56 lines
1.7 KiB
Go
56 lines
1.7 KiB
Go
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// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
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// SPDX-License-Identifier: MIT
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package nfsfs
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import (
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"errors"
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"fmt"
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"io"
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)
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// A ReadIntoer is the optional read half that fills a caller provided
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// buffer instead of allocating its own: the reply path of a server reads
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// straight into the buffer it is about to send. A backend that carries
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// only Read keeps its allocating behaviour.
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type ReadIntoer interface {
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// ReadInto reads up to len(buf) bytes at the offset into buf and
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// answers how many landed and whether the end of file was reached.
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ReadInto(h Handle, off int64, buf []byte) (int, bool, error)
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}
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// ReadInto fills buf from the regular file the handle names. The
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// descriptor comes from the cache or a fresh verified open, and the
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// identity is revalidated before anything is read, exactly as Read.
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func (l *Local) ReadInto(h Handle, off int64, buf []byte) (int, bool, error) {
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f, release, err := l.dataFD(h, false)
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if err != nil {
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return 0, false, err
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}
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defer release()
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n, rerr := f.ReadAt(buf, off)
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switch {
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case errors.Is(rerr, io.EOF):
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return n, true, nil
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case rerr != nil:
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return n, false, fmt.Errorf("%w: %v", ErrIO, rerr)
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}
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// A full buffer proves the end of file only against the size; the
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// descriptor's own stat answers it without a second path walk.
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if fst, serr := f.Stat(); serr == nil {
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return n, int64(off)+int64(n) >= fst.Size(), nil
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}
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return n, false, nil
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}
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// ReadInto forwards to the wrapped export: a read only export reads as
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// its backend does.
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func (ro roFS) ReadInto(h Handle, off int64, buf []byte) (int, bool, error) {
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ri, ok := ro.FS.(ReadIntoer)
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if !ok {
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data, err := ro.Read(h, off, len(buf))
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return len(data), false, err
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}
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return ri.ReadInto(h, off, buf)
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}
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