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* feat: add caller push of binary data Allows a caller to push binary data to an output stream rather than having to provide a byte array or input stream. This gives the caller more control over buffering strategy and allows explicit cleanup of off-heap buffers or other non-garbage-collected resources. * feat: Introduce ByteStreamTarget * Fix rename in PGStream * Change copyright dates of added files to 2020 Co-authored-by: Tom Dunstan <tomdcc@users.noreply.github.com>
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52 changes: 52 additions & 0 deletions
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pgjdbc/src/main/java/org/postgresql/core/FixedLengthOutputStream.java
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| /* | ||
| * Copyright (c) 2020, PostgreSQL Global Development Group | ||
| * See the LICENSE file in the project root for more information. | ||
| */ | ||
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| package org.postgresql.core; | ||
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| import java.io.IOException; | ||
| import java.io.OutputStream; | ||
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| /** | ||
| * A stream that refuses to write more than a maximum number of bytes. | ||
| */ | ||
| public class FixedLengthOutputStream extends OutputStream { | ||
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| private final int size; | ||
| private final OutputStream target; | ||
| private int written; | ||
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| public FixedLengthOutputStream(int size, OutputStream target) { | ||
| this.size = size; | ||
| this.target = target; | ||
| } | ||
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| @Override | ||
| public void write(int b) throws IOException { | ||
| verifyAllowed(1); | ||
| written++; | ||
| target.write(b); | ||
| } | ||
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| public void write(byte[] buf, int offset, int len) throws IOException { | ||
| if ((offset < 0) || (len < 0) || ((offset + len) > buf.length)) { | ||
| throw new IndexOutOfBoundsException(); | ||
| } else if (len == 0) { | ||
| return; | ||
| } | ||
| verifyAllowed(len); | ||
| target.write(buf, offset, len); | ||
| written += len; | ||
| } | ||
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| public int remaining() { | ||
| return size - written; | ||
| } | ||
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| private void verifyAllowed(int wanted) throws IOException { | ||
| if (remaining() < wanted) { | ||
| throw new IOException("Attempt to write more than the specified " + size + " bytes"); | ||
| } | ||
| } | ||
| } |
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48 changes: 48 additions & 0 deletions
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pgjdbc/src/main/java/org/postgresql/util/ByteBufferByteStreamWriter.java
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| @@ -0,0 +1,48 @@ | ||
| /* | ||
| * Copyright (c) 2020, PostgreSQL Global Development Group | ||
| * See the LICENSE file in the project root for more information. | ||
| */ | ||
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| package org.postgresql.util; | ||
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| import java.io.IOException; | ||
| import java.nio.ByteBuffer; | ||
| import java.nio.channels.Channels; | ||
| import java.nio.channels.WritableByteChannel; | ||
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| /** | ||
| * A {@link ByteStreamWriter} that writes a {@link ByteBuffer java.nio.ByteBuffer} to a byte array | ||
| * parameter. | ||
| */ | ||
| public class ByteBufferByteStreamWriter implements ByteStreamWriter { | ||
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| private final ByteBuffer buf; | ||
| private final int length; | ||
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| /** | ||
| * Construct the writer with the given {@link ByteBuffer} | ||
| * | ||
| * @param buf the buffer to use. | ||
| */ | ||
| public ByteBufferByteStreamWriter(ByteBuffer buf) { | ||
| this.buf = buf; | ||
| this.length = buf.remaining(); | ||
| } | ||
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| @Override | ||
| public int getLength() { | ||
| return length; | ||
| } | ||
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| @Override | ||
| public void writeTo(ByteStreamTarget target) throws IOException { | ||
| // this _does_ involve some copying to a temporary buffer, but that's unavoidable | ||
| // as OutputStream itself only accepts single bytes or heap allocated byte arrays | ||
| WritableByteChannel c = Channels.newChannel(target.getOutputStream()); | ||
| try { | ||
| c.write(buf); | ||
| } finally { | ||
| c.close(); | ||
| } | ||
| } | ||
| } |
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pgjdbc/src/main/java/org/postgresql/util/ByteStreamWriter.java
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| /* | ||
| * Copyright (c) 2020, PostgreSQL Global Development Group | ||
| * See the LICENSE file in the project root for more information. | ||
| */ | ||
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| package org.postgresql.util; | ||
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| import java.io.IOException; | ||
| import java.io.InputStream; | ||
| import java.io.OutputStream; | ||
|
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| /** | ||
| * A class that can be used to set a byte array parameter by writing to an OutputStream. | ||
| * | ||
| * <p>The intended use case is wanting to write data to a byte array parameter that is stored off | ||
| * heap in a direct memory pool or in some other form that is inconvenient to assemble into a single | ||
| * heap-allocated buffer.</p> | ||
| * <p> Users should write their own implementation depending on the | ||
| * original data source. The driver provides a built-in implementation supporting the {@link | ||
| * java.nio.ByteBuffer} class, see {@link ByteBufferByteStreamWriter}.</p> | ||
| * <p> Intended usage is to simply pass in an instance using | ||
| * {@link java.sql.PreparedStatement#setObject(int, Object)}:</p> | ||
| * <pre> | ||
| * int bufLength = someBufferObject.length(); | ||
| * preparedStatement.setObject(1, new MyByteStreamWriter(bufLength, someBufferObject)); | ||
| * </pre> | ||
| * <p>The length must be known ahead of the stream being written to. </p> | ||
| * <p>This provides the application more control over memory management than calling | ||
| * {@link java.sql.PreparedStatement#setBinaryStream(int, InputStream)} as with the latter the | ||
| * caller has no control over the buffering strategy. </p> | ||
| */ | ||
| public interface ByteStreamWriter { | ||
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| /** | ||
| * Returns the length of the stream. | ||
| * | ||
| * <p> This must be known ahead of calling {@link #writeTo(ByteStreamTarget)}. </p> | ||
| * | ||
| * @return the number of bytes in the stream. | ||
| */ | ||
| int getLength(); | ||
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| /** | ||
| * Write the data to the provided {@link OutputStream}. | ||
| * | ||
| * <p> Should not write more than {@link #getLength()} bytes. If attempted, the provided stream | ||
| * will throw an {@link java.io.IOException}. </p> | ||
| * | ||
| * @param target the stream to write the data to | ||
| * @throws IOException if the underlying stream throws or there is some other error. | ||
| */ | ||
| void writeTo(ByteStreamTarget target) throws IOException; | ||
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| /** | ||
| * Provides a target to write bytes to. | ||
| */ | ||
| interface ByteStreamTarget { | ||
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| /** | ||
| * Provides an output stream to write bytes to. | ||
| * | ||
| * @return an output stream | ||
| */ | ||
| OutputStream getOutputStream(); | ||
| } | ||
| } |
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