io_utils.h

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/* Copyright (C) 2006-2025 Olly Betts
 * Copyright (C) 2010 Richard Boulton
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see
 * <https://www.gnu.org/licenses/>.
 */
 
#ifndef XAPIAN_INCLUDED_IO_UTILS_H
#define XAPIAN_INCLUDED_IO_UTILS_H
 
#ifndef PACKAGE
# error config.h must be included first in each C++ source file
#endif
 
#include <sys/types.h>
#include "safefcntl.h"
#include "safeunistd.h"
#include <string>
 
inline int io_open_block_rd(const char* filename) {
    return ::open(filename, O_RDONLY | O_BINARY | O_CLOEXEC);
}
 
inline int io_open_block_rd(const std::string& filename)
{
    return io_open_block_rd(filename.c_str());
}
 
int io_open_block_wr(const char* filename, bool anew);
 
inline int io_open_block_wr(const std::string& filename, bool anew)
{
    return io_open_block_wr(filename.c_str(), anew);
}
 
inline int io_open_stream_rd(const char* filename) {
    return ::open(filename, O_RDONLY | O_BINARY | O_CLOEXEC);
}
 
inline int io_open_stream_rd(const std::string& filename)
{
    return io_open_stream_rd(filename.c_str());
}
 
int io_open_stream_wr(const char* filename, bool anew);
 
inline int io_open_stream_wr(const std::string& filename, bool anew)
{
    return io_open_stream_wr(filename.c_str(), anew);
}
 
inline bool io_sync(int fd)
{
#if defined HAVE_FDATASYNC
    // If we have it, prefer fdatasync() over fsync() as the former avoids
    // updating the access time so is probably a little more efficient.
    return fdatasync(fd) == 0;
#elif defined HAVE_FSYNC
    return fsync(fd) == 0;
#elif defined __WIN32__
    return _commit(fd) == 0;
#else
# error Cannot implement io_sync() without fdatasync(), fsync(), or _commit()
#endif
}
 
inline bool io_full_sync(int fd)
{
#ifdef F_FULLFSYNC
    /* Only supported on macOS (at the time of writing at least).
     *
     * This call ensures that data has actually been written to disk, not just
     * to the drive's write cache, so it provides better protection from power
     * failures, etc.  It does take longer though.
     *
     * According to the sqlite sources, this shouldn't fail on a local FS so
     * a failure means that the file system doesn't support this operation and
     * therefore it's best to fallback to fdatasync()/fsync().
     */
    if (fcntl(fd, F_FULLFSYNC, 0) == 0)
        return true;
#endif
    return io_sync(fd);
}
 
size_t io_read(int fd, char * p, size_t n, size_t min = 0);
 
void io_write(int fd, const char * p, size_t n);
 
inline void io_write(int fd, const unsigned char * p, size_t n) {
    io_write(fd, reinterpret_cast<const char *>(p), n);
}
 
size_t io_pread(int fd, char * p, size_t n, off_t o, size_t min = 0);
 
void io_pwrite(int fd, const char * p, size_t n, off_t o);
 
#ifdef HAVE_POSIX_FADVISE
bool io_readahead_block(int fd, size_t n, off_t b, off_t o = 0);
#else
inline bool io_readahead_block(int, size_t, off_t, off_t = 0) { return false; }
#endif
 
void io_read_block(int fd, char * p, size_t n, off_t b, off_t o = 0);
 
void io_write_block(int fd, const char * p, size_t n, off_t b, off_t o = 0);
 
inline void io_write_block(int fd, const unsigned char * p, size_t n, off_t b) {
    io_write_block(fd, reinterpret_cast<const char *>(p), n, b);
}
 
bool io_unlink(const std::string & filename);
 
bool io_tmp_rename(const std::string & tmp_file, const std::string & real_file);
 
#endif // XAPIAN_INCLUDED_IO_UTILS_H