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PC/SC Wait for Smart Card Status Change (Inserted, Removed from Reader, etc.)
See more SCard Examples
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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const std = @import("std");
const chilkat = @import("chilkat");
pub fn main(init: std.process.Init) !void {
const alloc = init.arena.allocator();
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.
const scard = try chilkat.SCard.init();
defer scard.deinit();
// First establish a context to the PC/SC Resource Manager
scard.establishContext("user") catch {
std.debug.print("{s}\n", .{try scard.getLastErrorText(alloc)});
return;
};
// 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.
const json = try chilkat.JsonObject.init();
defer json.deinit();
scard.findSmartcards(json) catch {
std.debug.print("{s}\n", .{try scard.getLastErrorText(alloc)});
return;
};
// 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"
// }
// ]
// }
json.setEmitCompact(false);
std.debug.print("{s}\n", .{try json.emit(alloc)});
std.debug.print(" \n", .{});
// We can iterate over the JSON to find the readers with a smart card already inserted..
var name: [:0]const u8 = "";
const sb_state = try chilkat.StringBuilder.init();
defer sb_state.deinit();
var i: i32 = 0;
var count_i: i32 = json.sizeOfArray("reader");
while (i < count_i) {
json.setI(i);
name = try json.stringOf(alloc, "reader[i].name");
sb_state.clear();
json.stringOfSb("reader[i].state", sb_state) catch {};
if (sb_state.contains("present", true)) {
std.debug.print("{s} has a smart card inserted.\n", .{name});
} else {
std.debug.print("{s} does not have a smart card inserted.\n", .{name});
}
i = i + 1;
}
std.debug.print(" \n", .{});
// 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.
const st_readers = try chilkat.StringTable.init();
defer st_readers.deinit();
scard.listReaders(st_readers) catch {
std.debug.print("{s}\n", .{try scard.getLastErrorText(alloc)});
return;
};
// Show the reader names..
const num_readers = st_readers.getCount();
i = 0;
while (i < num_readers) {
std.debug.print("{d}: {s}\n", .{ i, try st_readers.stringAt(alloc, i) });
i = i + 1;
}
// 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.
const json2 = try chilkat.JsonObject.init();
defer json2.deinit();
scard.getStatusChange(30000, st_readers, json2) catch {
std.debug.print("{s}\n", .{try scard.getLastErrorText(alloc)});
return;
};
std.debug.print(" \n", .{});
// Let's see what happened...
json2.setEmitCompact(false);
std.debug.print("{s}\n", .{try json2.emit(alloc)});
std.debug.print(" \n", .{});
// 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...
var changed: bool = false;
var state: [:0]const u8 = "";
var atr: [:0]const u8 = "";
const num_changed = json2.intOf("numChanged");
std.debug.print("number of readers with a changed state: {d}\n", .{num_changed});
i = 0;
count_i = json2.sizeOfArray("reader");
while (i < count_i) {
json2.setI(i);
changed = json2.boolOf("reader[i].changed");
if (changed) {
name = try json2.stringOf(alloc, "reader[i].name");
state = try json2.stringOf(alloc, "reader[i].state");
std.debug.print("Changed: \n", .{});
std.debug.print(" reader name: {s}\n", .{name});
std.debug.print(" new state: {s}\n", .{state});
// If a card is now in this reader, we should have the ATR of the card..
if (json2.hasMember("reader[i].atr")) {
atr = try json2.stringOf(alloc, "reader[i].atr");
std.debug.print(" ATR of card inserted into this reader: {s}\n", .{atr});
}
}
i = i + 1;
}
// 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.
scard.releaseContext() catch {
std.debug.print("{s}\n", .{try scard.getLastErrorText(alloc)});
};
}