index.js
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"use strict";
/**
* A minimal UTF8 implementation for number arrays.
* @memberof util
* @namespace
*/
var utf8 = exports;
/**
* Calculates the UTF8 byte length of a string.
* @param {string} string String
* @returns {number} Byte length
*/
utf8.length = function utf8_length(string) {
var len = 0,
c = 0;
for (var i = 0; i < string.length; ++i) {
c = string.charCodeAt(i);
if (c < 128)
len += 1;
else if (c < 2048)
len += 2;
else if ((c & 0xFC00) === 0xD800 && (string.charCodeAt(i + 1) & 0xFC00) === 0xDC00) {
++i;
len += 4;
} else
len += 3;
}
return len;
};
/**
* Reads UTF8 bytes as a string.
* @param {Uint8Array} buffer Source buffer
* @param {number} start Source start
* @param {number} end Source end
* @returns {string} String read
*/
utf8.read = function utf8_read(buffer, start, end) {
var len = end - start;
if (len < 1)
return "";
var parts = null,
chunk = [],
i = 0, // char offset
t; // temporary
while (start < end) {
t = buffer[start++];
if (t < 128)
chunk[i++] = t;
else if (t > 191 && t < 224)
chunk[i++] = (t & 31) << 6 | buffer[start++] & 63;
else if (t > 239 && t < 365) {
t = ((t & 7) << 18 | (buffer[start++] & 63) << 12 | (buffer[start++] & 63) << 6 | buffer[start++] & 63) - 0x10000;
chunk[i++] = 0xD800 + (t >> 10);
chunk[i++] = 0xDC00 + (t & 1023);
} else
chunk[i++] = (t & 15) << 12 | (buffer[start++] & 63) << 6 | buffer[start++] & 63;
if (i > 8191) {
(parts || (parts = [])).push(String.fromCharCode.apply(String, chunk));
i = 0;
}
}
if (parts) {
if (i)
parts.push(String.fromCharCode.apply(String, chunk.slice(0, i)));
return parts.join("");
}
return String.fromCharCode.apply(String, chunk.slice(0, i));
};
/**
* Writes a string as UTF8 bytes.
* @param {string} string Source string
* @param {Uint8Array} buffer Destination buffer
* @param {number} offset Destination offset
* @returns {number} Bytes written
*/
utf8.write = function utf8_write(string, buffer, offset) {
var start = offset,
c1, // character 1
c2; // character 2
for (var i = 0; i < string.length; ++i) {
c1 = string.charCodeAt(i);
if (c1 < 128) {
buffer[offset++] = c1;
} else if (c1 < 2048) {
buffer[offset++] = c1 >> 6 | 192;
buffer[offset++] = c1 & 63 | 128;
} else if ((c1 & 0xFC00) === 0xD800 && ((c2 = string.charCodeAt(i + 1)) & 0xFC00) === 0xDC00) {
c1 = 0x10000 + ((c1 & 0x03FF) << 10) + (c2 & 0x03FF);
++i;
buffer[offset++] = c1 >> 18 | 240;
buffer[offset++] = c1 >> 12 & 63 | 128;
buffer[offset++] = c1 >> 6 & 63 | 128;
buffer[offset++] = c1 & 63 | 128;
} else {
buffer[offset++] = c1 >> 12 | 224;
buffer[offset++] = c1 >> 6 & 63 | 128;
buffer[offset++] = c1 & 63 | 128;
}
}
return offset - start;
};