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25 lines
675 B
JavaScript
25 lines
675 B
JavaScript
2 years ago
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/**
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* evaluate the difficulty of hex32 according to nip-13.
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* @param hex32 a string of 64 chars - 32 bytes in hex representation
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*/
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export const zeroLeadingBitsCount = (hex32) => {
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let count = 0;
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for (let i = 0; i < 64; i += 2) {
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const hexbyte = hex32.slice(i, i + 2); // grab next byte
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if (hexbyte == '00') {
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count += 8;
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continue;
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}
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// reached non-zero byte; count number of 0 bits in hexbyte
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const bits = parseInt(hexbyte, 16).toString(2).padStart(8, '0');
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for (let b = 0; b < 8; b++) {
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if (bits[b] == '1' ) {
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break; // reached non-zero bit; stop
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}
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count += 1;
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}
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break;
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}
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return count;
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};
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