core: expose thread pool

Author: Grok Compression

src/lib/codec/CMakeLists.txt

@@ -14,6 +14,7 @@ include_directories(
   ${CMAKE_CURRENT_BINARY_DIR}/../../lib/core # grk_config.h and grk_config_private.h
   ${GROK_SOURCE_DIR}/src/lib/core
   ${GROK_SOURCE_DIR}/src/lib/core/util
+  ${GROK_SOURCE_DIR}/src/lib/core/scheduling
   ${GROK_SOURCE_DIR}/src/include
   ${GROK_SOURCE_DIR}/src/include/CLI11/include
   ${CMAKE_CURRENT_SOURCE_DIR}/formats

src/lib/core/grok.cpp

@@ -223,6 +223,21 @@ void grk_deinitialize(void)
   TFSingleton::destroy();
 }
 
+void* grk_thread_pool(void)
+{
+  return &TFSingleton::get();
+}
+
+size_t grk_num_workers(void)
+{
+  return TFSingleton::num_threads();
+}
+
+uint32_t grk_worker_id(void)
+{
+  return TFSingleton::workerId();
+}
+
 static inline bool areStringsEqual(const char* lhs, const char* rhs)
 {
   if(lhs == nullptr && rhs == nullptr)

src/lib/core/grok.h

@@ -2325,6 +2325,43 @@ GRK_API int32_t GRK_CALLCONV grk_plugin_batch_decompress(void);
  */
 GRK_API void GRK_CALLCONV grk_plugin_stop_batch_decompress(void);
 
+/*******************************************************************************
+ *  Thread-pool access
+ *
+ *  These functions expose the core library's TaskFlow thread pool so that
+ *  other libraries (e.g. the codec library) can submit work to the same
+ *  pool, avoiding thread contention.
+ *
+ *  The returned handle is only valid between grk_initialize() and
+ *  grk_deinitialize().  Internal C++ consumers should prefer the typed
+ *  wrappers in grk_thread_pool.h.
+ ******************************************************************************/
+
+/**
+ * @brief Returns an opaque handle to the core thread-pool executor.
+ *
+ * The handle is a pointer to the internal tf::Executor.  Cast it back
+ * with the helpers in grk_thread_pool.h (C++ only) or use
+ * grk_num_workers() / grk_worker_id() from C.
+ *
+ * @return opaque executor handle, or NULL if the library is not initialised
+ */
+GRK_API void* GRK_CALLCONV grk_thread_pool(void);
+
+/**
+ * @brief Returns the number of worker threads in the core thread pool.
+ *
+ * @return total number of threads (including the driver thread)
+ */
+GRK_API size_t GRK_CALLCONV grk_num_workers(void);
+
+/**
+ * @brief Returns the TaskFlow worker id of the calling thread.
+ *
+ * @return worker id if called from inside a TaskFlow task, 0 otherwise
+ */
+GRK_API uint32_t GRK_CALLCONV grk_worker_id(void);
+
 #ifndef SWIG
 #ifdef __cplusplus
 }

src/lib/core/scheduling/grk_thread_pool.h

@@ -0,0 +1,55 @@
+/*
+ *    Copyright (C) 2016-2026 Grok Image Compression Inc.
+ *
+ *    This source code is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This source code is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#pragma once
+
+#include "grok.h"
+#include "grk_taskflow.h"
+
+namespace grk
+{
+
+/**
+ * @brief Returns a reference to the core library's tf::Executor.
+ *
+ * The executor is created by grk_initialize() and destroyed by
+ * grk_deinitialize().  Calling this outside that window is undefined.
+ */
+inline tf::Executor& executor()
+{
+  return *static_cast<tf::Executor*>(grk_thread_pool());
+}
+
+/**
+ * @brief Returns the total number of worker threads in the core pool.
+ */
+inline size_t num_workers()
+{
+  return grk_num_workers();
+}
+
+/**
+ * @brief Returns the TaskFlow worker id of the calling thread.
+ *
+ * @return worker id if called from inside a TaskFlow task, 0 otherwise
+ */
+inline uint32_t worker_id()
+{
+  return grk_worker_id();
+}
+
+} // namespace grk