Package org.python.core.buffer

Class BaseBuffer

java.lang.Object
org.python.core.buffer.BaseBuffer
All Implemented Interfaces:
AutoCloseable, BufferProtocol, PyBUF, PyBuffer
Direct Known Subclasses:
Base1DBuffer
public abstract class BaseBuffer extends Object implements PyBuffer
Base implementation of the Buffer API providing variables and accessors for the navigation arrays, methods for expressing and checking the buffer request flags, methods and mechanism for get-release counting, boilerplate error checks and their associated exceptions, and default implementations of some methods for access to the buffer content. The design aim is to ensure unglamorous common code need only be implemented once.

This class leaves undefined the storage mechanism for the bytes (typically byte[] or java.nio.ByteBuffer), while remaining definite that it is an indexable sequence of bytes. A concrete class that extends this one must provide elementary accessors byteAtImpl(int), storeAtImpl(byte, int) that abstract this storage, a factory getNIOByteBufferImpl() for ByteBuffers that wrap the storage, and a factory for slices PyBuffer.getBufferSlice(int, int, int, int).

The sub-class constructor must specify the feature flags (see BaseBuffer(int, int, int[], int[])), set index0, shape and strides, and finally check the client capabilities with checkRequestFlags(int). A sub-class intended to represent slices of an exporter that counts its exports, as part of a locking protocol like bytearray's, must override getRoot() so that a call to release() on a view of slice, propagates to the buffer view that provided the slice.

Access methods provided here necessarily work with the abstracted byteAtImpl(int), storeAtImpl(byte, int) interface, but subclasses are able to override them with more efficient versions that employ knowledge of the particular storage type used.

This base implementation is writable only if PyBUF.WRITABLE is in the feature flags passed to the constructor. Otherwise, all methods for write access raise a TypeError and isReadonly() returns true. However, a client intending to write should have presented PyBUF.WRITABLE in its client request flags when getting the buffer, and been prevented by a BufferError exception at that point.

At the time of writing, only one-dimensional buffers of item size one are used in the Jython core.

  • Nested Class Summary

    Nested classes/interfaces inherited from interface org.python.core.PyBuffer

    PyBuffer.Pointer

  • Field Summary

    Fields inherited from interface org.python.core.PyBUF

    ANY_CONTIGUOUS, AS_ARRAY, C_CONTIGUOUS, CONTIG, CONTIG_RO, CONTIGUITY, F_CONTIGUOUS, FORMAT, FULL, FULL_RO, INDIRECT, IS_C_CONTIGUOUS, IS_F_CONTIGUOUS, MAX_NDIM, NAVIGATION, ND, RECORDS, RECORDS_RO, SIMPLE, STRIDED, STRIDED_RO, STRIDES, WRITABLE

