Gabime/fwrite unlocked (#3276)

* Use locking fwrite_unlocked if possible

* Added compile definitions to header_only

CMakeLists.txt

@@ -238,6 +238,20 @@ if(SPDLOG_FMT_EXTERNAL OR SPDLOG_FMT_EXTERNAL_HO)
     set(PKG_CONFIG_REQUIRES fmt) # add dependency to pkg-config
 endif()
 
+# ---------------------------------------------------------------------------------------
+# Check if fwrite_unlocked/_fwrite_nolock is available
+# ---------------------------------------------------------------------------------------
+include(CheckSymbolExists)
+if(WIN32)
+    check_symbol_exists(_fwrite_nolock "stdio.h" HAVE_FWRITE_UNLOCKED)
+else ()
+    check_symbol_exists(fwrite_unlocked "stdio.h" HAVE_FWRITE_UNLOCKED)
+endif()
+if(HAVE_FWRITE_UNLOCKED)
+    target_compile_definitions(spdlog PRIVATE SPDLOG_FWRITE_UNLOCKED)
+    target_compile_definitions(spdlog_header_only INTERFACE SPDLOG_FWRITE_UNLOCKED)
+endif()
+
 # ---------------------------------------------------------------------------------------
 # Add required libraries for Android CMake build
 # ---------------------------------------------------------------------------------------

include/spdlog/details/file_helper-inl.h

@@ -101,7 +101,8 @@ SPDLOG_INLINE void file_helper::write(const memory_buf_t &buf) {
     if (fd_ == nullptr) return;
     size_t msg_size = buf.size();
     auto data = buf.data();
-    if (std::fwrite(data, 1, msg_size, fd_) != msg_size) {
+
+    if (!details::os::fwrite_bytes(data, msg_size, fd_)) {
         throw_spdlog_ex("Failed writing to file " + os::filename_to_str(filename_), errno);
     }
 }

include/spdlog/details/os-inl.h

@@ -589,6 +589,18 @@ SPDLOG_INLINE bool fsync(FILE *fp) {
 #endif
 }
 
+// Do non-locking fwrite if possible by the os or use the regular locking fwrite
+// Return true on success.
+SPDLOG_INLINE bool fwrite_bytes(const void *ptr, const size_t n_bytes, FILE *fp) {
+    #if defined(_WIN32) && defined(SPDLOG_FWRITE_UNLOCKED)
+    return _fwrite_nolock(ptr, 1, n_bytes, fp) == n_bytes;
+    #elif defined(SPDLOG_FWRITE_UNLOCKED)
+    return ::fwrite_unlocked(ptr, 1, n_bytes, fp) == n_bytes;
+    #else
+    return std::fwrite(ptr, 1, n_bytes, fp) == n_bytes;
+    #endif
+}
+
 }  // namespace os
 }  // namespace details
 }  // namespace spdlog

include/spdlog/details/os.h

@@ -114,6 +114,10 @@ SPDLOG_API std::string getenv(const char *field);
 // Return true on success.
 SPDLOG_API bool fsync(FILE *fp);
 
+// Do non-locking fwrite if possible by the os or use the regular locking fwrite
+// Return true on success.
+SPDLOG_API bool fwrite_bytes(const void *ptr, const size_t n_bytes, FILE *fp);
+
 }  // namespace os
 }  // namespace details
 }  // namespace spdlog

include/spdlog/sinks/ansicolor_sink-inl.h

@@ -106,14 +106,14 @@ SPDLOG_INLINE void ansicolor_sink<ConsoleMutex>::set_color_mode(color_mode mode)
 
 template <typename ConsoleMutex>
 SPDLOG_INLINE void ansicolor_sink<ConsoleMutex>::print_ccode_(const string_view_t &color_code) {
-    fwrite(color_code.data(), sizeof(char), color_code.size(), target_file_);
+    details::os::fwrite_bytes(color_code.data(), color_code.size(), target_file_);
 }
 
