From d08f0549506714d417b667fb5af75b7471bbd4d4 Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Tue, 12 Mar 2024 11:24:27 +0000
Subject: [PATCH] [ENHANCEMENT] TSDB: Check CRC without allocating (#13742)

Use the existing utility function which does this.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
---
 tsdb/chunks/head_chunks.go | 21 +++------------------
 1 file changed, 3 insertions(+), 18 deletions(-)

diff --git a/tsdb/chunks/head_chunks.go b/tsdb/chunks/head_chunks.go
index 5ba538132..087f25fbb 100644
--- a/tsdb/chunks/head_chunks.go
+++ b/tsdb/chunks/head_chunks.go
@@ -15,7 +15,6 @@ package chunks
 
 import (
 	"bufio"
-	"bytes"
 	"encoding/binary"
 	"errors"
 	"fmt"
@@ -690,7 +689,6 @@ func (cdm *ChunkDiskMapper) Chunk(ref ChunkDiskMapperRef) (chunkenc.Chunk, error
 	sgmIndex, chkStart := ref.Unpack()
 	// We skip the series ref and the mint/maxt beforehand.
 	chkStart += SeriesRefSize + (2 * MintMaxtSize)
-	chkCRC32 := newCRC32()
 
 	// If it is the current open file, then the chunks can be in the buffer too.
 	if sgmIndex == cdm.curFileSequence {
@@ -755,20 +753,13 @@ func (cdm *ChunkDiskMapper) Chunk(ref ChunkDiskMapperRef) (chunkenc.Chunk, error
 
 	// Check the CRC.
 	sum := mmapFile.byteSlice.Range(chkDataEnd, chkDataEnd+CRCSize)
-	if _, err := chkCRC32.Write(mmapFile.byteSlice.Range(chkStart-(SeriesRefSize+2*MintMaxtSize), chkDataEnd)); err != nil {
+	if err := checkCRC32(mmapFile.byteSlice.Range(chkStart-(SeriesRefSize+2*MintMaxtSize), chkDataEnd), sum); err != nil {
 		return nil, &CorruptionErr{
 			Dir:       cdm.dir.Name(),
 			FileIndex: sgmIndex,
 			Err:       err,
 		}
 	}
-	if act := chkCRC32.Sum(nil); !bytes.Equal(act, sum) {
-		return nil, &CorruptionErr{
-			Dir:       cdm.dir.Name(),
-			FileIndex: sgmIndex,
-			Err:       fmt.Errorf("checksum mismatch expected:%x, actual:%x", sum, act),
-		}
-	}
 
 	// The chunk data itself.
 	chkData := mmapFile.byteSlice.Range(chkDataEnd-int(chkDataLen), chkDataEnd)
@@ -802,8 +793,6 @@ func (cdm *ChunkDiskMapper) IterateAllChunks(f func(seriesRef HeadSeriesRef, chu
 		cdm.fileMaxtSet = true
 	}()
 
-	chkCRC32 := newCRC32()
-
 	// Iterate files in ascending order.
 	segIDs := make([]int, 0, len(cdm.mmappedChunkFiles))
 	for seg := range cdm.mmappedChunkFiles {
@@ -838,7 +827,6 @@ func (cdm *ChunkDiskMapper) IterateAllChunks(f func(seriesRef HeadSeriesRef, chu
 						" - required:%v, available:%v, file:%d", idx+MaxHeadChunkMetaSize, fileEnd, segID),
 				}
 			}
-			chkCRC32.Reset()
 			chunkRef := newChunkDiskMapperRef(uint64(segID), uint64(idx))
 
 			startIdx := idx
@@ -877,14 +865,11 @@ func (cdm *ChunkDiskMapper) IterateAllChunks(f func(seriesRef HeadSeriesRef, chu
 
 			// Check CRC.
 			sum := mmapFile.byteSlice.Range(idx, idx+CRCSize)
-			if _, err := chkCRC32.Write(mmapFile.byteSlice.Range(startIdx, idx)); err != nil {
-				return err
-			}
-			if act := chkCRC32.Sum(nil); !bytes.Equal(act, sum) {
+			if err := checkCRC32(mmapFile.byteSlice.Range(startIdx, idx), sum); err != nil {
 				return &CorruptionErr{
 					Dir:       cdm.dir.Name(),
 					FileIndex: segID,
-					Err:       fmt.Errorf("checksum mismatch expected:%x, actual:%x", sum, act),
+					Err:       err,
 				}
 			}
 			idx += CRCSize