PyBUF (Jython API documentation)

All Known Subinterfaces:

PyBuffer

All Known Implementing Classes:

BaseBuffer, SimpleBuffer, SimpleStringBuffer, SimpleWritableBuffer, Strided1DBuffer, Strided1DWritableBuffer, ZeroByteBuffer
```
public interface PyBUF
```
This interface provides a base for the key interface of the buffer API, PyBuffer, including symbolic constants used by the consumer of a PyBuffer to specify its requirements and assumptions. The Jython buffer API emulates the CPython buffer API. There are two reasons for separating parts of PyBuffer into this interface:
- The constants defined in CPython have the names PyBUF_SIMPLE, PyBUF_WRITABLE, etc., and the trick of defining ours here means we can write PyBUF.SIMPLE, PyBUF.WRITABLE, etc. so source code looks similar.
- It is not so easy in Java as it is in C to treat a byte array as storing anything other than byte, and we prepare for the possibility of buffers with a series of different primitive types by defining here those methods that would be in common between (Byte)Buffer and an assumed future FloatBuffer or TypedBuffer<T>. (Compare java.nio.Buffer.)
It is unlikely any classes would implement PyBUF, except indirectly through other interfaces. Users of the Jython buffer API can mostly overlook the distinction and just use PyBuffer.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`ANY_CONTIGUOUS` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it will assume a contiguous organisation of the units, but will enquire which organisation it actually is.
`static int`	`AS_ARRAY` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it expects to access the buffer contents directly as an array (rather than through the purely abstract part of the API).
`static int`	`C_CONTIGUOUS` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it will assume C-order organisation of the units.
`static int`	`CONTIG` Equivalent to `(ND \| WRITABLE)`
`static int`	`CONTIG_RO` Equivalent to `ND`
`static int`	`CONTIGUITY` Field mask, used as in `if ((flags&CONTIGUITY)== ... ) ...`
`static int`	`F_CONTIGUOUS` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it will assume Fortran-order organisation of the units.
`static int`	`FORMAT` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it requires `PyBuffer.getFormat()` to return a `String` indicating the type of the unit.
`static int`	`FULL` Equivalent to `(INDIRECT \| WRITABLE \| FORMAT)`.
`static int`	`FULL_RO` Equivalent to `(INDIRECT \| FORMAT)`.
`static int`	`INDIRECT` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it understands the `suboffsets` array.
`static int`	`IS_C_CONTIGUOUS` A constant used by the exporter in processing `BufferProtocol.getBuffer(int)` to check for assumed C-order organisation of the units.
`static int`	`IS_F_CONTIGUOUS` A constant used by the exporter in processing `BufferProtocol.getBuffer(int)` to check for assumed C-order Fortran-order organisation of the units.
`static int`	`MAX_NDIM` The maximum allowed number of dimensions (CPython restriction).
`static int`	`NAVIGATION` Field mask, used as in `if ((flags&NAVIGATION) == STRIDES) ...`
`static int`	`ND` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it is prepared to navigate the buffer as multi-dimensional using the `shape` array.
`static int`	`RECORDS` Equivalent to `(STRIDES \| WRITABLE \| FORMAT)`
`static int`	`RECORDS_RO` Equivalent to `(STRIDES \| FORMAT)`
`static int`	`SIMPLE` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it assumes a simple one-dimensional organisation of the exported storage with item size of one.
`static int`	`STRIDED` Equivalent to `(STRIDES \| WRITABLE)`
`static int`	`STRIDED_RO` Equivalent to `STRIDES`
`static int`	`STRIDES` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it expects to use the `strides` array.
`static int`	`WRITABLE` A constant used by the consumer in its call to `BufferProtocol.getBuffer(int)` to specify that it expects to write to the buffer contents.

Method Summary

Methods
Modifier and Type	Method and Description
`int`	`getItemsize()` The number of units (bytes) stored in each indexable item.
`int`	`getLen()` The total number of units (bytes) stored, which will be the product of the elements of the `shape` array, and the item size in units.
`int`	`getNdim()` The number of dimensions to the buffer.
`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`	`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.

