optimize

README.md

@@ -12,35 +12,35 @@ go get github.com/bddjr/cryptorandstr
 
 ```
 MustRand10 6
-  961812
-  186418
-  476781
-  683053
-  189178
+  227679
+  901676
+  193607
+  026687
+  243505
 
 MustRand16 27
-  d4ff1e125208f0e2954001b3c6e
-  36c517865848a7444454a7711ca
-  f5348bba35053bfeb962d3822b9
-  df46ffa337732945d6c98ed0276
-  280a987f779f9775d8decffb150
+  017ced60ee75751a027605270fe
+  2d89aa349e78988585524c5d074
+  d155483394a0c8f75becd533faf
+  7714135085cb7967f6ee645edb5
+  0d0e22c51fe5cad882d6a0867d7
 
 MustRand32 27
-  fjq0iakoubcl2sp92ekaq9ftsan
-  mgu2bms5d90ai35mtjdrru3rkfe
-  pt6k8rmsneovn3bq3q1ru2m26bk
-  91rn0793voe4tupdcm2b31rfdd1
-  ank42vo7ju49t0irpmmn65osj5p
+  5e9hoqmhspbsnng2ct2hgosko4e
+  e9f5e7i5i24d9tlf1tef8fgcsba
+  0dhkjpef6nqj1bnm81rhnjgjqjj
+  kj968dr8sc9srpk9roj3go45k8r
+  tvkb7pl542c3v5e3opqg5jcejhm
 
 MustRand64 27
-  bMPa2jTkoJF4NzWgv4wr6Qmc-OK
-  _oWdmJSErNbW1rval-gM7ult-6_
-  KhMddFuOkKCf9eHXx3s11H4AZmE
-  oCvBxMPnZwLV_Bi540RnH8_Nmk6
-  st-G5VLmETyHV8WLhAOEaIWfuEn
+  xA-ZoFjHgQ927Jxnhly7WWRMvjw
+  NIBvnag5JrYhvHZ-NaKEZkmBgco
+  YD3qxeMe7AGlXllP0M07GkTXnMA
+  fC7_-XWOEf-BPv-U5_bRXrkEDqi
+  b1t6xZLgmW2v9KdxGEKqVIp-WAH
 
 PASS
-ok      github.com/bddjr/cryptorandstr  0.253s
+ok      github.com/bddjr/cryptorandstr  0.034s
 ```
 
 ## License

rand.go

@@ -72,11 +72,12 @@ func Rand(strLen int, chars string) (string, error) {
 	r := randWithGC{
 		outBitLen: bitLen(maxB),
 	}
+	difference := 8 - r.outBitLen
 
 	out := make([]byte, strLen)
 	i := 0
 	for i < strLen {
-		b, err := r.byte(chunk)
+		b, err := r.byte(chunk, difference)
 		if err != nil {
 			return "", err
 		}
@@ -103,10 +104,7 @@ type randWithGC struct {
 	cache       uint16
 }
 
-// len(chunk) == 1
-func (r *randWithGC) byte(chunk []byte) (byte, error) {
-	difference := 8 - r.outBitLen
-
+func (r *randWithGC) byte(chunk []byte, difference byte) (byte, error) {
 	// read cache
 	if r.cacheBitLen >= r.outBitLen {
 		b := (byte(r.cache) << difference) >> difference
@@ -126,12 +124,10 @@ func (r *randWithGC) byte(chunk []byte) (byte, error) {
 		}
 	}
 
-	b := chunk[0]
-
 	// write cache
 	r.cache <<= difference
-	r.cache |= uint16(b >> r.outBitLen)
+	r.cache |= uint16(chunk[0] >> r.outBitLen)
 	r.cacheBitLen += difference
 
-	return (b << difference) >> difference, nil
+	return (chunk[0] << difference) >> difference, nil
 }