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Convert a signed 64-bit integer byte array to a double-precision floating-point number.
To use in Observable,
fromInt64Bytes = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/number-float64-base-from-int64-bytes@umd/browser.js' )To vendor stdlib functionality and avoid installing dependency trees for Node.js, you can use the UMD server build:
var fromInt64Bytes = require( 'path/to/vendor/umd/number-float64-base-from-int64-bytes/index.js' )To include the bundle in a webpage,
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/number-float64-base-from-int64-bytes@umd/browser.js"></script>If no recognized module system is present, access bundle contents via the global scope:
<script type="text/javascript">
(function () {
window.fromInt64Bytes;
})();
</script>Converts a signed 64-bit integer byte array to a double-precision floating-point number.
var Uint8Array = require( '@stdlib/array-uint8' );
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.
var Uint8Array = require( '@stdlib/array-uint8' );
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).
<!DOCTYPE html>
<html lang="en">
<body>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/assert-is-little-endian@umd/browser.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/random-base-discrete-uniform@umd/browser.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/random-base-bernoulli@umd/browser.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/array-uint8@umd/browser.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/number-float64-base-from-int64-bytes@umd/browser.js"></script>
<script type="text/javascript">
(function () {
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 );
}
})();
</script>
</body>
</html>@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 for JavaScript and Node.js, 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.
See LICENSE.
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