Skip to content

Instantly share code, notes, and snippets.

@mollyporph

mollyporph/base62.ts

Created July 13, 2018 12:25
Show Gist options
  • Save mollyporph/205e970000cc9f223784e3f7f2c812b9 to your computer and use it in GitHub Desktop.
Save mollyporph/205e970000cc9f223784e3f7f2c812b9 to your computer and use it in GitHub Desktop.
Download ZIP
Base62.ts
Raw
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;
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment