Package org.python.core.buffer

Class SimpleWritableBuffer

java.lang.Object
org.python.core.buffer.BaseBuffer
org.python.core.buffer.Base1DBuffer
org.python.core.buffer.BaseArrayBuffer
org.python.core.buffer.SimpleBuffer
org.python.core.buffer.SimpleWritableBuffer
All Implemented Interfaces:
AutoCloseable, BufferProtocol, PyBUF, PyBuffer
public class SimpleWritableBuffer extends SimpleBuffer
Buffer API over a writable one-dimensional array of one-byte items.

  • Constructor Details

    • SimpleWritableBuffer

      public SimpleWritableBuffer(int flags, BufferProtocol obj, byte[] storage, int index0, int size) throws PyException, NullPointerException
      Provide an instance of SimpleWritableBuffer, on a slice of a byte array, meeting the consumer's expectations as expressed in the flags argument, which is checked against the capabilities of the buffer type.
      Parameters:
      flags - consumer requirements
      obj - exporting object (or null)
      storage - the array of bytes storing the implementation of the exporting object
      index0 - offset where the data starts in that array (item[0])
      size - the number of bytes occupied
      Throws:
      PyException - BufferError when expectations do not correspond with the type
      NullPointerException

    • SimpleWritableBuffer

      public SimpleWritableBuffer(int flags, BufferProtocol obj, byte[] storage) throws PyException, NullPointerException
      Provide an instance of SimpleWritableBuffer, on the entirety of a byte array, meeting the consumer's expectations as expressed in the flags argument, which is checked against the capabilities of the buffer type.
      Parameters:
      flags - consumer requirements
      obj - exporting object (or null)
      storage - the array of bytes storing the implementation of the exporting object
      Throws:
      PyException - BufferError when expectations do not correspond with the type
      NullPointerException

  • Method Details

    • isReadonly

      public final boolean isReadonly()
      Determine whether the consumer is entitled to write to the exported storage.

      Declared final returning true in SimpleWritableBuffer to make checks unnecessary.

      Specified by:
      isReadonly in interface PyBUF
      Overrides:
      isReadonly in class BaseBuffer
      Returns:
      true if writing is not allowed, false if it is.

    • getBufferSlice

      public PyBuffer getBufferSlice(int flags, int start, int count)
      Equivalent to PyBuffer.getBufferSlice(int, int, int, int) with stride 1.

      SimpleWritableBuffer provides an implementation ensuring the returned slice is writable.

      Specified by:
      getBufferSlice in interface PyBuffer
      Overrides:
      getBufferSlice in class SimpleBuffer
      Parameters:
      flags - specifying features demanded and the navigational capabilities of the consumer
      start - index in the current buffer
      count - number of items in the required slice
      Returns:
      a buffer representing the slice

    • getBufferSlice

      public PyBuffer getBufferSlice(int flags, int start, int count, int stride)
      Get a PyBuffer that represents a slice of the current one described in terms of a start index, number of items to include in the slice, and the stride in the current buffer. A consumer that obtains a PyBuffer with getBufferSlice must release it with PyBuffer.release() just as if it had been obtained with PyBuffer.getBuffer(int)

      Suppose that x(i) denotes the ith element of the current buffer, that is, the byte retrieved by this.byteAt(i) or the unit indicated by this.getPointer(i). A request for a slice where start = s, count = N and stride = m, results in a buffer y such that y(k) = x(s+km) where k=0..(N-1). In Python terms, this is the slice x[s : s+(N-1)m+1 : m] (if m>0) or the slice x[s : s+(N-1)m-1 : m] (if m<0). Implementations should check that this range is entirely within the current buffer.

      In a simple buffer backed by a contiguous byte array, the result is a strided PyBuffer on the same storage but where the offset is adjusted by s and the stride is as supplied. If the current buffer is already strided and/or has an item size larger than single bytes, the new start index, count and stride will be translated from the arguments given, through this buffer's stride and item size. The caller always expresses start and strides in terms of the abstract view of this buffer.

      SimpleBuffer provides an implementation for slicing contiguous bytes in one dimension. In that case, x(i) = u(r+i) for i = 0..L-1 where u is the underlying buffer, and r and L are the start and count with which x was created from u. Thus y(k) = u(r+s+km), that is, the composite offset is r+s and the stride is m.

      SimpleWritableBuffer provides an implementation ensuring the returned slice is writable.

      Specified by:
      getBufferSlice in interface PyBuffer
      Overrides:
      getBufferSlice in class SimpleBuffer
      Parameters:
      flags - specifying features demanded and the navigational capabilities of the consumer
      start - index in the current buffer
      count - number of items in the required slice
      stride - index-distance in the current buffer between consecutive items in the slice
      Returns:
      a buffer representing the slice