fs.cpp

Go to the documentation of this file.

// Copyright (c) 2017 The Bitcoin Core developers
// Copyright (c) 2019 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#include <util/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
#ifndef NOMINMAX
#define NOMINMAX
#endif
#include <codecvt>
#include <windows.h>
#endif
 
#include <cassert>
#include <limits>
#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() {
    return Win32ErrorString(GetLastError());
}
 
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 = {};
    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
 
fs::path GetTempDirectoryPath() {
#ifndef WIN32
    return fs::temp_directory_path();
#else
    wchar_t dirPathWchars[MAX_PATH];
    GetTempPathW(MAX_PATH, dirPathWchars);
    std::wstring dirPathWstring(dirPathWchars);
    return fs::PathFromString(
        std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>>().to_bytes(
            dirPathWstring));
#endif
}
 
} // namespace fsbridge