53 lines
1.3 KiB
JavaScript
53 lines
1.3 KiB
JavaScript
// Encoding to encode/decode data with Hamming Error Correction
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export const DECODED_SIZE = 4;
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export const ENCODED_SIZE = 7;
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export const blockSize = () => ({
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encoded: ENCODED_SIZE,
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decoded: DECODED_SIZE
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});
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export const encode = (bits) => {
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const encodedBits = [];
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for(let i = 0; i < bits.length; i+= DECODED_SIZE) {
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const block = bits.slice(i, i + DECODED_SIZE);
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encodedBits.push(...encodeBlock(block));
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}
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return encodedBits;
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}
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export const decode = bits => {
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const decodedBits = [];
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for(let i = 0; i < bits.length; i += ENCODED_SIZE) {
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const block = bits.slice(i, i + ENCODED_SIZE);
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decodedBits.push(...decodeBlock(block));
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}
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return decodedBits;
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}
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const encodeBlock = bits => {
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if(bits.length !== DECODED_SIZE) return [];
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return [
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bits[0] ^ bits[1] ^ bits[3],
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bits[0] ^ bits[2] ^ bits[3],
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bits[0],
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bits[1] ^ bits[2] ^ bits[3],
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bits[1],
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bits[2],
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bits[3]
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]
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}
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const decodeBlock = bits => {
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if(bits.length !== ENCODED_SIZE) return [];
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const error_1 = bits[0] ^ bits[2] ^ bits[4] ^ bits[6];
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const error_2 = bits[1] ^ bits[2] ^ bits[5] ^ bits[6];
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const error_3 = bits[3] ^ bits[4] ^ bits[5] ^ bits[6];
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let error = (error_3 << 2) | (error_2 << 1) | error_1;
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if(error !== 0) bits[error - 1] ^= 1;
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return [
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bits[2],
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bits[4],
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bits[5],
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bits[6]
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];
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} |