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Messing around with the occasional last hash element #29

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Messing around with the occasional last hash element #29

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37 changes: 20 additions & 17 deletions ssdeep.go
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Original file line number Diff line number Diff line change
Expand Up @@ -47,27 +47,29 @@ func (rs *rollingState) rollSum() uint32 {
}

type ssdeepState struct {
rollingState rollingState
blockSize int
hashString1 string
hashString2 string
blockHash1 uint32
blockHash2 uint32
rState rollingState
blockSize int
hashString1 string
hashString2 string
blockHash1 uint32
blockHash2 uint32
lasthash uint32
}

func newSsdeepState() ssdeepState {
return ssdeepState{
blockHash1: hashInit,
blockHash2: hashInit,
rollingState: rollingState{
rState: rollingState{
window: make([]byte, rollingWindow),
},
blockSize: blockMin,
}
}

func (state *ssdeepState) newRollingState() {
state.rollingState = rollingState{}
state.rollingState.window = make([]byte, rollingWindow)
state.rState = rollingState{}
state.rState.window = make([]byte, rollingWindow)
}

// sumHash based on FNV hash
Expand All @@ -77,7 +79,7 @@ func sumHash(c byte, h uint32) uint32 {

// rollHash based on Adler checksum
func (state *ssdeepState) rollHash(c byte) {
rs := &state.rollingState
rs := &state.rState
rs.h2 -= rs.h1
rs.h2 += rollingWindow * uint32(c)
rs.h1 += uint32(c)
Expand All @@ -93,18 +95,17 @@ func (state *ssdeepState) rollHash(c byte) {

// getBlockSize calculates the block size based on file size
func (state *ssdeepState) setBlockSize(n int) {
blockSize := blockMin
for blockSize*spamSumLength < n {
blockSize = blockSize * 2
for state.blockSize*spamSumLength < n {
state.blockSize = state.blockSize * 2
}
state.blockSize = blockSize
}

func (state *ssdeepState) processByte(b byte) {
state.rollHash(b)
state.blockHash1 = sumHash(b, state.blockHash1)
state.blockHash2 = sumHash(b, state.blockHash2)
state.rollHash(b)
rh := int(state.rollingState.rollSum())
state.lasthash = sumHash(b, state.lasthash)
rh := int(state.rState.rollSum())
if rh%state.blockSize == (state.blockSize - 1) {
if len(state.hashString1) < spamSumLength-1 {
state.hashString1 += string(b64[state.blockHash1%64])
Expand Down Expand Up @@ -177,11 +178,13 @@ func FuzzyReader(f Reader, fileSize int) (string, error) {
state.hashString1 = ""
state.hashString2 = ""
} else {
rh := state.rollingState.rollSum()
rh := state.rState.rollSum()
if rh != 0 {
// Finalize the hash string with the remaining data
state.hashString1 += string(b64[state.blockHash1%64])
state.hashString2 += string(b64[state.blockHash2%64])
} else {
state.hashString1 += string(b64[state.lasthash%64] - 1)
}
break
}
Expand Down
10 changes: 4 additions & 6 deletions ssdeep_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,13 +9,11 @@ import (
"testing"

"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
)

func assertHashEqual(t *testing.T, expected, actual string) {
if expected != actual {
t.Fatalf("Hash mismatch: %s (expected)\n"+
" != %s (actual)", expected, actual)
}
require.Equal(t, expected, actual, "hash mismatch")
}

func TestIntegrity(t *testing.T) {
Expand Down Expand Up @@ -58,12 +56,12 @@ func concatCopyPreAllocate(slices [][]byte) []byte {

func TestRollingHash(t *testing.T) {
s := ssdeepState{
rollingState: rollingState{
rState: rollingState{
window: make([]byte, rollingWindow),
},
}
s.rollHash(byte('A'))
rh := s.rollingState.rollSum()
rh := s.rState.rollSum()
if rh != 585 {
t.Fatal("Rolling hash not matching")
}
Expand Down