Add botan_ffi_supports_api function

This lets us upgrade the FFI version over time and still allow
applications to reliably detect if the current library binary
supports their version.

As an example, it would be useful to be able to add features to FFI
sometime in 2.x. In that case, we would increase the value of the
FFI API version, even though anything calling the old API would still
work perfectly. Applications can verify at runtime the API they want to
use is supported using this new call.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/tests/test_ffi.cpp b/src/tests/test_ffi.cpp
index dd066e248..243583e8f 100644
--- a/src/tests/test_ffi.cpp
+++ b/src/tests/test_ffi.cpp
@@ -42,6 +42,7 @@ class FFI_Unit_Tests : public Test
          result.test_is_eq("Patch version", botan_version_patch(), Botan::version_patch());
          result.test_is_eq("Botan version", botan_version_string(), Botan::version_cstr());
          result.test_is_eq("Botan version datestamp", botan_version_datestamp(), Botan::version_datestamp());
+         result.test_is_eq("FFI supports its own version", botan_ffi_supports_api(botan_ffi_api_version()), 0);
 
          const std::vector<uint8_t> mem1 = { 0xFF, 0xAA, 0xFF };
          const std::vector<uint8_t> mem2 = mem1;