@stdlib/ndarray-base-ctor
Version:
Base multidimensional array.
207 lines (179 loc) • 6.14 kB
JavaScript
/**
* @license Apache-2.0
*
* Copyright (c) 2021 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
;
// MODULES //
var IS_LITTLE_ENDIAN = require( '@stdlib/assert-is-little-endian' );
var ArrayBuffer = require( '@stdlib/array-buffer' );
var DataView = require( '@stdlib/array-dataview' );
var BigInt = require( '@stdlib/bigint-ctor' );
var dtypes = require( '@stdlib/ndarray-dtypes' ).enum;
var orders = require( '@stdlib/ndarray-orders' ).enum;
var modes = require( '@stdlib/ndarray-index-modes' ).enum;
// VARIABLES //
var DTYPES = dtypes();
var ORDERS = orders();
var MODES = modes();
// FUNCTIONS //
/**
* Serializes ndarray meta data to a `DataView`.
*
* ## Notes
*
* - This function takes into account ndarray-like objects which may support index modes.
*
* - This function defaults to returning cached serialized meta data. To force serialization, set the private `__meta_dataview__` property to `null`.
*
* - Serialization is performed according to host byte order (endianness).
*
* - Meta data format:
*
* ```text
* | endianness (1 byte) | <dtype> (2 bytes) | <ndims> (8 bytes) | <shape> (ndims*8 bytes) | <strides> (ndims*8 bytes) | <offset> (8 bytes) | <order> (1 byte) | <mode> (1 byte) | <nsubmodes> (8 bytes) | <submodes> (nsubmodes*1 bytes) | <flags> (4 bytes) |
* ```
*
* which translates to the following `ArrayBuffer` layout:
*
* ```text
* ArrayBuffer[
* <endianness>[int8],
* <dtype>[int16],
* <ndims>[int64],
* <shape>[ndims*int64],
* <strides>[ndims*int64],
* <offset>[int64],
* <order>[int8],
* <mode>[int8],
* <nsubmodes>[int64],
* <submodes>[nsubmodes*int8],
* <flags>[int32]
* ]
* ```
*
* where `strides` and `offset` are in units of bytes.
*
* - If the endianness is `1`, the byte order is little endian. If the endianness is `0`, the byte order is big endian.
*
* - Buffer length:
*
* ```text
* 1 + 2 + 8 + (ndims*8) + (ndims*8) + 8 + 1 + 1 + 8 + (nsubmodes*1) + 4 = 33 + (ndims*16) + nsubmodes
* ```
*
* For example, consider a three-dimensional ndarray with one subscript index mode (submode):
*
* ```text
* 33 + (3*16) + 1 = 82 bytes
* ```
*
* - Views:
*
* - endianness: `Int8Array( buf, 0, 1 )`
* - dtype: `Int16Array( buf, 1, 1 )`
* - ndims: `Int64Array( buf, 3, 1 )`
* - shape: `Int64Array( buf, 11, ndims )`
* - strides: `Int64Array( buf, 11+(ndims*8), ndims )`
* - offset: `Int64Array( buf, 11+(ndims*16), 1 )`
* - order: `Int8Array( buf, 19+(ndims*16), 1 )`
* - mode: `Int8Array( buf, 20+(ndims*16), 1 )`
* - nsubmodes: `Int64Array( buf, 21+(ndims*16), 1 )`
* - submodes: `Int8Array( buf, 29+(ndims*16), nsubmodes )`
* - flags: `Int32Array( buf, 29+(ndims*16)+nsubmodes, 1 )`
*
* @private
* @returns {DataView} serialized meta data
*/
function meta2dataview() {
/* eslint-disable no-invalid-this */
var nbytes;
var flgs;
var len;
var dt;
var sh;
var st;
var sm;
var v;
var m;
var o;
var s;
var N;
var M;
var i;
m = this._mode || 'throw';
sm = this._submode || [ m ];
N = this._ndims;
M = sm.length;
// Compute the amount of memory we need to allocate for storing meta data:
len = 33 + (N*16) + M;
// Check if we've already serialized ndarray meta data and can reuse an already allocated array buffer...
v = this.__meta_dataview__;
if ( v && v.byteLength === len ) { // Note: the byte length check is only a bare minimum sanity check, as cached contents may still be "stale" (e.g., shape and/or strides may have changed)
return v;
}
// Allocate raw memory and create a view for interfacing with the allocated memory:
v = new DataView( new ArrayBuffer( len ) );
// Retrieve ndarray meta data:
sh = this._shape;
st = this._strides;
dt = this._dtype;
nbytes = this._bytesPerElement;
// Endianness: (byteoffset: 0; bytelength: 1)
o = 0;
v.setInt8( o, ( IS_LITTLE_ENDIAN ) ? 1 : 0 );
// Data type: (byteoffset: 1; bytelength: 2)
o += 1;
v.setInt16( o, DTYPES[ dt ], IS_LITTLE_ENDIAN );
// Number of dimensions: (byteoffset: 3; bytelength: 8)
o += 2;
v.setBigInt64( o, BigInt( N ), IS_LITTLE_ENDIAN );
// Shape and strides: (byteoffset: 11 and 11+(ndims*8), respectively; bytelength: ndims*8 for both shape and strides, and, thus, ndims*16 total)
s = N * 8; // stride length between a dimension (shape[i]) and its associated stride
o += 8;
for ( i = 0; i < N; i++ ) {
v.setBigInt64( o, BigInt( sh[i] ), IS_LITTLE_ENDIAN );
v.setBigInt64( o+s, BigInt( st[i]*nbytes ), IS_LITTLE_ENDIAN );
o += 8;
}
// Offset: (byteoffset: 11+(ndims*16); bytelength: 8)
o += s;
v.setBigInt64( o, BigInt( this._offset*nbytes ), IS_LITTLE_ENDIAN );
// Order: (byteoffset: 19+(ndims*16); bytelength: 1)
o += 8;
v.setInt8( o, ORDERS[ this._order ] );
// Mode: (byteoffset: 20+(ndims*16); bytelength: 1)
o += 1;
v.setInt8( o, MODES[ m ] );
// Number of submodes: (byteoffset: 21+(ndims*16); bytelength: 8)
o += 1;
v.setBigInt64( o, BigInt( M ), IS_LITTLE_ENDIAN );
// Submodes: (byteoffset: 29+(ndims*16); bytelength: nsubmodes*1)
o += 8;
for ( i = 0; i < M; i++ ) {
v.setInt8( o, MODES[ sm[i] ] );
o += 1;
}
// Flags: (byteoffset: 29+(ndims*16)+nsubmodes; bytelength: 4)
flgs = 0|0;
flgs |= ( this._flags.READONLY ) ? 4 : 0; // 00000000 00000000 00000000 00000100
v.setInt32( o, flgs, IS_LITTLE_ENDIAN );
// Cache the serialized meta data:
this.__meta_dataview__ = v;
return v;
/* eslint-enable no-invalid-this */
}
// EXPORTS //
module.exports = meta2dataview;