fileWriteFilePositional

fn fileWriteFilePositional(
    userdata: ?*anyopaque,
    file: File,
    header: []const u8,
    file_reader: *File.Reader,
    limit: Io.Limit,
    offset: u64,
) File.WriteFilePositionalError!usize

File

Code

fn fileWriteFilePositional(
    userdata: ?*anyopaque,
    file: File,
    header: []const u8,
    file_reader: *File.Reader,
    limit: Io.Limit,
    offset: u64,
) File.WriteFilePositionalError!usize {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    const reader_buffered = file_reader.interface.buffered();
    if (reader_buffered.len >= @backingInt(limit)) {
        const n = try fileWritePositional(t, file, header, &.{limit.slice(reader_buffered)}, 1, offset);
        file_reader.interface.toss(n -| header.len);
        return n;
    }
    const out_fd = file.handle;
    const in_fd = file_reader.file.handle;

    if (file_reader.size) |size| {
        if (size - file_reader.pos == 0) {
            if (reader_buffered.len != 0) {
                const n = try fileWritePositional(t, file, header, &.{limit.slice(reader_buffered)}, 1, offset);
                file_reader.interface.toss(n -| header.len);
                return n;
            } else {
                return error.EndOfStream;
            }
        }
    }

    if (have_copy_file_range) cfr: {
        if (@atomicLoad(UseCopyFileRange, &t.use_copy_file_range, .monotonic) == .disabled) break :cfr;
        if (header.len != 0 or reader_buffered.len != 0) {
            const n = try fileWritePositional(t, file, header, &.{limit.slice(reader_buffered)}, 1, offset);
            file_reader.interface.toss(n -| header.len);
            return n;
        }
        var len: usize = @min(@backingInt(limit), std.math.maxInt(usize) - offset);
        var off_in: i64 = undefined;
        const off_in_ptr: ?*i64 = switch (file_reader.mode) {
            .positional_simple, .streaming_simple => return error.Unimplemented,
            .positional => p: {
                len = @min(len, std.math.maxInt(usize) - file_reader.pos);
                off_in = @intCast(file_reader.pos);
                break :p &off_in;
            },
            .streaming => null,
            .failure => return error.ReadFailed,
        };
        var off_out: i64 = @intCast(offset);
        const n: usize = switch (native_os) {
            .linux => n: {
                const syscall: Syscall = try .start();
                while (true) {
                    const rc = linux_copy_file_range_sys.copy_file_range(in_fd, off_in_ptr, out_fd, &off_out, len, 0);
                    switch (linux_copy_file_range_sys.errno(rc)) {
                        .SUCCESS => {
                            syscall.finish();
                            break :n @intCast(rc);
                        },
                        .INTR => {
                            try syscall.checkCancel();
                            continue;
                        },
                        .OPNOTSUPP, .INVAL, .NOSYS => {
                            // Give calling code chance to observe before trying
                            // something else.
                            syscall.finish();
                            @atomicStore(UseCopyFileRange, &t.use_copy_file_range, .disabled, .monotonic);
                            return 0;
                        },
                        else => |e| {
                            syscall.finish();
                            assert(error.Unexpected == switch (e) {
                                .FBIG => return error.FileTooBig,
                                .IO => return error.InputOutput,
                                .NOMEM => return error.SystemResources,
                                .NOSPC => return error.NoSpaceLeft,
                                .OVERFLOW => |err| errnoBug(err), // We avoid passing too large a count.
                                .NXIO => return error.Unseekable,
                                .SPIPE => return error.Unseekable,
                                .PERM => return error.PermissionDenied,
                                .TXTBSY => return error.FileBusy,
                                // copy_file_range can still work but not on
                                // this pair of file descriptors.
                                .XDEV => return error.Unimplemented,
                                .ISDIR => |err| errnoBug(err),
                                .BADF => |err| errnoBug(err),
                                else => |err| posix.unexpectedErrno(err),
                            });
                            @atomicStore(UseCopyFileRange, &t.use_copy_file_range, .disabled, .monotonic);
                            return 0;
                        },
                    }
                }
            },
            .freebsd => n: {
                const syscall: Syscall = try .start();
                while (true) {
                    const rc = std.c.copy_file_range(in_fd, off_in_ptr, out_fd, &off_out, @backingInt(limit), 0);
                    switch (std.c.errno(rc)) {
                        .SUCCESS => {
                            syscall.finish();
                            break :n @intCast(rc);
                        },
                        .INTR => {
                            try syscall.checkCancel();
                            continue;
                        },
                        .OPNOTSUPP, .INVAL, .NOSYS => {
                            // Give calling code chance to observe before trying
                            // something else.
                            syscall.finish();
                            @atomicStore(UseCopyFileRange, &t.use_copy_file_range, .disabled, .monotonic);
                            return 0;
                        },
                        else => |e| {
                            syscall.finish();
                            assert(error.Unexpected == switch (e) {
                                .FBIG => return error.FileTooBig,
                                .IO => return error.InputOutput,
                                .INTEGRITY => return error.CorruptedData,
                                .NOSPC => return error.NoSpaceLeft,
                                .OVERFLOW => return error.Unseekable,
                                .NXIO => return error.Unseekable,
                                .SPIPE => return error.Unseekable,
                                .ISDIR => |err| errnoBug(err),
                                .BADF => |err| errnoBug(err),
                                else => |err| posix.unexpectedErrno(err),
                            });
                            @atomicStore(UseCopyFileRange, &t.use_copy_file_range, .disabled, .monotonic);
                            return 0;
                        },
                    }
                }
            },
            else => comptime unreachable,
        };
        if (n == 0) {
            file_reader.size = file_reader.pos;
            return error.EndOfStream;
        }
        file_reader.pos += n;
        return n;
    }

    if (is_darwin) fcf: {
        if (@atomicLoad(UseFcopyfile, &t.use_fcopyfile, .monotonic) == .disabled) break :fcf;
        if (file_reader.pos != 0) break :fcf;
        if (offset != 0) break :fcf;
        if (limit != .unlimited) break :fcf;
        const size = file_reader.getSize() catch break :fcf;
        if (header.len != 0 or reader_buffered.len != 0) {
            const n = try fileWritePositional(t, file, header, &.{limit.slice(reader_buffered)}, 1, offset);
            file_reader.interface.toss(n -| header.len);
            return n;
        }
        const syscall: Syscall = try .start();
        while (true) {
            const rc = std.c.fcopyfile(in_fd, out_fd, null, .{ .DATA = true });
            switch (posix.errno(rc)) {
                .SUCCESS => {
                    syscall.finish();
                    break;
                },
                .INTR => {
                    try syscall.checkCancel();
                    continue;
                },
                .OPNOTSUPP => {
                    // Give calling code chance to observe before trying
                    // something else.
                    syscall.finish();
                    @atomicStore(UseFcopyfile, &t.use_fcopyfile, .disabled, .monotonic);
                    return 0;
                },
                else => |e| {
                    syscall.finish();
                    assert(error.Unexpected == switch (e) {
                        .NOMEM => return error.SystemResources,
                        .INVAL => |err| errnoBug(err),
                        else => |err| posix.unexpectedErrno(err),
                    });
                    return 0;
                },
            }
        }
        file_reader.pos = size;
        return size;
    }

    return error.Unimplemented;
}