sail_context_init_callback.patch

diff --git a/src/libsail/context.c b/src/libsail/context.c
index 77a706e9..9a8203c2 100644
--- a/src/libsail/context.c
+++ b/src/libsail/context.c
@@ -40,6 +40,10 @@ sail_status_t sail_init_with_flags(int flags) {
     return SAIL_OK;
 }
 
+void sail_set_on_context_init(sail_status_t(* on_context_init)(int *flags)) {
+    g_on_sail_context_init = on_context_init;
+}
+
 void sail_finish(void) {
 
     SAIL_LOG_INFO("Finish");
diff --git a/src/libsail/context.h b/src/libsail/context.h
index c248d0da..ba0d8aa1 100644
--- a/src/libsail/context.h
+++ b/src/libsail/context.h
@@ -97,6 +97,21 @@ enum SailInitFlags {
  */
 SAIL_EXPORT sail_status_t sail_init_with_flags(int flags);
 
+/*
+ * Registers a callback function that's called just before a new thread-local static context is initialized.
+ *
+ * The callback receives a pointer to the SailInitFlags used to create the new context. It may inspect
+ * and modify them. If the callback returns an error code other than SAIL_OK, context creation will
+ * fail with that error code.
+ *
+ * The callback is registered globally; there can only be one for the entire program.
+ * The callback may be NULL, in which case it will be unregistered.
+ *
+ * Note that this function is not thread-safe. It is an error to call this function while other threads
+ * may be creating new SAIL contexts. It is best to only call it once at program startup.
+ */
+SAIL_EXPORT void sail_set_on_context_init(sail_status_t (* on_context_init)(int *flags));
+
 /*
  * Finalizes working with the thread-local static context that was implicitly or explicitly allocated by
  * reading or writing functions.
diff --git a/src/libsail/context_private.c b/src/libsail/context_private.c
index 83d1941a..489d9b9d 100644
--- a/src/libsail/context_private.c
+++ b/src/libsail/context_private.c
@@ -591,6 +591,8 @@ static void print_build_statistics(void) {
 #endif
 }
 
+SAIL_HIDDEN sail_status_t (* g_on_sail_context_init)(int *flags);
+
 /* Initializes the context and loads all the codec info files if the context is not initialized. */
 static sail_status_t init_context(struct sail_context *context, int flags) {
 
@@ -599,6 +601,14 @@ static sail_status_t init_context(struct sail_context *context, int flags) {
     if (context->initialized) {
         return SAIL_OK;
     }
+
+    sail_status_t callback_result = SAIL_OK;
+    if (g_on_sail_context_init) {
+        callback_result = g_on_sail_context_init(&flags);
+    }
+    if (callback_result != SAIL_OK) {
+        return callback_result;
+    }
 
     context->initialized = true;
 
diff --git a/src/libsail/context_private.h b/src/libsail/context_private.h
index bdc4ed57..fb944d11 100644
--- a/src/libsail/context_private.h
+++ b/src/libsail/context_private.h
@@ -79,4 +79,9 @@ SAIL_HIDDEN sail_status_t current_tls_context(struct sail_context **context);
  */
 SAIL_HIDDEN sail_status_t current_tls_context_with_flags(struct sail_context **context, int flags);
 
+/*
+ * Callback to call before context creation.
+ */
+SAIL_HIDDEN extern sail_status_t (* g_on_sail_context_init)(int *flags);
+
 #endif