Add one extra byte to return value of compressBound and deflateBound for small lengths due to shift returning 0.

* Treat 0 byte input as 1 byte input when calculating compressBound and deflateBound

2 files changed, 4 insertions, 0 deletions

diff --git a/compress.c b/compress.c
index fded2a4..1cf5d5f 100644
--- a/compress.c
+++ b/compress.c
@@ -92,6 +92,8 @@ z_size_t Z_EXPORT PREFIX(compressBound)(z_size_t sourceLen) {
 
 #ifndef NO_QUICK_STRATEGY
     return sourceLen                       /* The source size itself */
+      + (sourceLen == 0 ? 1 : 0)           /* Always at least one byte for any input */
+      + (sourceLen < 9 ? 1 : 0)            /* One extra byte for lengths less than 9 */
       + DEFLATE_QUICK_OVERHEAD(sourceLen)  /* Source encoding overhead, padded to next full byte */
       + DEFLATE_BLOCK_OVERHEAD             /* Deflate block overhead bytes */
       + ZLIB_WRAPLEN;                      /* zlib wrapper */
diff --git a/deflate.c b/deflate.c
index 031a1bb..4c7e179 100644
--- a/deflate.c
+++ b/deflate.c
@@ -723,6 +723,8 @@ unsigned long Z_EXPORT PREFIX(deflateBound)(PREFIX3(stream) *strm, unsigned long
 
 #ifndef NO_QUICK_STRATEGY
     return sourceLen                       /* The source size itself */
+      + (sourceLen == 0 ? 1 : 0)           /* Always at least one byte for any input */
+      + (sourceLen < 9 ? 1 : 0)            /* One extra byte for lengths less than 9 */
       + DEFLATE_QUICK_OVERHEAD(sourceLen)  /* Source encoding overhead, padded to next full byte */
       + DEFLATE_BLOCK_OVERHEAD             /* Deflate block overhead bytes */
       + wraplen;                           /* none, zlib or gzip wrapper */