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SimpleWritableBuffer.java
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138 lines (123 loc) · 5.23 KB
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package org.python.core.buffer;
import org.python.core.BufferProtocol;
import org.python.core.PyBuffer;
import org.python.core.PyException;
/**
* Buffer API over a writable one-dimensional array of one-byte items.
*/
public class SimpleWritableBuffer extends SimpleBuffer {
/**
* Provide an instance of <code>SimpleWritableBuffer</code>, on a slice of a byte array, meeting
* the consumer's expectations as expressed in the <code>flags</code> argument, which is checked
* against the capabilities of the buffer type.
*
* @param flags consumer requirements
* @param obj exporting object (or <code>null</code>)
* @param storage the array of bytes storing the implementation of the exporting object
* @param index0 offset where the data starts in that array (item[0])
* @param size the number of bytes occupied
* @throws PyException {@code BufferError} when expectations do not correspond with the type
*/
public SimpleWritableBuffer(int flags, BufferProtocol obj, byte[] storage, int index0, int size)
throws PyException, NullPointerException {
super(obj, storage, index0, size); // Construct checked SimpleBuffer
addFeatureFlags(WRITABLE);
checkRequestFlags(flags); // Check request is compatible with type
}
/**
* Provide an instance of <code>SimpleWritableBuffer</code>, on the entirety of a byte array,
* meeting the consumer's expectations as expressed in the <code>flags</code> argument, which is
* checked against the capabilities of the buffer type.
*
* @param flags consumer requirements
* @param obj exporting object (or <code>null</code>)
* @param storage the array of bytes storing the implementation of the exporting object
* @throws PyException {@code BufferError} when expectations do not correspond with the type
*/
public SimpleWritableBuffer(int flags, BufferProtocol obj, byte[] storage) throws PyException,
NullPointerException {
this(flags, obj, storage, 0, storage.length);
}
/**
* {@inheritDoc}
* <p>
* Declared <code>final</code> returning <code>true</code> in <code>SimpleWritableBuffer</code>
* to make checks unnecessary.
*/
@Override
public final boolean isReadonly() {
return false;
}
/** Do nothing: the buffer is writable. */
@Override
protected final void checkWritable() {}
@Override
protected void storeAtImpl(byte value, int byteIndex) {
// Implement directly and don't ask whether read-only
storage[byteIndex] = value;
}
/**
* {@inheritDoc}
* <p>
* <code>SimpleWritableBuffer</code> provides an implementation ensuring the returned slice is
* writable.
*/
@Override
public PyBuffer getBufferSlice(int flags, int start, int count) {
if (count > 0) {
// Translate relative to underlying buffer
int compIndex0 = index0 + start;
// Create the slice from the sub-range of the buffer
return new SimpleView(getRoot(), flags, storage, compIndex0, count);
} else {
// Special case for count==0 where above logic would fail. Efficient too.
return new ZeroByteBuffer.View(getRoot(), flags);
}
}
/**
* {@inheritDoc}
* <p>
* <code>SimpleWritableBuffer</code> provides an implementation ensuring the returned slice is
* writable.
*/
@Override
public PyBuffer getBufferSlice(int flags, int start, int count, int stride) {
if (stride == 1 || count < 2) {
// Unstrided slice of simple buffer is itself simple
return getBufferSlice(flags, start, count);
} else {
// Translate relative to underlying buffer
int compIndex0 = index0 + start;
// Construct a view, taking a lock on the root object (this or this.root)
return new Strided1DWritableBuffer.SlicedView(getRoot(), flags, storage, compIndex0,
count, stride);
}
}
/**
* A <code>SimpleWritableBuffer.SimpleView</code> represents a contiguous subsequence of another
* <code>SimpleWritableBuffer</code>.
*/
static class SimpleView extends SimpleWritableBuffer {
/** The buffer on which this is a slice view */
PyBuffer root;
/**
* Construct a slice of a SimpleBuffer.
*
* @param root buffer which will be acquired and must be released ultimately
* @param flags the request flags of the consumer that requested the slice
* @param storage the array of bytes storing the implementation of the exporting object
* @param index0 offset where the data starts in that array (item[0])
* @param size the number of bytes occupied
*/
public SimpleView(PyBuffer root, int flags, byte[] storage, int index0, int size) {
// Create a new SimpleBuffer on the buffer passed in (part of the root)
super(flags, root.getObj(), storage, index0, size);
// Get a lease on the root PyBuffer
this.root = root.getBuffer(FULL_RO);
}
@Override
protected PyBuffer getRoot() {
return root;
}
}
}