first implementation supporting Process Substitution

programs/fileio.c

@@ -537,15 +537,13 @@ static int FIO_removeFile(const char* path)
     return remove(path);
 }
 
-/** FIO_openSrcFile() :
- *  condition : `srcFileName` must be non-NULL. `prefs` may be NULL.
- * @result : FILE* to `srcFileName`, or NULL if it fails */
 static FILE* FIO_openSrcFile(const FIO_prefs_t* const prefs, const char* srcFileName, stat_t* statbuf)
 {
     int allowBlockDevices = prefs != NULL ? prefs->allowBlockDevices : 0;
     assert(srcFileName != NULL);
     assert(statbuf != NULL);
-    if (!strcmp (srcFileName, stdinmark)) {
+
+    if (!strcmp(srcFileName, stdinmark)) {
         DISPLAYLEVEL(4,"Using stdin for input \n");
         SET_BINARY_MODE(stdin);
         return stdin;
@@ -557,8 +555,10 @@ static FILE* FIO_openSrcFile(const FIO_prefs_t* const prefs, const char* srcFile
         return NULL;
     }
 
+    /* Accept regular files, FIFOs, and process substitution file descriptors */
     if (!UTIL_isRegularFileStat(statbuf)
      && !UTIL_isFIFOStat(statbuf)
+     && !UTIL_isFileDescriptorPipe(srcFileName)  /* Process substitution support */
      && !(allowBlockDevices && UTIL_isBlockDevStat(statbuf))
     ) {
         DISPLAYLEVEL(1, "zstd: %s is not a regular file -- ignored \n",