1 files changed, 86 insertions, 0 deletions
diff --git a/libs/usvfs/src/thooklib/utility.cpp b/libs/usvfs/src/thooklib/utility.cpp
new file mode 100644
index 0000000..124141f
--- /dev/null
+++ b/libs/usvfs/src/thooklib/utility.cpp
@@ -0,0 +1,86 @@
+/*
+Userspace Virtual Filesystem
+
+Copyright (C) 2015 Sebastian Herbord. All rights reserved.
+
+This file is part of usvfs.
+
+usvfs is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+usvfs is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with usvfs. If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "utility.h"
+#include "exceptionex.h"
+#include <cstdlib>
+
+namespace HookLib
+{
+
+FARPROC MyGetProcAddress(HMODULE module, LPCSTR functionName)
+{
+  // determine position of the exports of the module
+  PIMAGE_DOS_HEADER dosHeader = (PIMAGE_DOS_HEADER)module;
+  if (dosHeader->e_magic != IMAGE_DOS_SIGNATURE) {
+    return nullptr;
+  }
+
+  PIMAGE_NT_HEADERS ntHeaders =
+      (PIMAGE_NT_HEADERS)(((LPBYTE)dosHeader) + dosHeader->e_lfanew);
+  if (ntHeaders->Signature != IMAGE_NT_SIGNATURE) {
+    return nullptr;
+  }
+
+  PIMAGE_OPTIONAL_HEADER optionalHeader = &ntHeaders->OptionalHeader;
+  if (optionalHeader->NumberOfRvaAndSizes <= IMAGE_DIRECTORY_ENTRY_EXPORT) {
+    return nullptr;
+  }
+  PIMAGE_DATA_DIRECTORY dataDirectory =
+      &optionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
+  PIMAGE_EXPORT_DIRECTORY exportDirectory =
+      (PIMAGE_EXPORT_DIRECTORY)((LPBYTE)dosHeader + dataDirectory->VirtualAddress);
+
+  ULONG* addressOfNames = (ULONG*)((LPBYTE)module + exportDirectory->AddressOfNames);
+  ULONG* funcAddr = (ULONG*)((LPBYTE)module + exportDirectory->AddressOfFunctions);
+
+  // search exports for the specified name
+  for (DWORD i = 0; i < exportDirectory->NumberOfNames; ++i) {
+    char* curFunctionName = (char*)((LPBYTE)module + addressOfNames[i]);
+    USHORT* nameOrdinals =
+        (USHORT*)((LPBYTE)module + exportDirectory->AddressOfNameOrdinals);
+    if (strcmp(functionName, curFunctionName) == 0) {
+      if (funcAddr[nameOrdinals[i]] >= dataDirectory->VirtualAddress &&
+          funcAddr[nameOrdinals[i]] <
+              dataDirectory->VirtualAddress + dataDirectory->Size) {
+        char* forwardLibName = _strdup((LPSTR)module + funcAddr[nameOrdinals[i]]);
+        ON_BLOCK_EXIT([forwardLibName]() {
+          free(forwardLibName);
+        });
+        char* forwardFunctionName = strchr(forwardLibName, '.');
+        *forwardFunctionName      = 0;
+        ++forwardFunctionName;
+
+        HMODULE forwardLib = LoadLibraryA(forwardLibName);
+        FARPROC forward    = nullptr;
+        if (forwardLib != nullptr) {
+          forward = MyGetProcAddress(forwardLib, forwardFunctionName);
+          FreeLibrary(forwardLib);
+        }
+
+        return forward;
+      }
+      return (FARPROC)((LPBYTE)module + funcAddr[nameOrdinals[i]]);
+    }
+  }
+  return nullptr;
+}
+
+}  // namespace HookLib