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"use strict"
var Buffer = require("safer-buffer").Buffer
// Note: UTF16-LE (or UCS2) codec is Node.js native. See encodings/internal.js
// == UTF16-BE codec. ==========================================================
exports.utf16be = Utf16BECodec
function Utf16BECodec () {
}
Utf16BECodec.prototype.encoder = Utf16BEEncoder
Utf16BECodec.prototype.decoder = Utf16BEDecoder
Utf16BECodec.prototype.bomAware = true
// -- Encoding
function Utf16BEEncoder () {
}
Utf16BEEncoder.prototype.write = function (str) {
var buf = Buffer.from(str, "ucs2")
for (var i = 0; i < buf.length; i += 2) {
var tmp = buf[i]; buf[i] = buf[i + 1]; buf[i + 1] = tmp
}
return buf
}
Utf16BEEncoder.prototype.end = function () {
}
// -- Decoding
function Utf16BEDecoder () {
this.overflowByte = -1
}
Utf16BEDecoder.prototype.write = function (buf) {
if (buf.length == 0) { return "" }
var buf2 = Buffer.alloc(buf.length + 1)
var i = 0; var j = 0
if (this.overflowByte !== -1) {
buf2[0] = buf[0]
buf2[1] = this.overflowByte
i = 1; j = 2
}
for (; i < buf.length - 1; i += 2, j += 2) {
buf2[j] = buf[i + 1]
buf2[j + 1] = buf[i]
}
this.overflowByte = (i == buf.length - 1) ? buf[buf.length - 1] : -1
return buf2.slice(0, j).toString("ucs2")
}
Utf16BEDecoder.prototype.end = function () {
this.overflowByte = -1
}
// == UTF-16 codec =============================================================
// Decoder chooses automatically from UTF-16LE and UTF-16BE using BOM and space-based heuristic.
// Defaults to UTF-16LE, as it's prevalent and default in Node.
// http://en.wikipedia.org/wiki/UTF-16 and http://encoding.spec.whatwg.org/#utf-16le
// Decoder default can be changed: iconv.decode(buf, 'utf16', {defaultEncoding: 'utf-16be'});
// Encoder uses UTF-16LE and prepends BOM (which can be overridden with addBOM: false).
exports.utf16 = Utf16Codec
function Utf16Codec (codecOptions, iconv) {
this.iconv = iconv
}
Utf16Codec.prototype.encoder = Utf16Encoder
Utf16Codec.prototype.decoder = Utf16Decoder
// -- Encoding (pass-through)
function Utf16Encoder (options, codec) {
options = options || {}
if (options.addBOM === undefined) { options.addBOM = true }
this.encoder = codec.iconv.getEncoder("utf-16le", options)
}
Utf16Encoder.prototype.write = function (str) {
return this.encoder.write(str)
}
Utf16Encoder.prototype.end = function () {
return this.encoder.end()
}
// -- Decoding
function Utf16Decoder (options, codec) {
this.decoder = null
this.initialBufs = []
this.initialBufsLen = 0
this.options = options || {}
this.iconv = codec.iconv
}
Utf16Decoder.prototype.write = function (buf) {
if (!this.decoder) {
// Codec is not chosen yet. Accumulate initial bytes.
this.initialBufs.push(buf)
this.initialBufsLen += buf.length
if (this.initialBufsLen < 16) // We need more bytes to use space heuristic (see below)
{ return "" }
// We have enough bytes -> detect endianness.
var encoding = detectEncoding(this.initialBufs, this.options.defaultEncoding)
this.decoder = this.iconv.getDecoder(encoding, this.options)
var resStr = ""
for (var i = 0; i < this.initialBufs.length; i++) { resStr += this.decoder.write(this.initialBufs[i]) }
this.initialBufs.length = this.initialBufsLen = 0
return resStr
}
return this.decoder.write(buf)
}
Utf16Decoder.prototype.end = function () {
if (!this.decoder) {
var encoding = detectEncoding(this.initialBufs, this.options.defaultEncoding)
this.decoder = this.iconv.getDecoder(encoding, this.options)
var resStr = ""
for (var i = 0; i < this.initialBufs.length; i++) { resStr += this.decoder.write(this.initialBufs[i]) }
var trail = this.decoder.end()
if (trail) { resStr += trail }
this.initialBufs.length = this.initialBufsLen = 0
return resStr
}
return this.decoder.end()
}
function detectEncoding (bufs, defaultEncoding) {
var b = []
var charsProcessed = 0
// Number of ASCII chars when decoded as LE or BE.
var asciiCharsLE = 0
var asciiCharsBE = 0
outerLoop:
for (var i = 0; i < bufs.length; i++) {
var buf = bufs[i]
for (var j = 0; j < buf.length; j++) {
b.push(buf[j])
if (b.length === 2) {
if (charsProcessed === 0) {
// Check BOM first.
if (b[0] === 0xFF && b[1] === 0xFE) return "utf-16le"
if (b[0] === 0xFE && b[1] === 0xFF) return "utf-16be"
}
if (b[0] === 0 && b[1] !== 0) asciiCharsBE++
if (b[0] !== 0 && b[1] === 0) asciiCharsLE++
b.length = 0
charsProcessed++
if (charsProcessed >= 100) {
break outerLoop
}
}
}
}
// Make decisions.
// Most of the time, the content has ASCII chars (U+00**), but the opposite (U+**00) is uncommon.
// So, we count ASCII as if it was LE or BE, and decide from that.
if (asciiCharsBE > asciiCharsLE) return "utf-16be"
if (asciiCharsBE < asciiCharsLE) return "utf-16le"
// Couldn't decide (likely all zeros or not enough data).
return defaultEncoding || "utf-16le"
}
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