Documentation
¶
Overview ¶
Package adler32 implements the Adler-32 rolling checksum.
Example ¶
package main
import (
"fmt"
"log"
adler32 "github.com/greatroar/rolling/adler32"
)
func main() {
const w = 16 // Window size.
s := []byte("The quick brown fox jumps over the lazy dog")
classic := adler32.New()
rolling := adler32.NewRolling(w)
// You must load an initial window into the rolling hash before being
// able to roll bytes.
rolling.WriteInitial(s[:w])
for i := rolling.WindowSize(); i < len(s); i++ {
// Reset and write the window in the "classic" hash.
classic.Reset()
classic.Write(s[i-w+1 : i+1])
// Roll the hash by showing it the incoming and outgoing bytes.
rolling.Roll(s[i], s[i-w])
fmt.Printf("%v: checksum %08x\n", string(s[i-w+1:i+1]), rolling.Sum32())
// Compare the hashes
if classic.Sum32() != rolling.Sum32() {
log.Fatalf("%v: expected %x, got %x",
s[i-w+1:i+1], classic.Sum32(), rolling.Sum32())
}
}
}
Output: he quick brown f: checksum 31e905d9 e quick brown fo: checksum 314805e0 quick brown fox: checksum 30ea05f3 quick brown fox : checksum 34dc05f3 uick brown fox j: checksum 33b705ec ick brown fox ju: checksum 325205ec ck brown fox jum: checksum 31b105f0 k brown fox jump: checksum 317d05fd brown fox jumps: checksum 30d10605 brown fox jumps : checksum 34d50605 rown fox jumps o: checksum 34c60612 own fox jumps ov: checksum 33bb0616 wn fox jumps ove: checksum 32d6060c n fox jumps over: checksum 316c0607 fox jumps over : checksum 304405b9 fox jumps over t: checksum 3450060d ox jumps over th: checksum 33fe060f x jumps over the: checksum 33120605 jumps over the : checksum 313e05ad jumps over the l: checksum 353605f9 umps over the la: checksum 348505f0 mps over the laz: checksum 332905f5 ps over the lazy: checksum 32590601 s over the lazy : checksum 310905b1 over the lazy d: checksum 2f7a05a2 over the lazy do: checksum 336a05f1 ver the lazy dog: checksum 326205e9
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
Types ¶
type Hash ¶
type Hash struct {
// contains filtered or unexported fields
}
A Hash computes the Adler-32 checksum without rolling.
This is a fast replacement for the standard hash/adler32 package.
type Rolling ¶
type Rolling struct {
// contains filtered or unexported fields
}
A Rolling computes the Adler-32 checksum with rolling.
func NewRolling ¶
NewRolling returns a new rolling Adler-32 hasher.
func (*Rolling) Reset ¶
func (h *Rolling) Reset()
Reset sets h to its initial state. The window size is unmodified.
func (*Rolling) WindowSize ¶
WindowSize returns the window size passed to New.
func (*Rolling) WriteInitial ¶
WriteInitial feeds initial data p to h.
Source Files
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