Moving some of the BPF filtering code into base class.

This will allow packet sources that don't support BPF natively to
emulate the filtering via libpcap.

src/iosource/BPF_Program.h

@@ -0,0 +1,52 @@
+// See the file "COPYING" in the main distribution directory for copyright.
+
+#ifndef bpf_program_h
+#define bpf_program_h
+
+extern "C" {
+#include <pcap.h>
+}
+
+#include "util.h"
+
+// BPF_Programs are an abstraction around struct bpf_program,
+// to create a clean facility for creating, compiling, and
+// freeing such programs.
+
+class BPF_Program {
+public:
+	// Creates an empty, uncompiled BPF program.
+	BPF_Program();
+	~BPF_Program();
+
+	// Creates a BPF program for the given pcap handle.
+	// Parameters are like in pcap_compile(). Returns true
+	// for successful compilation, false otherwise.
+	bool Compile(pcap_t* pcap, const char* filter, uint32 netmask,
+		 char* errbuf = 0, unsigned int errbuf_len = 0,
+		 bool optimize = true);
+
+	// Creates a BPF program when no pcap handle is around,
+	// similarly to pcap_compile_nopcap(). Parameters are
+	// similar. Returns true on success.
+	bool Compile(int snaplen, int linktype, const char* filter,
+		uint32 netmask, char* errbuf = 0, bool optimize = true);
+
+	// Returns true if this program currently contains compiled
+	// code, false otherwise.
+	bool IsCompiled()	{ return m_compiled; }
+
+	// Accessor to the compiled program. Returns nil when
+	// no program is currently compiled.
+	bpf_program* GetProgram();
+
+protected:
+	void FreeCode();
+
+	// (I like to prefix member variables with m_, makes it clear
+	// in the implementation whether it's a global or not. --ck)
+	bool m_compiled;
+	struct bpf_program m_program;
+};
+
+#endif