File size: 2,919 Bytes
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function byteLength (string) {
let length = 0
for (let i = 0, n = string.length; i < n; i++) {
const code = string.charCodeAt(i)
if (code >= 0xd800 && code <= 0xdbff && i + 1 < n) {
const code = string.charCodeAt(i + 1)
if (code >= 0xdc00 && code <= 0xdfff) {
length += 4
i++
continue
}
}
if (code <= 0x7f) length += 1
else if (code <= 0x7ff) length += 2
else length += 3
}
return length
}
let toString
if (typeof TextDecoder !== 'undefined') {
const decoder = new TextDecoder()
toString = function toString (buffer) {
return decoder.decode(buffer)
}
} else {
toString = function toString (buffer) {
const len = buffer.byteLength
let output = ''
let i = 0
while (i < len) {
let byte = buffer[i]
if (byte <= 0x7f) {
output += String.fromCharCode(byte)
i++
continue
}
let bytesNeeded = 0
let codePoint = 0
if (byte <= 0xdf) {
bytesNeeded = 1
codePoint = byte & 0x1f
} else if (byte <= 0xef) {
bytesNeeded = 2
codePoint = byte & 0x0f
} else if (byte <= 0xf4) {
bytesNeeded = 3
codePoint = byte & 0x07
}
if (len - i - bytesNeeded > 0) {
let k = 0
while (k < bytesNeeded) {
byte = buffer[i + k + 1]
codePoint = (codePoint << 6) | (byte & 0x3f)
k += 1
}
} else {
codePoint = 0xfffd
bytesNeeded = len - i
}
output += String.fromCodePoint(codePoint)
i += bytesNeeded + 1
}
return output
}
}
let write
if (typeof TextEncoder !== 'undefined') {
const encoder = new TextEncoder()
write = function write (buffer, string, offset = 0, length = byteLength(string)) {
const len = Math.min(length, buffer.byteLength - offset)
encoder.encodeInto(string, buffer.subarray(offset, offset + len))
return len
}
} else {
write = function write (buffer, string, offset = 0, length = byteLength(string)) {
const len = Math.min(length, buffer.byteLength - offset)
buffer = buffer.subarray(offset, offset + len)
let i = 0
let j = 0
while (i < string.length) {
const code = string.codePointAt(i)
if (code <= 0x7f) {
buffer[j++] = code
i++
continue
}
let count = 0
let bits = 0
if (code <= 0x7ff) {
count = 6
bits = 0xc0
} else if (code <= 0xffff) {
count = 12
bits = 0xe0
} else if (code <= 0x1fffff) {
count = 18
bits = 0xf0
}
buffer[j++] = bits | (code >> count)
count -= 6
while (count >= 0) {
buffer[j++] = 0x80 | ((code >> count) & 0x3f)
count -= 6
}
i += code >= 0x10000 ? 2 : 1
}
return len
}
}
module.exports = {
byteLength,
toString,
write
}
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