- Field Detail
  - MAX_NDIM
```
static final int MAX_NDIM
```
    The maximum allowed number of dimensions (CPython restriction).
    
    See Also:
    Constant Field Values
  - WRITABLE
```
static final int WRITABLE
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it expects to write to the buffer contents. getBuffer will raise an exception if the exporter's buffer cannot meet this requirement.
    
    See Also:
    Constant Field Values
  - SIMPLE
```
static final int SIMPLE
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it assumes a simple one-dimensional organisation of the exported storage with item size of one. getBuffer will raise an exception if the consumer sets this flag and the exporter's buffer cannot be navigated that simply.
    
    See Also:
    Constant Field Values
  - FORMAT
```
static final int FORMAT
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it requires PyBuffer.getFormat() to return a String indicating the type of the unit. This exists for compatibility with CPython, as Jython as the format is always provided by getFormat().
    
    See Also:
    Constant Field Values
  - ND
```
static final int ND
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it is prepared to navigate the buffer as multi-dimensional using the shape array. getBuffer will raise an exception if consumer does not specify the flag but the exporter's buffer cannot be navigated without taking into account its multiple dimensions.
    
    See Also:
    Constant Field Values
  - STRIDES
```
static final int STRIDES
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it expects to use the strides array. getBuffer will raise an exception if consumer does not specify the flag but the exporter's buffer cannot be navigated without using the strides array.
    
    See Also:
    Constant Field Values
  - C_CONTIGUOUS
```
static final int C_CONTIGUOUS
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it will assume C-order organisation of the units. getBuffer will raise an exception if the exporter's buffer is not C-ordered. C_CONTIGUOUS implies STRIDES.
    
    See Also:
    Constant Field Values
  - F_CONTIGUOUS
```
static final int F_CONTIGUOUS
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it will assume Fortran-order organisation of the units. getBuffer will raise an exception if the exporter's buffer is not Fortran-ordered. F_CONTIGUOUS implies STRIDES.
    
    See Also:
    Constant Field Values
  - ANY_CONTIGUOUS
```
static final int ANY_CONTIGUOUS
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it will assume a contiguous organisation of the units, but will enquire which organisation it actually is. getBuffer will raise an exception if the exporter's buffer is not contiguous. ANY_CONTIGUOUS implies STRIDES.
    
