Base62.ts

base62.ts

import BitStream from './bit-stream'

const Base62CharSet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

function encodeBase62ByteArrayToString(original: Array<number>) {
  var sb = []; 
  var stream = new BitStream(original); 
  var read = [];
  read.push(0);

  while (true) {
    read[0] = 0;

    var length = stream.Read(read, 0, 6);
    if (length == 6) 
    {
      if ((read[0] >> 3) == 0x1f) 
      {
        sb.push(Base62CharSet.charAt(61));
        stream.Seek(-1, 2); 
      } else if ((read[0] >> 3) == 0x1e) 
      {
        sb.push(Base62CharSet.charAt(60));
        stream.Seek(-1, 2);
      } else 
      {
        sb.push(Base62CharSet.charAt((read[0] >> 2)));
      }
    } else if (length == 0) {
      break;
    } else {
      sb.push(Base62CharSet.charAt((read[0] >> (8 - length))));
      break;
    }
  }
  var str = sb.join('');
  return str;
};

function encodeBase62(str: string) {

  if (typeof str !== 'string' || str === '') {
    return '';
  }

  var bytes = [];
  var len = str.length;
  for (var i = 0; i < len; i++) {
    bytes.push(str.charCodeAt(i));
  }
  return encodeBase62ByteArrayToString(bytes);
};

export default encodeBase62

...

class BitStream {
  Source: any;
  Position: number;
  constructor(source: Array<number>) {
    this.Source = source
    this.Position = 0;
  }

  Length() {
    return this.Source.length * 8;
  };

  Read (buffer: Array<number>, offset: number, count: number) {
    var tempPos = this.Position;
    tempPos += offset;
    var readPosCount = 0;
    var readPosMod = 0;
    var posCount = tempPos >> 3;
    var posMod = (tempPos - ((tempPos >> 3) << 3));
    while (tempPos < this.Position + offset + count && tempPos < this.Length()) {

      if (((this.Source[posCount]) & (0x1 << (7 - posMod))) != 0) {
        buffer[readPosCount] = ((buffer[readPosCount]) | (0x1 << (7 - readPosMod)));
      } else {
        buffer[readPosCount] = ((buffer[readPosCount]) & (0xffffffff - (0x1 << (7 - readPosMod))));
      }
      tempPos++;
      if (posMod == 7) {
        posMod = 0;
        posCount++;
      } else {
        posMod++;
      }
      if (readPosMod == 7) {
        readPosMod = 0;
        readPosCount++;
      } else {
        readPosMod++;
      }
    }
    var bits = (tempPos - this.Position - offset);
    this.Position = tempPos;
    return bits;
  };

  Seek(offset: number, origin: number) {
    switch (origin) {
      case (1):
        {
          this.Position = offset;
          break;
        }
      case (2):
        {
          this.Position += offset;
          break;
        }
      case (3):
        {
          this.Position = this.Length() + offset;
          break;
        }
    }
    return this.Position;
  };

  Write(buffer: Array<number>, offset: number, count: number) {
    var tempPos = this.Position;
    var readPosCount = offset >> 3,
      readPosMod = offset - ((offset >> 3) << 3);
    var posCount = tempPos >> 3;
    var posMod = (tempPos - ((tempPos >> 3) << 3));
    while (tempPos < this.Position + count && tempPos < this.Length()) {
      if (((buffer[readPosCount]) & (0x1 << (7 - readPosMod))) != 0) {
        this.Source[posCount] = ((this.Source[posCount]) | (0x1 << (7 - posMod)));
      } else {
        this.Source[posCount] = ((this.Source[posCount]) & (0xffffffff - (0x1 << (7 - posMod))));
      }

      tempPos++;
      if (posMod == 7) {
        posMod = 0;
        posCount++;
      } else {
        posMod++;
      }
      if (readPosMod == 7) {
        readPosMod = 0;
        readPosCount++;
      } else {
        readPosMod++;
      }
    }
    this.Position = tempPos;
  };
};
export default BitStream;