/**

 * threads.c: set of generic threading related routines

 *

 * See Copyright for the status of this software.

 *

 * Gary Pennington <Gary.Pennington@uk.sun.com>

 * daniel@veillard.com

 */

#define IN_LIBXML

#include "libxml.h"

#include <string.h>

#include <stdlib.h>

#include <libxml/threads.h>

#include <libxml/parser.h>

#ifdef LIBXML_CATALOG_ENABLED

#include <libxml/catalog.h>

#endif

#ifdef LIBXML_SCHEMAS_ENABLED

#include <libxml/xmlschemastypes.h>

#include <libxml/relaxng.h>

#endif

#if defined(SOLARIS)

#include <note.h>

#endif

#include "private/dict.h"

#include "private/enc.h"

#include "private/globals.h"

#include "private/memory.h"

#include "private/threads.h"

#include "private/xpath.h"

#if defined(HAVE_POSIX_THREADS) && \

    defined(__GLIBC__) && \

    __GLIBC__ * 100 + __GLIBC_MINOR__ >= 234

/*

 * The modern way available since glibc 2.32.

 *

 * The check above is for glibc 2.34 which merged the pthread symbols into

 * libc. Since we still allow linking without pthread symbols (see below),

 * this only works if pthread symbols are guaranteed to be available.

 */

#include <sys/single_threaded.h>

#define XML_IS_THREADED() (!__libc_single_threaded)

#define XML_IS_NEVER_THREADED() 0

#elif defined(HAVE_POSIX_THREADS) && \

      defined(__GLIBC__) && \

      defined(__GNUC__)

/*

 * The traditional way to check for single-threaded applications with

 * glibc was to check whether the separate libpthread library is

 * linked in. This works by not linking libxml2 with libpthread (see

 * BASE_THREAD_LIBS in configure.ac and Makefile.am) and declaring

 * pthread functions as weak symbols.

 *

 * In glibc 2.34, the pthread symbols were moved from libpthread to libc,

 * so this doesn't work anymore.

 *

 * At some point, this legacy code and the BASE_THREAD_LIBS hack in

 * configure.ac can probably be removed.

 */

#pragma weak pthread_mutex_init

#pragma weak pthread_mutex_destroy

#pragma weak pthread_mutex_lock

#pragma weak pthread_mutex_unlock

#pragma weak pthread_cond_init

#pragma weak pthread_cond_destroy

#pragma weak pthread_cond_wait

#pragma weak pthread_equal

#pragma weak pthread_self

#pragma weak pthread_cond_signal

#define XML_PTHREAD_WEAK

#define XML_IS_THREADED() libxml_is_threaded

#define XML_IS_NEVER_THREADED() (!libxml_is_threaded)

static int libxml_is_threaded = -1;

#else /* other POSIX platforms */

#define XML_IS_THREADED() 1

#define XML_IS_NEVER_THREADED() 0

#endif

/*

 * TODO: this module still uses malloc/free and not xmlMalloc/xmlFree

 *       to avoid some craziness since xmlMalloc/xmlFree may actually

 *       be hosted on allocated blocks needing them for the allocation ...

 */

/*

 * xmlRMutex are reentrant mutual exception locks

 */

struct _xmlRMutex {

#ifdef HAVE_POSIX_THREADS

    pthread_mutex_t lock;

    unsigned int held;

    unsigned int waiters;

    pthread_t tid;

    pthread_cond_t cv;

#elif defined HAVE_WIN32_THREADS

    CRITICAL_SECTION cs;

#else

    int empty;

#endif

};

static xmlRMutexPtr xmlLibraryLock = NULL;

/**

 * xmlInitMutex:

 * @mutex:  the mutex

 *

 * Initialize a mutex.

