[pcsx_rearmed.git] / deps / libchdr / deps / zstd-1.5.5 / lib / common / pool.c

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */


/* ======   Dependencies   ======= */
#include "../common/allocations.h"  /* ZSTD_customCalloc, ZSTD_customFree */
#include "zstd_deps.h" /* size_t */
#include "debug.h"     /* assert */
#include "pool.h"

/* ======   Compiler specifics   ====== */
#if defined(_MSC_VER)
#  pragma warning(disable : 4204)        /* disable: C4204: non-constant aggregate initializer */
#endif


#ifdef ZSTD_MULTITHREAD

#include "threading.h"   /* pthread adaptation */

/* A job is a function and an opaque argument */
typedef struct POOL_job_s {
    POOL_function function;
    void *opaque;
} POOL_job;

struct POOL_ctx_s {
    ZSTD_customMem customMem;
    /* Keep track of the threads */
    ZSTD_pthread_t* threads;
    size_t threadCapacity;
    size_t threadLimit;

    /* The queue is a circular buffer */
    POOL_job *queue;
    size_t queueHead;
    size_t queueTail;
    size_t queueSize;

    /* The number of threads working on jobs */
    size_t numThreadsBusy;
    /* Indicates if the queue is empty */
    int queueEmpty;

    /* The mutex protects the queue */
    ZSTD_pthread_mutex_t queueMutex;
    /* Condition variable for pushers to wait on when the queue is full */
    ZSTD_pthread_cond_t queuePushCond;
    /* Condition variables for poppers to wait on when the queue is empty */
    ZSTD_pthread_cond_t queuePopCond;
    /* Indicates if the queue is shutting down */
    int shutdown;
};

/* POOL_thread() :
 * Work thread for the thread pool.
 * Waits for jobs and executes them.
 * @returns : NULL on failure else non-null.
 */
static void* POOL_thread(void* opaque) {
    POOL_ctx* const ctx = (POOL_ctx*)opaque;
    if (!ctx) { return NULL; }
    for (;;) {
        /* Lock the mutex and wait for a non-empty queue or until shutdown */
        ZSTD_pthread_mutex_lock(&ctx->queueMutex);

        while ( ctx->queueEmpty
            || (ctx->numThreadsBusy >= ctx->threadLimit) ) {
            if (ctx->shutdown) {
                /* even if !queueEmpty, (possible if numThreadsBusy >= threadLimit),
                 * a few threads will be shutdown while !queueEmpty,
                 * but enough threads will remain active to finish the queue */
                ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
                return opaque;
            }
            ZSTD_pthread_cond_wait(&ctx->queuePopCond, &ctx->queueMutex);
        }
        /* Pop a job off the queue */
        {   POOL_job const job = ctx->queue[ctx->queueHead];
            ctx->queueHead = (ctx->queueHead + 1) % ctx->queueSize;
            ctx->numThreadsBusy++;
            ctx->queueEmpty = (ctx->queueHead == ctx->queueTail);
            /* Unlock the mutex, signal a pusher, and run the job */
            ZSTD_pthread_cond_signal(&ctx->queuePushCond);
            ZSTD_pthread_mutex_unlock(&ctx->queueMutex);

            job.function(job.opaque);

            /* If the intended queue size was 0, signal after finishing job */
            ZSTD_pthread_mutex_lock(&ctx->queueMutex);
            ctx->numThreadsBusy--;
            ZSTD_pthread_cond_signal(&ctx->queuePushCond);
            ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
        }
    }  /* for (;;) */
    assert(0);  /* Unreachable */
}

/* ZSTD_createThreadPool() : public access point */
POOL_ctx* ZSTD_createThreadPool(size_t numThreads) {
    return POOL_create (numThreads, 0);
}

POOL_ctx* POOL_create(size_t numThreads, size_t queueSize) {
    return POOL_create_advanced(numThreads, queueSize, ZSTD_defaultCMem);
}

