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TypeScript class for Base64 encoding/decoding
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class Base64 { | |
private PADCHAR: string = '='; | |
private ALPHA: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'; | |
private getByte(s: string, i: number): number { | |
const x = s.charCodeAt(i); | |
return x; | |
} | |
private getByte64(s: string, i: number): number { | |
const idx = this.ALPHA.indexOf(s.charAt(i)); | |
return idx; | |
} | |
public decode (s: string): string { | |
let pads = 0, | |
i, b10, imax = s.length, | |
x = []; | |
s = String(s); | |
if (imax === 0) { | |
return s; | |
} | |
if (s.charAt(imax - 1) === this.PADCHAR) { | |
pads = 1; | |
if (s.charAt(imax - 2) === this.PADCHAR) { | |
pads = 2; | |
} | |
imax -= 4; | |
} | |
for (i = 0; i < imax; i += 4) { | |
b10 = (this.getByte64(s, i) << 18) | (this.getByte64(s, i + 1) << 12) | (this.getByte64(s, i + 2) << 6) | this.getByte64(s, i + 3); | |
x.push(String.fromCharCode(b10 >> 16, (b10 >> 8) & 255, b10 & 255)); | |
} | |
switch (pads) { | |
case 1: | |
b10 = (this.getByte64(s, i) << 18) | (this.getByte64(s, i + 1) << 12) | (this.getByte64(s, i + 2) << 6); | |
x.push(String.fromCharCode(b10 >> 16, (b10 >> 8) & 255)); | |
break; | |
case 2: | |
b10 = (this.getByte64(s, i) << 18) | (this.getByte64(s, i + 1) << 12); | |
x.push(String.fromCharCode(b10 >> 16)); | |
break; | |
} | |
return x.join(''); | |
} | |
public encode(s: string): string { | |
s = String(s); | |
let i, b10, x = [], | |
imax = s.length - s.length % 3; | |
if (s.length === 0) { | |
return s; | |
} | |
for (i = 0; i < imax; i += 3) { | |
b10 = (this.getByte(s, i) << 16) | (this.getByte(s, i + 1) << 8) | this.getByte(s, i + 2); | |
x.push(this.ALPHA.charAt(b10 >> 18)); | |
x.push(this.ALPHA.charAt((b10 >> 12) & 63)); | |
x.push(this.ALPHA.charAt((b10 >> 6) & 63)); | |
x.push(this.ALPHA.charAt(b10 & 63)); | |
} | |
switch (s.length - imax) { | |
case 1: | |
b10 = this.getByte(s, i) << 16; | |
x.push(this.ALPHA.charAt(b10 >> 18) + this.ALPHA.charAt((b10 >> 12) & 63) + this.PADCHAR + this.PADCHAR); | |
break; | |
case 2: | |
b10 = (this.getByte(s, i) << 16) | (this.getByte(s, i + 1) << 8); | |
x.push(this.ALPHA.charAt(b10 >> 18) + this.ALPHA.charAt((b10 >> 12) & 63) + this.ALPHA.charAt((b10 >> 6) & 63) + this.PADCHAR); | |
break; | |
} | |
return x.join(''); | |
} | |
} |
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