bitcoin/src/fs.cpp

// Copyright (c) 2017-2021 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <fs.h>
#include <util/syserror.h>

#ifndef WIN32
#include <cstring>
#include <fcntl.h>
#include <sys/file.h>
#include <sys/utsname.h>
#include <unistd.h>
#else
#include <codecvt>
#include <limits>
#include <windows.h>
#endif

#include <cassert>
#include <string>

namespace fsbridge {

FILE *fopen(const fs::path& p, const char *mode)
{
#ifndef WIN32
    return ::fopen(p.c_str(), mode);
#else
    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>,wchar_t> utf8_cvt;
    return ::_wfopen(p.wstring().c_str(), utf8_cvt.from_bytes(mode).c_str());
#endif
}

fs::path AbsPathJoin(const fs::path& base, const fs::path& path)
{
    assert(base.is_absolute());
    return path.empty() ? base : fs::path(base / path);
}

#ifndef WIN32

static std::string GetErrorReason()
{
    return SysErrorString(errno);
}

FileLock::FileLock(const fs::path& file)
{
    fd = open(file.c_str(), O_RDWR);
    if (fd == -1) {
        reason = GetErrorReason();
    }
}

FileLock::~FileLock()
{
    if (fd != -1) {
        close(fd);
    }
}

static bool IsWSL()
{
    struct utsname uname_data;
    return uname(&uname_data) == 0 && std::string(uname_data.version).find("Microsoft") != std::string::npos;
}

bool FileLock::TryLock()
{
    if (fd == -1) {
        return false;
    }

    // Exclusive file locking is broken on WSL using fcntl (issue #18622)
    // This workaround can be removed once the bug on WSL is fixed
    static const bool is_wsl = IsWSL();
    if (is_wsl) {
        if (flock(fd, LOCK_EX | LOCK_NB) == -1) {
            reason = GetErrorReason();
            return false;
        }
    } else {
        struct flock lock;
        lock.l_type = F_WRLCK;
        lock.l_whence = SEEK_SET;
        lock.l_start = 0;
        lock.l_len = 0;
        if (fcntl(fd, F_SETLK, &lock) == -1) {
            reason = GetErrorReason();
            return false;
        }
    }

    return true;
}
#else

static std::string GetErrorReason() {
    wchar_t* err;
    FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
        nullptr, GetLastError(), MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), reinterpret_cast<WCHAR*>(&err), 0, nullptr);
    std::wstring err_str(err);
    LocalFree(err);
    return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>>().to_bytes(err_str);
}

FileLock::FileLock(const fs::path& file)
{
    hFile = CreateFileW(file.wstring().c_str(),  GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
        nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
    if (hFile == INVALID_HANDLE_VALUE) {
        reason = GetErrorReason();
    }
}

FileLock::~FileLock()
{
    if (hFile != INVALID_HANDLE_VALUE) {
        CloseHandle(hFile);
    }
}

bool FileLock::TryLock()
{
    if (hFile == INVALID_HANDLE_VALUE) {
        return false;
    }
    _OVERLAPPED overlapped = {0};
    if (!LockFileEx(hFile, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY, 0, std::numeric_limits<DWORD>::max(), std::numeric_limits<DWORD>::max(), &overlapped)) {
        reason = GetErrorReason();
        return false;
    }
    return true;
}
#endif

std::string get_filesystem_error_message(const fs::filesystem_error& e)
{
#ifndef WIN32
    return e.what();
#else
    // Convert from Multi Byte to utf-16
    std::string mb_string(e.what());
    int size = MultiByteToWideChar(CP_ACP, 0, mb_string.data(), mb_string.size(), nullptr, 0);

    std::wstring utf16_string(size, L'\0');
    MultiByteToWideChar(CP_ACP, 0, mb_string.data(), mb_string.size(), &*utf16_string.begin(), size);
    // Convert from utf-16 to utf-8
    return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t>().to_bytes(utf16_string);
#endif
}

} // fsbridge