Merge 7973cc5a37 into 0816badf3a

c/.gitignore

@@ -1,4 +1,5 @@
 blake3
 example
+example-mmap
 build/
 *.o

c/CMakeLists.txt

@@ -46,6 +46,7 @@ add_library(blake3
   blake3.c
   blake3_dispatch.c
   blake3_portable.c
+  blake3_thread.c
 )
 add_library(BLAKE3::blake3 ALIAS blake3)
 

c/Makefile.testing

@@ -46,7 +46,7 @@ ifdef BLAKE3_NO_NEON
 EXTRAFLAGS += -DBLAKE3_USE_NEON=0
 endif
 
-all: blake3.c blake3_dispatch.c blake3_portable.c main.c $(TARGETS)
+all: blake3.c blake3_dispatch.c blake3_portable.c main.c blake3_thread.c $(TARGETS)
 	$(CC) $(CFLAGS) $(EXTRAFLAGS) $^ -o $(NAME) $(LDFLAGS)
 
 blake3_sse2.o: blake3_sse2.c
@@ -68,14 +68,17 @@ test: CFLAGS += -DBLAKE3_TESTING -fsanitize=address,undefined
 test: all
 	./test.py
 
-asm: blake3.c blake3_dispatch.c blake3_portable.c main.c $(ASM_TARGETS)
+asm: blake3.c blake3_dispatch.c blake3_portable.c main.c blake3_thread.c $(ASM_TARGETS)
 	$(CC) $(CFLAGS) $(EXTRAFLAGS) $^ -o $(NAME) $(LDFLAGS)
 
 test_asm: CFLAGS += -DBLAKE3_TESTING -fsanitize=address,undefined 
 test_asm: asm
 	./test.py
 
-example: example.c blake3.c blake3_dispatch.c blake3_portable.c $(ASM_TARGETS)
+example: example.c blake3.c blake3_dispatch.c blake3_portable.c blake3_thread.c $(ASM_TARGETS)
+	$(CC) $(CFLAGS) $(EXTRAFLAGS) $^ -o $@ $(LDFLAGS)
+
+example-mmap: example-mmap.c blake3.c blake3_dispatch.c blake3_portable.c blake3_thread.c $(ASM_TARGETS)
 	$(CC) $(CFLAGS) $(EXTRAFLAGS) $^ -o $@ $(LDFLAGS)
 
 clean: 

c/blake3.c

@@ -4,6 +4,7 @@
 
 #include "blake3.h"
 #include "blake3_impl.h"
+#include "blake3_thread.h"
 
 const char *blake3_version(void) { return BLAKE3_VERSION_STRING; }
 
@@ -11,7 +12,6 @@ INLINE void chunk_state_init(blake3_chunk_state *self, const uint32_t key[8],
                              uint8_t flags) {
   memcpy(self->cv, key, BLAKE3_KEY_LEN);
   self->chunk_counter = 0;
-  memset(self->buf, 0, BLAKE3_BLOCK_LEN);
   self->buf_len = 0;
   self->blocks_compressed = 0;
   self->flags = flags;
@@ -22,7 +22,6 @@ INLINE void chunk_state_reset(blake3_chunk_state *self, const uint32_t key[8],
   memcpy(self->cv, key, BLAKE3_KEY_LEN);
   self->chunk_counter = chunk_counter;
   self->blocks_compressed = 0;
-  memset(self->buf, 0, BLAKE3_BLOCK_LEN);
   self->buf_len = 0;
 }
 
@@ -65,7 +64,9 @@ INLINE output_t make_output(const uint32_t input_cv[8],
                             uint8_t flags) {
   output_t ret;
   memcpy(ret.input_cv, input_cv, 32);
-  memcpy(ret.block, block, BLAKE3_BLOCK_LEN);
+  // copy out what's there and fill the rest with zeroes
+  memcpy(ret.block, block, block_len);
+  memset(ret.block + block_len, 0, BLAKE3_BLOCK_LEN - block_len);
   ret.block_len = block_len;
   ret.counter = counter;
   ret.flags = flags;
@@ -121,7 +122,6 @@ INLINE void chunk_state_update(blake3_chunk_state *self, const uint8_t *input,
           self->flags | chunk_state_maybe_start_flag(self));
       self->blocks_compressed += 1;
       self->buf_len = 0;
-      memset(self->buf, 0, BLAKE3_BLOCK_LEN);
     }
   }
 
