[libxml2/python3-windows: 2/5] python: Port python 3.x module to Windows

[Chun-wei Fan <fanchunwei src gnome org>]

commit 99497d5d879f9230564d6e38b253e8bcbdfe70c1
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Tue Mar 30 16:11:13 2021 +0800

    python: Port python 3.x module to Windows
    
    On Windows, we don't have fcntl() which helps us to find out how a file was
    opened, so we need to resort to the Windows API NtQueryInformationFile() in
    ntdll.dll to help us, and compare the file access modes as appropriate to
    deduce the modes we want to pass into fdopen().
    
    As all official Python 3.x releases are built against newer Windows CRTs that
    toughen checks on the validity of the file descriptor when we convert the fd to
    a native Windows File Handle using _get_osfhandle(), we need to define an empty
    handler so that the program does not abort if the fd that was passed in was
    invalid; instead, we just return NULL if _get_osfhandle() could not return us a
    valid Windows File Handle.

 python/types.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 126 insertions(+), 2 deletions(-)
---
diff --git a/python/types.c b/python/types.c
index ed284ec7..75213dd4 100644
--- a/python/types.c
+++ b/python/types.c
@@ -21,16 +21,139 @@
 
 #if PY_MAJOR_VERSION >= 3
 #include <stdio.h>
+#include <stdint.h>
+
+#ifdef _WIN32
+
+#include <windows.h>
+#include <crtdbg.h>
+
+/* Taken from info on MSDN site, as we may not have the Windows WDK/DDK headers */
+typedef struct _IO_STATUS_BLOCK {
+  union {
+    NTSTATUS Status;
+    PVOID    Pointer;
+  } DUMMYUNIONNAME;
+  ULONG_PTR Information;
+} IO_STATUS_BLOCK;
+
+typedef struct _FILE_ACCESS_INFORMATION {
+  ACCESS_MASK AccessFlags;
+} FILE_ACCESS_INFORMATION;
+
+typedef NTSTATUS (*t_NtQueryInformationFile) (HANDLE           FileHandle,
+                                              IO_STATUS_BLOCK *IoStatusBlock,
+                                              PVOID            FileInformation,
+                                              ULONG            Length,
+                                              int              FileInformationClass); /* this is an Enum */
+
+#if (defined (_MSC_VER) && _MSC_VER >= 1400)
+/*
+ * This is the (empty) invalid parameter handler
+ * that is used for Visual C++ 2005 (and later) builds
+ * so that we can use this instead of the system automatically
+ * aborting the process.
+ *
+ * This is necessary as we use _get_oshandle() to check the validity
+ * of the file descriptors as we close them, so when an invalid file
+ * descriptor is passed into that function as we check on it, we get
+ * -1 as the result, instead of the gspawn helper program aborting.
+ *
+ * Please see http://msdn.microsoft.com/zh-tw/library/ks2530z6%28v=vs.80%29.aspx
+ * for an explanation on this.
+ */
+void
+myInvalidParameterHandler(const wchar_t *expression,
+                          const wchar_t *function,
+                          const wchar_t *file,
+                          unsigned int   line,
+                          uintptr_t      pReserved)
+{
+}
+#endif
+#else
 #include <unistd.h>
 #include <fcntl.h>
+#endif
 
 FILE *
 libxml_PyFileGet(PyObject *f) {
-    int fd, flags;
+    int flags;
     FILE *res;
     const char *mode;
 
-    fd = PyObject_AsFileDescriptor(f);
+    int fd = PyObject_AsFileDescriptor(f);
+    intptr_t w_fh = -1;
+
+#ifdef _WIN32
+    HMODULE hntdll = NULL;
+    IO_STATUS_BLOCK status_block;
+    FILE_ACCESS_INFORMATION ai;
+    t_NtQueryInformationFile NtQueryInformationFile;
+    BOOL is_read = FALSE;
+    BOOL is_write = FALSE;
+    BOOL is_append = FALSE;
+
+#if (defined (_MSC_VER) && _MSC_VER >= 1400)
+    /* set up our empty invalid parameter handler */
+    _invalid_parameter_handler oldHandler, newHandler;
+    newHandler = myInvalidParameterHandler;
+    oldHandler = _set_invalid_parameter_handler(newHandler);
+
+    /* Disable the message box for assertions. */
+    _CrtSetReportMode(_CRT_ASSERT, 0);
+#endif
+
+    w_fh = _get_osfhandle(fd);
+
+    if (w_fh == -1)
+        return(NULL);
+
+    hntdll = GetModuleHandleW(L"ntdll.dll");
+
+    if (hntdll == NULL)
+        return(NULL);
+
+    NtQueryInformationFile = (t_NtQueryInformationFile)GetProcAddress(hntdll, "NtQueryInformationFile");
+
+    if (NtQueryInformationFile != NULL &&
+        (NtQueryInformationFile((HANDLE)w_fh,
+                               &status_block,
+                               &ai,
+                                sizeof(FILE_ACCESS_INFORMATION),
+                                8) == 0)) /* 8 means "FileAccessInformation" */
+        {
+            if (ai.AccessFlags & FILE_READ_DATA)
+                is_read = TRUE;
+            if (ai.AccessFlags & FILE_WRITE_DATA)
+                is_write = TRUE;
+            if (ai.AccessFlags & FILE_APPEND_DATA)
+                is_append = TRUE;
+
+            if (is_write && is_read)
+                if (is_append)
+                    mode = "a+";
+                else
+                    mode = "rw";
+
+            if (!is_write && is_read)
+                if (is_append)
+                    mode = "r+";
+                else
+                    mode = "r";
+
+            if (is_write && !is_read)
+                if (is_append)
+                    mode = "a";
+                else
+                    mode = "w";
+        }
+
+    FreeLibrary(hntdll);
+
+    if (!is_write && !is_read) /* also happens if we did not load or run NtQueryInformationFile() 
successfully */
+        return(NULL);
+#else
     /*
      * Get the flags on the fd to understand how it was opened
      */
@@ -57,6 +180,7 @@ libxml_PyFileGet(PyObject *f) {
        default:
            return(NULL);
     }
+#endif
 
     /*
      * the FILE struct gets a new fd, so that it can be closed