org.python.core.buffer

## Class BaseBuffer

- java.lang.Object
- - org.python.core.buffer.BaseBuffer

All Implemented Interfaces:
  java.lang.AutoCloseable, BufferProtocol, PyBUF, PyBuffer

Direct Known Subclasses:
  Base1DBuffer

    public abstract class BaseBuffer
    extends java.lang.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 `ByteBuffer`s 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

All Methods Instance Methods Concrete Methods
`byte` `byteAt(int... indices)` Return the byte indexed from an N-dimensional buffer with item size one.
`byte` `byteAt(int index)` Return the byte indexed from a one-dimensional buffer with item size one.
`int` `byteIndex(int... indices)` Convert a multi-dimensional item index to an absolute byte index in the storage shared by the exporter.
`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.
`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.
`java.lang.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.
`java.nio.ByteBuffer` `getNIOByteBuffer()` Obtain a `ByteBuffer` giving access to the bytes that hold the data being exported by the original object.
`BufferProtocol` `getObj()` Return the underlying exporting object (or `null` if no object implementing the `BufferProtocol` is in that role).
`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.
`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.
`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... indices)` Return the unsigned byte value indexed from an N-dimensional buffer with item size one.
`int` `intAt(int index)` Return the unsigned byte value indexed from a one-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... indices)` Store the given byte at the indexed location in of an N-dimensional buffer with item size one.
`void` `storeAt(byte value, int index)` Store the given byte at the indexed location in of a one-dimensional buffer with item size one.
`java.lang.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 Detail

#### 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 java.lang.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:
  `java.lang.IndexOutOfBoundsException`

#### intAt

    public int intAt(int index)
              throws java.lang.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:
  `java.lang.IndexOutOfBoundsException`

#### storeAt

    public void storeAt(byte value,
                        int index)
                 throws java.lang.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:
  `java.lang.IndexOutOfBoundsException`
  `PyException`

#### byteAt

    public byte byteAt(int... indices)
                throws java.lang.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:
  `java.lang.IndexOutOfBoundsException`

#### intAt

    public int intAt(int... indices)
              throws java.lang.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:
  `java.lang.IndexOutOfBoundsException`

#### storeAt

    public void storeAt(byte value,
                        int... indices)
                 throws java.lang.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:
  `java.lang.IndexOutOfBoundsException`
  `PyException`

#### byteIndex

    public int byteIndex(int index)
                  throws java.lang.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:
  `java.lang.IndexOutOfBoundsException`

#### byteIndex

    public int byteIndex(int... indices)
                  throws java.lang.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:
  `java.lang.IndexOutOfBoundsException`

#### copyTo

    public void copyTo(byte[] dest,
                       int destPos)
                throws java.lang.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:
  `java.lang.IndexOutOfBoundsException` - if the destination cannot hold it

#### copyTo

    public void copyTo(int srcIndex,
                       byte[] dest,
                       int destPos,
                       int count)
                throws java.lang.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:
  `java.lang.IndexOutOfBoundsException` - if access out of bounds in source or destination
  `PyException`

#### copyFrom

    public void copyFrom(byte[] src,
                         int srcPos,
                         int destIndex,
                         int count)
                  throws java.lang.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:
  `java.lang.IndexOutOfBoundsException` - if access out of bounds in source or destination
  `PyException` - `TypeError` if read-only buffer

#### copyFrom

    public void copyFrom(PyBuffer src)
                  throws java.lang.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:
  `java.lang.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 `java.lang.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 java.nio.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 java.lang.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:
  `java.lang.IndexOutOfBoundsException`

#### getPointer

    public PyBuffer.Pointer getPointer(int... indices)
                                throws java.lang.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:
  `java.lang.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 java.lang.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 java.lang.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 `java.lang.Object`