@@ -244,6 +244,44 @@ INLINE size_t compress_parents_parallel(const uint8_t *child_chaining_values,
   }
 }
 
+
+// the state for the thread when doing compress subtree
+typedef struct {
+  // inputs
+  const uint8_t *input;
+  size_t input_len;
+  const uint32_t *key;
+  uint64_t chunk_counter;
+  uint8_t flags;
+  // outputs
+  uint8_t *out;
+  size_t n;
+} blake3_compress_subtree_state;
+
+static size_t blake3_compress_subtree_wide(const uint8_t *input,
+                                           size_t input_len,
+                                           const uint32_t key[8],
+                                           uint64_t chunk_counter,
+                                           uint8_t flags, uint8_t *out);
+
+static bool blake3_compress_subtree_wide_work_check(const void *arg) {
+  const blake3_compress_subtree_state *s = arg;
+
+  /* only off-load to thread if we have enough input (8 chunks at least) */
+  return s->input_len >= 8 * BLAKE3_CHUNK_LEN;
+}
+
+static void blake3_compress_subtree_wide_thread(void *arg) {
+  blake3_compress_subtree_state *s = arg;
+
+  s->n = blake3_compress_subtree_wide(
+              s->input, s->input_len,
+              s->key,
+              s->chunk_counter,
+              s->flags,
+              s->out);
+}
+
 // The wide helper function returns (writes out) an array of chaining values
 // and returns the length of that array. The number of chaining values returned
 // is the dynamically detected SIMD degree, at most MAX_SIMD_DEGREE. Or fewer,
@@ -299,12 +337,32 @@ static size_t blake3_compress_subtree_wide(const uint8_t *input,
   }
   uint8_t *right_cvs = &cv_array[degree * BLAKE3_OUT_LEN];
 
-  // Recurse! If this implementation adds multi-threading support in the
-  // future, this is where it will go.
-  size_t left_n = blake3_compress_subtree_wide(input, left_input_len, key,
-                                               chunk_counter, flags, cv_array);
-  size_t right_n = blake3_compress_subtree_wide(
-      right_input, right_input_len, key, right_chunk_counter, flags, right_cvs);
+  // Recurse! this is the multi-threaded implementation
+  blake3_compress_subtree_state states[2];
+
+  /* common */
+  states[0].key = states[1].key = key;
+  states[0].flags = states[1].flags = flags;
+
+  /* left */
+  states[0].input = input;
+  states[0].input_len = left_input_len;
+  states[0].chunk_counter = chunk_counter;
+  states[0].out = cv_array;
+
+  /* right */
+  states[1].input = right_input;
+  states[1].input_len = right_input_len;
+  states[1].chunk_counter = right_chunk_counter;
+  states[1].out = right_cvs;
+
+  blake3_thread_arg_array_join(blake3_get_thread_pool(),
+      blake3_compress_subtree_wide_thread,
+      blake3_compress_subtree_wide_work_check,
+      states, sizeof(states[0]), 2);
+
+  size_t left_n = states[0].n;
+  size_t right_n = states[1].n;
 
   // The special case again. If simd_degree=1, then we'll have left_n=1 and
   // right_n=1. Rather than compressing them into a single output, return
@@ -364,6 +422,7 @@ INLINE void compress_subtree_to_parent_node(
 
 INLINE void hasher_init_base(blake3_hasher *self, const uint32_t key[8],
                              uint8_t flags) {
+  memset(self, 0, sizeof(*self));
   memcpy(self->key, key, BLAKE3_KEY_LEN);
   chunk_state_init(&self->chunk, key, flags);
   self->cv_stack_len = 0;

c/blake3_dispatch.c

@@ -1,8 +1,10 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <stdatomic.h>
 
 #include "blake3_impl.h"
+#include "blake3_thread.h"
 
