44 lines
977 B
JavaScript
44 lines
977 B
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 truncate(getLength, string, byteLength) {
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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 curByteLength = 0;
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var codePoint;
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var segment;
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for (var i = 0; i < charLength; i += 1) {
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codePoint = string.charCodeAt(i);
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segment = string[i];
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if (isHighSurrogate(codePoint) && isLowSurrogate(string.charCodeAt(i + 1))) {
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i += 1;
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segment += string[i];
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}
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curByteLength += getLength(segment);
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if (curByteLength === byteLength) {
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return string.slice(0, i + 1);
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}
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else if (curByteLength > byteLength) {
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return string.slice(0, i - segment.length + 1);
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}
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}
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return string;
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};
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