  • Method Summary

    Modifier and Type
    Method
    Description
    byte
    byteAt(int index)
    Return the byte indexed from a one-dimensional buffer with item size one.
    byte
    byteAt(int... indices)
    Return the byte indexed from an N-dimensional buffer with item size one.
    int
    byteIndex(int index)
    Convert an item index (for a one-dimensional buffer) to an absolute byte index in the storage shared by the exporter.
    int
    byteIndex(int... indices)
    Convert a multi-dimensional item index to an absolute byte index in the storage shared by the exporter.
    void
    close()
    An alias for PyBuffer.release() to satisfy AutoCloseable.
    void
    copyFrom(byte[] src, int srcPos, int destIndex, int count)
    Copy from a slice of a (Java) byte array into the buffer starting at a given destination item-index.
    void
    copyFrom(PyBuffer src)
    Copy the whole of another PyBuffer into this buffer.
    void
    copyTo(byte[] dest, int destPos)
    Copy the contents of the buffer to the destination byte array.
    void
    copyTo(int srcIndex, byte[] dest, int destPos, int count)
    Copy a simple slice of the buffer-view to the destination byte array, defined by a starting item-index in the source buffer and the count of items to copy.
    PyBuffer.Pointer
    getBuf()
    Return a structure describing the slice of a byte array that holds the data being exported to the consumer.
    PyBuffer
    getBuffer(int flags)
    Method by which the consumer requests the buffer from the exporter.
    BaseBuffer
    getBufferAgain(int flags)
    Allow an exporter to re-use this object again even if it has been "finally" released.
    PyBuffer
    getBufferSlice(int flags, int start, int count)
    Equivalent to PyBuffer.getBufferSlice(int, int, int, int) with stride 1.
    String
    getFormat()
    A format string in the language of Python structs describing how the bytes of each item should be interpreted.
    int
    getItemsize()
    The number of bytes stored in each indexable item.
    int
    getLen()
    The total number of bytes represented by the view, which will be the product of the elements of the shape array, and the item size in bytes.
    int
    getNdim()
    The number of dimensions to the buffer.
    ByteBuffer
    getNIOByteBuffer()
    Obtain a ByteBuffer giving access to the bytes that hold the data being exported by the original object.
    final BufferProtocol
    getObj()
    Return the underlying exporting object (or null if no object implementing the BufferProtocol is in that role).
    PyBuffer.Pointer
    getPointer(int index)
    Return a structure describing the position in a byte array of a single item from the data being exported to the consumer.
    PyBuffer.Pointer
    getPointer(int... indices)
    Return a structure describing the position in a byte array of a single item from the data being exported to the consumer, in the case that array may be multi-dimensional.
    int[]
    getShape()
    An array reporting the size of the buffer, considered as a multidimensional array, in each dimension and (by its length) giving the number of dimensions.
    int[]
    getStrides()
    The strides array gives the distance in the storage array between adjacent items (in each dimension).
    int[]
    getSuboffsets()
    The suboffsets array is a further part of the support for interpreting the buffer as an n-dimensional array of items, where the array potentially uses indirect addressing (like a real Java array of arrays, in fact).
    boolean
    hasArray()
    Report whether the exporter is able to offer direct access to the exported storage as a Java byte array (through the API that involves class PyBuffer.Pointer), or only supports the abstract API.
    int
    intAt(int index)
    Return the unsigned byte value indexed from a one-dimensional buffer with item size one.
    int
    intAt(int... indices)
    Return the unsigned byte value indexed from an N-dimensional buffer with item size one.
    boolean
    isContiguous(char order)
    Enquire whether the array is represented contiguously in the backing storage, according to C or Fortran ordering.
    boolean
    isReadonly()
    Determine whether the consumer is entitled to write to the exported storage.
    boolean
    isReleased()
    True only if the buffer has been released with (the required number of calls to) PyBuffer.release() or some equivalent operation.
    void
    release()
    A buffer is (usually) a view onto to the internal state of an exporting object, and that object may have to restrict its behaviour while the buffer exists.
    void
    storeAt(byte value, int index)
    Store the given byte at the indexed location in of a one-dimensional buffer with item size one.
    void
    storeAt(byte value, int... indices)
    Store the given byte at the indexed location in of an N-dimensional buffer with item size one.
    String
    toString()
    The toString() method of a buffer reproduces the values in the buffer (as unsigned integers) as the character codes of a String.

    Methods inherited from class java.lang.Object

    equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

    Methods inherited from interface org.python.core.PyBuffer

    getBufferSlice

  • Method Details

    • isReadonly

      public boolean isReadonly()
      Description copied from interface: PyBUF
      Determine whether the consumer is entitled to write to the exported storage.
      Specified by:
      isReadonly in interface PyBUF
      Returns:
      true if writing is not allowed, false if it is.

    • getNdim

      public int getNdim()
      Description copied from interface: PyBUF
      The number of dimensions to the buffer. This number is the length of the shape array. The actual storage may be a linear array, but this is the number of dimensions in the interpretation that the exporting object gives the data.
      Specified by:
      getNdim in interface PyBUF
      Returns:
      number of dimensions

    • getShape

      public int[] getShape()
      Description copied from interface: PyBUF
      An array reporting the size of the buffer, considered as a multidimensional array, in each dimension and (by its length) giving the number of dimensions. The size of the buffer is its size in "items". An item is the amount of buffer content addressed by one index or set of indices. In the simplest case an item is a single unit (byte), and there is one dimension. In complex cases, the array is multi-dimensional, and the item at each location is multi-unit (multi-byte). The consumer must not modify this array. A valid shape array is always returned (difference from CPython).
      Specified by:
      getShape in interface PyBUF
      Returns:
      the dimensions of the buffer as an array

    • getLen

      public int getLen()
      Description copied from interface: PyBUF
      The total number of bytes represented by the view, which will be the product of the elements of the shape array, and the item size in bytes.
      Specified by:
      getLen in interface PyBUF
      Returns:
      the total number of bytes represented.

