95 lines
2.3 KiB
Go
95 lines
2.3 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 nfs4
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import (
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"slices"
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"sourcedock.dev/petrbalvin/nfs/internal/xdr"
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)
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// maxBitmapWords is the word count limit of a bitmap4. The protocol caps
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// the array at 100 words; the attribute table today ends far below that.
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const maxBitmapWords = 100
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// A Bitmap is a bitmap4: a compact set of attribute numbers.
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type Bitmap []uint32
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// OfBits returns a Bitmap carrying exactly the given attribute numbers.
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func OfBits(bits ...uint32) Bitmap {
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if len(bits) == 0 {
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return Bitmap{}
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}
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var words Bitmap
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for _, n := range bits {
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w := int(n / 32)
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for len(words) <= w {
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words = append(words, 0)
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}
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words[w] |= 1 << (n % 32)
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}
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return words
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}
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// Has reports whether the attribute number n is set.
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func (m Bitmap) Has(n uint32) bool {
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w := int(n / 32)
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return w < len(m) && m[w]&(1<<(n%32)) != 0
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}
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// With returns a bitmap carrying n in addition to what was already set.
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// Words the original bitmap already held are never dropped, even when the
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// new bit lands in a lower word.
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func (m Bitmap) With(n uint32) Bitmap {
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w := int(n / 32)
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out := make(Bitmap, max(w+1, len(m)))
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copy(out, m)
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out[w] |= 1 << (n % 32)
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return out
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}
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// AppendTo appends the bitmap in wire form: a count of words followed by
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// the words, with trailing zero words trimmed.
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func (m Bitmap) AppendTo(b []byte) []byte {
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trimmed := m
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for len(trimmed) > 0 && trimmed[len(trimmed)-1] == 0 {
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trimmed = trimmed[:len(trimmed)-1]
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}
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b = xdr.AppendUint32(b, uint32(len(trimmed)))
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for _, w := range trimmed {
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b = xdr.AppendUint32(b, w)
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}
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return b
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}
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// ReadBitmap reads a bitmap4. A bitmap beyond the word limit is refused
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// before any of it is buffered.
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func ReadBitmap(d *xdr.Decoder) (Bitmap, error) {
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n, err := d.Uint32()
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if err != nil {
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return nil, err
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}
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if n > maxBitmapWords {
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return nil, xdr.ErrBadLength
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}
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m := make(Bitmap, 0, n)
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for range n {
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w, err := d.Uint32()
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if err != nil {
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return nil, err
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}
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m = append(m, w)
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}
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return m, nil
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}
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// Words reports the words of the bitmap, without trailing zero words.
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func (m Bitmap) Words() []uint32 {
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trimmed := slices.Clone(m)
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for len(trimmed) > 0 && trimmed[len(trimmed)-1] == 0 {
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trimmed = trimmed[:len(trimmed)-1]
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}
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return trimmed
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}
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