From 2b9fde932b53502ca6fb59d9a9d7ca781ffeae55 Mon Sep 17 00:00:00 2001
From: Chris Burgess <9002722+cgbur@users.noreply.github.com>
Date: Fri, 29 Jul 2022 15:22:46 -0400
Subject: [PATCH] Fix small file passthrough (#3215)

---
 programs/fileio.c  |  5 ++++-
 tests/playTests.sh | 10 ++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/programs/fileio.c b/programs/fileio.c
index a83b8064a..7a479069a 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -2346,7 +2346,10 @@ static int FIO_decompressFrames(FIO_ctx_t* const fCtx,
             break;   /* no more input */
         }
         readSomething = 1;   /* there is at least 1 byte in srcFile */
-        if (ress.readCtx->srcBufferLoaded < toRead) {
+        if (ress.readCtx->srcBufferLoaded < toRead) { /* not enough input to check magic number */
+            if ((prefs->overwrite) && !strcmp (dstFileName, stdoutmark)) {  /* pass-through mode */
+                return FIO_passThrough(&ress);
+            }
             DISPLAYLEVEL(1, "zstd: %s: unknown header \n", srcFileName);
             return 1;
         }
diff --git a/tests/playTests.sh b/tests/playTests.sh
index 0e2b0fbb2..7c111e7a3 100755
--- a/tests/playTests.sh
+++ b/tests/playTests.sh
@@ -808,6 +808,16 @@ println "Hello world 1!" | zstd -df
 println "Hello world 2!" | zstd -dcf
 println "Hello world 3!" > tmp1
 zstd -dcf tmp1
+println "" | zstd -df > tmp1
+println "" > tmp2
+$DIFF -q tmp1 tmp2
+println "1" | zstd -df > tmp1
+println "1" > tmp2
+$DIFF -q tmp1 tmp2
+println "12" | zstd -df > tmp1
+println "12" > tmp2
+$DIFF -q tmp1 tmp2
+rm -rf tmp*
 
 
 println "\n===>  frame concatenation "