33 lines
994 B
TypeScript
33 lines
994 B
TypeScript
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const Base64 = ")!@#$%^&*(ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_";
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export function decodeBits(width: number, data: string): Array<number> {
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const maxValue = (1 << width) - 1;
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const result: Array<number> = [ ];
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let accum = 0, bits = 0, flood = 0;
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for (let i = 0; i < data.length; i++) {
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// Accumulate 6 bits of data
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accum = ((accum << 6) | Base64.indexOf(data[i]));
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bits += 6;
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// While we have enough for a word...
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while (bits >= width) {
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// ...read the word
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const value = (accum >> (bits - width));
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accum &= (1 << (bits - width)) - 1;
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bits -= width;
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// A value of 0 indicates we exceeded maxValue, it
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// floods over into the next value
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if (value === 0) {
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flood += maxValue;
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} else {
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result.push(value + flood);
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flood = 0;
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}
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}
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}
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return result;
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}
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