POOL_ctx* POOL_create_advanced(size_t numThreads, size_t queueSize,
                               ZSTD_customMem customMem)
{
    POOL_ctx* ctx;
    /* Check parameters */
    if (!numThreads) { return NULL; }
    /* Allocate the context and zero initialize */
    ctx = (POOL_ctx*)ZSTD_customCalloc(sizeof(POOL_ctx), customMem);
    if (!ctx) { return NULL; }
    /* Initialize the job queue.
     * It needs one extra space since one space is wasted to differentiate
     * empty and full queues.
     */
    ctx->queueSize = queueSize + 1;
    ctx->queue = (POOL_job*)ZSTD_customCalloc(ctx->queueSize * sizeof(POOL_job), customMem);
    ctx->queueHead = 0;
    ctx->queueTail = 0;
    ctx->numThreadsBusy = 0;
    ctx->queueEmpty = 1;
    {
        int error = 0;
        error |= ZSTD_pthread_mutex_init(&ctx->queueMutex, NULL);
        error |= ZSTD_pthread_cond_init(&ctx->queuePushCond, NULL);
        error |= ZSTD_pthread_cond_init(&ctx->queuePopCond, NULL);
        if (error) { POOL_free(ctx); return NULL; }
    }
    ctx->shutdown = 0;
    /* Allocate space for the thread handles */
    ctx->threads = (ZSTD_pthread_t*)ZSTD_customCalloc(numThreads * sizeof(ZSTD_pthread_t), customMem);
    ctx->threadCapacity = 0;
    ctx->customMem = customMem;
    /* Check for errors */
    if (!ctx->threads || !ctx->queue) { POOL_free(ctx); return NULL; }
    /* Initialize the threads */
    {   size_t i;
        for (i = 0; i < numThreads; ++i) {
            if (ZSTD_pthread_create(&ctx->threads[i], NULL, &POOL_thread, ctx)) {
                ctx->threadCapacity = i;
                POOL_free(ctx);
                return NULL;
        }   }
        ctx->threadCapacity = numThreads;
        ctx->threadLimit = numThreads;
    }
    return ctx;
}

/*! POOL_join() :
    Shutdown the queue, wake any sleeping threads, and join all of the threads.
*/
static void POOL_join(POOL_ctx* ctx) {
    /* Shut down the queue */
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    ctx->shutdown = 1;
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
    /* Wake up sleeping threads */
    ZSTD_pthread_cond_broadcast(&ctx->queuePushCond);
    ZSTD_pthread_cond_broadcast(&ctx->queuePopCond);
    /* Join all of the threads */
    {   size_t i;
        for (i = 0; i < ctx->threadCapacity; ++i) {
            ZSTD_pthread_join(ctx->threads[i]);  /* note : could fail */
    }   }
}

void POOL_free(POOL_ctx *ctx) {
    if (!ctx) { return; }
    POOL_join(ctx);
    ZSTD_pthread_mutex_destroy(&ctx->queueMutex);
    ZSTD_pthread_cond_destroy(&ctx->queuePushCond);
    ZSTD_pthread_cond_destroy(&ctx->queuePopCond);
    ZSTD_customFree(ctx->queue, ctx->customMem);
    ZSTD_customFree(ctx->threads, ctx->customMem);
    ZSTD_customFree(ctx, ctx->customMem);
}

/*! POOL_joinJobs() :
 *  Waits for all queued jobs to finish executing.
 */
void POOL_joinJobs(POOL_ctx* ctx) {
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    while(!ctx->queueEmpty || ctx->numThreadsBusy > 0) {
        ZSTD_pthread_cond_wait(&ctx->queuePushCond, &ctx->queueMutex);
    }
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
}

void ZSTD_freeThreadPool (ZSTD_threadPool* pool) {
  POOL_free (pool);
}

size_t POOL_sizeof(const POOL_ctx* ctx) {
    if (ctx==NULL) return 0;  /* supports sizeof NULL */
    return sizeof(*ctx)
        + ctx->queueSize * sizeof(POOL_job)
        + ctx->threadCapacity * sizeof(ZSTD_pthread_t);
}


