1 files changed, 295 insertions, 0 deletions
diff --git a/src/util/fs_helpers.cpp b/src/util/fs_helpers.cpp
new file mode 100644
index 0000000000..d05cb8a63d
--- /dev/null
+++ b/src/util/fs_helpers.cpp
@@ -0,0 +1,295 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2023 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 <util/fs_helpers.h>
+
+#if defined(HAVE_CONFIG_H)
+#include <config/bitcoin-config.h>
+#endif
+
+#include <logging.h>
+#include <sync.h>
+#include <tinyformat.h>
+#include <util/fs.h>
+#include <util/getuniquepath.h>
+
+#include <cerrno>
+#include <filesystem>
+#include <fstream>
+#include <map>
+#include <memory>
+#include <string>
+#include <system_error>
+#include <utility>
+
+#ifndef WIN32
+// for posix_fallocate, in configure.ac we check if it is present after this
+#ifdef __linux__
+
+#ifdef _POSIX_C_SOURCE
+#undef _POSIX_C_SOURCE
+#endif
+
+#define _POSIX_C_SOURCE 200112L
+
+#endif // __linux__
+
+#include <fcntl.h>
+#include <sys/resource.h>
+#include <unistd.h>
+#else
+#include <io.h> /* For _get_osfhandle, _chsize */
+#include <shlobj.h> /* For SHGetSpecialFolderPathW */
+#endif // WIN32
+
+/** Mutex to protect dir_locks. */
+static GlobalMutex cs_dir_locks;
+/** A map that contains all the currently held directory locks. After
+ * successful locking, these will be held here until the global destructor
+ * cleans them up and thus automatically unlocks them, or ReleaseDirectoryLocks
+ * is called.
+ */
+static std::map<std::string, std::unique_ptr<fsbridge::FileLock>> dir_locks GUARDED_BY(cs_dir_locks);
+
+bool LockDirectory(const fs::path& directory, const fs::path& lockfile_name, bool probe_only)
+{
+    LOCK(cs_dir_locks);
+    fs::path pathLockFile = directory / lockfile_name;
+
+    // If a lock for this directory already exists in the map, don't try to re-lock it
+    if (dir_locks.count(fs::PathToString(pathLockFile))) {
+        return true;
+    }
+
+    // Create empty lock file if it doesn't exist.
+    FILE* file = fsbridge::fopen(pathLockFile, "a");
+    if (file) fclose(file);
+    auto lock = std::make_unique<fsbridge::FileLock>(pathLockFile);
+    if (!lock->TryLock()) {
+        return error("Error while attempting to lock directory %s: %s", fs::PathToString(directory), lock->GetReason());
+    }
+    if (!probe_only) {
+        // Lock successful and we're not just probing, put it into the map
+        dir_locks.emplace(fs::PathToString(pathLockFile), std::move(lock));
+    }
+    return true;
+}
+
+void UnlockDirectory(const fs::path& directory, const fs::path& lockfile_name)
+{
+    LOCK(cs_dir_locks);
+    dir_locks.erase(fs::PathToString(directory / lockfile_name));
+}
+
+void ReleaseDirectoryLocks()
+{
+    LOCK(cs_dir_locks);
+    dir_locks.clear();
+}
+
+bool DirIsWritable(const fs::path& directory)
+{
+    fs::path tmpFile = GetUniquePath(directory);
+
+    FILE* file = fsbridge::fopen(tmpFile, "a");
+    if (!file) return false;
+
+    fclose(file);
+    remove(tmpFile);
+
+    return true;
+}
+
+bool CheckDiskSpace(const fs::path& dir, uint64_t additional_bytes)
+{
+    constexpr uint64_t min_disk_space = 52428800; // 50 MiB
+
+    uint64_t free_bytes_available = fs::space(dir).available;
+    return free_bytes_available >= min_disk_space + additional_bytes;
+}
+
+std::streampos GetFileSize(const char* path, std::streamsize max)
+{
+    std::ifstream file{path, std::ios::binary};
+    file.ignore(max);
+    return file.gcount();
+}
+
+bool FileCommit(FILE* file)
+{
+    if (fflush(file) != 0) { // harmless if redundantly called
+        LogPrintf("%s: fflush failed: %d\n", __func__, errno);
+        return false;
+    }
+#ifdef WIN32
+    HANDLE hFile = (HANDLE)_get_osfhandle(_fileno(file));
+    if (FlushFileBuffers(hFile) == 0) {
+        LogPrintf("%s: FlushFileBuffers failed: %d\n", __func__, GetLastError());
+        return false;
+    }
+#elif defined(MAC_OSX) && defined(F_FULLFSYNC)
+    if (fcntl(fileno(file), F_FULLFSYNC, 0) == -1) { // Manpage says "value other than -1" is returned on success
+        LogPrintf("%s: fcntl F_FULLFSYNC failed: %d\n", __func__, errno);
+        return false;
+    }
+#elif HAVE_FDATASYNC
+    if (fdatasync(fileno(file)) != 0 && errno != EINVAL) { // Ignore EINVAL for filesystems that don't support sync
+        LogPrintf("%s: fdatasync failed: %d\n", __func__, errno);
+        return false;
+    }
+#else
+    if (fsync(fileno(file)) != 0 && errno != EINVAL) {
+        LogPrintf("%s: fsync failed: %d\n", __func__, errno);
+        return false;
+    }
+#endif
+    return true;
+}
+
+void DirectoryCommit(const fs::path& dirname)
+{
+#ifndef WIN32
+    FILE* file = fsbridge::fopen(dirname, "r");
+    if (file) {
+        fsync(fileno(file));
+        fclose(file);
+    }
+#endif
+}
+
+bool TruncateFile(FILE* file, unsigned int length)
+{
+#if defined(WIN32)
+    return _chsize(_fileno(file), length) == 0;
+#else
+    return ftruncate(fileno(file), length) == 0;
+#endif
+}
+
+/**
+ * this function tries to raise the file descriptor limit to the requested number.
