added error detection for pthread initialization, added compression completion measurement, fixed const values

lib/compress/zstd_compress.c

@@ -140,6 +140,9 @@ struct ZSTD_CCtx_s {
     /* Multi-threading */
     U32 nbThreads;
     ZSTDMT_CCtx* mtctx;
+
+    /* adaptive compression */
+    double completion;
 };
 
 
@@ -2845,6 +2848,7 @@ static size_t ZSTD_compress_frameChunk (ZSTD_CCtx* cctx,
     BYTE* op = ostart;
     U32 const maxDist = 1 << cctx->appliedParams.cParams.windowLog;
 
+    cctx->completion = 0;
     if (cctx->appliedParams.fParams.checksumFlag && srcSize)
         XXH64_update(&cctx->xxhState, src, srcSize);
 
@@ -2895,6 +2899,7 @@ static size_t ZSTD_compress_frameChunk (ZSTD_CCtx* cctx,
         }
 
         remaining -= blockSize;
+        cctx->completion = 1 - (double)remaining/srcSize;
         dstCapacity -= cSize;
         ip += blockSize;
         op += cSize;
@@ -2997,6 +3002,10 @@ static size_t ZSTD_compressContinue_internal (ZSTD_CCtx* cctx,
         return fhSize;
 }
 
+ZSTDLIB_API double ZSTD_getCompletion(ZSTD_CCtx* cctx)
+{
+    return cctx->completion;
+}
 
 size_t ZSTD_compressContinue (ZSTD_CCtx* cctx,
                               void* dst, size_t dstCapacity,

lib/zstd.h

@@ -808,7 +808,11 @@ ZSTDLIB_API size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx,
 ZSTDLIB_API size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
 ZSTDLIB_API size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
 
-
+/*! ZSTD_getCompletion: get a double representing how much of a file/buffer has been compressed
+ *                      using ZSTD_compressContinue()
+ * return: a double value in the range of 0 to 1 representing how much a compression job has finished
+ */
+ZSTDLIB_API double ZSTD_getCompletion(ZSTD_CCtx* cctx);
 
 /*-
   Buffer-less streaming decompression (synchronous mode)