expo-image
Version:
A cross-platform, performant image component for React Native and Expo with Web support
105 lines (102 loc) • 1.1 kB
text/typescript
const digitCharacters = [
'0',
'1',
'2',
'3',
'4',
'5',
'6',
'7',
'8',
'9',
'A',
'B',
'C',
'D',
'E',
'F',
'G',
'H',
'I',
'J',
'K',
'L',
'M',
'N',
'O',
'P',
'Q',
'R',
'S',
'T',
'U',
'V',
'W',
'X',
'Y',
'Z',
'a',
'b',
'c',
'd',
'e',
'f',
'g',
'h',
'i',
'j',
'k',
'l',
'm',
'n',
'o',
'p',
'q',
'r',
's',
't',
'u',
'v',
'w',
'x',
'y',
'z',
'#',
'$',
'%',
'*',
'+',
',',
'-',
'.',
':',
';',
'=',
'?',
'@',
'[',
']',
'^',
'_',
'{',
'|',
'}',
'~',
];
export const decode83 = (str: string) => {
let value = 0;
for (let i = 0; i < str.length; i++) {
const c = str[i];
const digit = digitCharacters.indexOf(c);
value = value * 83 + digit;
}
return value;
};
export const encode83 = (n: number, length: number): string => {
let result = '';
for (let i = 1; i <= length; i++) {
const digit = (Math.floor(n) / Math.pow(83, length - i)) % 83;
result += digitCharacters[Math.floor(digit)];
}
return result;
};