+ * It returns the actual file descriptor limit (which may be more or less than nMinFD)
+ */
+int RaiseFileDescriptorLimit(int nMinFD)
+{
+#if defined(WIN32)
+    return 2048;
+#else
+    struct rlimit limitFD;
+    if (getrlimit(RLIMIT_NOFILE, &limitFD) != -1) {
+        if (limitFD.rlim_cur < (rlim_t)nMinFD) {
+            limitFD.rlim_cur = nMinFD;
+            if (limitFD.rlim_cur > limitFD.rlim_max)
+                limitFD.rlim_cur = limitFD.rlim_max;
+            setrlimit(RLIMIT_NOFILE, &limitFD);
+            getrlimit(RLIMIT_NOFILE, &limitFD);
+        }
+        return limitFD.rlim_cur;
+    }
+    return nMinFD; // getrlimit failed, assume it's fine
+#endif
+}
+
+/**
+ * this function tries to make a particular range of a file allocated (corresponding to disk space)
+ * it is advisory, and the range specified in the arguments will never contain live data
+ */
+void AllocateFileRange(FILE* file, unsigned int offset, unsigned int length)
+{
+#if defined(WIN32)
+    // Windows-specific version
+    HANDLE hFile = (HANDLE)_get_osfhandle(_fileno(file));
+    LARGE_INTEGER nFileSize;
+    int64_t nEndPos = (int64_t)offset + length;
+    nFileSize.u.LowPart = nEndPos & 0xFFFFFFFF;
+    nFileSize.u.HighPart = nEndPos >> 32;
+    SetFilePointerEx(hFile, nFileSize, 0, FILE_BEGIN);
+    SetEndOfFile(hFile);
+#elif defined(MAC_OSX)
+    // OSX specific version
+    // NOTE: Contrary to other OS versions, the OSX version assumes that
+    // NOTE: offset is the size of the file.
+    fstore_t fst;
+    fst.fst_flags = F_ALLOCATECONTIG;
+    fst.fst_posmode = F_PEOFPOSMODE;
+    fst.fst_offset = 0;
+    fst.fst_length = length; // mac os fst_length takes the # of free bytes to allocate, not desired file size
+    fst.fst_bytesalloc = 0;
+    if (fcntl(fileno(file), F_PREALLOCATE, &fst) == -1) {
+        fst.fst_flags = F_ALLOCATEALL;
+        fcntl(fileno(file), F_PREALLOCATE, &fst);
+    }
+    ftruncate(fileno(file), static_cast<off_t>(offset) + length);
+#else
+#if defined(HAVE_POSIX_FALLOCATE)
+    // Version using posix_fallocate
+    off_t nEndPos = (off_t)offset + length;
+    if (0 == posix_fallocate(fileno(file), 0, nEndPos)) return;
+#endif
+    // Fallback version
+    // TODO: just write one byte per block
+    static const char buf[65536] = {};
+    if (fseek(file, offset, SEEK_SET)) {
+        return;
+    }
+    while (length > 0) {
+        unsigned int now = 65536;
+        if (length < now)
+            now = length;
+        fwrite(buf, 1, now, file); // allowed to fail; this function is advisory anyway
+        length -= now;
+    }
+#endif
+}
+
+#ifdef WIN32
+fs::path GetSpecialFolderPath(int nFolder, bool fCreate)
+{
+    WCHAR pszPath[MAX_PATH] = L"";
+
+    if (SHGetSpecialFolderPathW(nullptr, pszPath, nFolder, fCreate)) {
+        return fs::path(pszPath);
+    }
+
+    LogPrintf("SHGetSpecialFolderPathW() failed, could not obtain requested path.\n");
+    return fs::path("");
+}
+#endif
+
+bool RenameOver(fs::path src, fs::path dest)
+{
+#ifdef __MINGW64__
+    // This is a workaround for a bug in libstdc++ which
+    // implements std::filesystem::rename with _wrename function.
+    // This bug has been fixed in upstream:
+    //  - GCC 10.3: 8dd1c1085587c9f8a21bb5e588dfe1e8cdbba79e
+    //  - GCC 11.1: 1dfd95f0a0ca1d9e6cbc00e6cbfd1fa20a98f312
+    // For more details see the commits mentioned above.
+    return MoveFileExW(src.wstring().c_str(), dest.wstring().c_str(),
+                       MOVEFILE_REPLACE_EXISTING) != 0;
+#else
+    std::error_code error;
+    fs::rename(src, dest, error);
+    return !error;
+#endif
+}
+
+/**
+ * Ignores exceptions thrown by create_directories if the requested directory exists.
+ * Specifically handles case where path p exists, but it wasn't possible for the user to
+ * write to the parent directory.
+ */
+bool TryCreateDirectories(const fs::path& p)
+{
+    try {
+        return fs::create_directories(p);
+    } catch (const fs::filesystem_error&) {
+        if (!fs::exists(p) || !fs::is_directory(p))
+            throw;
+    }
+
+    // create_directories didn't create the directory, it had to have existed already
+    return false;
+}