feat: add number/int64/ctor

lib/node_modules/@stdlib/number/int64/ctor/README.md

@@ -0,0 +1,273 @@
+<!--
+
+@license Apache-2.0
+
+Copyright (c) 2026 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.
+
+-->
+
+# Int64
+
+> 64-bit signed integer.
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- Package usage documentation. -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var Int64 = require( '@stdlib/number/int64/ctor' );
+```
+
+#### Int64( value )
+
+64-bit signed integer constructor.
+
+```javascript
+var x = new Int64( 5 );
+// returns <Int64>
+```
+
+* * *
+
+## Properties
+
+#### Int64.name
+
+Static property returning the constructor name.
+
+```javascript
+var str = Int64.name;
+// returns 'Int64'
+```
+
+#### Int64.BYTES_PER_ELEMENT
+
+Size (in bytes) of the underlying value.
+
+```javascript
+var nbytes = Int64.BYTES_PER_ELEMENT;
+// returns 8
+```
+
+#### Int64.prototype.BYTES_PER_ELEMENT
+
+Size (in bytes) of the underlying value.
+
+```javascript
+var x = new Int64( 5 );
+
+var nbytes = x.BYTES_PER_ELEMENT;
+// returns 8
+```
+
+#### Int64.prototype.byteLength
+
+Size (in bytes) of the underlying value.
+
+```javascript
+var x = new Int64( 5 );
+
+var nbytes = x.byteLength;
+// returns 8
+```
+
+#### Int64.prototype.hi
+
+High 32-bit word of a 64-bit signed integer.
+
+```javascript
+var x = Int64.from( [ 1234, 5678 ] );
+
+var w = x.hi;
+// returns 1234
+```
+
+#### Int64.prototype.lo
+
+Low 32-bit word of a 64-bit signed integer.
+
+```javascript
+var x = Int64.from( [ 1234, 5678 ] );
+
+var w = x.lo;
+// returns 5678
+```
+
+* * *
+
+## Methods
+
+### Static Methods
+
+#### Int64.from( array )
+
+Creates a new 64-bit signed integer from an array-like object containing a high and low word.
+
+```javascript
+var x = Int64.from( [ 1234, 5678 ] );
+// returns <Int64>
+```
+
+#### Int64.of( high, low )
+
+Creates a new 64-bit signed integer from a high and low word.
+
+```javascript
+var x = Int64.of( 1234, 5678 );
+// returns <Int64>
+```
+
+### Accessor Methods
+
+These methods do **not** mutate a `Int64` instance and, instead, return a 64-bit signed integer representation.
+
+#### Int64.prototype.toString()
+
+Returns a string representation of a `Int64` instance.
+
+```javascript
+var x = new Int64( 5 );
+var str = x.toString();
+// returns '5'
+```
+
+#### Int64.prototype.toJSON()
+
+Returns a [JSON][json] representation of a `Int64` instance. [`JSON.stringify()`][mdn-json-stringify] implicitly calls this method when stringifying a `Int64` instance.
+
+```javascript
+var x = new Int64( 5 );
+
+var o = x.toJSON();
+// returns { 'type': 'Int64', 'words': [ 0, 5 ] }
+```
+
+To [revive][mdn-json-parse] a `Int64` instance from a [JSON][json] string, see [@stdlib/number/int64/reviver][@stdlib/number/int64/reviver].
+
+#### Int64.prototype.valueOf()
+
+Converts a `Int64` instance to a primitive value.
+
+```javascript
+var x = new Int64( 5 );
+
+var v = x.valueOf();
+// e.g., returns <bigint>
+```
+
+</section>
+
+<!-- /.usage -->
+
+* * *
+
+<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+## Notes
+
+-   A 64-bit signed integer has a range of \[`-(2^63)`, `2^63-1`\].
+
+</section>
+
+<!-- /.notes -->
+
+* * *
+
+<!-- Package usage examples. -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var Int64 = require( '@stdlib/number/int64/ctor' );
+
+var x = new Int64( 1234 );
+
+console.log( 'type: %s', typeof x );
+// => 'type: object'
+
+console.log( 'str: %s', x );
+// => 'str: 1234'
+
+console.log( 'JSON: %s', JSON.stringify( x ) );
+// => 'JSON: {"type":"Int64","words":[0,1234]}'
+
+x = new Int64( -1234 );
+
+console.log( 'type: %s', typeof x );
+// => 'type: object'
+
+console.log( 'str: %s', x );
+// => 'str: -1234'
+
+console.log( 'JSON: %s', JSON.stringify( x ) );
+// => 'JSON: {"type":"Int64","words":[4294967295,4294966062]}'
+```
+
+</section>
+
+<!-- /.examples -->
+
+
+<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="references">
+
+</section>
+
+<!-- /.references -->
+
+<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
+
+<section class="related">
+
+</section>
+
+<!-- /.related -->
+
+<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="links">
+
+[json]: http://www.json.org/
+
+[mdn-json-stringify]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify
+
+[mdn-json-parse]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse
+
+[@stdlib/number/int64/reviver]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/number/int64/reviver
+
+<!-- <related-links> -->
+
+<!-- </related-links> -->
+
+</section>
+
+<!-- /.links -->