(Visual FoxPro) PC/SC Wait for Smart Card Status Change (Inserted, Removed from Reader, etc.)

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Demonstrates how to synchronously wait for a status change, such as for a smart card to be inserted into a reader, or removed from a reader.

Note: This functionality was introduced in Chilkat v9.5.0.87.

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LOCAL loScard
LOCAL lnSuccess
LOCAL loJson
LOCAL lcName
LOCAL loSbState
LOCAL i
LOCAL lnCount_i
LOCAL loStReaders
LOCAL lnNumReaders
LOCAL loJson2
LOCAL lnChanged
LOCAL lcState
LOCAL lcAtr
LOCAL lnNumChanged

* This example requires the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.SCard')
loScard = CreateObject('Chilkat.SCard')

* First establish a context to the PC/SC Resource Manager
lnSuccess = loScard.EstablishContext("user")
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
    RELEASE loScard
    CANCEL
ENDIF

* First we'll examine the state of all connected readers to see which have smartcards already inserted..
* Get JSON containing information about the smartcards currently inserted into readers.
* This also includes information about USB security tokens.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJson = CreateObject('Chilkat.JsonObject')
lnSuccess = loScard.FindSmartcards(loJson)
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
    RELEASE loScard
    RELEASE loJson
    CANCEL
ENDIF

* When writing this example, I have 3 smart card readers plugged into my system.
* One of them has a smart card inserted.
* Here's the JSON returned by FindSmartcards...

* {
*   "reader": [
*     {
*       "name": "Alcor Micro USB Smart Card Reader 0",
*       "state": "empty"
*     },
*     {
*       "name": "Generic Smart Card Reader Interface 0",
*       "state": "present",
*       "vendorName": "Generic",
*       "serialNumber": "3230303730383138303030303030303030",
*       "systemName": "Generic Smart Card Reader Interface 0",
*       "card": {
*         "atr": "3BFC180000813180459067464A00641606F2727E00E0",
*         "windows": {
*           "miniDriver": "tagliov70px.dll",
*           "cryptoProvider": "Microsoft Base Smart Card Crypto Provider",
*           "keyStorageProvider": "Microsoft Smart Card Key Storage Provider"
*         }
*       }
*     },
*     {
*       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
*       "state": "empty"
*     }
*   ]
* }

loJson.EmitCompact = 0
? loJson.Emit()
? " "

* We can iterate over the JSON to find the readers with a smart card already inserted..

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbState = CreateObject('Chilkat.StringBuilder')

i = 0
lnCount_i = loJson.SizeOfArray("reader")
DO WHILE i < lnCount_i
    loJson.I = i
    lcName = loJson.StringOf("reader[i].name")

    loSbState.Clear()
    loJson.StringOfSb("reader[i].state",loSbState)

    IF (loSbState.Contains("present",1) = 1) THEN
        ? lcName + " has a smart card inserted."
    ELSE
        ? lcName + " does not have a smart card inserted."
    ENDIF

    i = i + 1
ENDDO
? " "

* Now let's begin the code to wait for a change (where a smart card gets inserted or removed)

* Get the list of all readers.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringTable')
loStReaders = CreateObject('Chilkat.StringTable')
lnSuccess = loScard.ListReaders(loStReaders)
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
    RELEASE loScard
    RELEASE loJson
    RELEASE loSbState
    RELEASE loStReaders
    CANCEL
ENDIF

* Show the reader names..
lnNumReaders = loStReaders.Count
i = 0
DO WHILE i < lnNumReaders
    ? STR(i) + ": " + loStReaders.StringAt(i)
    i = i + 1
ENDDO

* Sample output from the above loop.
* 0: Alcor Micro USB Smart Card Reader 0
* 1: Generic Smart Card Reader Interface 0
* 2: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
* 

* Synchronously wait 30 seconds for a card to be inserted or removed from any of the above readers.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJson2 = CreateObject('Chilkat.JsonObject')
lnSuccess = loScard.GetStatusChange(30000,loStReaders,loJson2)
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
    RELEASE loScard
    RELEASE loJson
    RELEASE loSbState
    RELEASE loStReaders
    RELEASE loJson2
    CANCEL
ENDIF

? " "

* Let's see what happened...
loJson2.EmitCompact = 0
? loJson2.Emit()
? " "

* This is what json2 contains.
* A card was inserted into the reader named "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0"
* The "numChanged" indicates that one reader's status changed.  
* The "changed":true indicates the reader that changed.   The state is now "present".

* {
*   "numChanged": 1,
*   "reader": [
*     {
*       "name": "Alcor Micro USB Smart Card Reader 0",
*       "changed": false,
*       "state": "empty"
*     },
*     {
*       "name": "Generic Smart Card Reader Interface 0",
*       "changed": false,
*       "state": "present",
*       "atr": "3BFC180000813180459067464A00641606F2727E00E0"
*     },
*     {
*       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
*       "changed": true,
*       "state": "present",
*       "atr": "3BDF96FF8131FE455A018048494443313158587300011B09"
*     }
*   ]
* }

* Find the reader that changed...

lnNumChanged = loJson2.IntOf("numChanged")
? "number of readers with a changed state: " + STR(lnNumChanged)

i = 0
lnCount_i = loJson2.SizeOfArray("reader")
DO WHILE i < lnCount_i
    loJson2.I = i
    lnChanged = loJson2.BoolOf("reader[i].changed")
    IF (lnChanged = 1) THEN
        lcName = loJson2.StringOf("reader[i].name")
        lcState = loJson2.StringOf("reader[i].state")

        ? "Changed: "
        ? "    reader name: " + lcName
        ? "    new state: " + lcState

        * If a card is now in this reader, we should have the ATR of the card..
        IF (loJson2.HasMember("reader[i].atr") = 1) THEN
            lcAtr = loJson2.StringOf("reader[i].atr")
            ? "    ATR of card inserted into this reader: " + lcAtr
        ENDIF

    ENDIF

    i = i + 1
ENDDO

* The output from the above loop:

* number of readers with a changed state: 1
* Changed: 
*     reader name: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
*     new state: present
*     ATR of card inserted into this reader: 3BDF96FF8131FE455A018048494443313158587300011B09

* Applications should always release the context when finished.
lnSuccess = loScard.ReleaseContext()
IF (lnSuccess = 0) THEN
    ? loScard.LastErrorText
ENDIF

RELEASE loScard
RELEASE loJson
RELEASE loSbState
RELEASE loStReaders
RELEASE loJson2