add zstd fast levels from 1 to 7

zstd supports negative compression levels (`--fast=XXX` param in zstd CLI), so add them here also
commit_hash:ed7231a6f341cd120dfea0d4b0b481962df835ab

2 files changed, 58 insertions, 11 deletions

diff --git a/library/cpp/blockcodecs/codecs/zstd/README.md b/library/cpp/blockcodecs/codecs/zstd/README.md
new file mode 100644
index 00000000000..98236f837d7
--- /dev/null
+++ b/library/cpp/blockcodecs/codecs/zstd/README.md
@@ -0,0 +1,40 @@
+Zstd codecs
+=============
+
+This library registers zstd compression codecs as `zstd_1`, ..., `zstd_22`. 
+Fast levels are also registered as `zstd_fast_1`, ..., `zstd_fast_7`.
+
+Measured codec performance on every level. Values below are provided just for reference, exact numbers may vary depending on CPU model and type of data being compressed.
+
+| Codec        | Comp. Ratio | Comp. Speed  (MBps) | Decomp. Speed (MBps) |
+|--------------|-------------|---------------------|----------------------| 
+| lz4          | 0.5876      | 913                 | 4100                 |
+| zstd_fast_7  | 0.5783      | 1066                | 2887                 |
+| zstd_fast_6  | 0.5733      | 1050                | 2870                 |
+| zstd_fast_5  | 0.5528      | 942                 | 2594                 |
+| zstd_fast_4  | 0.5529      | 918                 | 2659                 |
+| zstd_fast_3  | 0.5408      | 885                 | 2519                 |
+| zstd_fast_2  | 0.5132      | 769                 | 2374                 |
+| zstd_fast_1  | 0.5119      | 707                 | 2386                 |
+| zstd_1       | 0.4691      | 690                 | 1692                 |
+| zstd_2       | 0.4083      | 467                 | 1496                 |
+| zstd_3       | 0.3505      | 358                 | 1801                 |
+| zstd_4       | 0.3356      | 310                 | 1932                 |
+| zstd_5       | 0.3175      | 218                 | 1832                 |
+| zstd_6       | 0.3168      | 173                 | 1920                 |
+| zstd_7       | 0.3081      | 149                 | 1965                 |
+| zstd_8       | 0.3077      | 125                 | 2005                 |
+| zstd_9       | 0.272       | 128                 | 2179                 |
+| zstd_10      | 0.2693      | 98.5                | 2228                 |
+| zstd_11      | 0.2684      | 78.6                | 2185                 |
+| zstd_12      | 0.2682      | 71.1                | 2231                 |
+| zstd_13      | 0.2687      | 27.8                | 2102                 |
+| zstd_14      | 0.2676      | 24                  | 2024                 |
+| zstd_15      | 0.2663      | 18.8                | 2225                 |
+| zstd_16      | 0.257       | 15.2                | 2093                 |
+| zstd_17      | 0.2521      | 12.3                | 2072                 |
+| zstd_18      | 0.241       | 9.68                | 1696                 |
+| zstd_19      | 0.2395      | 7.97                | 1709                 |
+| zstd_20      | 0.2337      | 6.26                | 1520                 |
+| zstd_21      | 0.2255      | 5.22                | 1442                 |
+| zstd_22      | 0.2037      | 3.88                | 1490                 |
diff --git a/library/cpp/blockcodecs/codecs/zstd/zstd.cpp b/library/cpp/blockcodecs/codecs/zstd/zstd.cpp
index 95299b3f6d3..3846ab85802 100644
--- a/library/cpp/blockcodecs/codecs/zstd/zstd.cpp
+++ b/library/cpp/blockcodecs/codecs/zstd/zstd.cpp
@@ -5,36 +5,38 @@
 #define ZSTD_STATIC_LINKING_ONLY
 #include <contrib/libs/zstd/include/zstd.h>
 
+#include <utility>
+
 using namespace NBlockCodecs;
 
 namespace {
     struct TZStd08Codec: public TAddLengthCodec<TZStd08Codec> {
-        inline TZStd08Codec(unsigned level)
+        TZStd08Codec(int level, TString name)
             : Level(level)
-            , MyName(TStringBuf("zstd08_") + ToString(Level))
+            , MyName(std::move(name))
         {
         }
 
-        static inline size_t CheckError(size_t ret, const char* what) {
-            if (ZSTD_isError(ret)) {
+        static size_t CheckError(size_t ret, const char* what) {
+            if (Y_UNLIKELY(ZSTD_isError(ret))) {
                 ythrow yexception() << what << TStringBuf(" zstd error: ") << ZSTD_getErrorName(ret);
             }
 
             return ret;
         }
 
-        static inline size_t DoMaxCompressedLength(size_t l) noexcept {
+        static size_t DoMaxCompressedLength(size_t l) noexcept {
             return ZSTD_compressBound(l);
         }
 
-        inline size_t DoCompress(const TData& in, void* out) const {
+        size_t DoCompress(const TData& in, void* out) const {
             return CheckError(ZSTD_compress(out, DoMaxCompressedLength(in.size()), in.data(), in.size(), Level), "compress");
         }
 
-        inline void DoDecompress(const TData& in, void* out, size_t dsize) const {
+        static void DoDecompress(const TData& in, void* out, size_t dsize) {
             const size_t res = CheckError(ZSTD_decompress(out, dsize, in.data(), in.size()), "decompress");
 
-            if (res != dsize) {
+            if (Y_UNLIKELY(res != dsize)) {
                 ythrow TDecompressError(dsize, res);
             }
         }
@@ -43,15 +45,20 @@ namespace {
             return MyName;
         }
 
-        const unsigned Level;
+        const int Level;
         const TString MyName;
     };
 
     struct TZStd08Registrar {
         TZStd08Registrar() {
             for (int i = 1; i <= ZSTD_maxCLevel(); ++i) {
-                RegisterCodec(MakeHolder<TZStd08Codec>(i));
-                RegisterAlias("zstd_" + ToString(i), "zstd08_" + ToString(i));
+                const TString name = "zstd08_"sv + ToString(i);
+                RegisterCodec(MakeHolder<TZStd08Codec>(i, name));
+                RegisterAlias("zstd_"sv + ToString(i), name);
+            }
+
+            for (int i = 1; i <= 7; ++i) {
+                RegisterCodec(MakeHolder<TZStd08Codec>(-i, "zstd_fast_"sv + ToString(i)));
             }
         }
     };