Create crc32.js

crc32.js

@@ -0,0 +1,41 @@
+/**
+ * 计算CRC32
+ * @param {ArrayBuffer} buffer - ArrayBuffer
+ */
+export default buffer => {
+  buffer = new Uint8Array(buffer)
+  const module = {
+    polynom: 0xEDB88320,
+    initValue: -1,
+    bytes: 4,
+    table: []
+  }
+  for (let a = 0; a < 256; ++a) {
+    let b = a
+    for (let c = 0; c < 8; ++c) {
+      b = b & 1 ? module.polynom ^ (b >>> 1) : b >>> 1
+    }
+    module.table[a] = b >>> 0
+  }
+  let crc = module.initValue
+  let length = buffer.length
+  let table = module.table
+  for (let a = 0; a < 256; ++a) {
+    let b = a
+    for (let c = 0; c < 8; ++c) {
+      b = b & 1 ? module.polynom ^ (b >>> 1) : b >>> 1
+    }
+    module.table[a] = b >>> 0
+  }
+  for (let i = 0; i < length; ++i) {
+    crc = table[(crc ^ buffer[i]) & 0xFF] ^ (crc >>> 8)
+  }
+  crc ^= module.initValue
+  let HEX_CHARS = '0123456789abcdef'.split('');
+  let hex = '';
+  if (module.bytes > 2) {
+    hex += HEX_CHARS[(crc >> 28) & 0x0F] + HEX_CHARS[(crc >> 24) & 0x0F] + HEX_CHARS[(crc >> 20) & 0x0F] + HEX_CHARS[(crc >> 16) & 0x0F]
+  }
+  hex += HEX_CHARS[(crc >> 12) & 0x0F] + HEX_CHARS[(crc >> 8) & 0x0F] + HEX_CHARS[(crc >> 4) & 0x0F] + HEX_CHARS[crc & 0x0F]
+  return hex
+}