zlibWrapper\README.md: minor tweaks
diff --git a/zlibWrapper/README.md b/zlibWrapper/README.md
index 5747e38..70cfb0e 100644
--- a/zlibWrapper/README.md
+++ b/zlibWrapper/README.md
@@ -54,37 +54,40 @@
#### Improving speed of streaming compression
-Zstandard compression can be improved by providing size of source data to compressor. By default compressor assumes that files are bigger than 256 KB but it can hurt compression speed on smaller files.
+During streaming compression the compressor never knows how big is data to compress.
+Zstandard compression can be improved by providing size of source data to the compressor. By default streaming compressor assumes that data is bigger than 256 KB but it can hurt compression speed on smaller data.
The zstd wrapper provides the `ZWRAP_setPledgedSrcSize()` function that allows to change a pledged source size for a given compression stream.
-The function should be called just after `deflateInit()`. The function is only helpful when data is compressed in blocks. There will be no change in case of `deflateInit()` immediately followed by `deflate(strm, Z_FINISH)`
+The function will change zstd compression parameters what may improve compression speed and/or ratio.
+It should be called just after `deflateInit()`. The function is only helpful when data is compressed in blocks. There will be no change in case of `deflateInit()` immediately followed by `deflate(strm, Z_FINISH)`
as this case is automatically detected.
#### Reusing contexts
-The ordinary zlib compression of two files/streams:
+The ordinary zlib compression of two files/streams allocates two contexts:
- for the 1st file calls `deflateInit`, `deflate`, `...`, `deflate`, `defalateEnd`
- for the 2nd file calls `deflateInit`, `deflate`, `...`, `deflate`, `defalateEnd`
-The speed of compression can be improved with reusing a context with following steps:
-- initialize a context with `deflateInit`
+The speed of compression can be improved with reusing a single context with following steps:
+- initialize the context with `deflateInit`
- for the 1st file call `deflate`, `...`, `deflate`
- for the 2nd file call `deflateReset`, `deflate`, `...`, `deflate`
-- free a context with `deflateEnd`
+- free the context with `deflateEnd`
-We made experiments using `zwrapbench` with zstd and zlib compression (both at level 3) in 4 KB blocks.
-The input data was decompressed git repository downloaded from https://github.com/git/git/archive/master.zip
-The table below shows that reusing contexts has minor influnce on zlib but for zstd it gives 15% better compression speed and 6% better decompression speed.
+To check the difference we made experiments using `zwrapbench` with zstd and zlib compression (both at level 3) with 4 KB blocks.
+The input data was git repository downloaded from https://github.com/git/git/archive/master.zip and converted to uncompressed tarball.
+The table below shows that reusing contexts has a minor influence on zlib but it gives improvement for zstd.
+In our example (the last 2 lines) is gives 15% better compression speed and 6% better decompression speed.
| Compression type | Compression | Decompress.| Compr. size | Ratio |
| ------------------------------------------------- | ------------| -----------| ----------- | ----- |
| zlib 1.2.8 | 54.77 MB/s | 176.2 MB/s | 8928115 | 2.910 |
| zlib 1.2.8 not reusing a context | 54.98 MB/s | 174.6 MB/s | 8928115 | 2.910 |
-| zlib 1.2.8 using zlibWrapper | 55.16 MB/s | 176.8 MB/s | 8928115 | 2.910 |
+| zlib 1.2.8 with zlibWrapper and reusing a context | 55.16 MB/s | 176.8 MB/s | 8928115 | 2.910 |
| zlib 1.2.8 with zlibWrapper not reusing a context | 54.11 MB/s | 174.5 MB/s | 8928115 | 2.910 |
| zstd 1.1.0 using ZSTD_CCtx | 108.03 MB/s | 319.8 MB/s | 8962336 | 2.899 |
| zstd 1.1.0 using ZSTD_CStream | 107.34 MB/s | 307.3 MB/s | 8981368 | 2.893 |
-| zstd 1.1.0 using zlibWrapper | 107.52 MB/s | 297.3 MB/s | 8981368 | 2.893 |
+| zstd 1.1.0 with zlibWrapper and reusing a context | 107.52 MB/s | 297.3 MB/s | 8981368 | 2.893 |
| zstd 1.1.0 with zlibWrapper not reusing a context | 91.45 MB/s | 279.8 MB/s | 8981368 | 2.893 |
diff --git a/zlibWrapper/zstd_zlibwrapper.c b/zlibWrapper/zstd_zlibwrapper.c
index 63dc44f..e4906a2 100644
--- a/zlibWrapper/zstd_zlibwrapper.c
+++ b/zlibWrapper/zstd_zlibwrapper.c
@@ -25,20 +25,8 @@
#define LOG_WRAPPERC(...) /* printf(__VA_ARGS__) */
#define LOG_WRAPPERD(...) /* printf(__VA_ARGS__) */
-
-#define FINISH_WITH_GZ_ERR(msg) { \
- (void)msg; \
- return Z_STREAM_ERROR; \
-}
-
-#define FINISH_WITH_NULL_ERR(msg) { \
- (void)msg; \
- return NULL; \
-}
-
-const char * zstdVersion(void) { return ZSTD_VERSION_STRING; }
-
-ZEXTERN const char * ZEXPORT z_zlibVersion OF((void)) { return zlibVersion(); }
+#define FINISH_WITH_GZ_ERR(msg) { (void)msg; return Z_STREAM_ERROR; }
+#define FINISH_WITH_NULL_ERR(msg) { (void)msg; return NULL; }
@@ -62,6 +50,11 @@
+const char * zstdVersion(void) { return ZSTD_VERSION_STRING; }
+
+ZEXTERN const char * ZEXPORT z_zlibVersion OF((void)) { return zlibVersion(); }
+
+
static void* ZWRAP_allocFunction(void* opaque, size_t size)
{
@@ -257,7 +250,6 @@
int res;
LOG_WRAPPERC("- deflate1 flush=%d avail_in=%d avail_out=%d total_in=%d total_out=%d\n", (int)flush, (int)strm->avail_in, (int)strm->avail_out, (int)strm->total_in, (int)strm->total_out);
res = deflate(strm, flush);
- LOG_WRAPPERC("- deflate2 flush=%d avail_in=%d avail_out=%d total_in=%d total_out=%d\n", (int)flush, (int)strm->avail_in, (int)strm->avail_out, (int)strm->total_in, (int)strm->total_out);
return res;
}
@@ -397,6 +389,7 @@
zwd->outBuffer.size = 0;
}
+
ZWRAP_DCtx* ZWRAP_createDCtx(z_streamp strm)
{
ZWRAP_DCtx* zwd;
@@ -585,8 +578,7 @@
if (strm->avail_in <= 0) return Z_OK;
- {
- size_t errorCode, srcSize;
+ { size_t errorCode, srcSize;
zwd = (ZWRAP_DCtx*) strm->state;
LOG_WRAPPERD("- inflate1 flush=%d avail_in=%d avail_out=%d total_in=%d total_out=%d\n", (int)flush, (int)strm->avail_in, (int)strm->avail_out, (int)strm->total_in, (int)strm->total_out);
@@ -762,6 +754,7 @@
+
/* Advanced compression functions */
ZEXTERN int ZEXPORT z_deflateCopy OF((z_streamp dest,
z_streamp source))