 */

void

xmlInitMutex(xmlMutexPtr mutex)

{

#ifdef HAVE_POSIX_THREADS

    if (XML_IS_NEVER_THREADED() == 0)

        pthread_mutex_init(&mutex->lock, NULL);

#elif defined HAVE_WIN32_THREADS

    InitializeCriticalSection(&mutex->cs);

#else

    (void) mutex;

#endif

}

/**

 * xmlNewMutex:

 *

 * xmlNewMutex() is used to allocate a libxml2 token struct for use in

 * synchronizing access to data.

 *

 * Returns a new simple mutex pointer or NULL in case of error

 */

xmlMutexPtr

xmlNewMutex(void)

{

    xmlMutexPtr tok;

    if ((tok = malloc(sizeof(xmlMutex))) == NULL)

        return (NULL);

    xmlInitMutex(tok);

    return (tok);

}

/**

 * xmlCleanupMutex:

 * @mutex:  the simple mutex

 *

 * Reclaim resources associated with a mutex.

 */

void

xmlCleanupMutex(xmlMutexPtr mutex)

{

#ifdef HAVE_POSIX_THREADS

    if (XML_IS_NEVER_THREADED() == 0)

        pthread_mutex_destroy(&mutex->lock);

#elif defined HAVE_WIN32_THREADS

    DeleteCriticalSection(&mutex->cs);

#else

    (void) mutex;

#endif

}

/**

 * xmlFreeMutex:

 * @tok:  the simple mutex

 *

 * Free a mutex.

 */

void

xmlFreeMutex(xmlMutexPtr tok)

{

    if (tok == NULL)

        return;

    xmlCleanupMutex(tok);

    free(tok);

}

/**

 * xmlMutexLock:

 * @tok:  the simple mutex

 *

 * xmlMutexLock() is used to lock a libxml2 token.

 */

void

xmlMutexLock(xmlMutexPtr tok)

{

    if (tok == NULL)

        return;

#ifdef HAVE_POSIX_THREADS

    /*

     * This assumes that __libc_single_threaded won't change while the

     * lock is held.

     */

    if (XML_IS_THREADED() != 0)

        pthread_mutex_lock(&tok->lock);

#elif defined HAVE_WIN32_THREADS

    EnterCriticalSection(&tok->cs);

#endif

}

/**

 * xmlMutexUnlock:

 * @tok:  the simple mutex

 *

 * xmlMutexUnlock() is used to unlock a libxml2 token.

 */

void

xmlMutexUnlock(xmlMutexPtr tok)

{

    if (tok == NULL)

        return;

#ifdef HAVE_POSIX_THREADS

    if (XML_IS_THREADED() != 0)

        pthread_mutex_unlock(&tok->lock);

#elif defined HAVE_WIN32_THREADS

    LeaveCriticalSection(&tok->cs);

#endif

}

/**

 * xmlNewRMutex:

 *

 * xmlRNewMutex() is used to allocate a reentrant mutex for use in

 * synchronizing access to data. token_r is a re-entrant lock and thus useful

 * for synchronizing access to data structures that may be manipulated in a

 * recursive fashion.

 *

 * Returns the new reentrant mutex pointer or NULL in case of error

 */

xmlRMutexPtr

xmlNewRMutex(void)

{

    xmlRMutexPtr tok;

    if ((tok = malloc(sizeof(xmlRMutex))) == NULL)

        return (NULL);

#ifdef HAVE_POSIX_THREADS

    if (XML_IS_NEVER_THREADED() == 0) {

        pthread_mutex_init(&tok->lock, NULL);

        tok->held = 0;

        tok->waiters = 0;

        pthread_cond_init(&tok->cv, NULL);

    }

#elif defined HAVE_WIN32_THREADS

    InitializeCriticalSection(&tok->cs);

#endif

    return (tok);

}

/**

 * xmlFreeRMutex:

 * @tok:  the reentrant mutex

 *

 * xmlRFreeMutex() is used to reclaim resources associated with a

 * reentrant mutex.

