alternative stream list api and unit tests for the api

Beside some small API rename the main difference is that the
list implementation is not responsible for deallocating streams.
Calling srtp_stream_list_dealloc() on a list that is not empty
results in an error.

This also changes the default implementation to be a double linked
list making removing items faster.

Author: pabuhler

.github/workflows/cmake.yml

@@ -77,3 +77,11 @@ jobs:
       working-directory: ${{github.workspace}}/build
       shell: bash
       run: ctest
+
+    - name: Test Stream List Replacement
+      working-directory: ${{github.workspace}}/build
+      shell: bash
+      run: |
+        make clean
+        make C_FLAGS="-DSRTP_NO_STREAM_LIST -DSRTP_USE_TEST_STREAM_LIST" srtp_driver
+        ./srtp_driver -v

include/srtp_priv.h

@@ -97,15 +97,6 @@ srtp_err_status_t srtp_steam_init_all_master_keys(
     srtp_master_key_t **keys,
     const unsigned int max_master_keys);
 
-/*
- * srtp_stream_init(s, p) initializes the srtp_stream_t s to
- * use the policy at the location p
- */
-srtp_err_status_t srtp_stream_init(srtp_stream_t srtp, const srtp_policy_t *p);
-
-srtp_err_status_t srtp_stream_dealloc(srtp_stream_ctx_t *stream,
-                                      const srtp_stream_ctx_t *stream_template);
-
 /*
  * libsrtp internal datatypes
  */
@@ -154,6 +145,7 @@ typedef struct srtp_stream_ctx_t_ {
     int enc_xtn_hdr_count;
     uint32_t pending_roc;
     struct srtp_stream_ctx_t_ *next; /* linked list of streams */
+    struct srtp_stream_ctx_t_ *prev; /* linked list of streams */
 } strp_stream_ctx_t_;
 
 /*

include/stream_list_priv.h

@@ -58,8 +58,8 @@ extern "C" {
  * the API was extracted to allow downstreams to override its
  * implementation by defining the `SRTP_NO_STREAM_LIST` preprocessor
  * directive, which removes the default implementation of these
- * functions. if this is done, the `next` field is free for the
- * implementation to use.
+ * functions. if this is done, the `next` & `prev` fields are free for
+ * the implementation to use.
  *
  * this is still an internal interface; there is no stability
  * guarantee--downstreams should watch this file for changes in
@@ -69,7 +69,14 @@ extern "C" {
 /**
  * allocate and initialize a stream list instance
  */
-srtp_err_status_t srtp_stream_list_create(srtp_stream_list_t *list);
+srtp_err_status_t srtp_stream_list_alloc(srtp_stream_list_t *list_ptr);
+
+/**
+ * deallocate a stream list instance
+ *
+ * the list must be empty or else an error is returned.
+ */
+srtp_err_status_t srtp_stream_list_dealloc(srtp_stream_list_t list);
 
 /**
  * insert a stream into the list
@@ -82,38 +89,33 @@ srtp_err_status_t srtp_stream_list_create(srtp_stream_list_t *list);
  * behavior is undefined. if the SSRC field is mutated while the
  * stream is inserted, further operations have undefined behavior
  */
-srtp_err_status_t srtp_stream_list_insert(srtp_stream_list_t *list,
+srtp_err_status_t srtp_stream_list_insert(srtp_stream_list_t list,
                                           srtp_stream_t stream);
 
 /*
  * look up the stream corresponding to the specified SSRC and return it.
  * if no such SSRC is found, NULL is returned.
  */
-srtp_stream_t srtp_stream_list_get(srtp_stream_list_t *list, uint32_t ssrc);
+srtp_stream_t srtp_stream_list_get(srtp_stream_list_t list, uint32_t ssrc);
 
 /**
- * delete the stream associated to the specified SSRC.
+ * remove the stream from the list.
  *
- * if a stream is found and removed, it's returned and ownership is
- * transferred to the caller. if not found, NULL is returned.
+ * ownership is transferred to the caller.
+ *
+ * if the stream is not in the list the behavior is undefined.
  */
-srtp_stream_t srtp_stream_list_delete(srtp_stream_list_t *list, uint32_t ssrc);
+void srtp_stream_list_remove(srtp_stream_list_t list, srtp_stream_t stream);
 
 /**
  * iterate through all stored streams. while iterating, it is allowed to delete
  * the current element; any other mutation to the list is undefined behavior.
  * returning non-zero from callback aborts the iteration.
  */
-void srtp_stream_list_for_each(srtp_stream_list_t *list,
+void srtp_stream_list_for_each(srtp_stream_list_t list,
                                int (*callback)(srtp_stream_t, void *),
                                void *data);
 
-/**
- * deallocate a stream list instance and all streams inserted in it
- */
-srtp_err_status_t srtp_stream_list_dealloc(srtp_stream_list_t *list,
-                                           srtp_stream_t template_);
-
 #ifdef __cplusplus
 }
 #endif