segatools/amex/nvram.c

#include <windows.h>

#include <assert.h>
#include <stddef.h>
#include <stdint.h>

#include "amex/nvram.h"

#include "util/dprintf.h"

HRESULT nvram_open_file(HANDLE *out, const wchar_t *path, size_t size)
{
    LARGE_INTEGER cur_size;
    LARGE_INTEGER pos;
    HANDLE file;
    HRESULT hr;
    BOOL ok;

    assert(out != NULL);
    assert(path != NULL);

    *out = NULL;

    /* This is somewhat sloppy: allow multiple processes to open the backing
       store simultaneously. Multiple processes don't actually need to open
       the backing store simultaneously, but it allows use to reuse the same
       chunihook.dll for both chuniApp.exe and aimeReaderHost.exe, since a
       backing store fd gets opened during process init and subsequentely
       re-used for all device open operations on that NVRAM.

       We could defer the file open until it is actually needed instead, but
       this requires some messy locking; naive solutions would be racy or would
       effectively block all but one thread at a time in the process from
       performing any I/O.

       Hopefully some day Chunithm will move to the new amdaemon-based system
       architecture. */

    file = CreateFileW(
            path,
            GENERIC_READ | GENERIC_WRITE,
            FILE_SHARE_READ | FILE_SHARE_WRITE,
            NULL,
            OPEN_ALWAYS,
            FILE_ATTRIBUTE_NORMAL,
            NULL);

    if (file == INVALID_HANDLE_VALUE) {
        hr = HRESULT_FROM_WIN32(GetLastError());
        dprintf("%S: Error opening backing store: %x\n", path, (int) hr);

        goto end;
    }

    ok = GetFileSizeEx(file, &cur_size);

    if (!ok) {
        hr = HRESULT_FROM_WIN32(GetLastError());
        dprintf("%S: GetFileSizeEx failed: %x\n", path, (int) hr);

        goto end;
    }

    if (cur_size.QuadPart != (uint64_t) size) {
        pos.QuadPart = (uint64_t) size;
        ok = SetFilePointerEx(file, pos, NULL, FILE_BEGIN);

        if (!ok) {
            hr = HRESULT_FROM_WIN32(GetLastError());
            dprintf("%S: SetFilePointerEx failed: %x\n", path, (int) hr);

            goto end;
        }

        ok = SetEndOfFile(file);

        if (!ok) {
            hr = HRESULT_FROM_WIN32(GetLastError());
            dprintf("%S: SetEndOfFile failed: %x\n", path, (int) hr);

            goto end;
        }
    }

    *out = file;
    file = INVALID_HANDLE_VALUE;

    hr = S_OK;

end:
    if (file != INVALID_HANDLE_VALUE) {
        CloseHandle(file);
    }

    return hr;
}