 template <typename ConsoleMutex>
 SPDLOG_INLINE void ansicolor_sink<ConsoleMutex>::print_range_(const memory_buf_t &formatted,
                                                               size_t start,
                                                               size_t end) {
-    fwrite(formatted.data() + start, sizeof(char), end - start, target_file_);
+    details::os::fwrite_bytes(formatted.data() + start, end - start, target_file_);
 }
 
 template <typename ConsoleMutex>

include/spdlog/sinks/stdout_sinks-inl.h

@@ -10,6 +10,7 @@
 #include <memory>
 #include <spdlog/details/console_globals.h>
 #include <spdlog/pattern_formatter.h>
+#include <spdlog/details/os.h>
 
 #ifdef _WIN32
     // under windows using fwrite to non-binary stream results in \r\r\n (see issue #1675)
@@ -22,7 +23,7 @@
 
     #include <io.h>     // _get_osfhandle(..)
     #include <stdio.h>  // _fileno(..)
-#endif                  // WIN32
+#endif                  // _WIN32
 
 namespace spdlog {
 
@@ -44,7 +45,7 @@ SPDLOG_INLINE stdout_sink_base<ConsoleMutex>::stdout_sink_base(FILE *file)
     if (handle_ == INVALID_HANDLE_VALUE && file != stdout && file != stderr) {
         throw_spdlog_ex("spdlog::stdout_sink_base: _get_osfhandle() failed", errno);
     }
-#endif  // WIN32
+#endif  // _WIN32
 }
 
 template <typename ConsoleMutex>
@@ -67,8 +68,8 @@ SPDLOG_INLINE void stdout_sink_base<ConsoleMutex>::log(const details::log_msg &m
     std::lock_guard<mutex_t> lock(mutex_);
     memory_buf_t formatted;
     formatter_->format(msg, formatted);
-    ::fwrite(formatted.data(), sizeof(char), formatted.size(), file_);
-#endif                // WIN32
+    details::os::fwrite_bytes(formatted.data(), formatted.size(), file_);
+#endif                // _WIN32
     ::fflush(file_);  // flush every line to terminal
 }
 

tests/test_misc.cpp

@@ -1,3 +1,7 @@
+#ifdef _WIN32 // to prevent fopen warning on windows
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+
 #include "includes.h"
 #include "test_sink.h"
 
@@ -185,3 +189,34 @@ TEST_CASE("utf8 to utf16 conversion using windows api", "[windows utf]") {
     REQUIRE(std::wstring(buffer.data(), buffer.size()) == std::wstring(L"\x306d\x3053"));
 }
 #endif
+
+struct auto_closer {
+    FILE* fp = nullptr;
+    explicit auto_closer(FILE* f) : fp(f) {}
+    auto_closer(const auto_closer&) = delete;
+    auto_closer& operator=(const auto_closer&) = delete;
+    ~auto_closer() {
+        if (fp != nullptr) (void)std::fclose(fp);
+    }
+};
+
+TEST_CASE("os::fwrite_bytes", "[os]") {
+    using spdlog::details::os::fwrite_bytes;
+    using spdlog::details::os::create_dir;
+    const char* filename = "log_tests/test_fwrite_bytes.txt";
+    const char *msg = "hello";
+    prepare_logdir();
+    REQUIRE(create_dir(SPDLOG_FILENAME_T("log_tests")) == true);
+    {
+        auto_closer closer(std::fopen(filename, "wb"));
+        REQUIRE(closer.fp != nullptr);
+        REQUIRE(fwrite_bytes(msg, std::strlen(msg), closer.fp) == true);
+        REQUIRE(fwrite_bytes(msg, 0, closer.fp) == true);
+        std::fflush(closer.fp);
+        REQUIRE(spdlog::details::os::filesize(closer.fp) == 5);
+    }
+    // fwrite_bytes should return false on write failure
+    auto_closer closer(std::fopen(filename, "r"));
+    REQUIRE(closer.fp != nullptr);
+    REQUIRE_FALSE(fwrite_bytes("Hello", 5, closer.fp));
+}