 #if defined(_MSC_VER)
 #include <Windows.h>
@@ -306,3 +308,21 @@ size_t blake3_simd_degree(void) {
 #endif
   return 1;
 }
+
+blake3_thread_pool *blake3_get_thread_pool(void) {
+  static _Atomic(blake3_thread_pool *)g_thread_pool;
+  blake3_thread_pool *tp, *exp_tp;
+
+  if ((tp = atomic_load(&g_thread_pool)) == NULL) {
+    tp = blake3_thread_pool_create(0);	/* let the pool implementation choose */
+    assert(tp);
+    exp_tp = NULL;
+    /* store it, if the comparison fails, some other thread won, use theirs */
+    if (!atomic_compare_exchange_strong(&g_thread_pool, &exp_tp, tp)) {
+      blake3_thread_pool_destroy(tp);
+      return exp_tp;
+    }
+  }
+
+  return tp;
+}

c/blake3_impl.h

@@ -8,6 +8,7 @@
 #include <string.h>
 
 #include "blake3.h"
+#include "blake3_thread.h"
 
 // internal flags
 enum blake3_flags {
@@ -281,5 +282,6 @@ void blake3_hash_many_neon(const uint8_t *const *inputs, size_t num_inputs,
                            uint8_t flags_end, uint8_t *out);
 #endif
 
+blake3_thread_pool *blake3_get_thread_pool(void);
 
