1 files changed, 126 insertions, 0 deletions
diff --git a/vendor/github.com/docker/distribution/uuid/uuid.go b/vendor/github.com/docker/distribution/uuid/uuid.go
new file mode 100644
index 000000000..d433ccaf5
--- /dev/null
+++ b/vendor/github.com/docker/distribution/uuid/uuid.go
@@ -0,0 +1,126 @@
+// Package uuid provides simple UUID generation. Only version 4 style UUIDs
+// can be generated.
+//
+// Please see http://tools.ietf.org/html/rfc4122 for details on UUIDs.
+package uuid
+
+import (
+	"crypto/rand"
+	"fmt"
+	"io"
+	"os"
+	"syscall"
+	"time"
+)
+
+const (
+	// Bits is the number of bits in a UUID
+	Bits = 128
+
+	// Size is the number of bytes in a UUID
+	Size = Bits / 8
+
+	format = "%08x-%04x-%04x-%04x-%012x"
+)
+
+var (
+	// ErrUUIDInvalid indicates a parsed string is not a valid uuid.
+	ErrUUIDInvalid = fmt.Errorf("invalid uuid")
+
+	// Loggerf can be used to override the default logging destination. Such
+	// log messages in this library should be logged at warning or higher.
+	Loggerf = func(format string, args ...interface{}) {}
+)
+
+// UUID represents a UUID value. UUIDs can be compared and set to other values
+// and accessed by byte.
+type UUID [Size]byte
+
+// Generate creates a new, version 4 uuid.
+func Generate() (u UUID) {
+	const (
+		// ensures we backoff for less than 450ms total. Use the following to
+		// select new value, in units of 10ms:
+		// 	n*(n+1)/2 = d -> n^2 + n - 2d -> n = (sqrt(8d + 1) - 1)/2
+		maxretries = 9
+		backoff    = time.Millisecond * 10
+	)
+
+	var (
+		totalBackoff time.Duration
+		count        int
+		retries      int
+	)
+
+	for {
+		// This should never block but the read may fail. Because of this,
+		// we just try to read the random number generator until we get
+		// something. This is a very rare condition but may happen.
+		b := time.Duration(retries) * backoff
+		time.Sleep(b)
+		totalBackoff += b
+
+		n, err := io.ReadFull(rand.Reader, u[count:])
+		if err != nil {
+			if retryOnError(err) && retries < maxretries {
+				count += n
+				retries++
+				Loggerf("error generating version 4 uuid, retrying: %v", err)
+				continue
+			}
+
+			// Any other errors represent a system problem. What did someone
+			// do to /dev/urandom?
+			panic(fmt.Errorf("error reading random number generator, retried for %v: %v", totalBackoff.String(), err))
+		}
+
+		break
+	}
+
+	u[6] = (u[6] & 0x0f) | 0x40 // set version byte
+	u[8] = (u[8] & 0x3f) | 0x80 // set high order byte 0b10{8,9,a,b}
+
+	return u
+}
+
+// Parse attempts to extract a uuid from the string or returns an error.
+func Parse(s string) (u UUID, err error) {
+	if len(s) != 36 {
+		return UUID{}, ErrUUIDInvalid
+	}
+
+	// create stack addresses for each section of the uuid.
+	p := make([][]byte, 5)
+
+	if _, err := fmt.Sscanf(s, format, &p[0], &p[1], &p[2], &p[3], &p[4]); err != nil {
+		return u, err
+	}
+
+	copy(u[0:4], p[0])
+	copy(u[4:6], p[1])
+	copy(u[6:8], p[2])
+	copy(u[8:10], p[3])
+	copy(u[10:16], p[4])
+
+	return
+}
+
+func (u UUID) String() string {
+	return fmt.Sprintf(format, u[:4], u[4:6], u[6:8], u[8:10], u[10:])
+}
+
+// retryOnError tries to detect whether or not retrying would be fruitful.
+func retryOnError(err error) bool {
+	switch err := err.(type) {
+	case *os.PathError:
+		return retryOnError(err.Err) // unpack the target error
+	case syscall.Errno:
+		if err == syscall.EPERM {
+			// EPERM represents an entropy pool exhaustion, a condition under
+			// which we backoff and retry.
+			return true
+		}
+	}
+
+	return false
+}