    See Also:
    Constant Field Values
  - INDIRECT
```
static final int INDIRECT
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it understands the suboffsets array. getBuffer will raise an exception if consumer does not specify the flag but the exporter's buffer cannot be navigated without understanding the suboffsets array. INDIRECT implies STRIDES.
    
    See Also:
    Constant Field Values
  - CONTIG
```
static final int CONTIG
```
    Equivalent to (ND | WRITABLE)
    
    See Also:
    Constant Field Values
  - CONTIG_RO
```
static final int CONTIG_RO
```
    Equivalent to ND
    
    See Also:
    Constant Field Values
  - STRIDED
```
static final int STRIDED
```
    Equivalent to (STRIDES | WRITABLE)
    
    See Also:
    Constant Field Values
  - STRIDED_RO
```
static final int STRIDED_RO
```
    Equivalent to STRIDES
    
    See Also:
    Constant Field Values
  - RECORDS
```
static final int RECORDS
```
    Equivalent to (STRIDES | WRITABLE | FORMAT)
    
    See Also:
    Constant Field Values
  - RECORDS_RO
```
static final int RECORDS_RO
```
    Equivalent to (STRIDES | FORMAT)
    
    See Also:
    Constant Field Values
  - FULL
```
static final int FULL
```
    Equivalent to (INDIRECT | WRITABLE | FORMAT). Also use this in the request if you plan only to use the fully-encapsulated API (byteAt, storeAt, copyTo, copyFrom, etc.), without ever calling PyBuffer.getBuf().
    
    See Also:
    Constant Field Values
  - FULL_RO
```
static final int FULL_RO
```
    Equivalent to (INDIRECT | FORMAT). Also use this in the request if you plan only to use the fully-encapsulated API (byteAt, copyTo, etc.), read only, without ever calling PyBuffer.getBuf().
    
    See Also:
    Constant Field Values
  - AS_ARRAY
```
static final int AS_ARRAY
```
    A constant used by the consumer in its call to BufferProtocol.getBuffer(int) to specify that it expects to access the buffer contents directly as an array (rather than through the purely abstract part of the API). getBuffer will raise an exception if the exporter cannot expose its storage as Java array.
    
    See Also:
    Constant Field Values
  - NAVIGATION
```
static final int NAVIGATION
```
    Field mask, used as in if ((flags&NAVIGATION) == STRIDES) .... The importance of the subset of flags defined by this mask is not so much in their "navigational" character as in the way they are treated in a buffer request.
    The NAVIGATION set are used to specify which navigation arrays the consumer will use, and therefore the consumer must ask for all those necessary to use the buffer successfully (which is a function of the buffer's actual type). Asking for extra ones is not an error, since all are supplied (in Jython): asking for too few is an error.
    Flags outside the NAVIGATION set, work the other way round. Asking for one the buffer cannot match is an error: not asking for a feature the buffer does not have is an error.
    
    See Also:
    Constant Field Values
  - IS_C_CONTIGUOUS
```
static final int IS_C_CONTIGUOUS
```
    A constant used by the exporter in processing BufferProtocol.getBuffer(int) to check for assumed C-order organisation of the units. C_CONTIGUOUS = IS_C_CONTIGUOUS | STRIDES.
    
    See Also:
    Constant Field Values
  - IS_F_CONTIGUOUS
```
static final int IS_F_CONTIGUOUS
```
    A constant used by the exporter in processing BufferProtocol.getBuffer(int) to check for assumed C-order Fortran-order organisation of the units. F_CONTIGUOUS = IS_F_CONTIGUOUS | STRIDES.
    
    See Also:
    Constant Field Values
  - CONTIGUITY
```
static final int CONTIGUITY
```
    Field mask, used as in if ((flags&CONTIGUITY)== ... ) ....
    
    See Also:
    Constant Field Values
- Method Detail
  - isReadonly
```
boolean isReadonly()
```
    Determine whether the consumer is entitled to write to the exported storage.
    
    Returns:
    true if writing is not allowed, false if it is.
  - getNdim
```
int getNdim()
```
    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.
    
    Returns:
    number of dimensions
  - getShape
```
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. 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).
    
    Returns:
    the dimensions of the buffer as an array
  - getItemsize
```
int getItemsize()
```
    The number of units (bytes) stored in each indexable item.
    
    Returns:
    the number of units (bytes) comprising each item.
  - getLen
```
int getLen()
```
    The total number of units (bytes) stored, which will be the product of the elements of the shape array, and the item size in units.
    
    Returns:
    the total number of units stored.
  - getStrides
```
int[] getStrides()
```
    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).
    
    Returns:
    the distance in the storage array between adjacent items (in each dimension)
  - getSuboffsets
```
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). 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).
    
    Returns:
    suboffsets array or null if not necessary for navigation
  - isContiguous
```
boolean isContiguous(char order)
```
    Enquire whether the array is represented contiguously in the backing storage, according to C or Fortran ordering. A one-dimensional contiguous array is both.
    
    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

Interface PyBUF

Field Summary

Method Summary

Field Detail

MAX_NDIM

WRITABLE

SIMPLE

FORMAT

ND

STRIDES

C_CONTIGUOUS

F_CONTIGUOUS

ANY_CONTIGUOUS

INDIRECT

CONTIG

CONTIG_RO

STRIDED

STRIDED_RO

RECORDS

RECORDS_RO

FULL

FULL_RO

AS_ARRAY

NAVIGATION

IS_C_CONTIGUOUS

IS_F_CONTIGUOUS

CONTIGUITY

Method Detail

isReadonly

getNdim

getShape

getItemsize

getLen

getStrides

getSuboffsets

isContiguous