shithub: furgit

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Revert "delta, packed: Use xxhash instead of murmurhash2"

This reverts commit ac400226b0b622aae21b09cb6c83f07924647d0d.

--- a/delta_write_deltify.go

+++ b/delta_write_deltify.go

@@ -3,7 +3,7 @@

 import (

 	"bytes"

-	"github.com/cespare/xxhash/v2"

+	"codeberg.org/lindenii/furgit/internal/murmurhash2"

 )

 const (

@@ -62,7 +62,7 @@

 type deltaBlock struct {

 	length int

 	offset int

-	hash   uint64

+	hash   uint32

 }

 type deltaTable struct {

@@ -82,7 +82,7 @@

 	data   []byte

 }

-func deltify(base, target []byte, seed uint64) ([]deltaInstruction, error) {

+func deltify(base, target []byte, seed uint32) ([]deltaInstruction, error) {

 	if base == nil {

 		base = []byte{}

 	}

@@ -96,7 +96,7 @@

 	return deltifyMemMem(target, 0, len(target), seed, dt, base, 0, len(base))

 }

-func deltifyMemMem(target []byte, fileoffset, filesize int, seed uint64, dt *deltaTable, base []byte, baseOffset0, baseSize int) ([]deltaInstruction, error) {

+func deltifyMemMem(target []byte, fileoffset, filesize int, seed uint32, dt *deltaTable, base []byte, baseOffset0, baseSize int) ([]deltaInstruction, error) {

 	const allocChunkSize = 64

 	instr := make([]deltaInstruction, 0, allocChunkSize)

 	offset0 := fileoffset

@@ -141,7 +141,7 @@

 	return instr, nil

 }

-func deltaTableInitMem(data []byte, fileoffset, filesize int, seed uint64) (*deltaTable, error) {

+func deltaTableInitMem(data []byte, fileoffset, filesize int, seed uint32) (*deltaTable, error) {

 	dt := &deltaTable{

 		nalloc: 128,

 		size:   128,

@@ -164,13 +164,8 @@

 	return dt, nil

 }

-func deltaHashBlock(p []byte, seed uint64) uint64 {

-	if seed == 0 {

-		return xxhash.Sum64(p)

-	}

-	d := xxhash.NewWithSeed(seed)

-	_, _ = d.Write(p)

-	return d.Sum64()

+func deltaHashBlock(p []byte, seed uint32) uint32 {

+	return murmurhash2.Sum32(p, seed)

 }

 func deltaNextBlockLen(data []byte, fileoffset, filesize int) int {

@@ -193,7 +188,7 @@

 	return p - fileoffset

 }

-func (dt *deltaTable) addBlock(data []byte, offset0, length, offset int, h uint64) error {

+func (dt *deltaTable) addBlock(data []byte, offset0, length, offset int, h uint32) error {

 	if length == 0 {

 		return nil

 	}

@@ -205,22 +200,22 @@

 		return nil

 	}

 	dt.offs[idx] = uint32(dt.nblocks + 1)

-		dt.blocks[dt.nblocks] = deltaBlock{

-			length: length,

-			offset: offset,

-			hash:   h,

-		}

+	dt.blocks[dt.nblocks] = deltaBlock{

+		length: length,

+		offset: offset,

+		hash:   h,

+	}

 	dt.nblocks++

 	dt.len++

 	return nil

 }

-func (dt *deltaTable) lookupBlock(chunk []byte, length int, seed uint64, base []byte, baseOffset0 int) *deltaBlock {

+func (dt *deltaTable) lookupBlock(chunk []byte, length int, seed uint32, base []byte, baseOffset0 int) *deltaBlock {

 	if dt == nil || dt.size == 0 {

 		return nil

 	}

 	h := deltaHashBlock(chunk, seed)

-	for i := int(h % uint64(dt.size)); dt.offs[i] != 0; i = (i + 1) % dt.size {

+	for i := int(h % uint32(dt.size)); dt.offs[i] != 0; i = (i + 1) % dt.size {

 		block := &dt.blocks[dt.offs[i]-1]

 		if block.hash != h || block.length != length {

 			continue

@@ -236,11 +231,11 @@

 	return nil

 }

-func (dt *deltaTable) lookupSlot(data []byte, offset0, offset, length int, h uint64) (int, bool) {

+func (dt *deltaTable) lookupSlot(data []byte, offset0, offset, length int, h uint32) (int, bool) {

 	if dt == nil || dt.size == 0 {

 		return 0, false

 	}

-	for i := int(h % uint64(dt.size)); ; i = (i + 1) % dt.size {

+	for i := int(h % uint32(dt.size)); ; i = (i + 1) % dt.size {

 		if dt.offs[i] == 0 {

 			return i, false

 		}

@@ -278,7 +273,7 @@

 		dt.offs = make([]uint32, dt.size)

 		for i := 0; i < dt.nblocks; i++ {

 			block := &dt.blocks[i]

-			idx := int(block.hash % uint64(dt.size))

+			idx := int(block.hash % uint32(dt.size))

 			for dt.offs[idx] != 0 {

 				idx = (idx + 1) % dt.size

 			}

--- a/delta_write_encode.go

+++ b/delta_write_encode.go

@@ -89,7 +89,7 @@

 	return out, nil

 }

-func deltaTry(base, target []byte, seed uint64, minSavings int) ([]byte, bool) {

+func deltaTry(base, target []byte, seed uint32, minSavings int) ([]byte, bool) {

 	if minSavings < 0 {

 		minSavings = 0

 	}

--- a/delta_write_select.go

+++ b/delta_write_select.go

@@ -26,7 +26,7 @@

 	}

 }

-func pickDeltaBase(ctx *deltaContext, obj *objectToPack, seed uint64, minSavings, maxDepth int) (*objectToPack, []byte) {

+func pickDeltaBase(ctx *deltaContext, obj *objectToPack, seed uint32, minSavings, maxDepth int) (*objectToPack, []byte) {

 	if ctx == nil || len(ctx.candidates) == 0 {

 		return nil, nil

 	}

--- a/packed_write_pack.go

+++ b/packed_write_pack.go

@@ -306,14 +306,14 @@

 	}

 	var dctx deltaContext

-	var deltaSeed uint64

+	var deltaSeed uint32

 	if opts.EnableDeltas {

 		dctx.window = defaultDeltaWindow

-		var seedBytes [8]byte

+		var seedBytes [4]byte

 		if _, err := rand.Read(seedBytes[:]); err != nil {

 			return Hash{}, err

 		}

-		deltaSeed = binary.LittleEndian.Uint64(seedBytes[:])

+		deltaSeed = binary.LittleEndian.Uint32(seedBytes[:])

 	}

 	for _, id := range objects {

-- 

⑨