rust/hg-core/src/repo.rs

49212:d3d3495a5749

            };

            let data_filename = format!("dirstate.{}", uuid);
            let data_filename = self.hg_vfs().join(data_filename);
            let mut options = std::fs::OpenOptions::new();
            if append {
                options.append(true);
            } else {
                options.write(true).create_new(true);
            }
            let data_size = (|| {
                // TODO: loop and try another random ID if !append and this
                // returns `ErrorKind::AlreadyExists`? Collision chance of two
                // random IDs is one in 2**32
                let mut file = options.open(&data_filename)?;
                if data.is_empty() {
                    // If we're not appending anything, the data size is the
                    // same as in the previous docket. It is *not* the file
                    // length, since it could have garbage at the end.
                    // We don't have to worry about it when we do have data
                    // to append since we rewrite the root node in this case.
                    Ok(old_data_size as u64)
                } else {
                    file.write_all(&data)?;
                    file.flush()?;
                    // TODO: use https://doc.rust-lang.org/std/io/trait.Seek.html#method.stream_position when we require Rust 1.51+
                    file.seek(SeekFrom::Current(0))
                }
            })()
            .when_writing_file(&data_filename)?;

            let packed_dirstate = DirstateDocket::serialize(
                parents,

49217:13dfad0f9f7a

            };

            let data_filename = format!("dirstate.{}", uuid);
            let data_filename = self.hg_vfs().join(data_filename);
            let mut options = std::fs::OpenOptions::new();
            options.write(true);

            // Why are we not using the O_APPEND flag when appending?
            //
            // - O_APPEND makes it trickier to deal with garbage at the end of
            //   the file, left by a previous uncommitted transaction. By
            //   starting the write at [old_data_size] we make sure we erase
            //   all such garbage.
            //
            // - O_APPEND requires to special-case 0-byte writes, whereas we
            //   don't need that.
            //
            // - Some OSes have bugs in implementation O_APPEND:
            //   revlog.py talks about a Solaris bug, but we also saw some ZFS
            //   bug: https://github.com/openzfs/zfs/pull/3124,
            //   https://github.com/openzfs/zfs/issues/13370
            //
            if !append {
                options.create_new(true);
            }

            let data_size = (|| {
                // TODO: loop and try another random ID if !append and this
                // returns `ErrorKind::AlreadyExists`? Collision chance of two
                // random IDs is one in 2**32
                let mut file = options.open(&data_filename)?;
                if append {
                    file.seek(SeekFrom::Start(old_data_size as u64))?;
                }
                file.write_all(&data)?;
                file.flush()?;
                file.seek(SeekFrom::Current(0))
            })()
            .when_writing_file(&data_filename)?;

            let packed_dirstate = DirstateDocket::serialize(
                parents,