 #endif /* BLAKE3_IMPL_H */

c/blake3_thread.c

@@ -0,0 +1,503 @@
+/*
+ * blake3_thread.h - minimal thread pool implementation for BLAKE3
+ *
+ * Copyright (c) 2023 Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+ *
+ * Released under the BLAKE3 License (CC0 1.0 or Apache License 2.0)
+ */
+#define _DEFAULT_SOURCE
+#include <assert.h>
+#include <stdbool.h>
+#include <string.h>
+#include <alloca.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+
+#if defined(__linux__)
+#include <sys/syscall.h>
+#include <linux/futex.h>
+#endif
+
+#include "blake3_impl.h"
+#include "blake3_thread.h"
+
+#undef BIT64
+#define BIT64(x) ((uint64_t)1 << (x))
+
+#define B3WORK_SHUTDOWN ((const blake3_thread_work *)(void *)-1)
+
+#if defined(__linux__) && !defined(BLAKE3_THREAD_PORTABLE)
+
+/* linux pedal to the metal implementation */
+static inline int futex(_Atomic(uint32_t) *uaddr, int futex_op, uint32_t val, const struct timespec *timeout, uint32_t *uaddr2, uint32_t val3)
+{
+	return syscall(SYS_futex, uaddr, futex_op, val, timeout, uaddr2, val3);
+}
+
+static inline int fwait(_Atomic(uint32_t) *futexp)
+{
+	long s;
+	uint32_t one = 1;
+
+	while (!atomic_compare_exchange_strong(futexp, &one, 0)) {
+		s = futex(futexp, FUTEX_WAIT, 0, NULL, NULL, 0);
+		if (s == -1 && errno != EAGAIN)
+			return -1;
+	}
+	return 0;
+}
+
+static inline int fpost(_Atomic(uint32_t) *futexp)
+{
+	long s;
+	uint32_t zero = 0;
+
+	if (atomic_compare_exchange_strong(futexp, &zero, 1)) {
+		s = futex(futexp, FUTEX_WAKE, 1, NULL, NULL, 0);
+		if (s == -1)
+			return -1;
+	}
+	return 0;
+}
+
+static inline void blake3_thread_init_sync(blake3_thread *t)
+{
+	/* nothing more needed for futexes */
+	atomic_store(&t->submit, 0);
+	atomic_store(&t->done, 0);
+}
+
+static inline const blake3_thread_work *blake3_worker_wait_for_work(blake3_thread *t)
+{
+	int ret;
+
+	(void)ret;	/* for when NDEBUG is set */
+	ret = fwait(&t->submit);
+	assert(!ret);
+	return t->work;
+}
+
+static inline void blake3_worker_signal_work_done(blake3_thread *t, const blake3_thread_work *work)
+{
+	const blake3_thread_work *exp_work;
+
+	/* note that the work won't be replaced if it's a shutdown */
+	exp_work = work;
+	if (!atomic_compare_exchange_strong(&t->work, &exp_work, NULL)) {
+		assert(exp_work == B3WORK_SHUTDOWN);
+		return;
+	}
+
+	(void)fpost(&t->done);
+}
+
+int blake3_thread_submit_work(blake3_thread *t, const blake3_thread_work *work)
+{
+	const blake3_thread_work *exp_work;
+
+	/* atomically update the work */
+	exp_work = NULL;
+	if (!atomic_compare_exchange_strong(&t->work, &exp_work, work)) {
+		assert(exp_work == B3WORK_SHUTDOWN);
+		return -1;
+	}
+
+	return fpost(&t->submit);
+}
+
+int blake3_thread_wait_work(blake3_thread *t)
+{
+	const blake3_thread_work *work;
+
+	while ((work = atomic_load(&t->work)) != NULL)
+		fwait(&t->done);
+
+	atomic_store(&t->done, 0);
+
+	return 0;
+}
+
+void blake3_worker_thread_shutdown(blake3_thread *t)
+{
+	atomic_store(&t->work, B3WORK_SHUTDOWN);
+	fpost(&t->submit);
+	pthread_join(t->tid, NULL);
+}
+
+#else
+
+/* portable pthread implementation */
+
+static inline void blake3_thread_init_sync(blake3_thread *t)
+{
+	pthread_mutex_init(&t->lock, NULL);
+	pthread_cond_init(&t->cond, NULL);
+
+	pthread_mutex_init(&t->wait_lock, NULL);
+	pthread_cond_init(&t->wait_cond, NULL);
+}
+
+static inline const blake3_thread_work *blake3_worker_wait_for_work(blake3_thread *t)
+{
+	const blake3_thread_work *work;
+
+	pthread_mutex_lock(&t->lock);
+	while ((work = atomic_load(&t->work)) == NULL)
+		pthread_cond_wait(&t->cond, &t->lock);
+	pthread_mutex_unlock(&t->lock);
+
+	return work;
+}
+
+static inline void blake3_worker_signal_work_done(blake3_thread *t, const blake3_thread_work *work)
+{
+	const blake3_thread_work *exp_work;
+
+	/* clear the work, so that the user knows we're done */
+	pthread_mutex_lock(&t->wait_lock);
+
+	/* note that the work won't be replaced if it's a shutdown */
+	exp_work = work;
