Opentracing support

vendor/github.com/openzipkin/zipkin-go-opentracing/logger.go

@@ -0,0 +1,64 @@
+package zipkintracer
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"strings"
+)
+
+// ErrMissingValue adds a Missing Value Error when the Logging Parameters are
+// not even in number
+var ErrMissingValue = errors.New("(MISSING)")
+
+// Logger is the fundamental interface for all log operations. Log creates a
+// log event from keyvals, a variadic sequence of alternating keys and values.
+// The signature is compatible with the Go kit log package.
+type Logger interface {
+	Log(keyvals ...interface{}) error
+}
+
+// NewNopLogger provides a Logger that discards all Log data sent to it.
+func NewNopLogger() Logger {
+	return &nopLogger{}
+}
+
+// LogWrapper wraps a standard library logger into a Logger compatible with this
+// package.
+func LogWrapper(l *log.Logger) Logger {
+	return &wrappedLogger{l: l}
+}
+
+// wrappedLogger implements Logger
+type wrappedLogger struct {
+	l *log.Logger
+}
+
+// Log implements Logger
+func (l *wrappedLogger) Log(k ...interface{}) error {
+	if len(k)%2 == 1 {
+		k = append(k, ErrMissingValue)
+	}
+	o := make([]string, len(k)/2)
+	for i := 0; i < len(k); i += 2 {
+		o[i/2] = fmt.Sprintf("%s=%q", k[i], k[i+1])
+	}
+	l.l.Println(strings.Join(o, " "))
+	return nil
+}
+
+// nopLogger implements Logger
+type nopLogger struct{}
+
+// Log implements Logger
+func (*nopLogger) Log(_ ...interface{}) error { return nil }
+
+// LoggerFunc is an adapter to allow use of ordinary functions as Loggers. If
+// f is a function with the appropriate signature, LoggerFunc(f) is a Logger
+// object that calls f.
+type LoggerFunc func(...interface{}) error
+
+// Log implements Logger by calling f(keyvals...).
+func (f LoggerFunc) Log(keyvals ...interface{}) error {
+	return f(keyvals...)
+}