fs.h

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// Copyright (c) 2017-present The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifndef BITCOIN_UTIL_FS_H
#define BITCOIN_UTIL_FS_H
 
// IWYU incorrectly suggests removing this header.
// See https://github.com/include-what-you-use/include-what-you-use/issues/1931.
#include <tinyformat.h> // IWYU pragma: keep
 
#include <cstdio>
// The `util/fs.h` header is designed to be a drop-in replacement for `filesystem`.
#include <filesystem> // IWYU pragma: export
#include <functional>
#include <iomanip>
#include <ios>
#include <string>
#include <string_view>
#include <type_traits>
#include <utility>
 
namespace fs {
 
using namespace std::filesystem;
 
class path : public std::filesystem::path
{
public:
    using std::filesystem::path::path;
 
    // Convenience method for accessing standard path type without needing a cast.
    std::filesystem::path& std_path() { return *this; }
    const std::filesystem::path& std_path() const { return *this; }
 
    // Allow path objects arguments for compatibility.
    path(std::filesystem::path path) : std::filesystem::path::path(std::move(path)) {}
    path& operator=(std::filesystem::path path) { std::filesystem::path::operator=(std::move(path)); return *this; }
    path& operator/=(const std::filesystem::path& path) { std::filesystem::path::operator/=(path); return *this; }
 
    // Allow literal string arguments, which are safe as long as the literals are ASCII.
    path(const char* c) : std::filesystem::path(c) {}
    path& operator=(const char* c) { std::filesystem::path::operator=(c); return *this; }
    path& operator/=(const char* c) { std::filesystem::path::operator/=(c); return *this; }
    path& append(const char* c) { std::filesystem::path::append(c); return *this; }
 
    // Disallow std::string arguments to avoid locale-dependent decoding on windows.
    path(std::string) = delete;
    path& operator=(std::string) = delete;
    path& operator/=(std::string) = delete;
    path& append(std::string) = delete;
 
    // Disallow std::string conversion method to avoid locale-dependent encoding on windows.
    std::string string() const = delete;
 
    // Disallow implicit string conversion to ensure code is portable.
    // `string_type` may be `string` or `wstring` depending on the platform, so
    // using this conversion could result in code that compiles on unix but
    // fails to compile on windows, or vice versa.
    operator string_type() const = delete;
 
    std::string utf8string() const
    {
        const std::u8string& utf8_str{std::filesystem::path::u8string()};
        return std::string{utf8_str.begin(), utf8_str.end()};
    }
};
 
static inline path u8path(std::string_view utf8_str)
{
    return std::filesystem::path(std::u8string{utf8_str.begin(), utf8_str.end()});
}
 
// Disallow implicit std::string conversion for absolute to avoid
// locale-dependent encoding on windows.
static inline path absolute(const path& p)
{
    return std::filesystem::absolute(p);
}
 
// Disallow implicit std::string conversion for exists to avoid
// locale-dependent encoding on windows.
static inline bool exists(const path& p)
{
    return std::filesystem::exists(p);
}
static inline bool exists(const std::filesystem::file_status& s)
{
    return std::filesystem::exists(s);
}
 
// Allow explicit quoted stream I/O.
static inline auto quoted(const std::string& s)
{
    return std::quoted(s, '"', '&');
}
 
// Allow safe path append operations.
static inline path operator/(path p1, const path& p2)
{
    p1 /= p2;
    return p1;
}
static inline path operator/(path p1, const char* p2)
{
    p1 /= p2;
    return p1;
}
static inline path operator+(path p1, const char* p2)
{
    p1 += p2;
    return p1;
}
static inline path operator+(path p1, path::value_type p2)
{
    p1 += p2;
    return p1;
}
 
// Disallow unsafe path append operations.
template<typename T> static inline path operator/(path p1, T p2) = delete;
template<typename T> static inline path operator+(path p1, T p2) = delete;
 
// Disallow implicit std::string conversion for copy_file
// to avoid locale-dependent encoding on Windows.
static inline bool copy_file(const path& from, const path& to, copy_options options)
{
    return std::filesystem::copy_file(from, to, options);
}
 
static inline std::string PathToString(const path& path)
{
    // Implementation note: On Windows, the std::filesystem::path(string)
    // constructor and std::filesystem::path::string() method are not safe to
    // use here, because these methods encode the path using C++'s narrow
    // multibyte encoding, which on Windows corresponds to the current "code
    // page", which is unpredictable and typically not able to represent all
    // valid paths. So fs::path::utf8string() and
    // fs::u8path() functions are used instead on Windows. On
    // POSIX, u8string/utf8string/u8path functions are not safe to use because paths are
    // not always valid UTF-8, so plain string methods which do not transform
    // the path there are used.
#ifdef WIN32
    return path.utf8string();
#else
    static_assert(std::is_same_v<path::string_type, std::string>, "PathToString not implemented on this platform");
    return path.std::filesystem::path::string();
#endif
}
 
static inline path PathFromString(const std::string& string)
{
#ifdef WIN32
    return u8path(string);
#else
    return std::filesystem::path(string);
#endif
}
} // namespace fs
 
namespace fsbridge {
    using FopenFn = std::function<FILE*(const fs::path&, const char*)>;
    FILE *fopen(const fs::path& p, const char *mode);
 
    fs::path AbsPathJoin(const fs::path& base, const fs::path& path);
 
    class FileLock
    {
    public:
        FileLock() = delete;
        FileLock(const FileLock&) = delete;
        FileLock(FileLock&&) = delete;
        explicit FileLock(const fs::path& file);
        ~FileLock();
        bool TryLock();
        std::string GetReason() { return reason; }
 
    private:
        std::string reason;
#ifndef WIN32
        int fd = -1;
#else
        void* hFile = (void*)-1; // INVALID_HANDLE_VALUE
#endif
    };
};
 
// Disallow path operator<< formatting in tinyformat to avoid locale-dependent
// encoding on windows.
namespace tinyformat {
template<> inline void formatValue(std::ostream&, const char*, const char*, int, const std::filesystem::path&) = delete;
template<> inline void formatValue(std::ostream&, const char*, const char*, int, const fs::path&) = delete;
} // namespace tinyformat
 
#endif // BITCOIN_UTIL_FS_H