    • getObj

      public final BufferProtocol getObj()
      Description copied from interface: PyBuffer
      Return the underlying exporting object (or null if no object implementing the BufferProtocol is in that role). This will often be a PyObject.
      Specified by:
      getObj in interface PyBuffer
      Returns:
      exporting object (or null)

    • byteAt

      public byte byteAt(int index) throws IndexOutOfBoundsException
      Return the byte indexed from a one-dimensional buffer with item size one. This is part of the fully-encapsulated API: the buffer implementation exported takes care of navigating the structure of the buffer. Results are undefined where the number of dimensions is not one or if itemsize>1.

      The BaseBuffer implementation delegates to byteAtImpl(int) via byteAtImpl(byteIndex(index)).

      Specified by:
      byteAt in interface PyBuffer
      Parameters:
      index - to retrieve from
      Returns:
      the item at index, which is a byte
      Throws:
      IndexOutOfBoundsException

    • intAt

      public int intAt(int index) throws IndexOutOfBoundsException
      Return the unsigned byte value indexed from a one-dimensional buffer with item size one. This is part of the fully-encapsulated API: the exporter takes care of navigating the structure of the buffer. Results are undefined where the number of dimensions is not one or if itemsize>1.

      The BaseBuffer implementation delegates to byteAtImpl(int) via byteAtImpl(byteIndex(index)), cast unsigned to an int.

      Specified by:
      intAt in interface PyBuffer
      Parameters:
      index - to retrieve from
      Returns:
      the item at index, treated as an unsigned byte, =0xff & byteAt(index)
      Throws:
      IndexOutOfBoundsException

    • storeAt

      public void storeAt(byte value, int index) throws IndexOutOfBoundsException, PyException
      Store the given byte at the indexed location in of a one-dimensional buffer with item size one. This is part of the fully-encapsulated API: the buffer implementation exported takes care of navigating the structure of the buffer. Results are undefined where the number of dimensions is not one or if itemsize>1.

      The BaseBuffer implementation delegates to storeAtImpl(byte, int) via storeAtImpl(value, byteIndex(index)).

      Specified by:
      storeAt in interface PyBuffer
      Parameters:
      value - to store
      index - to location
      Throws:
      IndexOutOfBoundsException
      PyException

    • byteAt

      public byte byteAt(int... indices) throws IndexOutOfBoundsException
      Return the byte indexed from an N-dimensional buffer with item size one. This is part of the fully-encapsulated API: the buffer implementation exported takes care of navigating the structure of the buffer. The indices must be correct in number and range for the array shape. Results are undefined where itemsize>1.

      The BaseBuffer implementation delegates to byteAtImpl(int) via byteAtImpl(byteIndex(indices)).

      Specified by:
      byteAt in interface PyBuffer
      Parameters:
      indices - specifying location to retrieve from
      Returns:
      the item at location, which is a byte
      Throws:
      IndexOutOfBoundsException

    • intAt

      public int intAt(int... indices) throws IndexOutOfBoundsException
      Return the unsigned byte value indexed from an N-dimensional buffer with item size one. This is part of the fully-encapsulated API: the buffer implementation exported takes care of navigating the structure of the buffer. The indices must be correct in number and range for the array shape. Results are undefined where itemsize>1.

      The BaseBuffer implementation delegates to byteAtImpl(int) via byteAtImpl(byteIndex(indices)), cast unsigned to an int.

      Specified by:
      intAt in interface PyBuffer
      Parameters:
      indices - specifying location to retrieve from
      Returns:
      the item at location, treated as an unsigned byte, =0xff & byteAt(index)
      Throws:
      IndexOutOfBoundsException

    • storeAt

      public void storeAt(byte value, int... indices) throws IndexOutOfBoundsException, PyException
      Store the given byte at the indexed location in of an N-dimensional buffer with item size one. This is part of the fully-encapsulated API: the exporter takes care of navigating the structure of the buffer. The indices must be correct in number and range for the array shape. Results are undefined where itemsize>1.