/* @return : 0 on success, 1 on error */
static int POOL_resize_internal(POOL_ctx* ctx, size_t numThreads)
{
    if (numThreads <= ctx->threadCapacity) {
        if (!numThreads) return 1;
        ctx->threadLimit = numThreads;
        return 0;
    }
    /* numThreads > threadCapacity */
    {   ZSTD_pthread_t* const threadPool = (ZSTD_pthread_t*)ZSTD_customCalloc(numThreads * sizeof(ZSTD_pthread_t), ctx->customMem);
        if (!threadPool) return 1;
        /* replace existing thread pool */
        ZSTD_memcpy(threadPool, ctx->threads, ctx->threadCapacity * sizeof(*threadPool));
        ZSTD_customFree(ctx->threads, ctx->customMem);
        ctx->threads = threadPool;
        /* Initialize additional threads */
        {   size_t threadId;
            for (threadId = ctx->threadCapacity; threadId < numThreads; ++threadId) {
                if (ZSTD_pthread_create(&threadPool[threadId], NULL, &POOL_thread, ctx)) {
                    ctx->threadCapacity = threadId;
                    return 1;
            }   }
    }   }
    /* successfully expanded */
    ctx->threadCapacity = numThreads;
    ctx->threadLimit = numThreads;
    return 0;
}

/* @return : 0 on success, 1 on error */
int POOL_resize(POOL_ctx* ctx, size_t numThreads)
{
    int result;
    if (ctx==NULL) return 1;
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    result = POOL_resize_internal(ctx, numThreads);
    ZSTD_pthread_cond_broadcast(&ctx->queuePopCond);
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
    return result;
}

/**
 * Returns 1 if the queue is full and 0 otherwise.
 *
 * When queueSize is 1 (pool was created with an intended queueSize of 0),
 * then a queue is empty if there is a thread free _and_ no job is waiting.
 */
static int isQueueFull(POOL_ctx const* ctx) {
    if (ctx->queueSize > 1) {
        return ctx->queueHead == ((ctx->queueTail + 1) % ctx->queueSize);
    } else {
        return (ctx->numThreadsBusy == ctx->threadLimit) ||
               !ctx->queueEmpty;
    }
}


static void
POOL_add_internal(POOL_ctx* ctx, POOL_function function, void *opaque)
{
    POOL_job job;
    job.function = function;
    job.opaque = opaque;
    assert(ctx != NULL);
    if (ctx->shutdown) return;

    ctx->queueEmpty = 0;
    ctx->queue[ctx->queueTail] = job;
    ctx->queueTail = (ctx->queueTail + 1) % ctx->queueSize;
    ZSTD_pthread_cond_signal(&ctx->queuePopCond);
}

void POOL_add(POOL_ctx* ctx, POOL_function function, void* opaque)
{
    assert(ctx != NULL);
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    /* Wait until there is space in the queue for the new job */
    while (isQueueFull(ctx) && (!ctx->shutdown)) {
        ZSTD_pthread_cond_wait(&ctx->queuePushCond, &ctx->queueMutex);
    }
    POOL_add_internal(ctx, function, opaque);
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
}


int POOL_tryAdd(POOL_ctx* ctx, POOL_function function, void* opaque)
{
    assert(ctx != NULL);
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    if (isQueueFull(ctx)) {
        ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
        return 0;
    }
    POOL_add_internal(ctx, function, opaque);
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
    return 1;
}


#else  /* ZSTD_MULTITHREAD  not defined */

/* ========================== */
/* No multi-threading support */
/* ========================== */


/* We don't need any data, but if it is empty, malloc() might return NULL. */
struct POOL_ctx_s {
    int dummy;
};
static POOL_ctx g_poolCtx;

POOL_ctx* POOL_create(size_t numThreads, size_t queueSize) {
    return POOL_create_advanced(numThreads, queueSize, ZSTD_defaultCMem);
}

