From a8219903cfce3f735e842afbf4ff442ce5358218 Mon Sep 17 00:00:00 2001
From: Jan Kasiak <jan@cybojanek.net>
Date: Sun, 1 Sep 2019 15:35:53 -0400
Subject: [PATCH] Fix streaming compression/decompression examples

* Handle compression of empty file
* Error in decompression in case of trailing data
---
 examples/streaming_compression.c   |  8 ++++++--
 examples/streaming_decompression.c | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/examples/streaming_compression.c b/examples/streaming_compression.c
index d1353a684..d0b04895f 100644
--- a/examples/streaming_compression.c
+++ b/examples/streaming_compression.c
@@ -44,8 +44,8 @@ static void compressFile_orDie(const char* fname, const char* outName, int cLeve
      * and writes all output produced to the output file.
      */
     size_t const toRead = buffInSize;
-    size_t read;
-    while ((read = fread_orDie(buffIn, toRead, fin))) {
+    for (;;) {
+        size_t read = fread_orDie(buffIn, toRead, fin);
         /* Select the flush mode.
          * If the read may not be finished (read == toRead) we use
          * ZSTD_e_continue. If this is the last chunk, we use ZSTD_e_end.
@@ -76,6 +76,10 @@ static void compressFile_orDie(const char* fname, const char* outName, int cLeve
         } while (!finished);
         CHECK(input.pos == input.size,
               "Impossible: zstd only returns 0 when the input is completely consumed!");
+
+        if (lastChunk) {
+            break;
+        }
     }
 
     ZSTD_freeCCtx(cctx);
diff --git a/examples/streaming_decompression.c b/examples/streaming_decompression.c
index bcd861b75..d26b45b34 100644
--- a/examples/streaming_decompression.c
+++ b/examples/streaming_decompression.c
@@ -34,7 +34,10 @@ static void decompressFile_orDie(const char* fname)
      */
     size_t const toRead = buffInSize;
     size_t read;
+    size_t lastRet = 0;
+    int isEmpty = 1;
     while ( (read = fread_orDie(buffIn, toRead, fin)) ) {
+        isEmpty = 0;
         ZSTD_inBuffer input = { buffIn, read, 0 };
         /* Given a valid frame, zstd won't consume the last byte of the frame
          * until it has flushed all of the decompressed data of the frame.
@@ -53,9 +56,24 @@ static void decompressFile_orDie(const char* fname)
             size_t const ret = ZSTD_decompressStream(dctx, &output , &input);
             CHECK_ZSTD(ret);
             fwrite_orDie(buffOut, output.pos, fout);
+            lastRet = ret;
         }
     }
 
+    if (isEmpty) {
+        fprintf(stderr, "input is empty\n");
+        exit(1);
+    }
+
+    if (lastRet != 0) {
+        /* The last return value from ZSTD_decompressStream did not end on a
+         * frame, but we reached the end of the file! We assume this is an
+         * error, and the input was truncated.
+         */
+        fprintf(stderr, "EOF before end of stream: %zu\n", lastRet);
+        exit(1);
+    }
+
     ZSTD_freeDCtx(dctx);
     fclose_orDie(fin);
     fclose_orDie(fout);