twitst4tz

twitter statistics web application
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sbcs-codec.js (2191B)

      1 "use strict";
      2 var Buffer = require("safer-buffer").Buffer;
      3 
      4 // Single-byte codec. Needs a 'chars' string parameter that contains 256 or 128 chars that
      5 // correspond to encoded bytes (if 128 - then lower half is ASCII). 
      6 
      7 exports._sbcs = SBCSCodec;
      8 function SBCSCodec(codecOptions, iconv) {
      9     if (!codecOptions)
     10         throw new Error("SBCS codec is called without the data.")
     11     
     12     // Prepare char buffer for decoding.
     13     if (!codecOptions.chars || (codecOptions.chars.length !== 128 && codecOptions.chars.length !== 256))
     14         throw new Error("Encoding '"+codecOptions.type+"' has incorrect 'chars' (must be of len 128 or 256)");
     15     
     16     if (codecOptions.chars.length === 128) {
     17         var asciiString = "";
     18         for (var i = 0; i < 128; i++)
     19             asciiString += String.fromCharCode(i);
     20         codecOptions.chars = asciiString + codecOptions.chars;
     21     }
     22 
     23     this.decodeBuf = Buffer.from(codecOptions.chars, 'ucs2');
     24     
     25     // Encoding buffer.
     26     var encodeBuf = Buffer.alloc(65536, iconv.defaultCharSingleByte.charCodeAt(0));
     27 
     28     for (var i = 0; i < codecOptions.chars.length; i++)
     29         encodeBuf[codecOptions.chars.charCodeAt(i)] = i;
     30 
     31     this.encodeBuf = encodeBuf;
     32 }
     33 
     34 SBCSCodec.prototype.encoder = SBCSEncoder;
     35 SBCSCodec.prototype.decoder = SBCSDecoder;
     36 
     37 
     38 function SBCSEncoder(options, codec) {
     39     this.encodeBuf = codec.encodeBuf;
     40 }
     41 
     42 SBCSEncoder.prototype.write = function(str) {
     43     var buf = Buffer.alloc(str.length);
     44     for (var i = 0; i < str.length; i++)
     45         buf[i] = this.encodeBuf[str.charCodeAt(i)];
     46     
     47     return buf;
     48 }
     49 
     50 SBCSEncoder.prototype.end = function() {
     51 }
     52 
     53 
     54 function SBCSDecoder(options, codec) {
     55     this.decodeBuf = codec.decodeBuf;
     56 }
     57 
     58 SBCSDecoder.prototype.write = function(buf) {
     59     // Strings are immutable in JS -> we use ucs2 buffer to speed up computations.
     60     var decodeBuf = this.decodeBuf;
     61     var newBuf = Buffer.alloc(buf.length*2);
     62     var idx1 = 0, idx2 = 0;
     63     for (var i = 0; i < buf.length; i++) {
     64         idx1 = buf[i]*2; idx2 = i*2;
     65         newBuf[idx2] = decodeBuf[idx1];
     66         newBuf[idx2+1] = decodeBuf[idx1+1];
     67     }
     68     return newBuf.toString('ucs2');
     69 }
     70 
     71 SBCSDecoder.prototype.end = function() {
     72 }