Add commit 43aab01 of BenHanson/lexertl14 from github

YACReaderLibrary/lexertl/memory_file.hpp

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+// memory_file.hpp
+// Copyright (c) 2015-2018 Ben Hanson (http://www.benhanson.net/)
+// Inspired by http://en.wikibooks.org/wiki/Optimizing_C%2B%2B/
+// General_optimization_techniques/Input/Output#Memory-mapped_file
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file licence_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef LEXERTL_MEMORY_FILE_HPP
+#define LEXERTL_MEMORY_FILE_HPP
+
+#include <cstddef>
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#endif
+
+// Only files small enough to fit into memory are supported.
+namespace lexertl
+{
+template<typename char_type>
+class basic_memory_file
+{
+public:
+    basic_memory_file()
+    {
+    }
+
+    basic_memory_file(const char *pathname_)
+    {
+        open(pathname_);
+    }
+
+    ~basic_memory_file()
+    {
+        close();
+    }
+
+    void open(const char *pathname_)
+    {
+        if (_data) close();
+
+#ifdef _WIN32
+        _fh = ::CreateFileA(pathname_, GENERIC_READ, FILE_SHARE_READ, 0,
+            OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
+        _fmh = 0;
+
+        if (_fh != INVALID_HANDLE_VALUE)
+        {
+            _fmh = ::CreateFileMapping(_fh, 0, PAGE_READONLY, 0, 0, 0);
+
+            if (_fmh != 0)
+            {
+                _data = static_cast<char_type *>(::MapViewOfFile
+                    (_fmh, FILE_MAP_READ, 0, 0, 0));
+
+                if (_data) _size = ::GetFileSize(_fh, 0) / sizeof(char_type);
+            }
+        }
+#else
+        _fh = ::open(pathname_, O_RDONLY);
+
+        if (_fh > -1)
+        {
+            struct stat sbuf_;
+
+            if (::fstat(_fh, &sbuf_) > -1)
+            {
+                _data = static_cast<const char_type *>
+                    (::mmap(0, sbuf_.st_size, PROT_READ, MAP_SHARED, _fh, 0));
+
+                if (_data == MAP_FAILED)
+                {
+                    _data = nullptr;
+                }
+                else
+                {
+                    _size = sbuf_.st_size / sizeof(char_type);
+                }
+            }
+        }
+#endif
+    }
+
+    const char_type *data() const
+    {
+        return _data;
+    }
+
+    std::size_t size() const
+    {
+        return _size;
+    }
+
+    void close()
+    {
+#ifdef _WIN32
+        ::UnmapViewOfFile(_data);
+        ::CloseHandle(_fmh);
+        ::CloseHandle(_fh);
+#else
+        ::munmap(const_cast<char_type *>(_data), _size);
+        ::close(_fh);
+#endif
+        _data = nullptr;
+        _size = 0;
+        _fh = 0;
+#ifdef _WIN32
+        _fmh = 0;
+#endif
+    }
+
+private:
+    const char_type *_data = nullptr;
+    std::size_t _size = 0;
+#ifdef _WIN32
+    HANDLE _fh = 0;
+    HANDLE _fmh = 0;
+#else
+    int _fh = 0;
+#endif
+
+    // No copy construction.
+    basic_memory_file(const basic_memory_file &) = delete;
+    // No assignment.
+    basic_memory_file &operator =(const basic_memory_file &) = delete;
+};
+
+using memory_file = basic_memory_file<char>;
+using wmemory_file = basic_memory_file<wchar_t>;
+}
+
+#endif