UID on Windows too

Author: scivision

CMakeLists.txt

@@ -46,11 +46,13 @@ foreach(a IN ITEMS
   allocate bounds contiguous
   array bool error exception
   iterator
-  glibc malloc
+  malloc
   nullptr
   opaque pointer poly_function poly_type real struct
   sleep string submodule
-  time vector)
+  time
+  uid
+  vector)
 
   add_subdirectory(test/${a})
 

src/uid/uid.cpp

@@ -0,0 +1,86 @@
+// Windows doesn't have a numerid UID like Unix, so we return the SID as a string instead.
+
+#if defined(_WIN32)
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <sddl.h>        // For ConvertSidToStringSid
+#include <vector>
+#include <iostream>
+#else
+#include <unistd.h>
+#include <sys/types.h>
+#endif
+
+#include <string>
+#include <string_view>
+#include <system_error>
+
+#include "uid.h"
+
+
+extern "C" {
+std::string::size_type c_get_uid(char* result, const std::string::size_type buffer_size) {
+    return str2char(get_uid(), result, buffer_size);
+}
+}
+
+std::string::size_type str2char(std::string_view s, char* result, const std::string::size_type buffer_size)
+{
+  if(s.length() >= buffer_size) [[unlikely]]
+  {
+    std::cerr << "ERROR: " << s << " " << std::make_error_code(std::errc::result_out_of_range) << "\n";
+    return 0;
+  }
+
+  s.copy(result, buffer_size);
+  result[s.length()] = '\0';
+  return s.length();
+}
+
+std::string get_uid()
+{
+#if defined(_WIN32)
+    HANDLE hToken = nullptr;
+    if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &hToken)) {
+        std::cerr << "OpenProcessToken failed: " << GetLastError() << "\n";
+        return {};
+    }
+
+    // get required buffer size
+    DWORD dwLength = 0;
+    GetTokenInformation(hToken, TokenUser, nullptr, 0, &dwLength);
+
+    if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+        std::cerr << "GetTokenInformation (size) failed: " << GetLastError() << "\n";
+        CloseHandle(hToken);
+        return {};
+    }
+
+    std::vector<BYTE> buffer(dwLength);
+
+    if (!GetTokenInformation(hToken, TokenUser, buffer.data(), dwLength, &dwLength)) {
+        std::cerr << "GetTokenInformation failed: " << GetLastError() << "\n";
+        CloseHandle(hToken);
+        return {};
+    }
+
+    PTOKEN_USER pTokenUser = reinterpret_cast<PTOKEN_USER>(buffer.data());
+
+    // Convert SID to string
+    LPSTR sidString = nullptr;
+    if (!ConvertSidToStringSidA(pTokenUser->User.Sid, &sidString)) {
+        std::cerr << "ConvertSidToStringSidA failed: " << GetLastError() << "\n";
+        CloseHandle(hToken);
+        return {};
+    }
+
+    std::string result = sidString;
+    LocalFree(sidString);
+    CloseHandle(hToken);
+
+    return result;
+
+#else
+    return std::to_string(geteuid());
+#endif
+}

src/uid/uid.h

@@ -0,0 +1,10 @@
+#include <string>
+#include <string_view>
+
+extern "C" {
+std::string::size_type c_get_uid(char*, const std::string::size_type);
+}
+
+std::string::size_type str2char(std::string_view, char*, const std::string::size_type);
+
+std::string get_uid();

test/glibc/CMakeLists.txt

@@ -1,7 +1,11 @@
 #include <cstdlib>
 #include <string>
 #include <iostream>
+
 #include <memory>
+#ifndef __cpp_lib_to_address
+#error "C++20 std::to_address is required for this test"
+#endif
 
 
 char* iter_ptr(char* c){

test/glibc/getuid.f90

@@ -0,0 +1,4 @@
+set_property(DIRECTORY PROPERTY LABELS uid)
+
+add_executable(getuid getuid.f90 ${PROJECT_SOURCE_DIR}/src/uid/uid.cpp)
+add_test(NAME GetUID COMMAND getuid)

test/iterator/standalone.cpp

@@ -0,0 +1,34 @@
+program guid
+
+use, intrinsic :: iso_c_binding
+
+implicit none
+
+interface
+integer(C_SIZE_T) function c_get_uid(result, buffer_size) bind(C)
+import
+character(kind=C_CHAR), intent(out) :: result(*)
+integer(C_SIZE_T), intent(in), value :: buffer_size
+end function
+end interface
+
+
+print '(a)', "UID: " // get_uid()
+
+contains
+
+function get_uid() result(r)
+character(:), allocatable :: r
+character(kind=c_char, len=:), allocatable :: cbuf
+integer(C_SIZE_T) :: N
+
+!! 256 is reasonable max length for Windows SID string representation
+allocate(character(256) :: cbuf)
+N = len(cbuf)
+
+N = c_get_uid(cbuf, N)
+
+r = cbuf(:N)
+end function
+
+end program