add some customized tempfile code

utils/tempfile/tempfile.go

@@ -0,0 +1,55 @@
+package tempfile
+
+import (
+	"os"
+	"strconv"
+	"sync"
+	"time"
+)
+
+type Creator struct {
+	mu   sync.Mutex
+	idum uint32 // Psuedo-random number generator state.
+}
+
+// NewCreator returns a new Creator, for creating temp files.
+func NewCreator() *Creator {
+	return &Creator{idum: uint32(time.Now().UnixNano())}
+}
+
+// Fast "quick and dirty" linear congruential (pseudo-random) number
+// generator from Numerical Recipes. Excerpt here:
+// https://www.unf.edu/~cwinton/html/cop4300/s09/class.notes/LCGinfo.pdf
+// This is the same algorithm as used in the ioutil.TempFile go standard
+// library function.
+func (c *Creator) ranqd1() string {
+	c.mu.Lock()
+	c.idum = c.idum*1664525 + 1013904223
+	r := c.idum
+	c.mu.Unlock()
+	return strconv.Itoa(int(1e9 + r%1e9))[1:]
+}
+
+const flags = os.O_RDWR | os.O_CREATE | os.O_EXCL
+const mode = 0666 // Before the umask is applied.
+
+// Create attempts to create a temp file for eventualFile, and returns
+// the corresponding *os.File and an error if any occurred. The temp
+// file is created in the same directory as eventualFile, with permissions
+// 0666 before the umask is applied.
+func (c *Creator) Create(eventualFile string) (*os.File, error) {
+	var err error
+	var f *os.File
+
+	base := eventualFile + ".tmp"
+
+	for i := 0; i < 10000; i++ {
+		name := base + c.ranqd1()
+		f, err = os.OpenFile(name, flags, mode)
+		if os.IsExist(err) {
+			continue
+		}
+		return f, err
+	}
+	return nil, err
+}