Fix issue #8 and release 2.0.2.

 B Fix error handling in (*Device).InitiatorSelectPassiveTarget()
 B Fix initData handling (ibid.), these fix issue #8
 R Improve documentation (ibid.)

Author: clausecker

2.0/nfc/initiator.go

@@ -345,21 +345,32 @@ func (d Device) InitiatorInitSecureElement() error {
 	return Error(C.nfc_initiator_init_secure_element(*d.d))
 }
 
-// Select a passive or emulated tag.
+// Select a passive or emulated tag. initData is used with different kind of
+// data depending on modulation type:
+//  * for an ISO/IEC 14443 type A modulation, initData contains the UID you want to select;
+//  * for an ISO/IEC 14443 type B modulation, initData contains Application Family Identifier (AFI) (see ISO/IEC 14443-3) and optionally a second byte = 0x01 if you want to use probabilistic approach instead of timeslot approach;
+//  * for a FeliCa modulation, initData contains a 5-byte polling payload (see ISO/IEC 18092 11.2.2.5).
+//  * for ISO14443B', ASK CTx and ST SRx, see corresponding standards
+// if nil, default values adequate for the chosen modulation will be used.
 func (d Device) InitiatorSelectPassiveTarget(m Modulation, initData []byte) (Target, error) {
 	if *d.d == nil {
 		return nil, errors.New("device closed")
 	}
 
 	var pnt C.nfc_target
+	var initDataPtr *C.uint8_t = nil
+	var initDataLen C.size_t = 0
+
+	if (initData != nil) {
+		initDataPtr = (*C.uint8_t)(&initData[0])
+		initDataLen = C.size_t(len(initData))
+	}
 
 	n := C.nfc_initiator_select_passive_target(
 		*d.d,
 		C.nfc_modulation{C.nfc_modulation_type(m.Type), C.nfc_baud_rate(m.BaudRate)},
-		(*C.uint8_t)(&initData[0]),
-		C.size_t(len(initData)),
-		&pnt)
-	if n != 0 {
+		initDataPtr, initDataLen, &pnt)
+	if n < 0 {
 		return nil, Error(n)
 	}
 

CHANGES

@@ -38,6 +38,11 @@ Release 2.0 (2014-08-30)
 Release 2.0.1 (2015-09-28)
  B Set device pointer to nil after calling nfc_close(), not before.
 
+Release 2.0.2 (2016-01-14)
+ B Fix error handling in (*Device).InitiatorSelectPassiveTarget()
+ B Fix initData handling (ibid.), these fix issue #8
+ R Improve documentation (ibid.)
+
 Upcoming release 2.1
  N Introduce a new function nfc.Device.SupportedBaudRatesTargetMode()
    wrapping the corresponding new function in the upcoming 1.7.2 release

README

@@ -3,7 +3,7 @@ The code has not been thoroughly tested yet. Please report any errors to the
 project. The API is considered stable as of version 2.0 and will probably not
 change in incompatible ways in the near future.
 
-The current release of this wrapper is release 2.0.1. Successive minor releases
+The current release of this wrapper is release 2.0.2. Successive minor releases
 will be placed in different subfolders as to not change the semantics of code
 that links against a specific version of this wrapper. The patch level is not
 reflected in this scheme as an increase in patch level does not lead to

dev/nfc/initiator.go

@@ -351,21 +351,32 @@ func (d Device) InitiatorInitSecureElement() error {
 	return Error(C.nfc_initiator_init_secure_element(*d.d))
 }
 
-// Select a passive or emulated tag.
+// Select a passive or emulated tag. initData is used with different kind of
+// data depending on modulation type:
+//  * for an ISO/IEC 14443 type A modulation, initData contains the UID you want to select;
+//  * for an ISO/IEC 14443 type B modulation, initData contains Application Family Identifier (AFI) (see ISO/IEC 14443-3) and optionally a second byte = 0x01 if you want to use probabilistic approach instead of timeslot approach;
+//  * for a FeliCa modulation, initData contains a 5-byte polling payload (see ISO/IEC 18092 11.2.2.5).
+//  * for ISO14443B', ASK CTx and ST SRx, see corresponding standards
+// if nil, default values adequate for the chosen modulation will be used.
 func (d Device) InitiatorSelectPassiveTarget(m Modulation, initData []byte) (Target, error) {
 	if *d.d == nil {
 		return nil, errors.New("device closed")
 	}
 
 	var pnt C.nfc_target
+	var initDataPtr *C.uint8_t = nil
+	var initDataLen C.size_t = 0
+
+	if (initData != nil) {
+		initDataPtr = (*C.uint8_t)(&initData[0])
+		initDataLen = C.size_t(len(initData))
+	}
 
 	n := C.nfc_initiator_select_passive_target(
 		*d.d,
 		C.nfc_modulation{C.nfc_modulation_type(m.Type), C.nfc_baud_rate(m.BaudRate)},
-		(*C.uint8_t)(&initData[0]),
-		C.size_t(len(initData)),
-		&pnt)
-	if n != 0 {
+		initDataPtr, initDataLen, &pnt)
+	if n < 0 {
 		return nil, Error(n)
 	}