From b11bea56a53d300f43b500be55890dbd01393d60 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 00:09:29 -0400
Subject: [PATCH 01/14] Introduce Dedicated Helper to Call stat()

---
 programs/util.c | 11 +++++++++++
 programs/util.h |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/programs/util.c b/programs/util.c
index 2493a4adc..c172150d9 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -99,6 +99,17 @@ int g_utilDisplayLevel;
 *  Functions
 ***************************************/
 
+int UTIL_stat(const char* filename, stat_t* statbuf)
+{
+#if defined(_MSC_VER)
+    return !_stat64(filename, statbuf);
+#elif defined(__MINGW32__) && defined (__MSVCRT__)
+    return !_stati64(filename, statbuf);
+#else
+    return !stat(filename, statbuf);
+#endif
+}
+
 int UTIL_fileExist(const char* filename)
 {
     stat_t statbuf;
diff --git a/programs/util.h b/programs/util.h
index 580266e71..0b58dfbbf 100644
--- a/programs/util.h
+++ b/programs/util.h
@@ -100,6 +100,8 @@ extern int g_utilDisplayLevel;
 #if defined(_MSC_VER)
     typedef struct __stat64 stat_t;
     typedef int mode_t;
+#elif defined(__MINGW32__) && defined (__MSVCRT__)
+    typedef struct _stati64 stat_t;
 #else
     typedef struct stat stat_t;
 #endif
@@ -113,6 +115,11 @@ extern int g_utilDisplayLevel;
 #define STRDUP(s) strdup(s)
 #endif
 
+/**
+ * Calls platform's equivalent of stat() on filename and writes info to statbuf.
+ * Returns success (1) or failure (0).
+ */
+int UTIL_stat(const char* filename, stat_t* statbuf);
 int UTIL_fileExist(const char* filename);
 int UTIL_isRegularFile(const char* infilename);
 int UTIL_isDirectory(const char* infilename);

From 69cb9e77986b5ede06ced25f4bcf1a68e8307959 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 00:21:41 -0400
Subject: [PATCH 02/14] Use New Stat Helper

---
 programs/util.c | 42 +++++++++++++-----------------------------
 1 file changed, 13 insertions(+), 29 deletions(-)

diff --git a/programs/util.c b/programs/util.c
index c172150d9..3df3d3d02 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -113,12 +113,7 @@ int UTIL_stat(const char* filename, stat_t* statbuf)
 int UTIL_fileExist(const char* filename)
 {
     stat_t statbuf;
-#if defined(_MSC_VER)
-    int const stat_error = _stat64(filename, &statbuf);
-#else
-    int const stat_error = stat(filename, &statbuf);
-#endif
-    return !stat_error;
+    return UTIL_stat(filename, &statbuf);
 }
 
 int UTIL_isRegularFile(const char* infilename)
@@ -129,27 +124,22 @@ int UTIL_isRegularFile(const char* infilename)
 
 int UTIL_getFileStat(const char* infilename, stat_t *statbuf)
 {
-    int r;
+    const int r = UTIL_stat(infilename, statbuf);
 #if defined(_MSC_VER)
-    r = _stat64(infilename, statbuf);
-    if (r || !(statbuf->st_mode & S_IFREG)) return 0;   /* No good... */
+    return r && (statbuf->st_mode & S_IFREG);
 #else
-    r = stat(infilename, statbuf);
-    if (r || !S_ISREG(statbuf->st_mode)) return 0;   /* No good... */
+    return r && S_ISREG(statbuf->st_mode);
 #endif
-    return 1;
 }
 
 int UTIL_getDirectoryStat(const char* infilename, stat_t *statbuf)
 {
+    const int r = UTIL_stat(infilename, statbuf);
 #if defined(_MSC_VER)
-    int const r = _stat64(infilename, statbuf);
-    if (!r && (statbuf->st_mode & _S_IFDIR)) return 1;
+    return r && (statbuf->st_mode & _S_IFDIR);
 #else
-    int const r = stat(infilename, statbuf);
-    if (!r && S_ISDIR(statbuf->st_mode)) return 1;
+    return r && S_ISDIR(statbuf->st_mode);
 #endif
-    return 0;
 }
 