 */

void

xmlFreeRMutex(xmlRMutexPtr tok ATTRIBUTE_UNUSED)

{

    if (tok == NULL)

        return;

#ifdef HAVE_POSIX_THREADS

    if (XML_IS_NEVER_THREADED() == 0) {

        pthread_mutex_destroy(&tok->lock);

        pthread_cond_destroy(&tok->cv);

    }

#elif defined HAVE_WIN32_THREADS

    DeleteCriticalSection(&tok->cs);

#endif

    free(tok);

}

/**

 * xmlRMutexLock:

 * @tok:  the reentrant mutex

 *

 * xmlRMutexLock() is used to lock a libxml2 token_r.

 */

void

xmlRMutexLock(xmlRMutexPtr tok)

{

    if (tok == NULL)

        return;

#ifdef HAVE_POSIX_THREADS

    if (XML_IS_THREADED() == 0)

        return;

    pthread_mutex_lock(&tok->lock);

    if (tok->held) {

        if (pthread_equal(tok->tid, pthread_self())) {

            tok->held++;

            pthread_mutex_unlock(&tok->lock);

            return;

        } else {

            tok->waiters++;

            while (tok->held)

                pthread_cond_wait(&tok->cv, &tok->lock);

            tok->waiters--;

        }

    }

    tok->tid = pthread_self();

    tok->held = 1;

    pthread_mutex_unlock(&tok->lock);

#elif defined HAVE_WIN32_THREADS

    EnterCriticalSection(&tok->cs);

#endif

}

/**

 * xmlRMutexUnlock:

 * @tok:  the reentrant mutex

 *

 * xmlRMutexUnlock() is used to unlock a libxml2 token_r.

 */

void

xmlRMutexUnlock(xmlRMutexPtr tok ATTRIBUTE_UNUSED)

{

    if (tok == NULL)

        return;

#ifdef HAVE_POSIX_THREADS

    if (XML_IS_THREADED() == 0)

        return;

    pthread_mutex_lock(&tok->lock);

    tok->held--;

    if (tok->held == 0) {

        if (tok->waiters)

            pthread_cond_signal(&tok->cv);

        memset(&tok->tid, 0, sizeof(tok->tid));

    }

    pthread_mutex_unlock(&tok->lock);

#elif defined HAVE_WIN32_THREADS

    LeaveCriticalSection(&tok->cs);

#endif

}

/************************************************************************

 *                  *

 *      Library wide thread interfaces      *

 *                  *

 ************************************************************************/

/**

 * xmlGetThreadId:

 *

 * DEPRECATED: Internal function, do not use.

 *

 * xmlGetThreadId() find the current thread ID number

 * Note that this is likely to be broken on some platforms using pthreads

 * as the specification doesn't mandate pthread_t to be an integer type

 *

 * Returns the current thread ID number

 */

int

xmlGetThreadId(void)

{

#ifdef HAVE_POSIX_THREADS

    pthread_t id;

    int ret;

    if (XML_IS_THREADED() == 0)

        return (0);

    id = pthread_self();

    /* horrible but preserves compat, see warning above */

    memcpy(&ret, &id, sizeof(ret));

    return (ret);

#elif defined HAVE_WIN32_THREADS

    return GetCurrentThreadId();

#else

    return ((int) 0);

#endif

}

/**

 * xmlLockLibrary:

 *

 * xmlLockLibrary() is used to take out a re-entrant lock on the libxml2

 * library.

 */

void

xmlLockLibrary(void)

{

    xmlRMutexLock(xmlLibraryLock);

}

/**

 * xmlUnlockLibrary:

 *

 * xmlUnlockLibrary() is used to release a re-entrant lock on the libxml2

 * library.

 */

void

xmlUnlockLibrary(void)

{

    xmlRMutexUnlock(xmlLibraryLock);

}

/**

 * xmlInitThreads:

 *

 * DEPRECATED: Alias for xmlInitParser.

 */

void

xmlInitThreads(void)

{

    xmlInitParser();

}

/**

 * xmlCleanupThreads:

 *

 * DEPRECATED: This function is a no-op. Call xmlCleanupParser

 * to free global state but see the warnings there. xmlCleanupParser

 * should be only called once at program exit. In most cases, you don't

 * have call cleanup functions at all.