      The BaseBuffer implementation delegates to storeAtImpl(byte, int) via storeAtImpl(value, byteIndex(indices)).

      Specified by:
      storeAt in interface PyBuffer
      Parameters:
      value - to store
      indices - specifying location to store at
      Throws:
      IndexOutOfBoundsException
      PyException

    • byteIndex

      public int byteIndex(int index) throws IndexOutOfBoundsException
      Description copied from interface: PyBuffer
      Convert an item index (for a one-dimensional buffer) to an absolute byte index in the storage shared by the exporter. The storage exported as a PyBuffer is a linearly-indexed sequence of bytes, although it may not actually be a heap-allocated Java byte[] object. The purpose of this method is to allow the exporter to define the relationship between the item index (as used in PyBuffer.byteAt(int)) and the byte-index (as used with the ByteBuffer returned by PyBuffer.getNIOByteBuffer()). See PyBuffer.byteIndex(int[]) for discussion of the multi-dimensional case.
      Specified by:
      byteIndex in interface PyBuffer
      Parameters:
      index - item-index from consumer
      Returns:
      corresponding byte-index in actual storage
      Throws:
      IndexOutOfBoundsException

    • byteIndex

      public int byteIndex(int... indices) throws IndexOutOfBoundsException
      Description copied from interface: PyBuffer
      Convert a multi-dimensional item index to an absolute byte index in the storage shared by the exporter. The storage exported as a PyBuffer is a linearly-indexed sequence of bytes, although it may not actually be a heap-allocated Java byte[] object. The purpose of this method is to allow the exporter to define the relationship between the item index (as used in PyBuffer.byteAt(int...) and the byte-index (as used with the ByteBuffer returned by PyBuffer.getNIOByteBuffer()).
      Specified by:
      byteIndex in interface PyBuffer
      Parameters:
      indices - n-dimensional item-index from consumer
      Returns:
      corresponding byte-index in actual storage
      Throws:
      IndexOutOfBoundsException

    • copyTo

      public void copyTo(byte[] dest, int destPos) throws IndexOutOfBoundsException
      Copy the contents of the buffer to the destination byte array. The number of bytes will be that returned by PyBUF.getLen(), and the order is the storage order in the exporter. (Note: Correct ordering for multidimensional arrays, including those with indirection needs further study.)

      The default implementation in BaseBuffer deals with the general one-dimensional case of arbitrary item size and stride.

      Specified by:
      copyTo in interface PyBuffer
      Parameters:
      dest - destination byte array
      destPos - byte-index in the destination array of the byte [0]
      Throws:
      IndexOutOfBoundsException - if the destination cannot hold it

    • copyTo

      public void copyTo(int srcIndex, byte[] dest, int destPos, int count) throws IndexOutOfBoundsException, PyException
      Copy a simple slice of the buffer-view to the destination byte array, defined by a starting item-index in the source buffer and the count of items to copy. This may validly be done only for a one-dimensional buffer, as the meaning of the starting item-index is otherwise not defined. count*itemsize bytes will be occupied in the destination.

      The default implementation in BaseBuffer deals with the general one-dimensional case of arbitrary item size and stride, but is unable to optimise access to sequential bytes.

      Specified by:
      copyTo in interface PyBuffer
      Parameters:
      srcIndex - starting item-index in the source buffer
      dest - destination byte array
      destPos - byte-index in the destination array of the source item [0,...]
      count - number of items to copy
      Throws:
      IndexOutOfBoundsException - if access out of bounds in source or destination
      PyException

    • copyFrom

      public void copyFrom(byte[] src, int srcPos, int destIndex, int count) throws IndexOutOfBoundsException, PyException
      Copy from a slice of a (Java) byte array into the buffer starting at a given destination item-index. This may validly be done only for a one-dimensional buffer, as the meaning of the destination index is not otherwise defined. count*itemsize bytes will be read from the source.

      The default implementation in BaseBuffer deals with the general one-dimensional case of arbitrary item size and stride, but is unable to optimise access to sequential bytes.

