Working on non-blocking reading

PureSwift · Sep 11, 2018 · 3376d17 · 3376d17
1 parent 8bce039
commit 3376d17
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Showing 2 changed files with 81 additions and 6 deletions.
diff --git a/Sources/BluetoothLinux/L2CAP.swift b/Sources/BluetoothLinux/L2CAP.swift
@@ -14,6 +14,7 @@
 
 import Foundation
 import Bluetooth
+import CSwiftBluetoothLinux
 
 /// L2CAP Bluetooth socket
 public final class L2CAPSocket: L2CAPSocketProtocol {
@@ -133,7 +134,9 @@ public final class L2CAPSocket: L2CAPSocketProtocol {
                                      addressType: AddressType?) throws -> (CInt, sockaddr_l2) {
 
         // open socket
-        let internalSocket = socket(AF_BLUETOOTH, SOCK_SEQPACKET, BluetoothProtocol.l2cap.rawValue)
+        let internalSocket = socket(AF_BLUETOOTH,
+                                    SOCK_SEQPACKET,
+                                    BluetoothProtocol.l2cap.rawValue)
 
         // error creating socket
         guard internalSocket >= 0
@@ -252,8 +255,13 @@ public final class L2CAPSocket: L2CAPSocketProtocol {
     }
 
     /// Reads from the socket.
-    public func recieve(_ bufferSize: Int = 1024) throws -> Data {
-
+    public func recieve(_ bufferSize: Int = 1024) throws -> Data? {
+
+        // check if reading buffer has data.
+        guard try canRead()
+            else { return nil }
+
+        // read socket
         var buffer = [UInt8](repeating: 0, count: bufferSize)
 
         let actualByteCount = read(internalSocket, &buffer, bufferSize)
@@ -264,6 +272,22 @@ public final class L2CAPSocket: L2CAPSocketProtocol {
 
         return Data(bytes: actualBytes)
     }
+
+    private func canRead() throws -> Bool {
+
+        var readSockets = FileDescriptorSet()
+        readSockets.zero()
+        readSockets.add(internalSocket)
+
+        var time = timeval()
+
+        let fdCount = select(internalSocket + 1, &readSockets, nil, nil, &time)
+
+        guard fdCount != -1
+            else { throw POSIXError.fromErrno! }
+
+        return readSockets.contains(internalSocket)
+    }
 
     /// Write to the socket.
     public func send(_ data: Data) throws {
@@ -389,8 +413,8 @@ struct bt_security {
 
 #if os(Linux)
 
-    public let SOCK_SEQPACKET: CInt = 5
-    
+let SOCK_SEQPACKET: CInt = CInt(Glibc.SOCK_SEQPACKET.rawValue)
+
 #endif
 
 // MARK: - OS X support
@@ -400,5 +424,5 @@ struct bt_security {
 let SO_PROTOCOL: CInt = 38
 
 let SO_DOMAIN: CInt = 39
-    
+
 #endif
diff --git a/Sources/CSwiftBluetoothLinux/include/bluetooth.h b/Sources/CSwiftBluetoothLinux/include/bluetooth.h
@@ -7,7 +7,10 @@
  */
 
 #include <stdint.h>
+#include <stdbool.h>
 #include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/select.h>
 
 /**
  @brief Manipulates the underlying device parameters of special files.
@@ -32,3 +35,51 @@ __attribute__((swift_name("HCISetBit(_:_:)")))
 {
     *((uint32_t *) destination + (bit >> 5)) |= (1 << (bit & 31));
 }
+
+/**
+ A set of file descriptors.
+ */
+typedef fd_set FileDescriptorSet __attribute__((swift_name("FileDescriptorSet")));
+
+/**
+ Initializes a file descriptor set on the stack.
+ */
+static inline FileDescriptorSet* swift_bluetooth_fd_set_zero(FileDescriptorSet* set)
+__attribute__((swift_name("FileDescriptorSet.zero(self:)")))
+{
+    FD_ZERO(set);
+    return set;
+}
+
+/**
+ Add a given file descriptor to a set.
+ @param fd The file descriptor to add to the set.
+ @param set The file descriptor set.
+ */
+static inline void swift_bluetooth_fd_set_add(FileDescriptorSet* set, int fileDescriptor)
+__attribute__((swift_name("FileDescriptorSet.add(self:_:)")))
+{
+    FD_SET(fileDescriptor, set);
+}
+
+/**
+ Removed a given file descriptor from a set.
+ @param fd The file descriptor to add to the set.
+ @param set The file descriptor set.
+ */
+static inline void swift_bluetooth_fd_set_remove(FileDescriptorSet* set, int fileDescriptor)
+__attribute__((swift_name("FileDescriptorSet.remove(self:_:)")))
+{
+    FD_CLR(fileDescriptor, set);
+}
+
+/**
+ Checks if a file descriptor is part of the set.
+ @param fd The file descriptor to to check for membership.
+ @param set The targeted value.
+ */
+static inline bool swift_bluetooth_fd_set_contains(FileDescriptorSet* set, int fileDescriptor)
+__attribute__((swift_name("FileDescriptorSet.contains(self:_:)")))
+{
+    return FD_ISSET(fileDescriptor, set);
+}