 */

void

xmlCleanupThreads(void)

{

}

/************************************************************************

 *                  *

 *      Library wide initialization     *

 *                  *

 ************************************************************************/

static int xmlParserInitialized = 0;

static int xmlParserInnerInitialized = 0;

#ifdef HAVE_POSIX_THREADS

static pthread_mutex_t global_init_lock = PTHREAD_MUTEX_INITIALIZER;

#elif defined HAVE_WIN32_THREADS

static volatile LPCRITICAL_SECTION global_init_lock = NULL;

#endif

/**

 * xmlGlobalInitMutexLock

 *

 * Makes sure that the global initialization mutex is initialized and

 * locks it.

 */

static void

xmlGlobalInitMutexLock(void) {

#ifdef HAVE_POSIX_THREADS

#ifdef XML_PTHREAD_WEAK

    /*

     * This is somewhat unreliable since libpthread could be loaded

     * later with dlopen() and threads could be created. But it's

     * long-standing behavior and hard to work around.

     */

    if (libxml_is_threaded == -1)

        libxml_is_threaded =

            (pthread_mutex_init != NULL) &&

            (pthread_mutex_destroy != NULL) &&

            (pthread_mutex_lock != NULL) &&

            (pthread_mutex_unlock != NULL) &&

            (pthread_cond_init != NULL) &&

            (pthread_cond_destroy != NULL) &&

            (pthread_cond_wait != NULL) &&

            /*

             * pthread_equal can be inline, resuting in -Waddress warnings.

             * Let's assume it's available if all the other functions are.

             */

            /* (pthread_equal != NULL) && */

            (pthread_self != NULL) &&

            (pthread_cond_signal != NULL);

#endif

    /* The mutex is statically initialized, so we just lock it. */

    if (XML_IS_THREADED() != 0)

        pthread_mutex_lock(&global_init_lock);

#elif defined HAVE_WIN32_THREADS

    LPCRITICAL_SECTION cs;

    /* Create a new critical section */

    if (global_init_lock == NULL) {

        cs = malloc(sizeof(CRITICAL_SECTION));

        if (cs == NULL) {

            xmlGenericError(xmlGenericErrorContext,

                            "xmlGlobalInitMutexLock: out of memory\n");

            return;

        }

        InitializeCriticalSection(cs);

        /* Swap it into the global_init_lock */

#ifdef InterlockedCompareExchangePointer

        InterlockedCompareExchangePointer((void **) &global_init_lock,

                                          cs, NULL);

#else /* Use older void* version */

        InterlockedCompareExchange((void **) &global_init_lock,

                                   (void *) cs, NULL);

#endif /* InterlockedCompareExchangePointer */

        /* If another thread successfully recorded its critical

         * section in the global_init_lock then discard the one

         * allocated by this thread. */

        if (global_init_lock != cs) {

            DeleteCriticalSection(cs);

            free(cs);

        }

    }

    /* Lock the chosen critical section */

    EnterCriticalSection(global_init_lock);

#endif

}

static void

xmlGlobalInitMutexUnlock(void) {

#ifdef HAVE_POSIX_THREADS

    if (XML_IS_THREADED() != 0)

        pthread_mutex_unlock(&global_init_lock);

#elif defined HAVE_WIN32_THREADS

    if (global_init_lock != NULL)

  LeaveCriticalSection(global_init_lock);

#endif

}

/**

 * xmlGlobalInitMutexDestroy

 *

 * Makes sure that the global initialization mutex is destroyed before

 * application termination.

 */

static void

xmlGlobalInitMutexDestroy(void) {

#ifdef HAVE_POSIX_THREADS

#elif defined HAVE_WIN32_THREADS

    if (global_init_lock != NULL) {

        DeleteCriticalSection(global_init_lock);

        free(global_init_lock);

        global_init_lock = NULL;

    }

#endif

}

/**

 * xmlInitParser:

 *

 * Initialization function for the XML parser.