+	if (!atomic_compare_exchange_strong(&t->work, &exp_work, NULL))
+		assert(exp_work == B3WORK_SHUTDOWN);
+	pthread_cond_signal(&t->wait_cond);
+	pthread_mutex_unlock(&t->wait_lock);
+}
+
+int blake3_thread_submit_work(blake3_thread *t, const blake3_thread_work *work)
+{
+	const blake3_thread_work *exp_work;
+	int ret;
+
+	/* atomically update the work */
+
+	assert(t);
+	assert(work);
+
+	pthread_mutex_lock(&t->lock);
+	exp_work = NULL;
+	if (!atomic_compare_exchange_strong(&t->work, &exp_work, work)) {
+		assert(exp_work == B3WORK_SHUTDOWN);
+		ret = -1;
+	} else {
+		pthread_cond_signal(&t->cond);
+		ret = 0;
+	}
+	pthread_mutex_unlock(&t->lock);
+
+	return ret;
+}
+
+int blake3_thread_wait_work(blake3_thread *t)
+{
+	const blake3_thread_work *work;
+
+	pthread_mutex_lock(&t->wait_lock);
+	while ((work = atomic_load(&t->work)) != NULL)
+		pthread_cond_wait(&t->wait_cond, &t->wait_lock);
+	pthread_mutex_unlock(&t->wait_lock);
+
+	return 0;
+}
+
+void blake3_worker_thread_shutdown(blake3_thread *t)
+{
+	pthread_mutex_lock(&t->lock);
+	atomic_store(&t->work, B3WORK_SHUTDOWN);
+	pthread_cond_signal(&t->cond);
+	pthread_mutex_unlock(&t->lock);
+	pthread_join(t->tid, NULL);
+}
+
+#endif
+
+void *blake3_worker_thread(void *arg)
+{
+	blake3_thread *t = arg;
+	const blake3_thread_work *work;
+
+	while ((work = blake3_worker_wait_for_work(t)) != B3WORK_SHUTDOWN) {
+		work->fn(work->arg);
+		blake3_worker_signal_work_done(t, work);
+	}
+
+	return NULL;
+}
+
+blake3_thread *blake3_thread_pool_reserve(blake3_thread_pool *tp)
+{
+	blake3_thread *t;
+	unsigned int slot;
+	_Atomic(uint64_t) *free;
+	uint64_t exp, v;
+	unsigned int i;
+
+	t = NULL;
+	for (i = 0, free = tp->freep; i < tp->free_count; i++, free++) {
+		v = atomic_load(free);
+		while (v) {
+			slot = highest_one(v);
+			assert(v & BIT64(slot));
+			exp = v;		/* expecting the previous value */
+			v &= ~BIT64(slot);	/* clear this bit */
+			if (atomic_compare_exchange_strong(free, &exp, v)) {
+				slot += i * 64;
+				t = tp->threads + slot;
+				assert(slot == t->id);
+				return t;
+			}
+			v = exp;
+		}
+	}
+
+	return NULL;
+}
+
+void blake3_thread_pool_unreserve(blake3_thread_pool *tp, blake3_thread *t)
+{
+	_Atomic(uint64_t) *free;
+
+	free = tp->freep + (unsigned int)(t->id / 64);
+	atomic_fetch_or(free, BIT64(t->id & 63));
+}
+
+void blake3_thread_pool_cleanup(blake3_thread_pool *tp)
+{
+	blake3_thread *t;
+	unsigned int i;
+
+	if (!tp)
+		return;
+
+	if (tp->threads) {
+		for (i = 0; i < tp->num_threads; i++) {
+			t = &tp->threads[i];
+			if (t->id == i)
+				blake3_worker_thread_shutdown(t);
+		}
+
+		free(tp->threads);
+	}
+
+	if (tp->freep)
+		free(tp->freep);
+
+	memset(tp, 0, sizeof(*tp));
+}
+
+int blake3_thread_pool_init(blake3_thread_pool *tp, unsigned int num_threads)
+{
+	blake3_thread *t;
+	unsigned int i;
+	int rc;
+
+	assert(tp);
+
+	if (!num_threads) {
+		long scval;
+		scval = sysconf(_SC_NPROCESSORS_ONLN);
+		assert(scval > 0);
+		/* we spin num_cpus * 3 / 2 threads to cover I/O bubbles */
+		num_threads = (unsigned int)((scval * 3) / 2);
+	}
+
+	memset(tp, 0, sizeof(*tp));
+
+	tp->num_threads = num_threads;
+
+	tp->free_count = (tp->num_threads / 64) + ((tp->num_threads & 63) ? 1 : 0);
+
+	tp->freep = malloc(tp->free_count * sizeof(uint64_t));
+	if (!tp->freep)
+		goto err_out;
+
+	for (i = 0; i < tp->free_count; i++)
+		tp->freep[i] = (uint64_t)-1;
+	if (tp->num_threads & 63)
+		tp->freep[tp->free_count - 1] = BIT64(tp->num_threads & 63) - 1;
+
+	tp->threads = malloc(sizeof(*tp->threads) * tp->num_threads);
+	if (!tp->threads)
+		goto err_out;
+
+	memset(tp->threads, 0, sizeof(*tp->threads) * tp->num_threads);
+
+	for (i = 0, t = tp->threads; i < tp->num_threads; i++, t++) {
+
+		t->tp = tp;
+		t->id = (unsigned int)-1;
+
+		blake3_thread_init_sync(t);
+	}
+
+	for (i = 0, t = tp->threads; i < tp->num_threads; i++, t++) {
+
+		rc = pthread_create(&t->tid, NULL, blake3_worker_thread, t);
+		if (rc)
+			goto err_out;
