IBM Z: Adjust compressBound() for DFLTCC

When DFLTCC was introduced, deflateBound() was adjusted, but
compressBound() was not, leading to compression failures when using
compressBound() + compress() with poorly compressible data.

4 files changed, 44 insertions, 2 deletions

diff --git a/arch/s390/dfltcc_common.h b/arch/s390/dfltcc_common.h
index f46f9ca..6de8bb1 100644
--- a/arch/s390/dfltcc_common.h
+++ b/arch/s390/dfltcc_common.h
@@ -26,4 +26,28 @@ void Z_INTERNAL dfltcc_free_window(PREFIX3(streamp) strm, void *w);
 
 #define TRY_FREE_WINDOW dfltcc_free_window
 
+#define DFLTCC_BLOCK_HEADER_BITS 3
+#define DFLTCC_HLITS_COUNT_BITS 5
+#define DFLTCC_HDISTS_COUNT_BITS 5
+#define DFLTCC_HCLENS_COUNT_BITS 4
+#define DFLTCC_MAX_HCLENS 19
+#define DFLTCC_HCLEN_BITS 3
+#define DFLTCC_MAX_HLITS 286
+#define DFLTCC_MAX_HDISTS 30
+#define DFLTCC_MAX_HLIT_HDIST_BITS 7
+#define DFLTCC_MAX_SYMBOL_BITS 16
+#define DFLTCC_MAX_EOBS_BITS 15
+#define DFLTCC_MAX_PADDING_BITS 7
+
+#define DEFLATE_BOUND_COMPLEN(source_len) \
+    ((DFLTCC_BLOCK_HEADER_BITS + \
+      DFLTCC_HLITS_COUNT_BITS + \
+      DFLTCC_HDISTS_COUNT_BITS + \
+      DFLTCC_HCLENS_COUNT_BITS + \
+      DFLTCC_MAX_HCLENS * DFLTCC_HCLEN_BITS + \
+      (DFLTCC_MAX_HLITS + DFLTCC_MAX_HDISTS) * DFLTCC_MAX_HLIT_HDIST_BITS + \
+      (source_len) * DFLTCC_MAX_SYMBOL_BITS + \
+      DFLTCC_MAX_EOBS_BITS + \
+      DFLTCC_MAX_PADDING_BITS) >> 3)
+
 #endif
diff --git a/arch/s390/dfltcc_deflate.h b/arch/s390/dfltcc_deflate.h
index 7e32380..218e594 100644
--- a/arch/s390/dfltcc_deflate.h
+++ b/arch/s390/dfltcc_deflate.h
@@ -41,8 +41,7 @@ int Z_INTERNAL dfltcc_deflate_get_dictionary(PREFIX3(streamp) strm, unsigned cha
 #define DEFLATE_BOUND_ADJUST_COMPLEN(strm, complen, source_len) \
     do { \
         if (dfltcc_can_deflate((strm))) \
-            (complen) = (3 + 5 + 5 + 4 + 19 * 3 + (286 + 30) * 7 + \
-                         (source_len) * 16 + 15 + 7) >> 3; \
+            (complen) = DEFLATE_BOUND_COMPLEN(source_len); \
     } while (0)
 
 #define DEFLATE_NEED_CONSERVATIVE_BOUND(strm) (dfltcc_can_deflate((strm)))
diff --git a/compress.c b/compress.c
index 46e8f8e..fded2a4 100644
--- a/compress.c
+++ b/compress.c
@@ -12,6 +12,17 @@
 #endif
 
 /* ===========================================================================
+ *  Architecture-specific hooks.
+ */
+#ifdef S390_DFLTCC_DEFLATE
+#  include "arch/s390/dfltcc_common.h"
+#else
+/* Returns the upper bound on compressed data length based on uncompressed data length, assuming default settings.
+ * Zero means that arch-specific deflation code behaves identically to the regular zlib-ng algorithms. */
+#  define DEFLATE_BOUND_COMPLEN(source_len) 0
+#endif
+
+/* ===========================================================================
      Compresses the source buffer into the destination buffer. The level
    parameter has the same meaning as in deflateInit.  sourceLen is the byte
    length of the source buffer. Upon entry, destLen is the total size of the
@@ -73,6 +84,12 @@ int Z_EXPORT PREFIX(compress)(unsigned char *dest, z_size_t *destLen, const unsi
    this function needs to be updated.
  */
 z_size_t Z_EXPORT PREFIX(compressBound)(z_size_t sourceLen) {
+    z_size_t complen = DEFLATE_BOUND_COMPLEN(sourceLen);
+
+    if (complen > 0)
+        /* Architecture-specific code provided an upper bound. */
+        return complen + ZLIB_WRAPLEN;
+
 #ifndef NO_QUICK_STRATEGY
     return sourceLen                       /* The source size itself */
       + DEFLATE_QUICK_OVERHEAD(sourceLen)  /* Source encoding overhead, padded to next full byte */
diff --git a/zutil.h b/zutil.h
index 015219a..7578737 100644
--- a/zutil.h
+++ b/zutil.h
@@ -92,6 +92,8 @@ extern z_const char * const PREFIX(z_errmsg)[10]; /* indexed by 2-zlib_error */
 /* deflate_quick worst-case overhead: 9 bits per literal, round up to next byte (+7) */
 
 
+#define ZLIB_WRAPLEN 6 /* zlib format overhead */
+
         /* target dependencies */
 
 #ifdef AMIGA