 *

 * Call once from the main thread before using the library in

 * multithreaded programs.

 */

void

xmlInitParser(void) {

    /*

     * Note that the initialization code must not make memory allocations.

     */

    if (xmlParserInitialized != 0)

        return;

    xmlGlobalInitMutexLock();

    if (xmlParserInnerInitialized == 0) {

#if defined(_WIN32) && \

    !defined(LIBXML_THREAD_ALLOC_ENABLED) && \

    (!defined(LIBXML_STATIC) || defined(LIBXML_STATIC_FOR_DLL))

        if (xmlFree == free)

            atexit(xmlCleanupParser);

#endif

        xmlInitMemoryInternal(); /* Should come second */

        xmlInitGlobalsInternal();

        xmlInitRandom();

        xmlInitDictInternal();

        xmlInitEncodingInternal();

#if defined(LIBXML_XPATH_ENABLED) || defined(LIBXML_SCHEMAS_ENABLED)

        xmlInitXPathInternal();

#endif

        xmlRegisterDefaultInputCallbacks();

#ifdef LIBXML_OUTPUT_ENABLED

        xmlRegisterDefaultOutputCallbacks();

#endif /* LIBXML_OUTPUT_ENABLED */

        xmlParserInnerInitialized = 1;

    }

    xmlGlobalInitMutexUnlock();

    xmlParserInitialized = 1;

}

/**

 * xmlCleanupParser:

 *

 * This function name is somewhat misleading. It does not clean up

 * parser state, it cleans up memory allocated by the library itself.

 * It is a cleanup function for the XML library. It tries to reclaim all

 * related global memory allocated for the library processing.

 * It doesn't deallocate any document related memory. One should

 * call xmlCleanupParser() only when the process has finished using

 * the library and all XML/HTML documents built with it.

 * See also xmlInitParser() which has the opposite function of preparing

 * the library for operations.

 *

 * WARNING: if your application is multithreaded or has plugin support

 *          calling this may crash the application if another thread or

 *          a plugin is still using libxml2. It's sometimes very hard to

 *          guess if libxml2 is in use in the application, some libraries

 *          or plugins may use it without notice. In case of doubt abstain

 *          from calling this function or do it just before calling exit()

 *          to avoid leak reports from valgrind !

 */

void

xmlCleanupParser(void) {

    if (!xmlParserInitialized)

        return;

    /* These functions can call xmlFree. */

    xmlCleanupCharEncodingHandlers();

#ifdef LIBXML_CATALOG_ENABLED

    xmlCatalogCleanup();

#endif

#ifdef LIBXML_SCHEMAS_ENABLED

    xmlSchemaCleanupTypes();

    xmlRelaxNGCleanupTypes();

#endif

    /* These functions should never call xmlFree. */

    xmlCleanupInputCallbacks();

#ifdef LIBXML_OUTPUT_ENABLED

    xmlCleanupOutputCallbacks();

#endif

    xmlCleanupDictInternal();

    xmlCleanupRandom();

    xmlCleanupGlobalsInternal();

    /*

     * Must come last. On Windows, xmlCleanupGlobalsInternal can call

     * xmlFree which uses xmlMemMutex in debug mode.

     */

    xmlCleanupMemoryInternal();

    xmlGlobalInitMutexDestroy();

    xmlParserInitialized = 0;

    xmlParserInnerInitialized = 0;

}

#if defined(HAVE_ATTRIBUTE_DESTRUCTOR) && \

    !defined(LIBXML_THREAD_ALLOC_ENABLED) && \

    !defined(LIBXML_STATIC) && \

    !defined(_WIN32)

static void

ATTRIBUTE_DESTRUCTOR

xmlDestructor(void) {

    /*

     * Calling custom deallocation functions in a destructor can cause

     * problems, for example with Nokogiri.

     */

    if (xmlFree == free)

        xmlCleanupParser();

}

#endif