54 lines
1.5 KiB
Go
54 lines
1.5 KiB
Go
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package matchfinder
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import "fmt"
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// A TextEncoder is an Encoder that produces a human-readable representation of
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// the LZ77 compression. Matches are replaced with <Length,Distance> symbols.
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type TextEncoder struct{}
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func (t TextEncoder) Reset() {}
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func (t TextEncoder) Encode(dst []byte, src []byte, matches []Match, lastBlock bool) []byte {
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pos := 0
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for _, m := range matches {
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if m.Unmatched > 0 {
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dst = append(dst, src[pos:pos+m.Unmatched]...)
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pos += m.Unmatched
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}
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if m.Length > 0 {
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dst = append(dst, []byte(fmt.Sprintf("<%d,%d>", m.Length, m.Distance))...)
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pos += m.Length
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}
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}
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if pos < len(src) {
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dst = append(dst, src[pos:]...)
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}
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return dst
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}
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// A NoMatchFinder implements MatchFinder, but doesn't find any matches.
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// It can be used to implement the equivalent of the standard library flate package's
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// HuffmanOnly setting.
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type NoMatchFinder struct{}
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func (n NoMatchFinder) Reset() {}
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func (n NoMatchFinder) FindMatches(dst []Match, src []byte) []Match {
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return append(dst, Match{
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Unmatched: len(src),
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})
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}
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// AutoReset wraps a MatchFinder that can return references to data in previous
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// blocks, and calls Reset before each block. It is useful for (e.g.) using a
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// snappy Encoder with a MatchFinder designed for flate. (Snappy doesn't
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// support references between blocks.)
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type AutoReset struct {
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MatchFinder
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}
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func (a AutoReset) FindMatches(dst []Match, src []byte) []Match {
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a.Reset()
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return a.MatchFinder.FindMatches(dst, src)
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}
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