lib: wrapper to manage memory-mapped files

Signed-off-by: Rick Altherr <kc8apf@kc8apf.net>
Signed-off-by: Tim 'mithro' Ansell <mithro@mithis.com>

CMakeLists.txt

@@ -1,15 +1,22 @@
 cmake_minimum_required(VERSION 3.5.0)
 
 project(prjxray)
+option(PRJXRAY_BUILD_TESTING "" ON)
 
 set(CMAKE_CXX_FLAGS "-std=c++11 -Wall -Werror ${CMAKE_CXX_FLAGS} -O3" )
 
 # Hack for missing option in cctz
 option(BUILD_TESTING "" OFF)
 
+
+if(PRJXRAY_BUILD_TESTING)
+	enable_testing()
+endif()
+
 add_subdirectory(third_party/googletest EXCLUDE_FROM_ALL)
 add_subdirectory(third_party/gflags EXCLUDE_FROM_ALL)
 add_subdirectory(third_party/cctz EXCLUDE_FROM_ALL)
 add_subdirectory(third_party/abseil-cpp EXCLUDE_FROM_ALL)
 
+add_subdirectory(lib)
 add_subdirectory(tools)

lib/CMakeLists.txt

@@ -0,0 +1,11 @@
+add_library(libprjxray
+	memory_mapped_file.cc)
+target_include_directories(libprjxray PUBLIC "include")
+
+if (PRJXRAY_BUILD_TESTING)
+	add_executable(memory_mapped_file_test memory_mapped_file_test.cc)
+	target_link_libraries(memory_mapped_file_test libprjxray gtest_main)
+	add_test(NAME memory_mapped_file_test
+		 COMMAND memory_mapped_file_test
+		 WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/test_data)
+endif()

lib/include/prjxray/memory_mapped_file.h

@@ -0,0 +1,29 @@
+#ifndef PRJXRAY_LIB_MEMORY_MAPPED_FILE
+#define PRJXRAY_LIB_MEMORY_MAPPED_FILE
+
+#include <memory>
+#include <string>
+
+namespace prjxray {
+
+class MemoryMappedFile {
+ public:
+	~MemoryMappedFile();
+
+	static std::unique_ptr<MemoryMappedFile> InitWithFile(
+			const std::string &path);
+
+	const void* data() { return data_; }
+	const size_t size() { return size_; }
+
+ private:
+	MemoryMappedFile(void *data, size_t size)
+		: data_(data), size_(size) {};
+
+	void *data_;
+	size_t size_;
+};
+
+} // namespace prjxray
+
+#endif  // PRJXRAY_LIB_MEMORY_MAPPED_FILE

lib/memory_mapped_file.cc

@@ -0,0 +1,40 @@
+#include <prjxray/memory_mapped_file.h>
+
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+namespace prjxray {
+
+std::unique_ptr<MemoryMappedFile> MemoryMappedFile::InitWithFile(
+	const std::string &path) {
+
+	int fd = open(path.c_str(), O_RDONLY, 0);
+	if (fd == -1) return nullptr;
+
+	struct stat statbuf;
+	if (fstat(fd, &statbuf) < 0) {
+		close(fd);
+	}
+
+	void *file_map = mmap(NULL, statbuf.st_size, PROT_READ,
+			      MAP_PRIVATE | MAP_POPULATE, fd, 0);
+
+	// If mmap() succeeded, the fd is no longer needed as the mapping will
+	// keep the file open.  If mmap() failed, the fd needs to be closed
+	// anyway.
+	close(fd);
+
+	if (file_map == MAP_FAILED) return nullptr;
+
+	return std::unique_ptr<MemoryMappedFile>(
+		new MemoryMappedFile(file_map, statbuf.st_size));
+}
+
+MemoryMappedFile::~MemoryMappedFile() {
+	munmap(data_, size_);
+}
+
+}  // namepsace prjxray

lib/memory_mapped_file_test.cc

@@ -0,0 +1,14 @@
+#include <prjxray/memory_mapped_file.h>
+
+#include <gtest/gtest.h>
+
+TEST(MemoryMappedFileTest, NonExistantFile) {
+	EXPECT_FALSE(prjxray::MemoryMappedFile::InitWithFile("does_not_exist"));
+}
+
+TEST(MemoryMappedFileTest, ExistingFile) {
+	auto file = prjxray::MemoryMappedFile::InitWithFile("small_file");
+	ASSERT_TRUE(file);
+	EXPECT_EQ(static_cast<size_t>(4), file->size());
+	EXPECT_EQ(0, memcmp("foo\n", file->data(), 4));
+}

lib/test_data/small_file

@@ -0,0 +1 @@
+foo