+		t->id = i;
+	}
+
+	return 0;
+
+err_out:
+	blake3_thread_pool_cleanup(tp);
+	return -1;
+}
+
+blake3_thread_pool *blake3_thread_pool_create(unsigned int num_threads)
+{
+	blake3_thread_pool *tp;
+	int rc;
+
+	tp = malloc(sizeof(*tp));
+	if (!tp)
+		return NULL;
+
+	rc = blake3_thread_pool_init(tp, num_threads);
+	if (rc) {
+		free(tp);
+		return NULL;
+	}
+
+	return tp;
+}
+
+void blake3_thread_pool_destroy(blake3_thread_pool *tp)
+{
+	if (!tp)
+		return;
+
+	blake3_thread_pool_cleanup(tp);
+	free(tp);
+}
+
+void blake3_thread_work_join(blake3_thread_pool *tp, const blake3_thread_work *works, size_t work_count, blake3_work_check_fn check_fn)
+{
+	const blake3_thread_work **direct_work, **thread_work, *w;
+	blake3_thread **threads, *t;
+	size_t i, direct_work_count, thread_work_count;
+	int rc;
+
+	/* just a single (or no) work, or no threads? execute directly */
+	if (work_count <= 1 || !tp || !tp->num_threads) {
+		for (i = 0, w = works; i < work_count; i++, w++)
+			w->fn(w->arg);
+		return;
+	}
+
+	/* allocate the keeper of direct work */
+	direct_work = alloca(work_count * sizeof(*direct_work));
+	direct_work_count = 0;
+
+	threads = alloca(work_count * sizeof(*threads));
+	thread_work = alloca(work_count * sizeof(*thread_work));
+	thread_work_count = 0;
+
+	for (i = 0, w = works; i < work_count; i++, w++) {
+
+		t = NULL;
+		if (!check_fn || check_fn(w->arg))
+			t = blake3_thread_pool_reserve(tp);
+
+		if (t) {
+			threads[thread_work_count] = t;
+			thread_work[thread_work_count++] = w;
+		} else
+			direct_work[direct_work_count++] = w;
+	}
+
+	/* if we don't have any direct_work, steal the last threaded work as direct */
+	if (!direct_work_count) {
+		assert(thread_work_count > 0);
+		t = threads[thread_work_count - 1];
+		w = thread_work[thread_work_count - 1];
+		thread_work_count--;
+
+		/* unreserve this */
+		blake3_thread_pool_unreserve(tp, t);
+		direct_work[direct_work_count++] = w;
+	}
+
+	/* submit the threaded work */
+	for (i = 0; i < thread_work_count; i++) {
+		t = threads[i];
+		w = thread_work[i];
+		rc = blake3_thread_submit_work(t, w);
+		if (rc) {
+			/* unable to submit? remove work, and move to direct */
+			threads[i] = NULL;
+			thread_work[i] = NULL;
+			blake3_thread_pool_unreserve(tp, t);
+			direct_work[direct_work_count++] = w;
+		}
+	}
+
+	/* now perform the direct work while the threaded work is being performed in parallel */
+	for (i = 0; i < direct_work_count; i++) {
+		w = direct_work[i];
+		w->fn(w->arg);
+	}
+
+	/* finally wait for all threaded work to complete */
+	for (i = 0; i < thread_work_count; i++) {
+		t = threads[i];
+		assert(t);
+		blake3_thread_wait_work(t);
+		blake3_thread_pool_unreserve(tp, t);
+	}
+}
+
+void blake3_thread_args_join(blake3_thread_pool *tp, blake3_work_exec_fn fn, blake3_work_check_fn check_fn, void **args, size_t count)
+{
+	blake3_thread_work *works;
+	size_t i;
+
+	if (!count)
+		return;
+
+	works = alloca(sizeof(*works) * count);
+	for (i = 0; i < count; i++) {
+		works[i].fn = fn;
+		works[i].arg = args ? args[i] : NULL;
+	}
+
+	blake3_thread_work_join(tp, works, count, check_fn);
+}
+
+void blake3_thread_arg_array_join(blake3_thread_pool *tp, blake3_work_exec_fn fn, blake3_work_check_fn check_fn, void *args, size_t argsize, size_t count)
+{
+	blake3_thread_work *works;
+	uint8_t *p;
+	size_t i;
+
+	if (!count)
+		return;
+
+	works = alloca(sizeof(*works) * count);
+	for (i = 0, p = args; i < count; i++, p += argsize) {
+		works[i].fn = fn;
+		works[i].arg = p;
+	}
+
+	blake3_thread_work_join(tp, works, count, check_fn);
+}
+
+void blake3_thread_arg_join(blake3_thread_pool *tp, blake3_work_exec_fn fn, blake3_work_check_fn check_fn, void *arg, size_t count)
+{
+	blake3_thread_work *works;
+	size_t i;
+
+	if (!count)
+		return;
+
+	works = alloca(sizeof(*works) * count);
+	for (i = 0; i < count; i++) {
+		works[i].fn = fn;
+		works[i].arg = arg;
+	}
+
+	blake3_thread_work_join(tp, works, count, check_fn);
+}

