V1_commit_RGC

SuiviREForamteur/node_modules/fast-png/lib/helpers/crc.js

@@ -0,0 +1,39 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.checkCrc = checkCrc;
+exports.writeCrc = writeCrc;
+const crcTable = [];
+for (let n = 0; n < 256; n++) {
+    let c = n;
+    for (let k = 0; k < 8; k++) {
+        if (c & 1) {
+            c = 0xedb88320 ^ (c >>> 1);
+        }
+        else {
+            c = c >>> 1;
+        }
+    }
+    crcTable[n] = c;
+}
+const initialCrc = 0xffffffff;
+function updateCrc(currentCrc, data, length) {
+    let c = currentCrc;
+    for (let n = 0; n < length; n++) {
+        c = crcTable[(c ^ data[n]) & 0xff] ^ (c >>> 8);
+    }
+    return c;
+}
+function crc(data, length) {
+    return (updateCrc(initialCrc, data, length) ^ initialCrc) >>> 0;
+}
+function checkCrc(buffer, crcLength, chunkName) {
+    const expectedCrc = buffer.readUint32();
+    const actualCrc = crc(new Uint8Array(buffer.buffer, buffer.byteOffset + buffer.offset - crcLength - 4, crcLength), crcLength); // "- 4" because we already advanced by reading the CRC
+    if (actualCrc !== expectedCrc) {
+        throw new Error(`CRC mismatch for chunk ${chunkName}. Expected ${expectedCrc}, found ${actualCrc}`);
+    }
+}
+function writeCrc(buffer, length) {
+    buffer.writeUint32(crc(new Uint8Array(buffer.buffer, buffer.byteOffset + buffer.offset - length, length), length));
+}
+//# sourceMappingURL=crc.js.map