |
47 private ByteBufferWriter() {} | 46 private ByteBufferWriter() {} |
48 | 47 |
49 /** | 48 /** |
50 * Minimum size for a cached buffer. This prevents us from allocating buffers
that are too | 49 * Minimum size for a cached buffer. This prevents us from allocating buffers
that are too |
51 * small to be easily reused. | 50 * small to be easily reused. |
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69 /** | 68 /** |
70 * Keeping a soft reference to a thread-local buffer. This buffer is used for
writing a | 69 * Keeping a soft reference to a thread-local buffer. This buffer is used for
writing a |
71 * {@link ByteBuffer} to an {@link OutputStream} when no zero-copy alternative
was available. | 70 * {@link ByteBuffer} to an {@link OutputStream} when no zero-copy alternative
was available. |
72 * Using a "soft" reference since VMs may keep this reference around longer th
an "weak" | 71 * Using a "soft" reference since VMs may keep this reference around longer th
an "weak" |
73 * (e.g. HotSpot will maintain soft references until memory pressure warrants
collection). | 72 * (e.g. HotSpot will maintain soft references until memory pressure warrants
collection). |
74 */ | 73 */ |
75 private static final ThreadLocal<SoftReference<byte[]>> BUFFER = | 74 private static final ThreadLocal<SoftReference<byte[]>> BUFFER = |
76 new ThreadLocal<SoftReference<byte[]>>(); | 75 new ThreadLocal<SoftReference<byte[]>>(); |
77 | 76 |
78 /** | 77 /** |
79 * This is a hack for GAE, where {@code FileOutputStream} is unavailable. | |
80 */ | |
81 private static final Class<?> FILE_OUTPUT_STREAM_CLASS = safeGetClass("java.io
.FileOutputStream"); | |
82 private static final long CHANNEL_FIELD_OFFSET = getChannelFieldOffset(FILE_OU
TPUT_STREAM_CLASS); | |
83 | |
84 /** | |
85 * For testing purposes only. Clears the cached buffer to force a new allocati
on on the next | 78 * For testing purposes only. Clears the cached buffer to force a new allocati
on on the next |
86 * invocation. | 79 * invocation. |
87 */ | 80 */ |
88 static void clearCachedBuffer() { | 81 static void clearCachedBuffer() { |
89 BUFFER.set(null); | 82 BUFFER.set(null); |
90 } | 83 } |
91 | 84 |
92 /** | 85 /** |
93 * Writes the remaining content of the buffer to the given stream. The buffer
{@code position} | 86 * Writes the remaining content of the buffer to the given stream. The buffer
{@code position} |
94 * will remain unchanged by this method. | 87 * will remain unchanged by this method. |
95 */ | 88 */ |
96 static void write(ByteBuffer buffer, OutputStream output) throws IOException { | 89 static void write(ByteBuffer buffer, OutputStream output) throws IOException { |
97 final int initialPos = buffer.position(); | 90 final int initialPos = buffer.position(); |
98 try { | 91 try { |
99 if (buffer.hasArray()) { | 92 if (buffer.hasArray()) { |
100 // Optimized write for array-backed buffers. | 93 // Optimized write for array-backed buffers. |
101 // Note that we're taking the risk that a malicious OutputStream could m
odify the array. | 94 // Note that we're taking the risk that a malicious OutputStream could m
odify the array. |
102 output.write(buffer.array(), buffer.arrayOffset() + buffer.position(), b
uffer.remaining()); | 95 output.write(buffer.array(), buffer.arrayOffset() + buffer.position(), b
uffer.remaining()); |
103 } else if (!writeToChannel(buffer, output)){ | 96 } else if (output instanceof FileOutputStream) { |
| 97 // Use a channel to write out the ByteBuffer. This will automatically em
pty the buffer. |
| 98 ((FileOutputStream) output).getChannel().write(buffer); |
| 99 } else { |
104 // Read all of the data from the buffer to an array. | 100 // Read all of the data from the buffer to an array. |
105 // TODO(nathanmittler): Consider performance improvements for other "kno
wn" stream types. | 101 // TODO(nathanmittler): Consider performance improvements for other "kno
wn" stream types. |
106 final byte[] array = getOrCreateBuffer(buffer.remaining()); | 102 final byte[] array = getOrCreateBuffer(buffer.remaining()); |
107 while (buffer.hasRemaining()) { | 103 while (buffer.hasRemaining()) { |
108 int length = min(buffer.remaining(), array.length); | 104 int length = min(buffer.remaining(), array.length); |
109 buffer.get(array, 0, length); | 105 buffer.get(array, 0, length); |
110 output.write(array, 0, length); | 106 output.write(array, 0, length); |
111 } | 107 } |
112 } | 108 } |
113 } finally { | 109 } finally { |
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139 } | 135 } |
140 | 136 |
141 private static byte[] getBuffer() { | 137 private static byte[] getBuffer() { |
142 SoftReference<byte[]> sr = BUFFER.get(); | 138 SoftReference<byte[]> sr = BUFFER.get(); |
143 return sr == null ? null : sr.get(); | 139 return sr == null ? null : sr.get(); |
144 } | 140 } |
145 | 141 |
146 private static void setBuffer(byte[] value) { | 142 private static void setBuffer(byte[] value) { |
147 BUFFER.set(new SoftReference<byte[]>(value)); | 143 BUFFER.set(new SoftReference<byte[]>(value)); |
148 } | 144 } |
149 | |
150 private static boolean writeToChannel(ByteBuffer buffer, OutputStream output)
throws IOException { | |
151 if (CHANNEL_FIELD_OFFSET >= 0 && FILE_OUTPUT_STREAM_CLASS.isInstance(output)
) { | |
152 // Use a channel to write out the ByteBuffer. This will automatically empt
y the buffer. | |
153 WritableByteChannel channel = null; | |
154 try { | |
155 channel = (WritableByteChannel) UnsafeUtil.getObject(output, CHANNEL_FIE
LD_OFFSET); | |
156 } catch (ClassCastException e) { | |
157 // Absorb. | |
158 } | |
159 if (channel != null) { | |
160 channel.write(buffer); | |
161 return true; | |
162 } | |
163 } | |
164 return false; | |
165 } | |
166 | |
167 private static Class<?> safeGetClass(String className) { | |
168 try { | |
169 return Class.forName(className); | |
170 } catch (ClassNotFoundException e) { | |
171 return null; | |
172 } | |
173 } | |
174 private static long getChannelFieldOffset(Class<?> clazz) { | |
175 try { | |
176 if (clazz != null && UnsafeUtil.hasUnsafeArrayOperations()) { | |
177 Field field = clazz.getDeclaredField("channel"); | |
178 return UnsafeUtil.objectFieldOffset(field); | |
179 } | |
180 } catch (Throwable e) { | |
181 // Absorb | |
182 } | |
183 return -1; | |
184 } | |
185 } | 145 } |
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