libscio/mapped_file.cpp

//
// mapped_file.cpp
// conceal
//
// Created by Bob Polis at 2020-01-06
// Copyright (c) 2020 SwiftCoder. All rights reserved.
//

#include "libscio.hpp"
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <utility>
#include <stdexcept>
#include <algorithm>
#include <libscerror.hpp>

using namespace sc::io;

mapped_file::mapped_file() : std::istream {&_membuf} {}

mapped_file::mapped_file(const std::string& path) : std::istream {&_membuf} {
    open(path);
}

mapped_file::~mapped_file() {
    if (_mapping) {
        munmap(_mapping, _length);
        _mapping = nullptr;
        _length = 0;
    }
    if (_fd != -1) {
        close(_fd);
        _fd = -1;
    }
}

mapped_file::mapped_file(mapped_file&& other) : std::istream {std::move(other)} {
    _fd = other._fd;
    _mapping = other._mapping;
    _length = other._length;
    _membuf = std::move(other._membuf);

    other._fd = -1;
    other._mapping = nullptr;
    other._length = 0;
    other._membuf.pubsetbuf(nullptr, 0);
}

mapped_file& mapped_file::operator=(mapped_file &&other) {
    if (&other != this) {
        mapped_file mf {std::move(other)};
        std::swap(mf, *this);
    }
    return *this;
}

void mapped_file::open(const std::string& path) {
    if (_fd != -1) throw std::runtime_error("already open");
    _fd = ::open(path.c_str(), O_RDONLY);
    throw_if_min1_msg(_fd, "could not open file");
    struct stat st;
    throw_if_min1_msg(fstat(_fd, &st), "could not stat file");
    _length = st.st_size;
    _mapping = reinterpret_cast<char*>(mmap(nullptr, _length, PROT_READ, MAP_PRIVATE, _fd, 0));
    if (_mapping == MAP_FAILED) throw std::runtime_error("could not map file");
    _membuf.pubsetbuf(_mapping, _length);
}