Add methods to get the hostname and network interfaces.

examples/usbstream/usbstream.cpp

@@ -2,7 +2,13 @@
 
 #include <stdio.h>
 
+#include "llvm/raw_ostream.h"
+
 int main() {
+  llvm::outs() << "hostname: " << cs::GetHostname() << '\n';
+  llvm::outs() << "IPv4 network addresses:\n";
+  for (const auto& addr : cs::GetNetworkInterfaces())
+    llvm::outs() << "  " << addr << '\n';
   cs::USBCamera camera{"usbcam", 1};
   camera.SetVideoMode(cs::VideoMode::kMJPEG, 320, 240, 30);
   cs::MJPEGServer mjpegServer{"httpserver", 8081};

include/cscore_c.h

@@ -297,6 +297,11 @@ void CS_FreeEnumPropertyChoices(char** choices, int count);
 void CS_FreeEnumeratedProperties(CS_Property* properties, int count);
 void CS_FreeEnumeratedVideoModes(CS_VideoMode* modes, int count);
 
+char* CS_GetHostname();
+
+char** CS_GetNetworkInterfaces(int* count);
+void CS_FreeNetworkInterfaces(char** interfaces, int count);
+
 #ifdef __cplusplus
 }
 #endif

include/cscore_cpp.h

@@ -275,6 +275,10 @@ llvm::ArrayRef<CS_Source> EnumerateSourceHandles(
 llvm::ArrayRef<CS_Sink> EnumerateSinkHandles(
     llvm::SmallVectorImpl<CS_Sink>& vec, CS_Status* status);
 
+std::string GetHostname();
+
+std::vector<std::string> GetNetworkInterfaces();
+
 }  // namespace cs
 
 #endif  // CSCORE_CPP_H_

java/lib/CameraServerJNI.cpp

@@ -1089,4 +1089,26 @@ JNIEXPORT jintArray JNICALL Java_edu_wpi_cscore_CameraServerJNI_enumerateSinks
   return MakeJIntArray(env, arr);
 }
 
+/*
+ * Class:     edu_wpi_cscore_CameraServerJNI
+ * Method:    getHostname
+ * Signature: ()Ljava/lang/String;
+ */
+JNIEXPORT jstring JNICALL Java_edu_wpi_cscore_CameraServerJNI_getHostname
+  (JNIEnv *env, jclass)
+{
+  return MakeJString(env, cs::GetHostname());
+}
+
+/*
+ * Class:     edu_wpi_cscore_CameraServerJNI
+ * Method:    getNetworkInterfaces
+ * Signature: ()[Ljava/lang/String;
+ */
+JNIEXPORT jobjectArray JNICALL Java_edu_wpi_cscore_CameraServerJNI_getNetworkInterfaces
+  (JNIEnv *env, jclass)
+{
+  return MakeJStringArray(env, cs::GetNetworkInterfaces());
+}
+
 }  // extern "C"

java/src/edu/wpi/cscore/CameraServerJNI.java

@@ -181,4 +181,8 @@ public class CameraServerJNI {
   public static native int[] enumerateSources();
 
   public static native int[] enumerateSinks();
+
+  public static native String getHostname();
+
+  public static native String[] getNetworkInterfaces();
 }

src/cscore_c.cpp

@@ -321,4 +321,24 @@ void CS_FreeEnumeratedVideoModes(CS_VideoMode* modes, int count) {
   std::free(modes);
 }
 
+char* CS_GetHostname() {
+  return cs::ConvertToC(cs::GetHostname());
+}
+
+char** CS_GetNetworkInterfaces(int* count) {
+  auto interfaces = cs::GetNetworkInterfaces();
+  char** out =
+      static_cast<char**>(std::malloc(interfaces.size() * sizeof(char*)));
+  *count = interfaces.size();
+  for (std::size_t i = 0; i < interfaces.size(); ++i)
+    out[i] = cs::ConvertToC(interfaces[i]);
+  return out;
+}
+
+void CS_FreeNetworkInterfaces(char** interfaces, int count) {
+  if (!interfaces) return;
+  for (int i = 0; i < count; ++i) std::free(interfaces[i]);
+  std::free(interfaces);
+}
+
 }  // extern "C"

src/cscore_cpp.cpp

@@ -7,6 +7,13 @@
 
 #include "cscore_cpp.h"
 
+#if defined(__linux__)
+#include <arpa/inet.h>
+#include <ifaddrs.h>
+#include <sys/types.h>
+#include <unistd.h>
+#endif
+
 #include "llvm/SmallString.h"
 
 #include "Notifier.h"
@@ -511,4 +518,39 @@ llvm::ArrayRef<CS_Sink> EnumerateSinkHandles(
   return Sinks::GetInstance().GetAll(vec);
 }
 
+std::string GetHostname() {
+#ifdef __linux__
+  char name[256];
+  if (::gethostname(name, sizeof(name)) != 0) return "";
+  name[255] = '\0';  // Per POSIX, may not be null terminated if too long
+  return name;
+#else
+  return "";  // TODO
+#endif
+}
+
+std::vector<std::string> GetNetworkInterfaces() {
+#ifdef __linux__
+  struct ifaddrs* ifa;
+  if (::getifaddrs(&ifa) != 0) return std::vector<std::string>{};
+
+  std::vector<std::string> rv;
+  char buf[256];
+  for (struct ifaddrs* i = ifa; i; i = i->ifa_next) {
+    if (!i->ifa_addr) continue;  // no address
+    if (i->ifa_addr->sa_family != AF_INET) continue;  // only return IPv4
+    struct sockaddr_in* addr_in = reinterpret_cast<sockaddr_in*>(i->ifa_addr);
+    const char* addr =
+        ::inet_ntop(addr_in->sin_family, &addr_in->sin_addr, buf, sizeof(buf));
+    if (!addr) continue;  // error converting address
+    rv.emplace_back(addr);
+  }
+
+  ::freeifaddrs(ifa);
+  return rv;
+#else
+  return std::vector<std::string>{};  // TODO
+#endif
+}
+
 }  // namespace cs