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Copy pathstring_decoder.js
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236 lines (218 loc) · 6.2 KB
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'use strict';
const Buffer = require('buffer').Buffer;
// Do not cache `Buffer.isEncoding` when checking encoding names as some
// modules monkey-patch it to support additional encodings
function normalizeEncoding(enc) {
if (!enc) return 'utf8';
var low;
for (;;) {
switch (enc) {
case 'utf8':
case 'utf-8':
return 'utf8';
case 'ucs2':
case 'utf16le':
case 'ucs-2':
case 'utf-16le':
return 'utf16le';
case 'base64':
case 'ascii':
case 'latin1':
case 'binary':
case 'hex':
return enc;
default:
if (low) {
if (!Buffer.isEncoding(enc))
throw new Error('Unknown encoding: ' + enc);
return enc;
}
low = true;
enc = ('' + enc).toLowerCase();
}
}
}
// StringDecoder provides an interface for efficiently splitting a series of
// buffers into a series of JS strings without breaking apart multi-byte
// characters.
exports.StringDecoder = StringDecoder;
function StringDecoder(encoding) {
this.encoding = normalizeEncoding(encoding);
var nb;
switch (this.encoding) {
case 'utf16le':
this.text = utf16Text;
this.end = utf16End;
// fall through
case 'utf8':
nb = 4;
break;
case 'base64':
this.text = base64Text;
this.end = base64End;
nb = 3;
break;
default:
this.write = simpleWrite;
this.end = simpleEnd;
return;
}
this.lastNeed = 0;
this.lastTotal = 0;
this.lastChar = Buffer.allocUnsafe(nb);
}
StringDecoder.prototype.write = function(buf) {
if (buf.length === 0)
return '';
var r;
var i;
if (this.lastNeed) {
r = this.fillLast(buf);
if (r === undefined)
return '';
i = this.lastNeed;
this.lastNeed = 0;
} else {
i = 0;
}
if (i < buf.length)
return (r ? r + this.text(buf, i) : this.text(buf, i));
return r || '';
};
StringDecoder.prototype.end = utf8End;
// Returns only complete characters in a Buffer
StringDecoder.prototype.text = utf8Text;
// Attempts to complete a partial character using bytes from a Buffer
StringDecoder.prototype.fillLast = function(buf) {
if (this.lastNeed <= buf.length) {
buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, this.lastNeed);
return this.lastChar.toString(this.encoding, 0, this.lastTotal);
}
buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, buf.length);
this.lastNeed -= buf.length;
};
// Checks the type of a UTF-8 byte, whether it's ASCII, a leading byte, or a
// continuation byte.
function utf8CheckByte(byte) {
if (byte <= 0x7F)
return 0;
else if (byte >> 5 === 0x06)
return 2;
else if (byte >> 4 === 0x0E)
return 3;
else if (byte >> 3 === 0x1E)
return 4;
return -1;
}
// Checks at most the last 3 bytes of a Buffer for an incomplete UTF-8
// character, returning the total number of bytes needed to complete the partial
// character (if applicable).
function utf8CheckIncomplete(self, buf, i) {
var j = buf.length - 1;
if (j < i)
return 0;
var nb = utf8CheckByte(buf[j--]);
if (nb >= 0) {
if (nb > 0)
self.lastNeed = nb + 1 - (buf.length - j);
return nb;
}
if (j < i)
return 0;
nb = utf8CheckByte(buf[j--]);
if (nb >= 0) {
if (nb > 0)
self.lastNeed = nb + 1 - (buf.length - j);
return nb;
}
if (j < i)
return 0;
nb = utf8CheckByte(buf[j--]);
if (nb >= 0) {
if (nb > 0)
self.lastNeed = nb + 1 - (buf.length - j);
return nb;
}
return 0;
}
// Returns all complete UTF-8 characters in a Buffer. If the Buffer ended on a
// partial character, the character's bytes are buffered until the required
// number of bytes are available.
function utf8Text(buf, i) {
const total = utf8CheckIncomplete(this, buf, i);
if (!this.lastNeed)
return buf.toString('utf8', i);
this.lastTotal = total;
const end = buf.length - (total - this.lastNeed);
buf.copy(this.lastChar, 0, end);
return buf.toString('utf8', i, end);
}
// For UTF-8, a replacement character for each buffered byte of a (partial)
// character needs to be added to the output.
function utf8End(buf) {
const r = (buf && buf.length ? this.write(buf) : '');
if (this.lastNeed)
return r + '\ufffd'.repeat(this.lastTotal - this.lastNeed);
return r;
}
// UTF-16LE typically needs two bytes per character, but even if we have an even
// number of bytes available, we need to check if we end on a leading/high
// surrogate. In that case, we need to wait for the next two bytes in order to
// decode the last character properly.
function utf16Text(buf, i) {
if ((buf.length - i) % 2 === 0) {
const r = buf.toString('utf16le', i);
if (r) {
const c = r.charCodeAt(r.length - 1);
if (c >= 0xD800 && c <= 0xDBFF) {
this.lastNeed = 2;
this.lastTotal = 4;
this.lastChar[0] = buf[buf.length - 2];
this.lastChar[1] = buf[buf.length - 1];
return r.slice(0, -1);
}
}
return r;
}
this.lastNeed = 1;
this.lastTotal = 2;
this.lastChar[0] = buf[buf.length - 1];
return buf.toString('utf16le', i, buf.length - 1);
}
// For UTF-16LE we do not explicitly append special replacement characters if we
// end on a partial character, we simply let v8 handle that.
function utf16End(buf) {
const r = (buf && buf.length ? this.write(buf) : '');
if (this.lastNeed) {
const end = this.lastTotal - this.lastNeed;
return r + this.lastChar.toString('utf16le', 0, end);
}
return r;
}
function base64Text(buf, i) {
const n = (buf.length - i) % 3;
if (n === 0)
return buf.toString('base64', i);
this.lastNeed = 3 - n;
this.lastTotal = 3;
if (n === 1) {
this.lastChar[0] = buf[buf.length - 1];
} else {
this.lastChar[0] = buf[buf.length - 2];
this.lastChar[1] = buf[buf.length - 1];
}
return buf.toString('base64', i, buf.length - n);
}
function base64End(buf) {
const r = (buf && buf.length ? this.write(buf) : '');
if (this.lastNeed)
return r + this.lastChar.toString('base64', 0, 3 - this.lastNeed);
return r;
}
// Pass bytes on through for single-byte encodings (e.g. ascii, latin1, hex)
function simpleWrite(buf) {
return buf.toString(this.encoding);
}
function simpleEnd(buf) {
return (buf && buf.length ? this.write(buf) : '');
}