From 1b1e195382daa95a5e3cf8b3e72b7be0dfbf7f63 Mon Sep 17 00:00:00 2001
From: Sutou Kouhei <kou@clear-code.com>
Date: Mon, 25 Aug 2025 15:31:26 +0900
Subject: [PATCH] feat: don't require crc32c with recent Abseil

cc2a5641e88a589d40551143401f21ea3659aed2 (#11061) introduced Abseil
based CRC32C implementation. So we don't require crc32c when we use
recent Abseil.

If we don't require crc32c with recent Abseil, downstream users such
as Apache Arrow don't need to bundle crc32c. It reduces maintenance
cost.

See also: https://github.com/apache/arrow/issues/45989
---
 google/cloud/storage/CMakeLists.txt              |  9 ++++++++-
 .../cloud/storage/google_cloud_cpp_storage.cmake | 11 +++++++++--
 google/cloud/storage/internal/crc32c.cc          | 16 ++++++++++------
 3 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/google/cloud/storage/CMakeLists.txt b/google/cloud/storage/CMakeLists.txt
index b3c2eaa890eb0..4a2b4a02a31ec 100644
--- a/google/cloud/storage/CMakeLists.txt
+++ b/google/cloud/storage/CMakeLists.txt
@@ -31,7 +31,14 @@ google_cloud_cpp_doxygen_targets("storage" DEPENDS cloud-docs
 include(GoogleCloudCppCommon)
 
 include(IncludeNlohmannJson)
-find_package(Crc32c)
+if (BUILD_TESTING OR absl_VERSION VERSION_LESS "20230125")
+    set(NEED_CRC32C TRUE)
+else ()
+    set(NEED_CRC32C FALSE)
+endif ()
+if (NEED_CRC32C)
+    find_package(Crc32c REQUIRED)
+endif()
 
 # Export the version information for Bazel.
 include(CreateBazelConfig)
diff --git a/google/cloud/storage/google_cloud_cpp_storage.cmake b/google/cloud/storage/google_cloud_cpp_storage.cmake
index d1fe20b4fa382..3c17c5561e098 100644
--- a/google/cloud/storage/google_cloud_cpp_storage.cmake
+++ b/google/cloud/storage/google_cloud_cpp_storage.cmake
@@ -273,9 +273,11 @@ target_link_libraries(
            google-cloud-cpp::common
            google-cloud-cpp::rest_internal
            nlohmann_json::nlohmann_json
-           Crc32c::crc32c
            CURL::libcurl
            Threads::Threads)
+if (NEED_CRC32C)
+    target_link_libraries(google_cloud_cpp_storage PUBLIC Crc32c::crc32c)
+endif()
 if (WIN32)
     target_compile_definitions(google_cloud_cpp_storage
                                PRIVATE WIN32_LEAN_AND_MEAN)
@@ -333,6 +335,11 @@ install(
 google_cloud_cpp_install_headers(google_cloud_cpp_storage
                                  include/google/cloud/storage)
 
+set(PKGCONFIG_LIBS)
+if (NEED_CRC32C)
+    list(APPEND PKGCONFIG_LIBS crc32c)
+endif()
+
 google_cloud_cpp_add_pkgconfig(
     "storage"
     "The Google Cloud Storage C++ Client Library"
@@ -348,7 +355,7 @@ google_cloud_cpp_add_pkgconfig(
     NON_WIN32_REQUIRES
     openssl
     LIBS
-    crc32c
+    ${PKGCONFIG_LIBS}
     WIN32_LIBS
     ws2_32
     bcrypt)
diff --git a/google/cloud/storage/internal/crc32c.cc b/google/cloud/storage/internal/crc32c.cc
index 57c16dfe38e20..6e8c7929c8e14 100644
--- a/google/cloud/storage/internal/crc32c.cc
+++ b/google/cloud/storage/internal/crc32c.cc
@@ -18,20 +18,15 @@
 #include "absl/crc/crc32c.h"
 #define GOOGLE_CLOUD_CPP_USE_ABSL_CRC32C 1
 #else
+#include <crc32c/crc32c.h>
 #define GOOGLE_CLOUD_CPP_USE_ABSL_CRC32C 0
 #endif  // ABSL_LTS_RELEASE_VERSION
-#include <crc32c/crc32c.h>
 
 namespace google {
 namespace cloud {
 namespace storage_internal {
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_BEGIN
 
-std::uint32_t ExtendCrc32c(std::uint32_t crc, absl::string_view data) {
-  return crc32c::Extend(crc, reinterpret_cast<uint8_t const*>(data.data()),
-                        data.size());
-}
-
 std::uint32_t ExtendCrc32c(std::uint32_t crc,
                            storage::internal::ConstBufferSequence const& data) {
   for (auto const& b : data) {
@@ -49,6 +44,10 @@ std::uint32_t ExtendCrc32c(std::uint32_t crc, absl::Cord const& data) {
 
 #if GOOGLE_CLOUD_CPP_USE_ABSL_CRC32C
 
+std::uint32_t ExtendCrc32c(std::uint32_t crc, absl::string_view data) {
+  return static_cast<std::uint32_t>(absl::ExtendCrc32c(absl::crc32c_t{crc}, data));
+}
+
 std::uint32_t ExtendCrc32c(std::uint32_t crc, absl::string_view data,
                            std::uint32_t data_crc) {
   return static_cast<std::uint32_t>(absl::ConcatCrc32c(
@@ -71,6 +70,11 @@ std::uint32_t ExtendCrc32c(std::uint32_t crc, absl::Cord const& data,
 
 #else
 
+std::uint32_t ExtendCrc32c(std::uint32_t crc, absl::string_view data) {
+  return crc32c::Extend(crc, reinterpret_cast<uint8_t const*>(data.data()),
+                        data.size());
+}
+
 std::uint32_t ExtendCrc32c(std::uint32_t crc, absl::string_view data,
                            std::uint32_t /*data_crc*/) {
   return ExtendCrc32c(crc, data);