From 30a1e466d387f7549bf05e5cef3f5bdd38daaefe Mon Sep 17 00:00:00 2001
From: Rick Altherr <kc8apf@kc8apf.net>
Date: Fri, 17 Nov 2017 01:20:12 -0800
Subject: [PATCH] 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                           |  7 +++++
 lib/CMakeLists.txt                       | 11 +++++++
 lib/include/prjxray/memory_mapped_file.h | 29 +++++++++++++++++
 lib/memory_mapped_file.cc                | 40 ++++++++++++++++++++++++
 lib/memory_mapped_file_test.cc           | 14 +++++++++
 lib/test_data/small_file                 |  1 +
 6 files changed, 102 insertions(+)
 create mode 100644 lib/CMakeLists.txt
 create mode 100644 lib/include/prjxray/memory_mapped_file.h
 create mode 100644 lib/memory_mapped_file.cc
 create mode 100644 lib/memory_mapped_file_test.cc
 create mode 100644 lib/test_data/small_file

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2483ca25..36bea5b9 100644
--- a/CMakeLists.txt
+++ b/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)
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
new file mode 100644
index 00000000..89a84071
--- /dev/null
+++ b/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()
diff --git a/lib/include/prjxray/memory_mapped_file.h b/lib/include/prjxray/memory_mapped_file.h
new file mode 100644
index 00000000..c62ea9b6
--- /dev/null
+++ b/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
diff --git a/lib/memory_mapped_file.cc b/lib/memory_mapped_file.cc
new file mode 100644
index 00000000..e01a5a3e
--- /dev/null
+++ b/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
diff --git a/lib/memory_mapped_file_test.cc b/lib/memory_mapped_file_test.cc
new file mode 100644
index 00000000..0c61d41e
--- /dev/null
+++ b/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));
+}
diff --git a/lib/test_data/small_file b/lib/test_data/small_file
new file mode 100644
index 00000000..257cc564
--- /dev/null
+++ b/lib/test_data/small_file
@@ -0,0 +1 @@
+foo