Instana tracer implementation

vendor/github.com/instana/go-sensor/util.go

@@ -0,0 +1,99 @@
+package instana
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io/ioutil"
+	"math/rand"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	seededIDGen  = rand.New(rand.NewSource(time.Now().UnixNano()))
+	seededIDLock sync.Mutex
+)
+
+func randomID() int64 {
+	seededIDLock.Lock()
+	defer seededIDLock.Unlock()
+	return int64(seededIDGen.Int63())
+}
+
+// ID2Header converts an Instana ID to a value that can be used in
+// context propagation (such as HTTP headers).  More specifically,
+// this converts a signed 64 bit integer into an unsigned hex string.
+func ID2Header(id int64) (string, error) {
+	// FIXME: We're assuming LittleEndian here
+
+	// Write out _signed_ 64bit integer to byte buffer
+	buf := new(bytes.Buffer)
+	if err := binary.Write(buf, binary.LittleEndian, id); err == nil {
+		// Read bytes back into _unsigned_ 64 bit integer
+		var unsigned uint64
+		if err = binary.Read(buf, binary.LittleEndian, &unsigned); err == nil {
+			// Convert uint64 to hex string equivalent and return that
+			return strconv.FormatUint(unsigned, 16), nil
+		}
+		log.debug(err)
+	} else {
+		log.debug(err)
+	}
+	return "", errors.New("context corrupted; could not convert value")
+}
+
+// Header2ID converts an header context value into an Instana ID.  More
+// specifically, this converts an unsigned 64 bit hex value into a signed
+// 64bit integer.
+func Header2ID(header string) (int64, error) {
+	// FIXME: We're assuming LittleEndian here
+
+	// Parse unsigned 64 bit hex string into unsigned 64 bit base 10 integer
+	if unsignedID, err := strconv.ParseUint(header, 16, 64); err == nil {
+		// Write out _unsigned_ 64bit integer to byte buffer
+		buf := new(bytes.Buffer)
+		if err = binary.Write(buf, binary.LittleEndian, unsignedID); err == nil {
+			// Read bytes back into _signed_ 64 bit integer
+			var signedID int64
+			if err = binary.Read(buf, binary.LittleEndian, &signedID); err == nil {
+				// The success case
+				return signedID, nil
+			}
+			log.debug(err)
+		} else {
+			log.debug(err)
+		}
+	} else {
+		log.debug(err)
+	}
+	return int64(0), errors.New("context corrupted; could not convert value")
+}
+
+func getCommandLine() (string, []string) {
+	var cmdlinePath string = "/proc/" + strconv.Itoa(os.Getpid()) + "/cmdline"
+
+	cmdline, err := ioutil.ReadFile(cmdlinePath)
+
+	if err != nil {
+		log.debug("No /proc.  Returning OS reported cmdline")
+		return os.Args[0], os.Args[1:]
+	}
+
+	parts := strings.FieldsFunc(string(cmdline), func(c rune) bool {
+		if c == '\u0000' {
+			return true
+		}
+		return false
+	})
+	log.debug("cmdline says:", parts[0], parts[1:])
+	return parts[0], parts[1:]
+}
+
+func abs(x int64) int64 {
+	y := x >> 63
+	return (x + y) ^ y
+}