device/nfc/nfc_tag_technology.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef DEVICE_NFC_NFC_TAG_TECHNOLOGY_H_
   6 #define DEVICE_NFC_NFC_TAG_TECHNOLOGY_H_
   7
   8 #include "base/callback.h"
   9 #include "device/nfc/nfc_ndef_record.h"
  10
  11 namespace device {
  12
  13 class NfcTag;
  14
  15 // NfcTagTechnology represents an NFC technology that allows a certain type of
  16 // I/O operation on an NFC tag. NFC tags can support a wide array of protocols.
  17 // The NfcTagTechnology hierarchy allows both raw and high-level I/O operations
  18 // on NFC tags. Do not create instances of these objects directly. Instead,
  19 // obtain a handle directly from an NfcTag object.
  20 class NfcTagTechnology {
  21  public:
  22   // The various I/O technologies that an NFC tag can support.
  23   enum TechnologyType {
  24     kTechnologyTypeNfcA = 1 << 0,
  25     kTechnologyTypeNfcB = 1 << 1,
  26     kTechnologyTypeNfcF = 1 << 2,
  27     kTechnologyTypeNfcV = 1 << 3,
  28     kTechnologyTypeIsoDep = 1 << 4,
  29     kTechnologyTypeNdef = 1 << 5
  30   };
  31   typedef uint32 TechnologyTypeMask;
  32
  33   virtual ~NfcTagTechnology();
  34
  35   // Returns true, if the underlying tag supports the NFC tag technology that
  36   // this instance represents.
  37   virtual bool IsSupportedByTag() const = 0;
  38
  39   // Returns a pointer to the associated NfcTag instance.
  40   NfcTag* tag() const { return tag_; }
  41
  42  protected:
  43   // Constructs a technology instance, where |tag| is the NFC tag that this
  44   // instance will operate on. Clients aren't allowed to instantiate classes
  45   // directly. They should use the static "Create" methods defined in each
  46   // subclass to obtain the platform specific implementation.
  47   explicit NfcTagTechnology(NfcTag* tag);
  48
  49  private:
  50   NfcTagTechnology();
  51
  52   // The underlying NfcTag instance that data exchange operations through this
  53   // instance are performed on.
  54   NfcTag* tag_;
  55
  56   DISALLOW_COPY_AND_ASSIGN(NfcTagTechnology);
  57 };
  58
  59 // NfcNdefTagTechnology allows reading and writing NDEF messages to a tag. This
  60 // is the most commonly used data exchange format in NFC. NDEF is a data
  61 // exchange format and is the top most layer of the protocol stack. NDEF itself
  62 // is not a protocol; data is typically formatted in a way that is defined by
  63 // the NDEF format and then transmitted via one of the underlying protocols.
  64 // Hence all tags are capable of NDEF data exchange, however, all tags don't
  65 // necessarily use NDEF to operate (e.g. a tag may contain a smart chip that
  66 // does data processing on ISO-DEP based APDUs and ignores NDEF). This is why,
  67 // even if a tag inherently supports NDEF, operations done via this class may
  68 // not necessarily succeed.
  69 class NfcNdefTagTechnology : public NfcTagTechnology {
  70  public:
  71   // The ErrorCallback is used by methods to asynchronously report errors.
  72   typedef base::Closure ErrorCallback;
  73
  74   ~NfcNdefTagTechnology() override;
  75
  76   // Interface for observing changes from NFC tags related to NDEF records.
  77   class Observer {
  78    public:
  79     virtual ~Observer() {}
  80
  81     // This method will be called when an NDEF record |record|, stored on the
  82     // NFC tag |tag| has been read. This method will be called multiple times
  83     // as records are read from the tag or when the tag's records change (e.g.
  84     // when the tag has been rewritten). All received records can be accessed by
  85     // calling GetNdefMessage().
  86     virtual void RecordReceived(NfcTag* tag, const NfcNdefRecord* record) {}
  87   };
  88
  89   // Adds and removes observers for events on this NFC tag. If monitoring
  90   // multiple tags, check the |tag| parameter of observer methods to determine
  91   // which tag is issuing the event.
  92   virtual void AddObserver(Observer* observer) = 0;
  93   virtual void RemoveObserver(Observer* observer) = 0;
  94
  95   // NfcTagTechnology override.
  96   bool IsSupportedByTag() const override;
  97
  98   // Returns all NDEF records that were received from the tag in the form of an
  99   // NDEF message. If the returned NDEF message contains no records, this only
 100   // means that no records have yet been received from the tag. Users should
 101   // use this method in conjunction with the NfcTag::Observer::RecordsReceived
 102   // method to be notified when the records are ready.
 103   virtual const NfcNdefMessage& GetNdefMessage() const = 0;
 104
 105   // Writes the given NDEF message to the underlying tag, overwriting any
 106   // existing NDEF message on it. On success, |callback| will be invoked. On
 107   // failure, |error_callback| will be invoked. This method can fail, if the
 108   // underlying tag does not support NDEF as a technology.
 109   virtual void WriteNdef(const NfcNdefMessage& message,
 110                          const base::Closure& callback,
 111                          const ErrorCallback& error_callback) = 0;
 112
 113  protected:
 114   // Constructs a technology instance, where |tag| is the NFC tag that this
 115   // instance will operate on.
 116   explicit NfcNdefTagTechnology(NfcTag* tag);
 117
 118   DISALLOW_COPY_AND_ASSIGN(NfcNdefTagTechnology);
 119 };
 120
 121 }  // namespace device
 122
 123 #endif  // DEVICE_NFC_NFC_TAG_TECHNOLOGY_H_