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@@ -7,18 +7,53 @@
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* @module utils/uid
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*/
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+// A hash table of hex numbers to avoid using toString() in uid() which is costly.
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+// [ '00', '01', '02', ..., 'fe', 'ff' ]
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+const HEX_NUMBERS = new Array( 256 ).fill()
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+ .map( ( val, index ) => ( '0' + ( index ).toString( 16 ) ).slice( -2 ) );
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+
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/**
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- * Returns a unique id. This id consist of an 'e' character and a randomly generated string of 32 aphanumeric characters.
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- * Each character in uid string represents a hexadecimal digit (base 16).
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+ * Returns a unique id. The id starts with an "e" character and a randomly generated string,
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+ * 32 alphanumeric characters in total.
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+ *
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+ * **Note**: The characters the unique id is built from correspond to hex number notation
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+ * (from "0" to "9", from "a" to "f"). In other words, each id represents 16 8-bit numbers
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+ * next to each other.
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*
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- * @returns {String} A hexadecimal number representing the id.
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+ * @returns {String} An unique id string.
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*/
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export default function uid() {
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- let uuid = 'e'; // Make sure that id does not start with number.
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-
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- for ( let i = 0; i < 8; i++ ) {
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- uuid += Math.floor( ( 1 + Math.random() ) * 0x10000 ).toString( 16 ).substring( 1 );
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- }
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+ // Let's create some positive random 32bit integers first.
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+ //
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+ // 1. Math.random() is a float between 0 and 1.
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+ // 2. 0x100000000 is 2^32 = 4294967296.
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+ // 3. >>> 0 enforces integer (in JS all numbers are floating point).
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+ //
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+ // For instance:
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+ // Math.random() * 0x100000000 = 3366450031.853859
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+ // but
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+ // Math.random() * 0x100000000 >>> 0 = 3366450031.
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+ const r1 = Math.random() * 0x100000000 >>> 0;
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+ const r2 = Math.random() * 0x100000000 >>> 0;
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+ const r3 = Math.random() * 0x100000000 >>> 0;
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+ const r4 = Math.random() * 0x100000000 >>> 0;
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- return uuid;
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+ // Make sure that id does not start with number.
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+ return 'e' +
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+ HEX_NUMBERS[ r1 >> 0 & 0xFF ] +
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+ HEX_NUMBERS[ r1 >> 8 & 0xFF ] +
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+ HEX_NUMBERS[ r1 >> 16 & 0xFF ] +
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+ HEX_NUMBERS[ r1 >> 24 & 0xFF ] +
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+ HEX_NUMBERS[ r2 >> 0 & 0xFF ] +
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+ HEX_NUMBERS[ r2 >> 8 & 0xFF ] +
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+ HEX_NUMBERS[ r2 >> 16 & 0xFF ] +
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+ HEX_NUMBERS[ r2 >> 24 & 0xFF ] +
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+ HEX_NUMBERS[ r3 >> 0 & 0xFF ] +
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+ HEX_NUMBERS[ r3 >> 8 & 0xFF ] +
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+ HEX_NUMBERS[ r3 >> 16 & 0xFF ] +
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+ HEX_NUMBERS[ r3 >> 24 & 0xFF ] +
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+ HEX_NUMBERS[ r4 >> 0 & 0xFF ] +
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+ HEX_NUMBERS[ r4 >> 8 & 0xFF ] +
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+ HEX_NUMBERS[ r4 >> 16 & 0xFF ] +
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+ HEX_NUMBERS[ r4 >> 24 & 0xFF ][ 0 ]; // Because of leading "e" and 32 character limit.
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}
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