Addressing comments: more comments, cleanup, remove extra function, checksum logic

lib/decompress/zstd_decompress.c

@@ -677,10 +677,10 @@ static size_t ZSTD_decompressFrame(ZSTD_DCtx* dctx,
                         corruption_detected, "");
     }
     if (dctx->fParams.checksumFlag) { /* Frame content checksum verification */
+        RETURN_ERROR_IF(remainingSrcSize<4, checksum_wrong, "");
         if (!dctx->forceIgnoreChecksum) {
             U32 const checkCalc = (U32)XXH64_digest(&dctx->xxhState);
             U32 checkRead;
-            RETURN_ERROR_IF(remainingSrcSize<4, checksum_wrong, "");
             checkRead = MEM_readLE32(ip);
             RETURN_ERROR_IF(checkRead != checkCalc, checksum_wrong, "");
         }
@@ -1403,11 +1403,6 @@ size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format)
     return ZSTD_DCtx_setParameter(dctx, ZSTD_d_format, format);
 }
 
-size_t ZSTD_DCtx_setForceIgnoreChecksum(ZSTD_DCtx* dctx, ZSTD_forceIgnoreChecksum_e value)
-{
-    return ZSTD_DCtx_setParameter(dctx, ZSTD_d_forceIgnoreChecksum, value);
-}
-
 ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam)
 {
     ZSTD_bounds bounds = { 0, 0, 0 };

lib/zstd.h

@@ -1163,6 +1163,7 @@ typedef enum {
 } ZSTD_format_e;
 
 typedef enum {
+    /* Note: this enum controls ZSTD_d_forceIgnoreChecksum */
     ZSTD_d_validateChecksum = 0,
     ZSTD_d_ignoreChecksum = 1
 } ZSTD_forceIgnoreChecksum_e;
@@ -1704,6 +1705,7 @@ ZSTDLIB_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowS
  * Tells the decompressor to skip checksum validation during decompression, regardless
  * of whether checksumming was specified during compression. This offers some
  * slight performance benefits, and may be useful for debugging.
+ * Param has values of type ZSTD_forceIgnoreChecksum_e
  */
 #define ZSTD_d_forceIgnoreChecksum ZSTD_d_experimentalParam3
 
@@ -1714,11 +1716,6 @@ ZSTDLIB_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowS
  * @return : 0, or an error code (which can be tested using ZSTD_isError()). */
 ZSTDLIB_API size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
 
-/*! ZSTD_DCtx_setForceIgnoreChecksum() :
- *  Instruct the decoder context to ignore checksums in compressed frame.
- * @return : 0, or an error code (which can be tested using ZSTD_isError()). */
-ZSTDLIB_API size_t ZSTD_DCtx_setForceIgnoreChecksum(ZSTD_DCtx* dctx, ZSTD_forceIgnoreChecksum_e value);
-
 /*! ZSTD_decompressStream_simpleArgs() :
  *  Same as ZSTD_decompressStream(),
  *  but using only integral types as arguments.