/* Copyright (C) 2001-2023 Artifex Software, Inc.
   All Rights Reserved.

   This software is provided AS-IS with no warranty, either express or
   implied.

   This software is distributed under license and may not be copied,
   modified or distributed except as expressly authorized under the terms
   of the license contained in the file LICENSE in this distribution.

   Refer to licensing information at http://www.artifex.com or contact
   Artifex Software, Inc.,  39 Mesa Street, Suite 108A, San Francisco,
   CA 94129, USA, for further information.
*/


/* MS Windows (Win32) thread / semaphore / monitor implementation */
/* original multi-threading code by John Desrosiers */
#include "windows_.h"
#include "malloc_.h"
#include "gserrors.h"
#include "gpsync.h"
#include "gp.h"
#include "globals.h"
#include <process.h>

/* We have 2 possible implementations of the routines to initialise
 * globals. One uses the InitOnceExecuteOnce facility present in
 * windows versions >= Vista, the other uses a mutex and
 * InterlockedCompareExchangePointer and works on versions >=
 * XP. Accordingly, we use the XP-capable version. The other version
 * is retained for reference. */
#define XP_COMPATIBLE_INIT

/* Whatever happens, if we are compiling for a version < Vista
 * we MUST use the XP version. */
#if _WIN32_WINNT < 0x600
#ifndef XP_COMPATIBLE_INIT
#define XP_COMPATIBLE_INIT
#endif
#endif

#ifndef INIT_ONCE_STATIC_INIT
#define INIT_ONCE_STATIC_INIT { 0 }
#endif

static struct
{
#ifdef XP_COMPATIBLE_INIT
    HANDLE once_mutex;
    int inited;
#else
    INIT_ONCE once;
#endif
    CRITICAL_SECTION lock;
    gs_globals globals;
#ifdef DEBUG
    DWORD tlsIndex;
#endif
} GhostscriptGlobals = { INIT_ONCE_STATIC_INIT };

static BOOL CALLBACK init_globals(
#ifndef XP_COMPATIBLE_INIT
                                  PINIT_ONCE InitOnce,
                                  PVOID Parameter,
#endif
                                  PVOID *lpContext)
{
#ifdef METRO
    InitializeCriticalSectionEx(&GhostscriptGlobals.lock, 0, 0);	/* returns no status */
#else
    InitializeCriticalSection(&GhostscriptGlobals.lock);	/* returns no status */
#endif
#ifdef DEBUG
    GhostscriptGlobals.tlsIndex = TlsAlloc();
#endif
    gs_globals_init(&GhostscriptGlobals.globals);
    return TRUE;
}

gs_globals *gp_get_globals(void)
{
    PVOID lpContext;
#ifdef XP_COMPATIBLE_INIT
    /* Prior to Windows Vista, we don't have InitOnceExecuteOnce
     * capability, so we have to fudge it. Windows XP provides
     * InterlockedCompareExchangePointer, so we can use that.
     * We don't care about anything earlier than XP. */

    /* If we haven't got a mutex yet...*/
    if (GhostscriptGlobals.once_mutex == NULL) {
        /* Make one */
        HANDLE p = CreateMutex(NULL, FALSE, NULL);
        /* Now atomically swap that one into the structure. */
        if (InterlockedCompareExchangePointer((PVOID *)&GhostscriptGlobals.once_mutex, (PVOID)p, NULL) != NULL) {
            /* If there was one there already, ditch ours and just use the one that was there already. */
            CloseHandle(p);
        }
    }
    WaitForSingleObject(GhostscriptGlobals.once_mutex, INFINITE);
    if (GhostscriptGlobals.inited == 0) {
        init_globals(&lpContext);
        GhostscriptGlobals.inited = 1;
    }
    ReleaseMutex(GhostscriptGlobals.once_mutex);
#else
    BOOL status = InitOnceExecuteOnce(&GhostscriptGlobals.once,
                                      init_globals,
                                      NULL,
                                      &lpContext);
    if (status == FALSE)
        return NULL;
#endif

    return &GhostscriptGlobals.globals;
}


void gp_global_lock(gs_globals *globals)
{
    if (globals == NULL)
        return;
    EnterCriticalSection(&GhostscriptGlobals.lock);
}

void gp_global_unlock(gs_globals *globals)
{
    if (globals == NULL)
        return;
    LeaveCriticalSection(&GhostscriptGlobals.lock);
}

void gp_set_debug_mem_ptr(gs_memory_t *mem)
{
#ifdef DEBUG
    if (GhostscriptGlobals.tlsIndex != TLS_OUT_OF_INDEXES)
        TlsSetValue(GhostscriptGlobals.tlsIndex, mem);
#endif
}

gs_memory_t *gp_get_debug_mem_ptr(void)
{
#ifdef DEBUG
    if (GhostscriptGlobals.tlsIndex == TLS_OUT_OF_INDEXES)
        return NULL;
    return (gs_memory_t *)TlsGetValue(GhostscriptGlobals.tlsIndex);
#else
    return NULL;
#endif
}

