make xxhash dependency optional

Author: irfanHaslanded

CMakeLists.txt

@@ -242,6 +242,7 @@ else()
     option(ENABLE_TESTS "Build tests" OFF)
     option(ENABLE_VALGRIND_TESTS "Build tests with valgrind" OFF)
 endif()
+option(USE_XXHASH "Use xxhash if available" ON)
 option(ENABLE_PERF_TESTS "Build performance tests" OFF)
 option(ENABLE_COVERAGE "Build code coverage report from tests" OFF)
 option(ENABLE_FUZZ_TARGETS "Build target programs suitable for fuzzing with AFL" OFF)
@@ -412,9 +413,14 @@ include_directories(${PCRE2_INCLUDE_DIRS})
 target_link_libraries(yang ${PCRE2_LIBRARIES})
 
 # XXHash include and library
-find_package(XXHash REQUIRED)
-include_directories(${XXHASH_INCLUDE_DIR})
-target_link_libraries(yang ${XXHASH_LIBRARY})
+find_package(XXHash)
+if (XXHASH_FOUND AND USE_XXHASH)
+    add_definitions(-DUSE_XXHASH)
+    include_directories(${XXHASH_INCLUDE_DIR})
+    target_link_libraries(yang ${XXHASH_LIBRARY})
+else()
+    set (USE_XXHASH OFF)
+endif()
 
 # generated header list
 foreach(h IN LISTS gen_headers)

src/hash_table.c

@@ -20,13 +20,15 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
-#include <xxhash.h>
 
 #include "compat.h"
 #include "dict.h"
 #include "log.h"
 #include "ly_common.h"
 
+#ifdef USE_XXHASH
+#include <xxhash.h>
+
 LIBYANG_API_DEF uint32_t
 lyht_hash_multi(uint32_t hash, const char *key_part, size_t len)
 {
@@ -43,6 +45,39 @@ lyht_hash(const char *key, size_t len)
     return XXH3_64bits(key, len);
 }
 
+#else
+
+LIBYANG_API_DEF uint32_t
+lyht_hash_multi(uint32_t hash, const char *key_part, size_t len)
+{
+    uint32_t i;
+
+    if (key_part && len) {
+        for (i = 0; i < len; ++i) {
+            hash += key_part[i];
+            hash += (hash << 10);
+            hash ^= (hash >> 6);
+        }
+    } else {
+        hash += (hash << 3);
+        hash ^= (hash >> 11);
+        hash += (hash << 15);
+    }
+
+    return hash;
+}
+
+LIBYANG_API_DEF uint32_t
+lyht_hash(const char *key, size_t len)
+{
+    uint32_t hash;
+
+    hash = lyht_hash_multi(0, key, len);
+    return lyht_hash_multi(hash, NULL, len);
+}
+
+#endif
+
 static LY_ERR
 lyht_init_hlists_and_records(struct ly_ht *ht)
 {

src/hash_table.h

@@ -49,7 +49,12 @@ LIBYANG_API_DECL uint32_t lyht_hash_multi(uint32_t hash, const char *key_part, s
 /**
  * @brief Compute hash from a string.
  *
- * Uses XXH3_64bits internally See: https://xxhash.com
+ * Bob Jenkin's one-at-a-time hash
+ * http://www.burtleburtle.net/bob/hash/doobs.html
+ *
+ * Spooky hash is faster, but it works only for little endian architectures.
+ *
+ * Uses XXH3_64bits internally if xxhash is available. See https://xxhash.com
  *
  * @param[in] key Key to hash.
  * @param[in] len Length of @p key.

tests/CMakeLists.txt

@@ -30,7 +30,9 @@ function(ly_add_utest)
         endif()
     endif()
 
-    target_link_libraries(${TEST_NAME} ${XXHASH_LIBRARY})
+    if (USE_XXHASH)
+        target_link_libraries(${TEST_NAME} ${XXHASH_LIBRARY})
+    endif()
     add_test(NAME ${TEST_NAME} COMMAND ${TEST_NAME})
     set_property(TEST ${TEST_NAME} APPEND PROPERTY ENVIRONMENT "MALLOC_CHECK_=3")
 

tests/perf/CMakeLists.txt

@@ -6,7 +6,10 @@ set(format_sources
 add_executable(ly_perf ${CMAKE_CURRENT_SOURCE_DIR}/perf.c $<TARGET_OBJECTS:yangobj>)
 set_target_properties(ly_perf PROPERTIES RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/tests")
 target_link_libraries(ly_perf ${CMAKE_THREAD_LIBS_INIT} ${PCRE2_LIBRARIES} ${CMAKE_DL_LIBS})
-target_link_libraries(ly_perf ${XXHASH_LIBRARY})
+if (USE_XXHASH)
+    target_link_libraries(ly_perf ${XXHASH_LIBRARY})
+endif()
+
 if (NOT WIN32)
     target_link_libraries(ly_perf m)
 endif()

tests/style/CMakeLists.txt

@@ -8,5 +8,9 @@ endif()
 # just compile
 add_executable(cpp_compat cpp_compat.c $<TARGET_OBJECTS:yangobj>)
 target_include_directories(cpp_compat BEFORE PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
-target_link_libraries(cpp_compat ${CMAKE_THREAD_LIBS_INIT} ${PCRE2_LIBRARIES} ${CMAKE_DL_LIBS} m ${XXHASH_LIBRARY})
+target_link_libraries(cpp_compat ${CMAKE_THREAD_LIBS_INIT} ${PCRE2_LIBRARIES} ${CMAKE_DL_LIBS} m)
+if (USE_XXHASH)
+    target_link_libraries(cpp_compat ${XXHASH_LIBRARY})
+endif()
+
 target_compile_options(cpp_compat PUBLIC "-Werror=c++-compat")