john-okeefe
46ae45ee92
Vendored the sevenzip package to eliminate dependency chain: - sevenzip -> go4.org -> 25+ Google/Cloud/telemetry packages Changes: - Added internal/sevenzip/ with full package source - Inlined go4.org/readerutil into multireaderat.go - Updated all internal imports to use bookhoard/internal/sevenzip - Preserved .cb7 comic archive support This reduces bloat by ~4.9 MB and removes unused telemetry dependencies while maintaining all functionality.
90 lines
1.5 KiB
Go
90 lines
1.5 KiB
Go
// Package delta implements the Delta filter.
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package delta
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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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type readCloser struct {
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rc io.ReadCloser
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state [stateSize]byte
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delta int
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}
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const (
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stateSize = 256
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)
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var (
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errAlreadyClosed = errors.New("delta: already closed")
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errNeedOneReader = errors.New("delta: need exactly one reader")
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errInsufficientProperties = errors.New("delta: not enough properties")
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)
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func (rc *readCloser) Close() error {
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if rc.rc == nil {
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return errAlreadyClosed
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}
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if err := rc.rc.Close(); err != nil {
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return fmt.Errorf("delta: error closing: %w", err)
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}
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rc.rc = nil
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return nil
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}
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func (rc *readCloser) Read(p []byte) (int, error) {
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if rc.rc == nil {
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return 0, errAlreadyClosed
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}
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n, err := rc.rc.Read(p)
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if err != nil && !errors.Is(err, io.EOF) {
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return n, fmt.Errorf("delta: error reading: %w", err)
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}
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var (
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buffer [stateSize]byte
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j int
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)
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copy(buffer[:], rc.state[:rc.delta])
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for i := 0; i < n; {
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for j = 0; j < rc.delta && i < n; i++ {
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p[i] = buffer[j] + p[i]
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buffer[j] = p[i]
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j++
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}
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}
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if j == rc.delta {
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j = 0
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}
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copy(rc.state[:], buffer[j:rc.delta])
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copy(rc.state[rc.delta-j:], buffer[:j])
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return n, nil
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}
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// NewReader returns a new Delta io.ReadCloser.
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func NewReader(p []byte, _ uint64, readers []io.ReadCloser) (io.ReadCloser, error) {
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if len(readers) != 1 {
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return nil, errNeedOneReader
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}
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if len(p) != 1 {
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return nil, errInsufficientProperties
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}
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return &readCloser{
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rc: readers[0],
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delta: int(p[0] + 1),
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}, nil
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}
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