Merged in remove-LocationStrBytes (pull request #118)

Get rid of LocationStrBytes func

Approved-by: kortschak <dan@kortschak.io>

stream/mts/psi/helpers.go

@@ -99,14 +99,6 @@ func LocationFrom(p []byte) (g string, err error) {
 	return g, nil
 }
 
-// LocationStrBytes take a string of location data and converts to a 32 byte slice -
-// easy update of slice representation of a pmt with location descriptor
-func LocationStrBytes(s string) []byte {
-	var b [LocationDataSize]byte
-	copy(b[:], s)
-	return b[:]
-}
-
 // UpdateLocation takes a byte slice representation of a psi-pmt containing a location
 // descriptor and attempts to update the location data value with the passed string.
 // If the psi does not contain a location descriptor, and error is returned.
@@ -114,8 +106,12 @@ func UpdateLocation(d []byte, s string) error {
 	if !HasLocation(d) {
 		return errors.New("pmt does not location descriptor, cannot update")
 	}
-	gb := LocationStrBytes(s)
-	copy(d[LocationDataIndx:LocationDataIndx+LocationDataSize], gb)
+	loc := d[LocationDataIndx : LocationDataIndx+LocationDataSize]
+	n := copy(loc, s)
+	loc = loc[n:]
+	for i := range loc {
+		loc[i] = 0
+	}
 	updateCrc(d)
 	return nil
 }

stream/mts/psi/psi_test.go

@@ -79,7 +79,7 @@ var (
 
 	// standardPmtTimeLocation is a standard PMT with time and location
 	// descriptors, but time and location fields zeroed out.
-	standardPmtTimeLocation = PSI{
+	standardPmtWithMeta = PSI{
 		Pf:  0x00,
 		Tid: 0x02,
 		Ssi: true,
@@ -142,7 +142,7 @@ var (
 
 // Parts to construct bytes of pmt with time and bytes
 var (
-	pmtTimeLocationBytesPart1 = []byte{
+	pmtWithMetaHead = []byte{
 		0x00, 0x02, 0xb0, 0x12, 0x00, 0x01, 0xc1, 0x00, 0x00, 0xe1, 0x00, 0xf0, 0x0a,
 		TimeDescTag,                                    // Descriptor tag for timestamp
 		TimeDataSize,                                   // Length of bytes to follow
@@ -150,7 +150,7 @@ var (
 		LocationDescTag,  // Descriptor tag for location
 		LocationDataSize, // Length of bytes to follow
 	}
-	pmtTimeLocationBytesPart2 = []byte{
+	pmtWithMetaTail = []byte{
 		0x1b, 0xe1, 0x00, 0xf0, 0x00,
 	}
 )
@@ -175,10 +175,10 @@ var (
 	}
 
 	// Bytes representing pmt with time1 and location1
-	pmtTimeLocationBytes1 = buildPmtTimeLocationBytes(locationTstStr1)
+	pmtWithMetaTst1 = buildPmtWithMeta(locationTstStr1)
 
 	// bytes representing pmt with with time1 and location 2
-	pmtTimeLocationBytes2 = buildPmtTimeLocationBytes(locationTstStr2)
+	pmtWithMetaTst2 = buildPmtWithMeta(locationTstStr2)
 )
 
 // bytesTests contains data for testing the Bytes() funcs for the PSI data struct
@@ -262,7 +262,7 @@ var bytesTests = []struct {
 						{
 							Dt: LocationDescTag,
 							Dl: LocationDataSize,
-							Dd: LocationStrBytes(locationTstStr1),
+							Dd: []byte(locationTstStr1),
 						},
 					},
 					Essd: &ESSD{
@@ -273,7 +273,7 @@ var bytesTests = []struct {
 				},
 			},
 		},
-		want: buildPmtTimeLocationBytes(locationTstStr1),
+		want: buildPmtWithMeta(locationTstStr1),
 	},
 }
 
@@ -325,7 +325,7 @@ func TestTimeGet(t *testing.T) {
 
 // TestLocationGet checks that we can correctly get location data from a pmt table
 func TestLocationGet(t *testing.T) {
-	pb := standardPmtTimeLocation.Bytes()
+	pb := standardPmtWithMeta.Bytes()
 	err := UpdateLocation(pb, locationTstStr1)
 	if err != nil {
 		t.Errorf("Error for TestLocationGet UpdateLocation(pb, locationTstStr1): %v", err)
@@ -341,16 +341,16 @@ func TestLocationGet(t *testing.T) {
 
 // TestLocationUpdate checks to see if we can update the location string in a pmt correctly
 func TestLocationUpdate(t *testing.T) {
-	cpy := make([]byte, len(pmtTimeLocationBytes1))
-	copy(cpy, pmtTimeLocationBytes1)
+	cpy := make([]byte, len(pmtWithMetaTst1))
+	copy(cpy, pmtWithMetaTst1)
 	cpy = addCrc(cpy)
 	err := UpdateLocation(cpy, locationTstStr2)
 	cpy = cpy[:len(cpy)-4]
 	if err != nil {
 		t.Errorf("Update time returned err: %v", err)
 	}
-	if !bytes.Equal(pmtTimeLocationBytes2, cpy) {
-		t.Errorf(errCmp, "TestLocationUpdate", pmtTimeLocationBytes2, cpy)
+	if !bytes.Equal(pmtWithMetaTst2, cpy) {
+		t.Errorf(errCmp, "TestLocationUpdate", pmtWithMetaTst2, cpy)
 	}
 }
 
@@ -363,10 +363,11 @@ func TestTrim(t *testing.T) {
 	}
 }
 
-// buildPmtTimeLocationBytes is a helper function to help construct the byte slices
-// for pmts with time and location, as the location data field is 32 bytes, i.e. quite large
-// to type out
-func buildPmtTimeLocationBytes(tstStr string) []byte {
-	return append(append(append(make([]byte, 0), pmtTimeLocationBytesPart1...),
-		LocationStrBytes(tstStr)...), pmtTimeLocationBytesPart2...)
+// buildPmtTimeLocationBytes returns a PMT with time and location from s.
+func buildPmtWithMeta(tstStr string) []byte {
+	dst := make([]byte, len(pmtWithMetaHead)+32+len(pmtWithMetaTail))
+	copy(dst, pmtWithMetaHead)
+	copy(dst[len(pmtWithMetaHead):], tstStr)
+	copy(dst[len(pmtWithMetaHead)+32:], pmtWithMetaTail)
+	return dst
 }