(Lianja) 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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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

loScard = createobject("CkSCard")

// First establish a context to the PC/SC Resource Manager
llSuccess = loScard.EstablishContext("user")
if (llSuccess = .F.) then
    ? loScard.LastErrorText
    release loScard
    return
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.
loJson = createobject("CkJsonObject")
llSuccess = loScard.FindSmartcards(loJson)
if (llSuccess = .F.) then
    ? loScard.LastErrorText
    release loScard
    release loJson
    return
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 = .F.
? loJson.Emit()
? " "

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

loSbState = createobject("CkStringBuilder")

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",.T.) = .T.) 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.
loStReaders = createobject("CkStringTable")
llSuccess = loScard.ListReaders(loStReaders)
if (llSuccess = .F.) then
    ? loScard.LastErrorText
    release loScard
    release loJson
    release loSbState
    release loStReaders
    return
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.
loJson2 = createobject("CkJsonObject")
llSuccess = loScard.GetStatusChange(30000,loStReaders,loJson2)
if (llSuccess = .F.) then
    ? loScard.LastErrorText
    release loScard
    release loJson
    release loSbState
    release loStReaders
    release loJson2
    return
endif

? " "

// Let's see what happened...
loJson2.EmitCompact = .F.
? 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
    llChanged = loJson2.BoolOf("reader[i].changed")
    if (llChanged = .T.) 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") = .T.) 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.
llSuccess = loScard.ReleaseContext()
if (llSuccess = .F.) then
    ? loScard.LastErrorText
endif



release loScard
release loJson
release loSbState
release loStReaders
release loJson2