UTF-16 to UTF-8

Convert a UTF-16 encoded string to an array of integers using UTF-8 encoding.

Usage

var utf16ToUTF8Array = require( '@stdlib/string/utf16-to-utf8-array' );

utf16ToUTF8Array( str )

Converts a UTF-16 encoded string to an array of integers using UTF-8 encoding.

var out = utf16ToUTF8Array( '☃' );
// returns [ 226, 152, 131 ]

Notes

UTF-16 encoding uses one 16-bit unit for non-surrogates (U+0000 to U+D7FF and U+E000 to U+FFFF).
UTF-16 encoding uses two 16-bit units (surrogate pairs) for U+10000 to U+10FFFF and encodes U+10000-U+10FFFF by subtracting 0x10000 from the code point, expressing the result as a 20-bit binary, and splitting the 20 bits of 0x0-0xFFFFF as upper and lower 10-bits. The respective 10-bits are stored in two 16-bit words: a high and a low surrogate.
UTF-8 is defined to encode code points in one to four bytes, depending on the number of significant bits in the numerical value of the code point. Encoding uses the following byte sequences:
```
0x00000000 - 0x0000007F:
    0xxxxxxx

0x00000080 - 0x000007FF:
    110xxxxx 10xxxxxx

0x00000800 - 0x0000FFFF:
    1110xxxx 10xxxxxx 10xxxxxx

0x00010000 - 0x001FFFFF:
    11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
```
where an x represents a code point bit. Only the shortest possible multi-byte sequence which can represent a code point is used.

Examples

var utf16ToUTF8Array = require( '@stdlib/string/utf16-to-utf8-array' );

var values;
var out;
var i;

values = [
    'Ladies + Gentlemen',
    'An encoded string!',
    'Dogs, Cats & Mice',
    '☃',
    'æ',
    '𐐷'
];
for ( i = 0; i < values.length; i++ ) {
    out = utf16ToUTF8Array( values[ i ] );
    console.log( '%s: %s', values[ i ], out.join( ',' ) );
}