48 lines
1.1 KiB
JavaScript
48 lines
1.1 KiB
JavaScript
'use strict';
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function isHighSurrogate(codePoint) {
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return codePoint >= 0xd800 && codePoint <= 0xdbff;
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}
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function isLowSurrogate(codePoint) {
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return codePoint >= 0xdc00 && codePoint <= 0xdfff;
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}
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// Truncate string by size in bytes
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module.exports = function getByteLength(string) {
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if (typeof string !== "string") {
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throw new Error("Input must be string");
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}
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var charLength = string.length;
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var byteLength = 0;
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var codePoint = null;
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var prevCodePoint = null;
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for (var i = 0; i < charLength; i++) {
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codePoint = string.charCodeAt(i);
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// handle 4-byte non-BMP chars
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// low surrogate
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if (isLowSurrogate(codePoint)) {
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// when parsing previous hi-surrogate, 3 is added to byteLength
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if (prevCodePoint != null && isHighSurrogate(prevCodePoint)) {
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byteLength += 1;
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}
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else {
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byteLength += 3;
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}
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}
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else if (codePoint <= 0x7f ) {
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byteLength += 1;
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}
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else if (codePoint >= 0x80 && codePoint <= 0x7ff) {
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byteLength += 2;
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}
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else if (codePoint >= 0x800 && codePoint <= 0xffff) {
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byteLength += 3;
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}
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prevCodePoint = codePoint;
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}
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return byteLength;
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};
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