From 6c10528cbd0d7e85f590bb1021e832038129c249 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Wed, 5 Jul 2023 22:27:16 +0530
Subject: [PATCH] Make the hasher var private in the rsync API

---
 tools/rsync/algorithm.go | 23 ++++++++++++++++-------
 tools/rsync/api.go       | 15 ++++++++-------
 2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/tools/rsync/algorithm.go b/tools/rsync/algorithm.go
index 896b7933b..59a47f75d 100644
--- a/tools/rsync/algorithm.go
+++ b/tools/rsync/algorithm.go
@@ -156,9 +156,14 @@ type RSync struct {
 	BlockSize int
 
 	// This must be non-nil before using any functions
-	UniqueHasher hash.Hash
+	hasher             hash.Hash
+	hasher_constructor func() hash.Hash
+	buffer             []byte
+}
 
-	buffer []byte
+func (r *RSync) SetHasher(c func() hash.Hash) {
+	r.hasher_constructor = c
+	r.hasher = c()
 }
 
 // If the target length is known the number of hashes in the
@@ -525,8 +530,8 @@ func (r *RSync) CreateDiff(source io.Reader, signature []BlockHash) func() (*Ope
 	ans := &diff{
 		block_size: r.BlockSize, buffer: make([]byte, 0, (r.BlockSize * 8)),
 		hash_lookup: make(map[uint32][]BlockHash, len(signature)),
-		source:      source, hasher: r.UniqueHasher,
-		hash_buf: make([]byte, 0, r.UniqueHasher.Size()),
+		source:      source, hasher: r.hasher_constructor(),
+		hash_buf: make([]byte, 0, r.hasher.Size()),
 	}
 	for _, h := range signature {
 		key := h.WeakHash
@@ -552,11 +557,15 @@ func (r *RSync) CreateDelta(source io.Reader, signature []BlockHash, ops Operati
 
 // Use a more unique way to identify a set of bytes.
 func (r *RSync) hash(v []byte) []byte {
-	r.UniqueHasher.Reset()
-	r.UniqueHasher.Write(v)
-	return r.UniqueHasher.Sum(nil)
+	r.hasher.Reset()
+	r.hasher.Write(v)
+	return r.hasher.Sum(nil)
 }
 
+func (r *RSync) HashSize() int      { return r.hasher.Size() }
+func (r *RSync) HashBlockSize() int { return r.hasher.BlockSize() }
+func (r *RSync) HasHasher() bool    { return r.hasher != nil }
+
 // Searches for a given strong hash among all strong hashes in this bucket.
 func find_hash(hh []BlockHash, hv []byte) (uint64, bool) {
 	if len(hv) == 0 {
diff --git a/tools/rsync/api.go b/tools/rsync/api.go
index e82ab8e12..c2da62575 100644
--- a/tools/rsync/api.go
+++ b/tools/rsync/api.go
@@ -4,6 +4,7 @@ package rsync
 
 import (
 	"fmt"
+	"hash"
 	"io"
 	"math"
 
@@ -59,7 +60,7 @@ func (self *Api) read_signature_header(data []byte) (consumed int, err error) {
 	switch strong_hash := StrongHashType(bin.Uint16(data[4:])); strong_hash {
 	case XXH3:
 		self.Strong_hash_type = strong_hash
-		self.rsync.UniqueHasher = xxh3.New()
+		self.rsync.SetHasher(func() hash.Hash { return xxh3.New() })
 	default:
 		return consumed, fmt.Errorf("Invalid strong_hash in signature header: %d", strong_hash)
 	}
@@ -83,7 +84,7 @@ func (self *Api) read_signature_header(data []byte) (consumed int, err error) {
 }
 
 func (self *Api) read_signature_blocks(data []byte) (consumed int) {
-	hash_size := self.rsync.UniqueHasher.Size()
+	hash_size := self.rsync.HashSize()
 	block_hash_size := hash_size + 12
 	for ; len(data) >= block_hash_size; data = data[block_hash_size:] {
 		bl := BlockHash{}
@@ -99,7 +100,7 @@ func (self *Differ) finish_signature_data() (err error) {
 		return fmt.Errorf("There were %d leftover bytes in the signature data", len(self.unconsumed_signature_data))
 	}
 	self.unconsumed_signature_data = nil
-	if self.rsync.UniqueHasher == nil {
+	if !self.rsync.HasHasher() {
 		return fmt.Errorf("No header was found in the signature data")
 	}
 	return
@@ -211,7 +212,7 @@ func (self *Differ) CreateDelta(src io.Reader) DeltaIterator {
 // Add more external signature data
 func (self *Differ) AddSignatureData(data []byte) (err error) {
 	self.unconsumed_signature_data = append(self.unconsumed_signature_data, data...)
-	if self.rsync.UniqueHasher == nil {
+	if !self.rsync.HasHasher() {
 		consumed, err := self.read_signature_header(self.unconsumed_signature_data)
 		if err != nil {
 			if consumed < 0 {
@@ -240,10 +241,10 @@ func NewPatcher(expected_input_size int64) (ans *Patcher) {
 	}
 	ans = &Patcher{}
 	ans.rsync.BlockSize = utils.Min(bs, MaxBlockSize)
-	ans.rsync.UniqueHasher = xxh3.New()
+	ans.rsync.SetHasher(func() hash.Hash { return xxh3.New() })
 
-	if ans.rsync.UniqueHasher.BlockSize() > 0 && ans.rsync.UniqueHasher.BlockSize() < ans.rsync.BlockSize {
-		ans.rsync.BlockSize = (ans.rsync.BlockSize / ans.rsync.UniqueHasher.BlockSize()) * ans.rsync.UniqueHasher.BlockSize()
+	if ans.rsync.HashBlockSize() > 0 && ans.rsync.HashBlockSize() < ans.rsync.BlockSize {
+		ans.rsync.BlockSize = (ans.rsync.BlockSize / ans.rsync.HashBlockSize()) * ans.rsync.HashBlockSize()
 	}
 
 	ans.expected_input_size_for_signature_generation = sz