Added buffer test case

tests/unittests/CMakeLists.txt

@@ -1,5 +1,6 @@
 project(unittests C)
 
+add_check_test(torture_buffer torture_buffer.c ${TORTURE_LIBRARY})
 add_check_test(torture_callbacks torture_callbacks.c ${TORTURE_LIBRARY})
 add_check_test(torture_init torture_init.c ${TORTURE_LIBRARY})
 add_check_test(torture_keyfiles torture_keyfiles.c ${TORTURE_LIBRARY})

tests/unittests/torture_buffer.c

@@ -0,0 +1,67 @@
+#define LIBSSH_STATIC
+
+#include "torture.h"
+#include "libssh/buffer.h"
+
+ssh_buffer buffer;
+#define LIMIT (8*1024*1024)
+
+static void setup(void) {
+    buffer=ssh_buffer_new();
+}
+
+static void teardown(void) {
+  ssh_buffer_free(buffer);
+}
+
+/* test if the continuously growing buffer size never exceeds 2 time its
+ * real capacity
+ */
+START_TEST (torture_growing_buffer)
+{
+  int i;
+  for(i=0;i<LIMIT;++i){
+    buffer_add_data(buffer,"A",1);
+    if(buffer->used >= 128){
+      if(buffer_get_rest_len(buffer) * 2 < buffer->allocated){
+        ck_assert(buffer_get_rest_len(buffer) * 2 >= buffer->allocated);
+      }
+    }
+  }
+}
+END_TEST
+
+/* test if the continuously growing buffer size never exceeds 2 time its
+ * real capacity, when we remove 1 byte after each call (sliding window)
+ */
+START_TEST (torture_growing_buffer_shifting)
+{
+  int i;
+  unsigned char c;
+  for(i=0; i<1024;++i){
+    buffer_add_data(buffer,"S",1);
+  }
+  for(i=0;i<LIMIT;++i){
+    buffer_get_u8(buffer,&c);
+    buffer_add_data(buffer,"A",1);
+    if(buffer->used >= 128){
+      if(buffer_get_rest_len(buffer) * 4 < buffer->allocated){
+        ck_assert(buffer_get_rest_len(buffer) * 4 >= buffer->allocated);
+        return;
+      }
+    }
+  }
+}
+END_TEST
+
+Suite *torture_make_suite(void) {
+  Suite *s = suite_create("libssh_buffer");
+
+  torture_create_case_fixture(s, "torture_growing_buffer",
+            torture_growing_buffer, setup, teardown);
+  torture_create_case_fixture(s, "torture_growing_buffer_shifting",
+            torture_growing_buffer_shifting, setup, teardown);
+
+  return s;
+}
+