/* It seems that both Borland and Watcom *should* be able to cope with the
 * new style threading using _beginthreadex/_endthreadex. I am unable to test
 * this properly however, and the tests I have done lead me to believe it
 * may be problematic. Given that these platforms are not a support priority,
 * we leave the code falling back to just using the old style code (which
 * presumably works).
 *
 * The upshot of this should be that we continue to work exactly as before.
 *
 * To try using the new functions, simply omit the definition of
 * FALLBACK_TO_OLD_THREADING_FUNCTIONS below. If you find this works for
 * either Borland or Watcom, then please let us know and we can make the
 * change permanently.
 */
#if defined(__BORLANDC__)
#define FALLBACK_TO_OLD_THREADING_FUNCTIONS
#elif defined(__WATCOMC__)
#define FALLBACK_TO_OLD_THREADING_FUNCTIONS
#endif

/* ------- Synchronization primitives -------- */

/* Semaphore supports wait/signal semantics */

typedef struct win32_semaphore_s {
    HANDLE handle;		/* returned from CreateSemaphore */
} win32_semaphore;

uint
gp_semaphore_sizeof(void)
{
    return sizeof(win32_semaphore);
}

int	/* if sema <> 0 rets -ve error, 0 ok; if sema == 0, 0 movable, 1 fixed */
gp_semaphore_open(
                  gp_semaphore * sema	/* create semaphore here */
)
{
    win32_semaphore *const winSema = (win32_semaphore *)sema;

    if (winSema) {
        winSema->handle =
#ifdef METRO
            CreateSemaphoreExW(NULL, 0, max_int, NULL, 0, 0);
#else
            CreateSemaphore(NULL, 0, max_int, NULL);
#endif
        return
            (winSema->handle != NULL ? 0 :
             gs_note_error(gs_error_unknownerror));
    } else
        return 0;		/* Win32 semaphores handles may be moved */
}

int
gp_semaphore_close(
                   gp_semaphore * sema	/* semaphore to affect */
)
{
    win32_semaphore *const winSema = (win32_semaphore *)sema;

    if (winSema->handle != NULL)
        CloseHandle(winSema->handle);
    winSema->handle = NULL;
    return 0;
}

int				/* rets 0 ok, -ve error */
gp_semaphore_wait(
                  gp_semaphore * sema	/* semaphore to affect */
)
{
    win32_semaphore *const winSema = (win32_semaphore *)sema;

    return
        (
#ifdef METRO
        WaitForSingleObjectEx(winSema->handle, INFINITE, FALSE)
#else
        WaitForSingleObject(winSema->handle, INFINITE)
#endif
          == WAIT_OBJECT_0 ? 0 : gs_error_unknownerror);
}

int				/* rets 0 ok, -ve error */
gp_semaphore_signal(
                    gp_semaphore * sema	/* semaphore to affect */
)
{
    win32_semaphore *const winSema = (win32_semaphore *)sema;

    return
        (ReleaseSemaphore(winSema->handle, 1, NULL) ? 0 :
         gs_error_unknownerror);
}

/* Monitor supports enter/leave semantics */

typedef struct win32_monitor_s {
    CRITICAL_SECTION lock;	/* critical section lock */
} win32_monitor;

uint
gp_monitor_sizeof(void)
{
    return sizeof(win32_monitor);
}

int	/* if sema <> 0 rets -ve error, 0 ok; if sema == 0, 0 movable, 1 fixed */
gp_monitor_open(
                gp_monitor * mon	/* create monitor here */
)
{
    win32_monitor *const winMon = (win32_monitor *)mon;

    if (mon) {
#ifdef METRO
        InitializeCriticalSectionEx(&winMon->lock, 0, 0);	/* returns no status */
#else
        InitializeCriticalSection(&winMon->lock);	/* returns no status */
#endif
        return 0;
    } else
        return 1;		/* Win32 critical sections mutsn't be moved */
}

int
gp_monitor_close(
                 gp_monitor * mon	/* monitor to affect */
)
{
    win32_monitor *const winMon = (win32_monitor *)mon;

    DeleteCriticalSection(&winMon->lock);	/* rets no status */
    return 0;
}

int				/* rets 0 ok, -ve error */
gp_monitor_enter(
                 gp_monitor * mon	/* monitor to affect */
)
{
    win32_monitor *const winMon = (win32_monitor *)mon;

    EnterCriticalSection(&winMon->lock);	/* rets no status */
    return 0;
}

int				/* rets 0 ok, -ve error */
gp_monitor_leave(
                 gp_monitor * mon	/* monitor to affect */
)
{
    win32_monitor *const winMon = (win32_monitor *)mon;

