132 lines
3.9 KiB
TypeScript
132 lines
3.9 KiB
TypeScript
/**
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* Compute SHA-256 checksum of a File.
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*
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* Uses the Web Crypto API when available (HTTPS / localhost).
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* Falls back to a pure-JS implementation for plain HTTP deployments
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* where crypto.subtle is unavailable.
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*
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* @returns lowercase hex-encoded SHA-256 digest
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*/
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export async function computeFileHash(file: File): Promise<string> {
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const buffer = await file.arrayBuffer();
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if (globalThis.crypto?.subtle) {
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const digest = await crypto.subtle.digest('SHA-256', buffer);
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return hexEncode(new Uint8Array(digest));
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}
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return sha256Fallback(new Uint8Array(buffer));
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}
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function hexEncode(bytes: Uint8Array): string {
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const hex: string[] = new Array(bytes.length);
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for (let i = 0; i < bytes.length; i++) {
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hex[i] = bytes[i].toString(16).padStart(2, '0');
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}
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return hex.join('');
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}
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// ── Pure-JS SHA-256 (RFC 6234) ──────────────────────────────────────────────
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// Used only when crypto.subtle is unavailable (HTTP deployments).
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const K: Uint32Array = new Uint32Array([
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0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
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0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
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0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
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0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
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0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
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0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
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0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
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0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
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]);
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function rotr(n: number, x: number): number {
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return (x >>> n) | (x << (32 - n));
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}
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function sha256Fallback(data: Uint8Array): string {
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// Pre-processing: padding
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const bitLen = data.length * 8;
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const padLen = (((data.length + 8) >>> 6) + 1) << 6;
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const padded = new Uint8Array(padLen);
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padded.set(data);
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padded[data.length] = 0x80;
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// Append original length in bits as 64-bit big-endian
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const view = new DataView(padded.buffer);
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view.setUint32(padLen - 4, bitLen, false);
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// Initial hash values
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let h0 = 0x6a09e667;
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let h1 = 0xbb67ae85;
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let h2 = 0x3c6ef372;
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let h3 = 0xa54ff53a;
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let h4 = 0x510e527f;
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let h5 = 0x9b05688c;
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let h6 = 0x1f83d9ab;
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let h7 = 0x5be0cd19;
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const w = new Uint32Array(64);
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for (let offset = 0; offset < padLen; offset += 64) {
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// Prepare message schedule
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for (let i = 0; i < 16; i++) {
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w[i] = view.getUint32(offset + i * 4, false);
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}
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for (let i = 16; i < 64; i++) {
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const s0 = rotr(7, w[i - 15]) ^ rotr(18, w[i - 15]) ^ (w[i - 15] >>> 3);
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const s1 = rotr(17, w[i - 2]) ^ rotr(19, w[i - 2]) ^ (w[i - 2] >>> 10);
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w[i] = (w[i - 16] + s0 + w[i - 7] + s1) | 0;
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}
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let a = h0,
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b = h1,
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c = h2,
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d = h3;
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let e = h4,
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f = h5,
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g = h6,
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h = h7;
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for (let i = 0; i < 64; i++) {
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const S1 = rotr(6, e) ^ rotr(11, e) ^ rotr(25, e);
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const ch = (e & f) ^ (~e & g);
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const temp1 = (h + S1 + ch + K[i] + w[i]) | 0;
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const S0 = rotr(2, a) ^ rotr(13, a) ^ rotr(22, a);
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const maj = (a & b) ^ (a & c) ^ (b & c);
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const temp2 = (S0 + maj) | 0;
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h = g;
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g = f;
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f = e;
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e = (d + temp1) | 0;
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d = c;
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c = b;
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b = a;
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a = (temp1 + temp2) | 0;
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}
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h0 = (h0 + a) | 0;
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h1 = (h1 + b) | 0;
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h2 = (h2 + c) | 0;
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h3 = (h3 + d) | 0;
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h4 = (h4 + e) | 0;
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h5 = (h5 + f) | 0;
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h6 = (h6 + g) | 0;
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h7 = (h7 + h) | 0;
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}
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const result = new Uint8Array(32);
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const out = new DataView(result.buffer);
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out.setUint32(0, h0, false);
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out.setUint32(4, h1, false);
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out.setUint32(8, h2, false);
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out.setUint32(12, h3, false);
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out.setUint32(16, h4, false);
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out.setUint32(20, h5, false);
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out.setUint32(24, h6, false);
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out.setUint32(28, h7, false);
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return hexEncode(result);
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}
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