POOL_ctx*
POOL_create_advanced(size_t numThreads, size_t queueSize, ZSTD_customMem customMem)
{
    (void)numThreads;
    (void)queueSize;
    (void)customMem;
    return &g_poolCtx;
}

void POOL_free(POOL_ctx* ctx) {
    assert(!ctx || ctx == &g_poolCtx);
    (void)ctx;
}

void POOL_joinJobs(POOL_ctx* ctx){
    assert(!ctx || ctx == &g_poolCtx);
    (void)ctx;
}

int POOL_resize(POOL_ctx* ctx, size_t numThreads) {
    (void)ctx; (void)numThreads;
    return 0;
}

void POOL_add(POOL_ctx* ctx, POOL_function function, void* opaque) {
    (void)ctx;
    function(opaque);
}

int POOL_tryAdd(POOL_ctx* ctx, POOL_function function, void* opaque) {
    (void)ctx;
    function(opaque);
    return 1;
}

size_t POOL_sizeof(const POOL_ctx* ctx) {
    if (ctx==NULL) return 0;  /* supports sizeof NULL */
    assert(ctx == &g_poolCtx);
    return sizeof(*ctx);
}

#endif  /* ZSTD_MULTITHREAD */
Commit	Line	Data
648db22b	1	/*
	2	* Copyright (c) Meta Platforms, Inc. and affiliates.
	3	* All rights reserved.
	4	*
	5	* This source code is licensed under both the BSD-style license (found in the
	6	* LICENSE file in the root directory of this source tree) and the GPLv2 (found
	7	* in the COPYING file in the root directory of this source tree).
	8	* You may select, at your option, one of the above-listed licenses.
	9	*/
	10
	11
	12	/* ====== Dependencies ======= */
	13	#include "../common/allocations.h" /* ZSTD_customCalloc, ZSTD_customFree */
	14	#include "zstd_deps.h" /* size_t */
	15	#include "debug.h" /* assert */
	16	#include "pool.h"
	17
	18	/* ====== Compiler specifics ====== */
	19	#if defined(_MSC_VER)
	20	# pragma warning(disable : 4204) /* disable: C4204: non-constant aggregate initializer */
	21	#endif
	22
	23
	24	#ifdef ZSTD_MULTITHREAD
	25
	26	#include "threading.h" /* pthread adaptation */
	27
	28	/* A job is a function and an opaque argument */
	29	typedef struct POOL_job_s {
	30	POOL_function function;
	31	void *opaque;
	32	} POOL_job;
	33
	34	struct POOL_ctx_s {
	35	ZSTD_customMem customMem;
	36	/* Keep track of the threads */
	37	ZSTD_pthread_t* threads;
	38	size_t threadCapacity;
	39	size_t threadLimit;
	40
	41	/* The queue is a circular buffer */
	42	POOL_job *queue;
	43	size_t queueHead;
	44	size_t queueTail;
	45	size_t queueSize;
	46
	47	/* The number of threads working on jobs */
	48	size_t numThreadsBusy;
	49	/* Indicates if the queue is empty */
	50	int queueEmpty;
	51
	52	/* The mutex protects the queue */
	53	ZSTD_pthread_mutex_t queueMutex;
	54	/* Condition variable for pushers to wait on when the queue is full */
	55	ZSTD_pthread_cond_t queuePushCond;
	56	/* Condition variables for poppers to wait on when the queue is empty */
	57	ZSTD_pthread_cond_t queuePopCond;
	58	/* Indicates if the queue is shutting down */
	59	int shutdown;
	60	};
	61
	62	/* POOL_thread() :
	63	* Work thread for the thread pool.
	64	* Waits for jobs and executes them.
65	* @returns : NULL on failure else non-null.
66	*/
67	static void* POOL_thread(void* opaque) {
68	POOL_ctx* const ctx = (POOL_ctx*)opaque;
69	if (!ctx) { return NULL; }
70	for (;;) {
71	/* Lock the mutex and wait for a non-empty queue or until shutdown */
72	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
