check first 8 bytes for CFB in readSync (#2038)

fix range for base64

Author: barronwei

bits/87_read.js

@@ -1,13 +1,13 @@
 function firstbyte(f/*:RawData*/,o/*:?TypeOpts*/)/*:Array<number>*/ {
 	var x = "";
 	switch((o||{}).type || "base64") {
-		case 'buffer': return [f[0], f[1], f[2], f[3]];
-		case 'base64': x = Base64.decode(f.slice(0,24)); break;
+		case 'buffer': return [f[0], f[1], f[2], f[3], f[4], f[5], f[6], f[7]];
+		case 'base64': x = Base64.decode(f.slice(0,12)); break;
 		case 'binary': x = f; break;
-		case 'array':  return [f[0], f[1], f[2], f[3]];
+		case 'array':  return [f[0], f[1], f[2], f[3], f[4], f[5], f[6], f[7]];
 		default: throw new Error("Unrecognized type " + (o && o.type || "undefined"));
 	}
-	return [x.charCodeAt(0), x.charCodeAt(1), x.charCodeAt(2), x.charCodeAt(3)];
+	return [x.charCodeAt(0), x.charCodeAt(1), x.charCodeAt(2), x.charCodeAt(3), x.charCodeAt(4), x.charCodeAt(5), x.charCodeAt(6), x.charCodeAt(7)];
 }
 
 function read_cfb(cfb/*:CFBContainer*/, opts/*:?ParseOpts*/)/*:Workbook*/ {
@@ -82,7 +82,7 @@ function readSync(data/*:RawData*/, opts/*:?ParseOpts*/)/*:Workbook*/ {
 		if(!vu.foo) {o=dup(o); o.type='array'; return readSync(ab2a(d), o);}
 	}
 	switch((n = firstbyte(d, o))[0]) {
-		case 0xD0: return read_cfb(CFB.read(d, o), o);
+		case 0xD0: if(n[1] === 0xCF && n[2] === 0x11 && n[3] === 0xE0 && n[4] === 0xA1 && n[5] === 0xB1 && n[6] === 0x1A && n[7] === 0xE1) return read_cfb(CFB.read(d, o), o); break;
 		case 0x09: if(n[1] <= 0x04) return parse_xlscfb(d, o); break;
 		case 0x3C: return parse_xlml(d, o);
 		case 0x49: if(n[1] === 0x44) return read_wb_ID(d, o); break;