sbcs-codec.js•2.11 kB
"use strict"
var Buffer = require("safer-buffer").Buffer
// Single-byte codec. Needs a 'chars' string parameter that contains 256 or 128 chars that
// correspond to encoded bytes (if 128 - then lower half is ASCII).
exports._sbcs = SBCSCodec
function SBCSCodec (codecOptions, iconv) {
if (!codecOptions) {
throw new Error("SBCS codec is called without the data.")
}
// Prepare char buffer for decoding.
if (!codecOptions.chars || (codecOptions.chars.length !== 128 && codecOptions.chars.length !== 256)) {
throw new Error("Encoding '" + codecOptions.type + "' has incorrect 'chars' (must be of len 128 or 256)")
}
if (codecOptions.chars.length === 128) {
var asciiString = ""
for (var i = 0; i < 128; i++) {
asciiString += String.fromCharCode(i)
}
codecOptions.chars = asciiString + codecOptions.chars
}
this.decodeBuf = Buffer.from(codecOptions.chars, "ucs2")
// Encoding buffer.
var encodeBuf = Buffer.alloc(65536, iconv.defaultCharSingleByte.charCodeAt(0))
for (var i = 0; i < codecOptions.chars.length; i++) {
encodeBuf[codecOptions.chars.charCodeAt(i)] = i
}
this.encodeBuf = encodeBuf
}
SBCSCodec.prototype.encoder = SBCSEncoder
SBCSCodec.prototype.decoder = SBCSDecoder
function SBCSEncoder (options, codec) {
this.encodeBuf = codec.encodeBuf
}
SBCSEncoder.prototype.write = function (str) {
var buf = Buffer.alloc(str.length)
for (var i = 0; i < str.length; i++) {
buf[i] = this.encodeBuf[str.charCodeAt(i)]
}
return buf
}
SBCSEncoder.prototype.end = function () {
}
function SBCSDecoder (options, codec) {
this.decodeBuf = codec.decodeBuf
}
SBCSDecoder.prototype.write = function (buf) {
// Strings are immutable in JS -> we use ucs2 buffer to speed up computations.
var decodeBuf = this.decodeBuf
var newBuf = Buffer.alloc(buf.length * 2)
var idx1 = 0; var idx2 = 0
for (var i = 0; i < buf.length; i++) {
idx1 = buf[i] * 2; idx2 = i * 2
newBuf[idx2] = decodeBuf[idx1]
newBuf[idx2 + 1] = decodeBuf[idx1 + 1]
}
return newBuf.toString("ucs2")
}
SBCSDecoder.prototype.end = function () {
}