well-goknown/vendor/github.com/andybalholm/brotli/matchfinder/textencoder.go
2024-09-25 21:59:44 -04:00

54 lines
1.5 KiB
Go

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