73
74	while ( ctx->queueEmpty
75	\|\| (ctx->numThreadsBusy >= ctx->threadLimit) ) {
76	if (ctx->shutdown) {
77	/* even if !queueEmpty, (possible if numThreadsBusy >= threadLimit),
78	* a few threads will be shutdown while !queueEmpty,
79	* but enough threads will remain active to finish the queue */
80	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
81	return opaque;
82	}
83	ZSTD_pthread_cond_wait(&ctx->queuePopCond, &ctx->queueMutex);
84	}
85	/* Pop a job off the queue */
86	{ POOL_job const job = ctx->queue[ctx->queueHead];
87	ctx->queueHead = (ctx->queueHead + 1) % ctx->queueSize;
88	ctx->numThreadsBusy++;
89	ctx->queueEmpty = (ctx->queueHead == ctx->queueTail);
90	/* Unlock the mutex, signal a pusher, and run the job */
91	ZSTD_pthread_cond_signal(&ctx->queuePushCond);
92	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
93
94	job.function(job.opaque);
95
96	/* If the intended queue size was 0, signal after finishing job */
97	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
98	ctx->numThreadsBusy--;
99	ZSTD_pthread_cond_signal(&ctx->queuePushCond);
100	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
101	}
102	} /* for (;;) */
103	assert(0); /* Unreachable */
104	}
105
106	/* ZSTD_createThreadPool() : public access point */
107	POOL_ctx* ZSTD_createThreadPool(size_t numThreads) {
108	return POOL_create (numThreads, 0);
109	}
110
111	POOL_ctx* POOL_create(size_t numThreads, size_t queueSize) {
112	return POOL_create_advanced(numThreads, queueSize, ZSTD_defaultCMem);
113	}
114
115	POOL_ctx* POOL_create_advanced(size_t numThreads, size_t queueSize,
116	ZSTD_customMem customMem)
117	{
118	POOL_ctx* ctx;
119	/* Check parameters */
120	if (!numThreads) { return NULL; }
121	/* Allocate the context and zero initialize */
122	ctx = (POOL_ctx*)ZSTD_customCalloc(sizeof(POOL_ctx), customMem);
123	if (!ctx) { return NULL; }
124	/* Initialize the job queue.
125	* It needs one extra space since one space is wasted to differentiate
126	* empty and full queues.
127	*/
128	ctx->queueSize = queueSize + 1;
129	ctx->queue = (POOL_job)ZSTD_customCalloc(ctx->queueSize sizeof(POOL_job), customMem);
130	ctx->queueHead = 0;
131	ctx->queueTail = 0;
132	ctx->numThreadsBusy = 0;
133	ctx->queueEmpty = 1;
134	{
135	int error = 0;
136	error \|= ZSTD_pthread_mutex_init(&ctx->queueMutex, NULL);
137	error \|= ZSTD_pthread_cond_init(&ctx->queuePushCond, NULL);
138	error \|= ZSTD_pthread_cond_init(&ctx->queuePopCond, NULL);
139	if (error) { POOL_free(ctx); return NULL; }
140	}
141	ctx->shutdown = 0;
142	/* Allocate space for the thread handles */
143	ctx->threads = (ZSTD_pthread_t)ZSTD_customCalloc(numThreads sizeof(ZSTD_pthread_t), customMem);
144	ctx->threadCapacity = 0;
145	ctx->customMem = customMem;
146	/* Check for errors */
147	if (!ctx->threads \|\| !ctx->queue) { POOL_free(ctx); return NULL; }
148	/* Initialize the threads */
149	{ size_t i;
150	for (i = 0; i < numThreads; ++i) {
151	if (ZSTD_pthread_create(&ctx->threads[i], NULL, &POOL_thread, ctx)) {
152	ctx->threadCapacity = i;
153	POOL_free(ctx);
154	return NULL;
155	} }
156	ctx->threadCapacity = numThreads;
157	ctx->threadLimit = numThreads;
158	}
159	return ctx;
160	}
161
162	/*! POOL_join() :