      Specified by:
      copyFrom in interface PyBuffer
      Parameters:
      src - source byte array
      srcPos - location in source of first byte to copy
      destIndex - starting item-index in the destination (i.e. this)
      count - number of items to copy in
      Throws:
      IndexOutOfBoundsException - if access out of bounds in source or destination
      PyException - TypeError if read-only buffer

    • copyFrom

      public void copyFrom(PyBuffer src) throws IndexOutOfBoundsException, PyException
      Copy the whole of another PyBuffer into this buffer. This may validly be done only for buffers that are consistent in their dimensions. When it is necessary to copy partial buffers, this may be achieved using a buffer slice on the source or destination.

      The default implementation in BaseBuffer deals with the general one-dimensional case of arbitrary item size and stride, but is unable to optimise access to sequential bytes.

      Specified by:
      copyFrom in interface PyBuffer
      Parameters:
      src - source buffer
      Throws:
      IndexOutOfBoundsException - if access out of bounds in source or destination
      PyException - TypeError if read-only buffer

    • getBuffer

      public PyBuffer getBuffer(int flags)
      Description copied from interface: PyBuffer
      Method by which the consumer requests the buffer from the exporter. The consumer provides information on its ability to understand buffer navigation. Each consumer requesting a buffer in this way, when it has finished using it, should make a corresponding call to PyBuffer.release() on the buffer it obtained, or PyBuffer.close() using try-with-resources, since some objects alter their behaviour while buffers are exported.

      When a PyBuffer is the target, the same checks are carried out on the consumer flags, and a return will normally be a reference to that buffer. A Jython PyBuffer keeps count of these re-exports in order to match them with the number of calls to PyBuffer.release(). When the last matching release() arrives it is considered "final", and release actions may then take place on the exporting object. After the final release of a buffer, a call to getBuffer should raise an exception.

      Specified by:
      getBuffer in interface BufferProtocol
      Specified by:
      getBuffer in interface PyBuffer
      Parameters:
      flags - specifying features demanded and the navigational capabilities of the consumer
      Returns:
      exported buffer

    • getBufferAgain

      public BaseBuffer getBufferAgain(int flags)
      Allow an exporter to re-use this object again even if it has been "finally" released. Many sub-classes of BaseBytes can be re-used even after a final release by consumers, simply by incrementing the exports count again: the navigation arrays and the buffer view of the exporter's state all remain valid. We do not let consumers do this through the PyBuffer interface: from their perspective, calling PyBuffer.release() should mean the end of their access, although we can't stop them holding a reference to the PyBuffer. Only the exporting object, which handles the implementation type is trusted to know when re-use is safe.

      An exporter will use this method as part of its implementation of BufferProtocol.getBuffer(int). On return from that, the buffer and the exporting object must then be in effectively the same state as if the buffer had just been constructed by that method. Exporters that destroy related resources on final release of their buffer (by overriding releaseAction()), or permit themselves structural change invalidating the buffer, must either reconstruct the missing resources or avoid getBufferAgain.

    • release

      public void release()
      A buffer is (usually) a view onto to the internal state of an exporting object, and that object may have to restrict its behaviour while the buffer exists. The consumer must therefore say when it has finished with the buffer if the exporting object is to be released from this constraint. Each consumer that obtains a reference to a buffer by means of a call to BufferProtocol.getBuffer(int) or PyBuffer.getBuffer(int) should make a matching call to PyBuffer.release(). The consumer may be sharing the PyBuffer with other consumers and the buffer uses the pairing of getBuffer and release to manage the lock on behalf of the exporter. It is an error to make more than one call to release for a single call to getBuffer.

      When the final matching release occurs (that is the number of release calls equals the number of getBuffer calls), the implementation here calls releaseAction(), which the implementer of a specific buffer type should override if it needs specific actions to take place.

      Note that, when this is a sliced view obtained from another PyBuffer the implementation in BaseBuffer automatically sends one release() Sub-classes should not propagate the release themselves when overriding releaseAction().

