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PC/import_nt.c
/********************************************************************

 import_nt.c

  Win32 specific import code.

*/

#include "Python.h"
#include "osdefs.h"
#include <windows.h>
#include "importdl.h"
#include "malloc.h" /* for alloca */

/* a string loaded from the DLL at startup */
extern const char *PyWin_DLLVersionString;

FILE *PyWin_FindRegisteredModule(const char *moduleName,
                                 struct filedescr **ppFileDesc,
                                 char *pathBuf,
                                 Py_ssize_t pathLen)
{
    char *moduleKey;
    const char keyPrefix[] = "Software\\Python\\PythonCore\\";
    const char keySuffix[] = "\\Modules\\";
#ifdef _DEBUG
    /* In debugging builds, we _must_ have the debug version
     * registered.
     */
    const char debugString[] = "\\Debug";
#else
    const char debugString[] = "";
#endif
    struct filedescr *fdp = NULL;
    FILE *fp;
    HKEY keyBase = HKEY_CURRENT_USER;
    int modNameSize;
    long regStat;

    /* Calculate the size for the sprintf buffer.
     * Get the size of the chars only, plus 1 NULL.
     */
    size_t bufSize = sizeof(keyPrefix)-1 +
                     strlen(PyWin_DLLVersionString) +
                     sizeof(keySuffix) +
                     strlen(moduleName) +
                     sizeof(debugString) - 1;
    /* alloca == no free required, but memory only local to fn,
     * also no heap fragmentation!
     */
    moduleKey = alloca(bufSize);
    PyOS_snprintf(moduleKey, bufSize,
                  "Software\\Python\\PythonCore\\%s\\Modules\\%s%s",
                  PyWin_DLLVersionString, moduleName, debugString);

    assert(pathLen < INT_MAX);
    modNameSize = (int)pathLen;
    regStat = RegQueryValue(keyBase, moduleKey, pathBuf, &modNameSize);
    if (regStat != ERROR_SUCCESS) {
        /* No user setting - lookup in machine settings */
        keyBase = HKEY_LOCAL_MACHINE;
        /* be anal - failure may have reset size param */
        modNameSize = (int)pathLen;
        regStat = RegQueryValue(keyBase, moduleKey,
                                pathBuf, &modNameSize);

        if (regStat != ERROR_SUCCESS)
            return NULL;
    }
    /* use the file extension to locate the type entry. */
    for (fdp = _PyImport_Filetab; fdp->suffix != NULL; fdp++) {
        size_t extLen = strlen(fdp->suffix);
        assert(modNameSize >= 0); /* else cast to size_t is wrong */
        if ((size_t)modNameSize > extLen &&
            strnicmp(pathBuf + ((size_t)modNameSize-extLen-1),
                     fdp->suffix,
                     extLen) == 0)
            break;
    }
    if (fdp->suffix == NULL)
        return NULL;
    fp = fopen(pathBuf, fdp->mode);
    if (fp != NULL)
        *ppFileDesc = fdp;
    return fp;
}