146 lines
2.9 KiB
Plaintext
146 lines
2.9 KiB
Plaintext
function byteLength (string) {
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let length = 0
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for (let i = 0, n = string.length; i < n; i++) {
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const code = string.charCodeAt(i)
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if (code >= 0xd800 && code <= 0xdbff && i + 1 < n) {
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const code = string.charCodeAt(i + 1)
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if (code >= 0xdc00 && code <= 0xdfff) {
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length += 4
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i++
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continue
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}
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}
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if (code <= 0x7f) length += 1
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else if (code <= 0x7ff) length += 2
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else length += 3
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}
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return length
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}
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let toString
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if (typeof TextDecoder !== 'undefined') {
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const decoder = new TextDecoder()
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toString = function toString (buffer) {
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return decoder.decode(buffer)
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}
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} else {
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toString = function toString (buffer) {
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const len = buffer.byteLength
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let output = ''
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let i = 0
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while (i < len) {
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let byte = buffer[i]
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if (byte <= 0x7f) {
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output += String.fromCharCode(byte)
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i++
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continue
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}
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let bytesNeeded = 0
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let codePoint = 0
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if (byte <= 0xdf) {
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bytesNeeded = 1
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codePoint = byte & 0x1f
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} else if (byte <= 0xef) {
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bytesNeeded = 2
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codePoint = byte & 0x0f
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} else if (byte <= 0xf4) {
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bytesNeeded = 3
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codePoint = byte & 0x07
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}
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if (len - i - bytesNeeded > 0) {
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let k = 0
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while (k < bytesNeeded) {
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byte = buffer[i + k + 1]
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codePoint = (codePoint << 6) | (byte & 0x3f)
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k += 1
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}
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} else {
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codePoint = 0xfffd
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bytesNeeded = len - i
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}
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output += String.fromCodePoint(codePoint)
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i += bytesNeeded + 1
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}
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return output
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}
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}
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let write
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if (typeof TextEncoder !== 'undefined') {
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const encoder = new TextEncoder()
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write = function write (buffer, string, offset = 0, length = byteLength(string)) {
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const len = Math.min(length, buffer.byteLength - offset)
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encoder.encodeInto(string, buffer.subarray(offset, offset + len))
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return len
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}
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} else {
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write = function write (buffer, string, offset = 0, length = byteLength(string)) {
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const len = Math.min(length, buffer.byteLength - offset)
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buffer = buffer.subarray(offset, offset + len)
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let i = 0
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let j = 0
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while (i < string.length) {
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const code = string.codePointAt(i)
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if (code <= 0x7f) {
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buffer[j++] = code
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i++
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continue
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}
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let count = 0
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let bits = 0
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if (code <= 0x7ff) {
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count = 6
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bits = 0xc0
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} else if (code <= 0xffff) {
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count = 12
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bits = 0xe0
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} else if (code <= 0x1fffff) {
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count = 18
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bits = 0xf0
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}
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buffer[j++] = bits | (code >> count)
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count -= 6
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while (count >= 0) {
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buffer[j++] = 0x80 | ((code >> count) & 0x3f)
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count -= 6
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}
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i += code >= 0x10000 ? 2 : 1
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}
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return len
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}
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}
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module.exports = {
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byteLength,
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toString,
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write
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}
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