      Specified by:
      release in interface PyBuffer

    • close

      public void close()
      Description copied from interface: PyBuffer
      An alias for PyBuffer.release() to satisfy AutoCloseable.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface PyBuffer

    • isReleased

      public boolean isReleased()
      Description copied from interface: PyBuffer
      True only if the buffer has been released with (the required number of calls to) PyBuffer.release() or some equivalent operation. The consumer may be sharing the reference with other consumers and the buffer only achieves the released state when all consumers who called getBuffer have called release.
      Specified by:
      isReleased in interface PyBuffer

    • getBufferSlice

      public PyBuffer getBufferSlice(int flags, int start, int count)
      Description copied from interface: PyBuffer
      Equivalent to PyBuffer.getBufferSlice(int, int, int, int) with stride 1.
      Specified by:
      getBufferSlice in interface PyBuffer
      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

    • getNIOByteBuffer

      public ByteBuffer getNIOByteBuffer()
      Description copied from interface: PyBuffer
      Obtain a ByteBuffer giving access to the bytes that hold the data being exported by the original object. The position of the buffer is at the first byte of the item with zero index (quite possibly not the lowest valid byte-index), the limit of the buffer is beyond the largest valid byte index, and the mark is undefined.

      For a one-dimensional contiguous buffer, the limit is one byte beyond the last item, so that consecutive reads from the ByteBuffer return the data in order. Assuming the following client code where obj has type BufferProtocol: 

       PyBuffer a = obj.getBuffer(PyBUF.SIMPLE);
 int itemsize = a.getItemsize();
 ByteBuffer bb = a.getNIOBuffer();
      the item with index k is in bb at positions bb.pos()+k*itemsize to bb.pos()+(k+1)*itemsize - 1 inclusive. And if itemsize==1, the item is simply the byte at position bb.pos()+k.

      If the buffer is multidimensional or non-contiguous (strided), the buffer position is still the (first byte of) the item at index [0] or [0,...,0]. However, it is necessary to navigate bb using the shape, strides and maybe suboffsets provided by the API.

      Specified by:
      getNIOByteBuffer in interface PyBuffer
      Returns:
      a ByteBuffer onto the exported data contents.

    • hasArray

      public boolean hasArray()
      Description copied from interface: PyBuffer
      Report whether the exporter is able to offer direct access to the exported storage as a Java byte array (through the API that involves class PyBuffer.Pointer), or only supports the abstract API. See also PyBUF.AS_ARRAY.
      Specified by:
      hasArray in interface PyBuffer
      Returns:
      true if array access is supported, false if it is not.

    • getBuf

      public PyBuffer.Pointer getBuf()
      Description copied from interface: PyBuffer
      Return a structure describing the slice of a byte array that holds the data being exported to the consumer. For a one-dimensional contiguous buffer, assuming the following client code where obj has type BufferProtocol: 
       PyBuffer a = obj.getBuffer(PyBUF.SIMPLE);
 int itemsize = a.getItemsize();
 PyBuffer.Pointer b = a.getBuf();
      the item with index k is in the array b.storage at index [b.offset + k*itemsize] to [b.offset + (k+1)*itemsize - 1] inclusive. And if itemsize==1, the item is simply the byte b.storage[b.offset + k]

      If the buffer is multidimensional or non-contiguous, storage[offset] is still the (first byte of) the item at index [0] or [0,...,0]. However, it is necessary to navigate b.storage using the shape, strides and maybe suboffsets provided by the API.

      Specified by:
      getBuf in interface PyBuffer
      Returns:
      structure defining the byte[] slice that is the shared data

    • getPointer

      public PyBuffer.Pointer getPointer(int index) throws IndexOutOfBoundsException
      Description copied from interface: PyBuffer
      Return a structure describing the position in a byte array of a single item from the data being exported to the consumer. For a one-dimensional contiguous buffer, assuming the following client code where obj has type BufferProtocol: 
       int k = ... ;
 PyBuffer a = obj.getBuffer(PyBUF.FULL);
 int itemsize = a.getItemsize();
 PyBuffer.Pointer b = a.getPointer(k);
      the item with index k is in the array b.storage at index [b.offset] to [b.offset + itemsize - 1] inclusive. And if itemsize==1, the item is simply the byte b.storage[b.offset]

      Essentially this is a method for computing the offset of a particular index. The client is free to navigate the underlying buffer b.storage without respecting these boundaries.

