Add plugin support

src/internal/dl.cc

@@ -0,0 +1,114 @@
+#include "internal/dl.h"
+
+#include <glog/logging.h>
+
+MYNTEYE_BEGIN_NAMESPACE
+
+#if defined(OS_WIN) && !defined(OS_MINGW) && !defined(OS_CYGWIN)
+
+namespace {
+
+// How to get the error message from the error code returned by GetLastError()?
+//   https://stackoverflow.com/questions/9272415/how-to-convert-dword-to-char
+std::string GetLastErrorAsString() {
+  DWORD dw = ::GetLastError();
+  if (dw == 0)
+    return std::string();
+  LPSTR lpMsgBuf;
+  size_t size = FormatMessageA(
+      FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
+          FORMAT_MESSAGE_IGNORE_INSERTS,
+      NULL, dw, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPSTR)&lpMsgBuf, 0,
+      NULL);
+  std::string message(lpMsgBuf, size);
+  LocalFree(lpMsgBuf);
+  return message;
+}
+
+}  // namespace
+
+#endif
+
+DL::DL() : handle(nullptr) {
+  VLOG(2) << __func__;
+}
+
+DL::DL(const char *filename) : handle(nullptr) {
+  VLOG(2) << __func__;
+  Open(filename);
+}
+
+DL::~DL() {
+  VLOG(2) << __func__;
+  Close();
+}
+
+bool DL::Open(const char *filename) {
+  if (handle != nullptr) {
+    VLOG(2) << "Already opened, do nothing";
+    // Close();
+    return false;
+  }
+#if defined(OS_WIN) && !defined(OS_MINGW) && !defined(OS_CYGWIN)
+  handle = LoadLibraryEx(filename, nullptr, 0);
+#else
+  handle = dlopen(filename, RTLD_LAZY);
+#endif
+  if (handle == nullptr) {
+    VLOG(2) << "Open library failed: " << filename;
+    return false;
+  } else {
+    return true;
+  }
+}
+
+bool DL::IsOpened() {
+  return handle != nullptr;
+}
+
+void *DL::Sym(const char *symbol) {
+  if (handle == nullptr) {
+    VLOG(2) << "Not opened, do nothing";
+    return nullptr;
+  }
+#if defined(OS_WIN) && !defined(OS_MINGW) && !defined(OS_CYGWIN)
+  void *f = GetProcAddress(handle, symbol);
+  if (f == nullptr) {
+    VLOG(2) << "Load symbol failed: " << symbol;
+  }
+#else
+  dlerror();  // reset errors
+  void *f = dlsym(handle, symbol);
+  const char *error = dlerror();
+  if (error != nullptr) {
+    VLOG(2) << "Load symbol failed: " << symbol;
+    f = nullptr;
+  }
+#endif
+  return f;
+}
+
+int DL::Close() {
+  int ret = 0;
+  if (handle == nullptr) {
+    VLOG(2) << "Not opened, do nothing";
+  } else {
+#if defined(OS_WIN) && !defined(OS_MINGW) && !defined(OS_CYGWIN)
+    ret = FreeLibrary(handle) ? 0 : 1;
+#else
+    ret = dlclose(handle);
+#endif
+    handle = nullptr;
+  }
+  return ret;
+}
+
+const char *DL::Error() {
+#if defined(OS_WIN) && !defined(OS_MINGW) && !defined(OS_CYGWIN)
+  return GetLastErrorAsString().c_str();
+#else
+  return dlerror();
+#endif
+}
+
+MYNTEYE_END_NAMESPACE

src/internal/dl.h

@@ -0,0 +1,56 @@
+#ifndef MYNTEYE_INTERNAL_DL_H_  // NOLINT
+#define MYNTEYE_INTERNAL_DL_H_
+#pragma once
+
+#include "mynteye/mynteye.h"
+
+#if defined(OS_WIN) && !defined(OS_MINGW) && !defined(OS_CYGWIN)
+#include <Windows.h>
+#else
+#include <dlfcn.h>
+#endif
+
+MYNTEYE_BEGIN_NAMESPACE
+
+#if defined(OS_WIN) && !defined(OS_MINGW) && !defined(OS_CYGWIN)
+using DLLIB = HMODULE;
+#else
+using DLLIB = void *;
+#endif
+
+// Dynamic loading
+//   https://en.wikipedia.org/wiki/Dynamic_loading
+// C++ dlopen mini HOWTO
+//   http://tldp.org/HOWTO/C++-dlopen/
+class MYNTEYE_API DL {
+ public:
+  DL();
+  explicit DL(const char *filename);
+  ~DL();
+
+  bool Open(const char *filename);
+
+  bool IsOpened();
+
+  void *Sym(const char *symbol);
+
+  template <typename Func>
+  Func *Sym(const char *symbol);
+
+  int Close();
+
+  const char *Error();
+
+ private:
+  DLLIB handle;
+};
+
+template <typename Func>
+Func *DL::Sym(const char *symbol) {
+  void *f = Sym(symbol);
+  return reinterpret_cast<Func *>(f);
+}
+
+MYNTEYE_END_NAMESPACE
+
+#endif  // MYNTEYE_INTERNAL_DL_H_  NOLINT