Avoid unnecessary overhead

app/src/main/cpp/CMakeLists.txt

@@ -45,6 +45,6 @@ SET(LIBARCHIVE_CUSTOM_LIBS "liblzma" "nettle")
 add_subdirectory(libarchive)
 
 # Build and link our app's native lib
-add_library(${PROJECT_NAME} SHARED archive.c fdutils.c)
+add_library(${PROJECT_NAME} SHARED archive.c fdutils.c gifUtils.c)
 target_include_directories(${PROJECT_NAME} PUBLIC libarchive/libarchive)
 target_link_libraries(${PROJECT_NAME} archive_static log -Wl,--gc-sections)

app/src/main/cpp/gifUtils.c

@@ -0,0 +1,11 @@
+#include <string.h>
+#include <jni.h>
+
+#define GIF_HEADER_87A "GIF87a"
+#define GIF_HEADER_89A "GIF89a"
+
+JNIEXPORT jboolean JNICALL
+Java_com_hippo_Native_isGif(JNIEnv *env, jobject thiz, jobject buffer) {
+    void *addr = (*env)->GetDirectBufferAddress(env, buffer);
+    return !memcmp(addr, GIF_HEADER_87A, 6) || !memcmp(addr, GIF_HEADER_89A, 6);
+}