    LeaveCriticalSection(&winMon->lock);	/* rets no status */
    return 0;
}

/* --------- Thread primitives ---------- */

typedef struct gp_thread_creation_closure_s {
    gp_thread_creation_callback_t function;	/* function to start */
    void *data;			/* magic data to pass to thread */
    gs_memory_t *mem;
} gp_thread_creation_closure;

/* Origin of new threads started by gp_create_thread */
static void
gp_thread_begin_wrapper(
                        void *thread_data	/* gp_thread_creation_closure passed as magic data */
)
{
    gp_thread_creation_closure closure;

    closure = *(gp_thread_creation_closure *)thread_data;
    free(thread_data);
#ifdef DEBUG
    if (GhostscriptGlobals.tlsIndex != TLS_OUT_OF_INDEXES)
        TlsSetValue(GhostscriptGlobals.tlsIndex, closure.mem);
#endif
    (*closure.function)(closure.data);
    _endthread();
}

/* Call a function on a brand new thread */
int				/* 0 ok, -ve error */
gp_create_thread(
                 gp_thread_creation_callback_t function,	/* function to start */
                 void *data	/* magic data to pass to thread fn */
)
{
    /* Create the magic closure that thread_wrapper gets passed */
    gp_thread_creation_closure *closure =
        (gp_thread_creation_closure *)malloc(sizeof(*closure));

    if (!closure)
        return_error(gs_error_VMerror);
    closure->function = function;
    closure->data = data;
#ifdef DEBUG
    if (GhostscriptGlobals.tlsIndex != TLS_OUT_OF_INDEXES)
        closure->mem = TlsGetValue(GhostscriptGlobals.tlsIndex);
#endif

    /*
     * Start thread_wrapper.  The Watcom _beginthread returns (int)(-1) if
     * the call fails.  The Microsoft _beginthread returns -1 (according to
     * the doc, even though the return type is "unsigned long" !!!) if the
     * call fails; we aren't sure what the Borland _beginthread returns.
     * The hack with ~ avoids a source code commitment as to whether the
     * return type is [u]int or [u]long.
     *
     * BEGIN_THREAD is a macro (defined in windows_.h) because _beginthread
     * takes different arguments in Watcom C.
     */
    if (~BEGIN_THREAD(gp_thread_begin_wrapper, 128*1024, closure) != 0)
    {
        free(closure);
        return 0;
    }
    return_error(gs_error_unknownerror);
}

/* gp_thread_creation_closure passed as magic data */
static unsigned __stdcall
gp_thread_start_wrapper(void *thread_data)
{
    gp_thread_creation_closure closure;

    closure = *(gp_thread_creation_closure *)thread_data;
    free(thread_data);
#ifdef DEBUG
    if (GhostscriptGlobals.tlsIndex != TLS_OUT_OF_INDEXES)
        TlsSetValue(GhostscriptGlobals.tlsIndex, closure.mem);
#endif
    (*closure.function)(closure.data);
    _endthreadex(0);
    return 0;
}

int gp_thread_start(gp_thread_creation_callback_t function,
                    void *data, gp_thread_id *thread)
{
#ifdef FALLBACK_TO_OLD_THREADING_FUNCTIONS
    *thread = (gp_thread_id)1;
    return gp_create_thread(function, data);
#else
    /* Create the magic closure that thread_wrapper gets passed */
    HANDLE hThread;
    unsigned threadID;
    gp_thread_creation_closure *closure =
        (gp_thread_creation_closure *)malloc(sizeof(*closure));

    if (!closure)
        return_error(gs_error_VMerror);
    closure->function = function;
    closure->data = data;
#ifdef DEBUG
    if (GhostscriptGlobals.tlsIndex != TLS_OUT_OF_INDEXES)
        closure->mem = TlsGetValue(GhostscriptGlobals.tlsIndex);
#endif
    hThread = (HANDLE)_beginthreadex(NULL, 0, &gp_thread_start_wrapper,
                                     closure, 0, &threadID);
    if (hThread == (HANDLE)0)
    {
        free(closure);
        *thread = NULL;
        return_error(gs_error_unknownerror);
    }
    *thread = (gp_thread_id)hThread;
    return 0;
#endif
}

void gp_thread_finish(gp_thread_id thread)
{
#ifndef FALLBACK_TO_OLD_THREADING_FUNCTIONS
    if (thread == NULL)
        return;
#ifdef METRO
    WaitForSingleObjectEx((HANDLE)thread, INFINITE, FALSE);
#else
    WaitForSingleObject((HANDLE)thread, INFINITE);
#endif
    CloseHandle((HANDLE)thread);
#endif
}