public interface PyBuffer extends PyBUF, BufferProtocol, AutoCloseable
Py_buffer
struct. Several concrete types implement
this interface in order to provide tailored support for different storage organisations.Modifier and Type | Interface and Description |
---|---|
static class |
PyBuffer.Pointer
Deprecated.
|
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
Modifier and Type | Method and Description |
---|---|
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
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.
|
PyBuffer |
getBufferSlice(int flags,
int start,
int count)
Equivalent to
getBufferSlice(int, int, int, int) with stride 1. |
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. |
String |
getFormat()
A format string in the language of Python structs describing how the bytes of each item
should be interpreted.
|
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.
|
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 |
isReleased()
True only if the buffer has been released with (the required number of calls to)
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.
|
String |
toString()
The toString() method of a buffer reproduces the byte values in the buffer (treated as
unsigned integers) as the character codes of a
String . |
getItemsize, getLen, getNdim, getShape, getStrides, getSuboffsets, isContiguous, isReadonly
BufferProtocol getObj()
null
if no object implementing the
BufferProtocol
is in that role). This will often be a PyObject
.null
)byte byteAt(int index) throws IndexOutOfBoundsException
itemsize>1
.index
- to retrieve fromIndexOutOfBoundsException
int intAt(int index) throws IndexOutOfBoundsException
itemsize>1
.index
- to retrieve from=0xff & byteAt(index)
IndexOutOfBoundsException
void storeAt(byte value, int index) throws IndexOutOfBoundsException
itemsize>1
.value
- to storeindex
- to locationIndexOutOfBoundsException
byte byteAt(int... indices) throws IndexOutOfBoundsException
itemsize>1
.indices
- specifying location to retrieve fromIndexOutOfBoundsException
int intAt(int... indices) throws IndexOutOfBoundsException
itemsize>1
.indices
- specifying location to retrieve from=0xff & byteAt(index)
IndexOutOfBoundsException
void storeAt(byte value, int... indices) throws IndexOutOfBoundsException
itemsize>1
.value
- to storeindices
- specifying location to store atIndexOutOfBoundsException
void copyTo(byte[] dest, int destPos) throws IndexOutOfBoundsException, PyException
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.)dest
- destination byte arraydestPos
- byte-index in the destination array of the byte [0]IndexOutOfBoundsException
- if the destination cannot hold itPyException
void copyTo(int srcIndex, byte[] dest, int destPos, int count) throws IndexOutOfBoundsException, PyException
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.srcIndex
- starting item-index in the source bufferdest
- destination byte arraydestPos
- byte-index in the destination array of the source item [0,...]count
- number of items to copyIndexOutOfBoundsException
- if access out of bounds in source or destinationPyException
void copyFrom(byte[] src, int srcPos, int destIndex, int count) throws IndexOutOfBoundsException, PyException
count*itemsize
bytes will be read
from the source.src
- source byte arraysrcPos
- location in source of first byte to copydestIndex
- starting item-index in the destination (i.e. this
)count
- number of items to copy inIndexOutOfBoundsException
- if access out of bounds in source or destinationPyException
- (TypeError) if read-only buffervoid copyFrom(PyBuffer src) throws IndexOutOfBoundsException, PyException
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.src
- source bufferIndexOutOfBoundsException
- if access out of bounds in source or destinationPyException
- (TypeError) if read-only bufferPyBuffer getBuffer(int flags) throws PyException
release()
on the buffer it
obtained, 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 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.
getBuffer
in interface BufferProtocol
flags
- specifying features demanded and the navigational capabilities of the consumerPyException
- (BufferError) when expectations do not correspond with the buffervoid release()
BufferProtocol.getBuffer(int)
or getBuffer(int)
should make a
matching call to 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
.void close()
release()
to satisfy AutoCloseable
.close
in interface AutoCloseable
boolean isReleased()
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
.PyBuffer getBufferSlice(int flags, int start, int count)
getBufferSlice(int, int, int, int)
with stride 1.flags
- specifying features demanded and the navigational capabilities of the consumerstart
- index in the current buffercount
- number of items in the required slicePyBuffer getBufferSlice(int flags, int start, int count, int stride)
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 release()
just as if it had been obtained with
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.
flags
- specifying features demanded and the navigational capabilities of the consumerstart
- index in the current buffercount
- number of items in the required slicestride
- index-distance in the current buffer between consecutive items in the sliceint byteIndex(int index) throws IndexOutOfBoundsException
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 byteAt(int)
) and the byte-index (as used with the
ByteBuffer
returned by getNIOByteBuffer()
). See
byteIndex(int[])
for discussion of the multi-dimensional case.index
- item-index from consumerIndexOutOfBoundsException
int byteIndex(int... indices)
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 byteAt(int...)
and the byte-index (as used with the
ByteBuffer
returned by getNIOByteBuffer()
).indices
- n-dimensional item-index from consumerByteBuffer getNIOByteBuffer()
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.
ByteBuffer
onto the exported data contents.boolean hasArray()
PyBuffer.Pointer
), or only supports the
abstract API. See also PyBUF.AS_ARRAY
.PyBuffer.Pointer getBuf()
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.
PyBuffer.Pointer getPointer(int index)
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.
index
- in the buffer to position the pointerPyBuffer.Pointer getPointer(int... indices)
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].
indices
- multidimensional index at which to position the pointerString getFormat()
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.