c/blake3_thread.h

@@ -0,0 +1,64 @@
+/*
+ * blake3_thread.h - minimal thread pool implementation for BLAKE3
+ *
+ * Copyright (c) 2023 Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+ *
+ * Released under the BLAKE3 License (CC0 1.0 or Apache License 2.0)
+ */
+#ifndef BLAKE3_THREAD_H
+#define BLAKE3_THREAD_H
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <stdatomic.h>
+#include <pthread.h>
+
+struct blake3_thread_pool;
+
+typedef void (*blake3_work_exec_fn)(void *arg);
+typedef bool (*blake3_work_check_fn)(const void *arg);
+
+typedef struct blake3_thread_work {
+	blake3_work_exec_fn fn;
+	void *arg;
+} blake3_thread_work;
+
+//#define BLAKE3_THREAD_PORTABLE
+typedef struct blake3_thread {
+	struct blake3_thread_pool *tp;
+	unsigned int id;
+	pthread_t tid;
+	void *arg;
+	_Atomic(const blake3_thread_work *)work;
+#if defined(__linux__) && !defined(BLAKE3_THREAD_PORTABLE)
+	_Atomic(uint32_t) submit;
+	_Atomic(uint32_t) done;
+#else
+	pthread_mutex_t lock;
+	pthread_cond_t cond;
+	pthread_mutex_t wait_lock;
+	pthread_cond_t wait_cond;
+#endif
+} blake3_thread;
+
+typedef struct blake3_thread_pool {
+	unsigned int num_threads;
+	struct blake3_thread *threads;
+	_Atomic(uint64_t) *freep;
+	unsigned int free_count;
+} blake3_thread_pool;
+
+blake3_thread_pool *blake3_thread_pool_create(unsigned int num_threads);
+void blake3_thread_pool_destroy(blake3_thread_pool *tp);
+blake3_thread *blake3_thread_pool_reserve(blake3_thread_pool *tp);
+void blake3_thread_pool_unreserve(blake3_thread_pool *tp, blake3_thread *t);
+int blake3_thread_submit_work(blake3_thread *t, const blake3_thread_work *work);
+int blake3_thread_wait_work(blake3_thread *t);
+
+void blake3_thread_work_join(blake3_thread_pool *tp, const blake3_thread_work *works, size_t work_count, blake3_work_check_fn check_fn);
+void blake3_thread_args_join(blake3_thread_pool *tp, blake3_work_exec_fn, blake3_work_check_fn check_fn, void **args, size_t count);
+void blake3_thread_arg_array_join(blake3_thread_pool *tp, blake3_work_exec_fn fn, blake3_work_check_fn check_fn, void *args, size_t argsize, size_t count);
+void blake3_thread_arg_join(blake3_thread_pool *tp, blake3_work_exec_fn fn, blake3_work_check_fn check_fn, void *arg, size_t count);
+
+#endif

