From a2cedc1bc2af3362f47e0518f35b5180b5b6187b Mon Sep 17 00:00:00 2001
From: James Darnley <jdarnley@obe.tv>
Date: Wed, 27 May 2026 18:46:50 +0200
Subject: [PATCH] upipe-pthread: add umutex_pthread_trylock

Allows the user to call pthread_mutex_trylock() on a umutex provided by
this module.  Lets the call return UBASE_ERR_BUSY if the mutex is
already locked on another thread.
---
 include/upipe-pthread/umutex_pthread.h |  7 +++++++
 lib/upipe-pthread/umutex_pthread.c     | 17 +++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/upipe-pthread/umutex_pthread.h b/include/upipe-pthread/umutex_pthread.h
index 6a504a14f..fd92b571c 100644
--- a/include/upipe-pthread/umutex_pthread.h
+++ b/include/upipe-pthread/umutex_pthread.h
@@ -28,6 +28,13 @@ extern "C" {
  */
 struct umutex *umutex_pthread_alloc(const pthread_mutexattr_t *mutexattr);
 
+/** @This tries to lock a mutex.
+ *
+ * @param umutex pointer to a umutex structure
+ * @return an error code, UBASE_ERR_BUSY for EBUSY
+ */
+int umutex_pthread_trylock(struct umutex *umutex);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/upipe-pthread/umutex_pthread.c b/lib/upipe-pthread/umutex_pthread.c
index e60f82370..0e418bfe0 100644
--- a/lib/upipe-pthread/umutex_pthread.c
+++ b/lib/upipe-pthread/umutex_pthread.c
@@ -51,6 +51,23 @@ static inline int umutex_pthread_lock(struct umutex *umutex)
     }
 }
 
+/** @This tries to lock a mutex.
+ *
+ * @param umutex pointer to a umutex structure
+ * @return an error code, UBASE_ERR_BUSY for EBUSY
+ */
+int umutex_pthread_trylock(struct umutex *umutex)
+{
+    struct umutex_pthread *umutex_pthread = umutex_pthread_from_umutex(umutex);
+    int err = pthread_mutex_trylock(&umutex_pthread->mutex);
+    switch (err) {
+        case 0: return UBASE_ERR_NONE;
+        case EBUSY: return UBASE_ERR_BUSY;
+        default:
+        case EINVAL: return UBASE_ERR_INVALID;
+    }
+}
+
 /** @This unlocks a mutex.
  *
  * @param umutex pointer to a umutex structure