163	Shutdown the queue, wake any sleeping threads, and join all of the threads.
164	*/
165	static void POOL_join(POOL_ctx* ctx) {
166	/* Shut down the queue */
167	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
168	ctx->shutdown = 1;
169	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
170	/* Wake up sleeping threads */
171	ZSTD_pthread_cond_broadcast(&ctx->queuePushCond);
172	ZSTD_pthread_cond_broadcast(&ctx->queuePopCond);
173	/* Join all of the threads */
174	{ size_t i;
175	for (i = 0; i < ctx->threadCapacity; ++i) {
176	ZSTD_pthread_join(ctx->threads[i]); /* note : could fail */
177	} }
178	}
179
180	void POOL_free(POOL_ctx *ctx) {
181	if (!ctx) { return; }
182	POOL_join(ctx);
183	ZSTD_pthread_mutex_destroy(&ctx->queueMutex);
184	ZSTD_pthread_cond_destroy(&ctx->queuePushCond);
185	ZSTD_pthread_cond_destroy(&ctx->queuePopCond);
186	ZSTD_customFree(ctx->queue, ctx->customMem);
187	ZSTD_customFree(ctx->threads, ctx->customMem);
188	ZSTD_customFree(ctx, ctx->customMem);
189	}
190
191	/*! POOL_joinJobs() :
192	* Waits for all queued jobs to finish executing.
193	*/
194	void POOL_joinJobs(POOL_ctx* ctx) {
195	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
196	while(!ctx->queueEmpty \|\| ctx->numThreadsBusy > 0) {
197	ZSTD_pthread_cond_wait(&ctx->queuePushCond, &ctx->queueMutex);
198	}
199	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
200	}
201
202	void ZSTD_freeThreadPool (ZSTD_threadPool* pool) {
203	POOL_free (pool);
204	}
205
206	size_t POOL_sizeof(const POOL_ctx* ctx) {
207	if (ctx==NULL) return 0; /* supports sizeof NULL */
208	return sizeof(*ctx)
209	+ ctx->queueSize * sizeof(POOL_job)
210	+ ctx->threadCapacity * sizeof(ZSTD_pthread_t);
211	}
212
213
214	/* @return : 0 on success, 1 on error */
215	static int POOL_resize_internal(POOL_ctx* ctx, size_t numThreads)
216	{
217	if (numThreads <= ctx->threadCapacity) {
218	if (!numThreads) return 1;
219	ctx->threadLimit = numThreads;
220	return 0;
221	}
222	/* numThreads > threadCapacity */
223	{ ZSTD_pthread_t* const threadPool = (ZSTD_pthread_t)ZSTD_customCalloc(numThreads sizeof(ZSTD_pthread_t), ctx->customMem);
224	if (!threadPool) return 1;
225	/* replace existing thread pool */
226	ZSTD_memcpy(threadPool, ctx->threads, ctx->threadCapacity * sizeof(*threadPool));
227	ZSTD_customFree(ctx->threads, ctx->customMem);
228	ctx->threads = threadPool;
229	/* Initialize additional threads */
230	{ size_t threadId;
231	for (threadId = ctx->threadCapacity; threadId < numThreads; ++threadId) {
232	if (ZSTD_pthread_create(&threadPool[threadId], NULL, &POOL_thread, ctx)) {
233	ctx->threadCapacity = threadId;
234	return 1;
235	} }
236	} }
237	/* successfully expanded */
238	ctx->threadCapacity = numThreads;
239	ctx->threadLimit = numThreads;
240	return 0;
241	}
242
243	/* @return : 0 on success, 1 on error */
244	int POOL_resize(POOL_ctx* ctx, size_t numThreads)
245	{
246	int result;
247	if (ctx==NULL) return 1;
248	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
249	result = POOL_resize_internal(ctx, numThreads);
250	ZSTD_pthread_cond_broadcast(&ctx->queuePopCond);
251	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
252	return result;
253	}
254
255	/**