c/example-mmap.c

@@ -0,0 +1,137 @@
+// vim: ts=2 sw=2 et
+#include "blake3.h"
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <alloca.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+/* 256K threshold for using alloca */
+#define BLAKE3_ALLOCA_BUFFER_SIZE  (256U << 10)
+
+int blake3_hash_file(const char *filename, uint8_t output[BLAKE3_OUT_LEN])
+{
+  blake3_hasher hasher;
+  FILE *fp = NULL;
+  void *mem = NULL;
+  void *buf = NULL;
+  int fd = -1, ret = -1;
+  size_t rdn, filesize, bufsz = BLAKE3_ALLOCA_BUFFER_SIZE;
+  struct stat sb;
+  int rc;
+
+  memset(output, 0, BLAKE3_OUT_LEN);
+
+  blake3_hasher_init(&hasher);
+
+  if (!strcmp(filename, "-")) {
+    fp = stdin;
+  } else {
+    fp = NULL;
+
+    fd = open(filename, O_RDONLY);
+    if (fd < 0)
+      goto err_out;
+
+    rc = fstat(fd, &sb);
+    if (rc < 0)
+      goto err_out;
+
+    filesize = (size_t)-1;
+
+    /* try to mmap */
+    if (sb.st_size > 0) {
+      filesize = sb.st_size;
+      mem = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+      if (mem != MAP_FAILED) {
+        close(fd);
+        fd = -1;
+      } else
+        mem = NULL;
+    }
+
+    /* unable to map? fallback to stream mode */
+    if (!mem) {
+      close(fd);
+      fd = -1;
+      fp = fopen(filename, "r");
+      if (!fp)
+        goto err_out;
+    }
+  }
+
+  /* mmap case, very simple */
+  if (mem) {
+    blake3_hasher_update(&hasher, mem, filesize);
+  } else {
+    /* slow path using file reads */
+
+    assert(fp);
+    if (bufsz <= BLAKE3_ALLOCA_BUFFER_SIZE) {
+      buf = alloca(bufsz);
+    } else {
+      buf = malloc(bufsz);
+      if (!buf)
+        goto err_out;
+    }
+
+    do {
+      rdn = fread(buf, 1, bufsz, fp);
+      if (rdn == 0)
+        break;
+      blake3_hasher_update(&hasher, buf, rdn);
+    } while (rdn >= bufsz);
+  }
+
+  // Finalize the hash. BLAKE3_OUT_LEN is the default output length, 32 bytes.
+  blake3_hasher_finalize(&hasher, output, BLAKE3_OUT_LEN);
+
+  ret = 0;
+
+out:
+  if (mem)
+    munmap(mem, filesize);
+
+  if (fp && fp != stdin)
+    fclose(fp);
+
+  if (fd >= 0)
+    close(fd);
+
+  if (buf && (bufsz > BLAKE3_ALLOCA_BUFFER_SIZE))
+    free(buf);
+
+  return ret;
+
+err_out:
+  ret = -1;
+  goto out;
+}
+
+int main(int argc, char *argv[])
+{
+  uint8_t output[BLAKE3_OUT_LEN];
+  int i, ok, rc;
+
+  ok = 1;
+  for (i = 1; i < argc; i++) {
+    rc = blake3_hash_file(argv[i], output);
+    if (rc) {
+      fprintf(stderr, "Error hashing file \"%s\": %s\n", argv[i], strerror(errno));
+      continue;
+    }
+
+    // Print the hash as hexadecimal.
+    for (size_t j = 0; j < BLAKE3_OUT_LEN; j++)
+      printf("%02x", output[j]);
+    printf("  %s\n", argv[i]);
+    ok++;
+  }
+  return ok == argc ? EXIT_SUCCESS : EXIT_FAILURE;
+}