From 3c1259389822ca1d24fe2350001b6bb7b7753dda Mon Sep 17 00:00:00 2001
From: Klaus Post <klauspost@gmail.com>
Date: Fri, 6 May 2022 15:51:31 +0200
Subject: [PATCH] zstd: Fix ignored crc

When `IgnoreChecksum(true)` was used, single threaded decodes would not consume CRC.

Bonus: Remove crc build tag for fuzzing.
---
 zstd/decoder.go   | 14 ++++++++++----
 zstd/framedec.go  |  2 +-
 zstd/fuzz.go      | 11 -----------
 zstd/fuzz_none.go | 11 -----------
 4 files changed, 11 insertions(+), 27 deletions(-)
 delete mode 100644 zstd/fuzz.go
 delete mode 100644 zstd/fuzz_none.go

diff --git a/zstd/decoder.go b/zstd/decoder.go
index b04e36f2ff..36119f385c 100644
--- a/zstd/decoder.go
+++ b/zstd/decoder.go
@@ -451,7 +451,7 @@ func (d *Decoder) nextBlock(blocking bool) (ok bool) {
 		got := d.current.crc.Sum64()
 		var tmp [4]byte
 		binary.LittleEndian.PutUint32(tmp[:], uint32(got))
-		if !d.o.ignoreChecksum && !bytes.Equal(tmp[:], next.d.checkCRC) && !ignoreCRC {
+		if !d.o.ignoreChecksum && !bytes.Equal(tmp[:], next.d.checkCRC) {
 			if debugDecoder {
 				println("CRC Check Failed:", tmp[:], " (got) !=", next.d.checkCRC, "(on stream)")
 			}
@@ -534,10 +534,16 @@ func (d *Decoder) nextBlockSync() (ok bool) {
 		}
 
 		// Update/Check CRC
-		if !d.o.ignoreChecksum && d.frame.HasCheckSum {
-			d.frame.crc.Write(d.current.b)
+		if d.frame.HasCheckSum {
+			if !d.o.ignoreChecksum {
+				d.frame.crc.Write(d.current.b)
+			}
 			if d.current.d.Last {
-				d.current.err = d.frame.checkCRC()
+				if !d.o.ignoreChecksum {
+					d.current.err = d.frame.checkCRC()
+				} else {
+					d.current.err = d.frame.consumeCRC()
+				}
 				if d.current.err != nil {
 					println("CRC error:", d.current.err)
 					return false
diff --git a/zstd/framedec.go b/zstd/framedec.go
index 4b15b2acc9..3ff109cce4 100644
--- a/zstd/framedec.go
+++ b/zstd/framedec.go
@@ -310,7 +310,7 @@ func (d *frameDec) checkCRC() error {
 	tmp[2] = byte(got >> 16)
 	tmp[3] = byte(got >> 24)
 
-	if !bytes.Equal(tmp[:], want) && !ignoreCRC {
+	if !bytes.Equal(tmp[:], want) {
 		if debugDecoder {
 			println("CRC Check Failed:", tmp[:], "!=", want)
 		}
diff --git a/zstd/fuzz.go b/zstd/fuzz.go
deleted file mode 100644
index 7f2210e053..0000000000
--- a/zstd/fuzz.go
+++ /dev/null
@@ -1,11 +0,0 @@
-//go:build ignorecrc
-// +build ignorecrc
-
-// Copyright 2019+ Klaus Post. All rights reserved.
-// License information can be found in the LICENSE file.
-// Based on work by Yann Collet, released under BSD License.
-
-package zstd
-
-// ignoreCRC can be used for fuzz testing to ignore CRC values...
-const ignoreCRC = true
diff --git a/zstd/fuzz_none.go b/zstd/fuzz_none.go
deleted file mode 100644
index 6811c68a89..0000000000
--- a/zstd/fuzz_none.go
+++ /dev/null
@@ -1,11 +0,0 @@
-//go:build !ignorecrc
-// +build !ignorecrc
-
-// Copyright 2019+ Klaus Post. All rights reserved.
-// License information can be found in the LICENSE file.
-// Based on work by Yann Collet, released under BSD License.
-
-package zstd
-
-// ignoreCRC can be used for fuzz testing to ignore CRC values...
-const ignoreCRC = false