256	* Returns 1 if the queue is full and 0 otherwise.
257	*
258	* When queueSize is 1 (pool was created with an intended queueSize of 0),
259	* then a queue is empty if there is a thread free _and_ no job is waiting.
260	*/
261	static int isQueueFull(POOL_ctx const* ctx) {
262	if (ctx->queueSize > 1) {
263	return ctx->queueHead == ((ctx->queueTail + 1) % ctx->queueSize);
264	} else {
265	return (ctx->numThreadsBusy == ctx->threadLimit) \|\|
266	!ctx->queueEmpty;
267	}
268	}
269
270
271	static void
272	POOL_add_internal(POOL_ctx* ctx, POOL_function function, void *opaque)
273	{
274	POOL_job job;
275	job.function = function;
276	job.opaque = opaque;
277	assert(ctx != NULL);
278	if (ctx->shutdown) return;
279
280	ctx->queueEmpty = 0;
281	ctx->queue[ctx->queueTail] = job;
282	ctx->queueTail = (ctx->queueTail + 1) % ctx->queueSize;
283	ZSTD_pthread_cond_signal(&ctx->queuePopCond);
284	}
285
286	void POOL_add(POOL_ctx* ctx, POOL_function function, void* opaque)
287	{
288	assert(ctx != NULL);
289	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
290	/* Wait until there is space in the queue for the new job */
291	while (isQueueFull(ctx) && (!ctx->shutdown)) {
292	ZSTD_pthread_cond_wait(&ctx->queuePushCond, &ctx->queueMutex);
293	}
294	POOL_add_internal(ctx, function, opaque);
295	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
296	}
297
298
299	int POOL_tryAdd(POOL_ctx* ctx, POOL_function function, void* opaque)
300	{
301	assert(ctx != NULL);
302	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
303	if (isQueueFull(ctx)) {
304	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
305	return 0;
306	}
307	POOL_add_internal(ctx, function, opaque);
308	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
309	return 1;
310	}
311
312
313	#else /* ZSTD_MULTITHREAD not defined */
314
315	/* ========================== */
316	/* No multi-threading support */
317	/* ========================== */
318
319
320	/* We don't need any data, but if it is empty, malloc() might return NULL. */
321	struct POOL_ctx_s {
322	int dummy;
323	};
324	static POOL_ctx g_poolCtx;
325
326	POOL_ctx* POOL_create(size_t numThreads, size_t queueSize) {
327	return POOL_create_advanced(numThreads, queueSize, ZSTD_defaultCMem);
328	}
329
330	POOL_ctx*
331	POOL_create_advanced(size_t numThreads, size_t queueSize, ZSTD_customMem customMem)
332	{
333	(void)numThreads;
334	(void)queueSize;
335	(void)customMem;
336	return &g_poolCtx;
337	}
338
339	void POOL_free(POOL_ctx* ctx) {
340	assert(!ctx \|\| ctx == &g_poolCtx);
341	(void)ctx;
342	}
343
344	void POOL_joinJobs(POOL_ctx* ctx){
345	assert(!ctx \|\| ctx == &g_poolCtx);
346	(void)ctx;
347	}
348
349	int POOL_resize(POOL_ctx* ctx, size_t numThreads) {
350	(void)ctx; (void)numThreads;
351	return 0;
352	}
353
354	void POOL_add(POOL_ctx* ctx, POOL_function function, void* opaque) {
355	(void)ctx;
356	function(opaque);
357	}
358
359	int POOL_tryAdd(POOL_ctx* ctx, POOL_function function, void* opaque) {
360	(void)ctx;
361	function(opaque);
362	return 1;
363	}
364
365	size_t POOL_sizeof(const POOL_ctx* ctx) {
366	if (ctx==NULL) return 0; /* supports sizeof NULL */
367	assert(ctx == &g_poolCtx);
368	return sizeof(*ctx);
369	}
370
371	#endif /* ZSTD_MULTITHREAD */