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Convert a signed 64-bit integer byte array to a double-precision floating-point number.
import fromInt64Bytes from 'https://cdn.jsdelivr.net/gh/stdlib-js/number-float64-base-from-int64-bytes@deno/mod.js';Converts a signed 64-bit integer byte array to a double-precision floating-point number.
import Uint8Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-uint8@deno/mod.js';
var bytes = new Uint8Array( [ 255, 255, 255, 255, 255, 255, 255, 255 ] );
var out = fromInt64Bytes( bytes, 1, 0 );
// returns -1.0The function supports providing a stride and an index offset for indexing into a provided byte array.
import Uint8Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-uint8@deno/mod.js';
var bytes = new Uint8Array( [ 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255 ] );
var out = fromInt64Bytes( bytes, 2, 1 );
// returns -1.0- The function assumes host byte order (endianness).
import IS_LITTLE_ENDIAN from 'https://cdn.jsdelivr.net/gh/stdlib-js/assert-is-little-endian@deno/mod.js';
import discreteUniform from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-base-discrete-uniform@deno/mod.js';
import bernoulli from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-base-bernoulli@deno/mod.js';
import Uint8Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-uint8@deno/mod.js';
import fromInt64Bytes from 'https://cdn.jsdelivr.net/gh/stdlib-js/number-float64-base-from-int64-bytes@deno/mod.js';
var bytes;
var sgn;
var x;
var b;
var s;
var i;
var j;
var k;
bytes = new Uint8Array( 8 );
if ( IS_LITTLE_ENDIAN ) {
k = 0;
s = 1;
} else {
k = 7;
s = -1;
}
// Generate random integer-valued doubles on the interval (-2^16, 2^16)...
for ( i = 0; i < 10; i++ ) {
// Determine the sign:
sgn = ( bernoulli( 0.5 ) ) ? 0 : 128; // 2^7
// Set a subset of individual (lower-order) bytes:
for ( j = 0; j < 2; j++ ) {
b = discreteUniform( 0, 255 ); // 2^8-1
bytes[ k+(j*s) ] = b;
}
// Set higher-order bytes using two's complement:
for ( j = 2; j < 8; j++ ) {
bytes[ k+(j*s) ] = ( sgn ) ? 255 : 0; // 2^8-1
}
// Convert the bytes to a double:
x = fromInt64Bytes( bytes, 1, 0 );
console.log( bytes + ' => ' + x );
}@stdlib/number-float64/base/to-int64-bytes: convert an integer-valued double-precision floating-point number to a signed 64-bit integer byte array according to host byte order.
This package is part of stdlib, a standard library with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
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