      Specified by:
      getPointer in interface PyBuffer
      Parameters:
      index - in the buffer to position the pointer
      Returns:
      structure defining the byte[] slice that is the shared data
      Throws:
      IndexOutOfBoundsException

    • getPointer

      public PyBuffer.Pointer getPointer(int... indices) throws IndexOutOfBoundsException
      Description copied from interface: PyBuffer
      Return a structure describing the position in a byte array of a single item from the data being exported to the consumer, in the case that array may be multi-dimensional. For a 3-dimensional contiguous buffer, assuming the following client code where obj has type BufferProtocol: 
       int i, j, k;
 // ... calculation that assigns i, j, k
 PyBuffer a = obj.getBuffer(PyBUF.FULL);
 int itemsize = a.getItemsize();
 PyBuffer.Pointer b = a.getPointer(i,j,k);
      the item with index [i,j,k] is in the array b.storage at index [b.offset] to [b.offset + itemsize - 1] inclusive. And if itemsize==1, the item is simply the byte b.storage[b.offset]

      Essentially this is a method for computing the offset of a particular index. The client is free to navigate the underlying buffer b.storage without respecting these boundaries. If the buffer is non-contiguous, the above description is still valid (since a multi-byte item must itself be contiguously stored), but in any additional navigation of b.storage[] to other items, the client must use the shape, strides and sub-offsets provided by the API. Normally one starts b = a.getBuf() in order to establish the offset of index [0,...,0].

      Specified by:
      getPointer in interface PyBuffer
      Parameters:
      indices - multidimensional index at which to position the pointer
      Returns:
      structure defining the byte[] slice that is the shared data
      Throws:
      IndexOutOfBoundsException

    • getStrides

      public int[] getStrides()
      Description copied from interface: PyBUF
      The strides array gives the distance in the storage array between adjacent items (in each dimension). In the rawest parts of the buffer API, the consumer of the buffer is able to navigate the exported storage. The "strides" array is part of the support for interpreting the buffer as an n-dimensional array of items. It provides the coefficients of the "addressing polynomial". (More on this in the CPython documentation.) The consumer must not modify this array. A valid strides array is always returned (difference from CPython).
      Specified by:
      getStrides in interface PyBUF
      Returns:
      the distance in the storage array between adjacent items (in each dimension)

    • getSuboffsets

      public int[] getSuboffsets()
      Description copied from interface: PyBUF
      The suboffsets array is a further part of the support for interpreting the buffer as an n-dimensional array of items, where the array potentially uses indirect addressing (like a real Java array of arrays, in fact). This is only applicable when there is more than 1 dimension, and it works in conjunction with the strides array. (More on this in the CPython documentation.) When used, suboffsets[k] is an integer index, not a byte offset as in CPython. The consumer must not modify this array. When not needed for navigation null is returned (as in CPython).
      Specified by:
      getSuboffsets in interface PyBUF
      Returns:
      suboffsets array or null if not necessary for navigation

    • isContiguous

      public boolean isContiguous(char order)
      Description copied from interface: PyBUF
      Enquire whether the array is represented contiguously in the backing storage, according to C or Fortran ordering. A one-dimensional contiguous array is both.
      Specified by:
      isContiguous in interface PyBUF
      Parameters:
      order - 'C', 'F' or 'A', as the storage order is C, Fortran or either.
      Returns:
      true iff the array is stored contiguously in the order specified

    • getFormat

      public String getFormat()
      Description copied from interface: PyBuffer
      A format string in the language of Python structs describing how the bytes of each item should be interpreted. Irrespective of the PyBUF.FORMAT bit in the consumer's call to getBuffer, a valid format string is always returned (difference from CPython).

      Jython only implements "B" so far, and it is debatable whether anything fancier than "<n>B" can be supported in Java.

      Specified by:
      getFormat in interface PyBuffer
      Returns:
      the format string

    • getItemsize

      public int getItemsize()
      Description copied from interface: PyBUF
      The number of bytes stored in each indexable item.
      Specified by:
      getItemsize in interface PyBUF
      Returns:
      the number of bytes comprising each item.

    • toString

      public String toString()
      The toString() method of a buffer reproduces the values in the buffer (as unsigned integers) as the character codes of a String.
      Specified by:
      toString in interface PyBuffer
      Overrides:
      toString in class Object