 /* like chmod, but avoid changing permission of /dev/null */
@@ -254,23 +244,17 @@ int UTIL_isLink(const char* infilename)
 
 U64 UTIL_getFileSize(const char* infilename)
 {
+    stat_t statbuf;
+    if (!UTIL_stat(infilename, &statbuf)) return UTIL_FILESIZE_UNKNOWN;
     if (!UTIL_isRegularFile(infilename)) return UTIL_FILESIZE_UNKNOWN;
-    {   int r;
 #if defined(_MSC_VER)
-        struct __stat64 statbuf;
-        r = _stat64(infilename, &statbuf);
-        if (r || !(statbuf.st_mode & S_IFREG)) return UTIL_FILESIZE_UNKNOWN;
+    if (!(statbuf.st_mode & S_IFREG)) return UTIL_FILESIZE_UNKNOWN;
 #elif defined(__MINGW32__) && defined (__MSVCRT__)
-        struct _stati64 statbuf;
-        r = _stati64(infilename, &statbuf);
-        if (r || !(statbuf.st_mode & S_IFREG)) return UTIL_FILESIZE_UNKNOWN;
+    if (!(statbuf.st_mode & S_IFREG)) return UTIL_FILESIZE_UNKNOWN;
 #else
-        struct stat statbuf;
-        r = stat(infilename, &statbuf);
-        if (r || !S_ISREG(statbuf.st_mode)) return UTIL_FILESIZE_UNKNOWN;
+    if (!S_ISREG(statbuf.st_mode)) return UTIL_FILESIZE_UNKNOWN;
 #endif
-        return (U64)statbuf.st_size;
-    }
+    return (U64)statbuf.st_size;
 }
 
 

From 5fbc6addb6a2a271d9164631f2fa81f24158a9c1 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 00:31:48 -0400
Subject: [PATCH 03/14] Additionally Convert UTIL_getFileStat() Calls to
 UTIL_stat() Where Appropriate

---
 programs/util.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/programs/util.c b/programs/util.c
index 3df3d3d02..56a0124ff 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -209,8 +209,8 @@ int UTIL_isSameFile(const char* fName1, const char* fName2)
 #else
     {   stat_t file1Stat;
         stat_t file2Stat;
-        return UTIL_getFileStat(fName1, &file1Stat)
-            && UTIL_getFileStat(fName2, &file2Stat)
+        return UTIL_stat(fName1, &file1Stat)
+            && UTIL_stat(fName2, &file2Stat)
             && (file1Stat.st_dev == file2Stat.st_dev)
             && (file1Stat.st_ino == file2Stat.st_ino);
     }
@@ -223,8 +223,8 @@ int UTIL_isFIFO(const char* infilename)
 /* macro guards, as defined in : https://linux.die.net/man/2/lstat */
 #if PLATFORM_POSIX_VERSION >= 200112L
     stat_t statbuf;
-    int const r = UTIL_getFileStat(infilename, &statbuf);
-    if (!r && S_ISFIFO(statbuf.st_mode)) return 1;
+    int const r = UTIL_stat(infilename, &statbuf);
+    if (r && S_ISFIFO(statbuf.st_mode)) return 1;
 #endif
     (void)infilename;
     return 0;

From 1a1003f996e069a4c0edb09b88aabcce76263ef6 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 00:35:21 -0400
Subject: [PATCH 04/14] Mark stat_t Arg to UTIL_setFileStat() const

---
 programs/util.c | 2 +-
 programs/util.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/programs/util.c b/programs/util.c
index 56a0124ff..785a37535 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -149,7 +149,7 @@ int UTIL_chmod(char const* filename, mode_t permissions)
     return chmod(filename, permissions);
 }
 
-int UTIL_setFileStat(const char *filename, stat_t *statbuf)
+int UTIL_setFileStat(const char *filename, const stat_t *statbuf)
 {
     int res = 0;
 
diff --git a/programs/util.h b/programs/util.h
index 0b58dfbbf..7618e2489 100644
--- a/programs/util.h
+++ b/programs/util.h
@@ -132,7 +132,7 @@ int UTIL_isFIFO(const char* infilename);
 U64 UTIL_getFileSize(const char* infilename);
 U64 UTIL_getTotalFileSize(const char* const * fileNamesTable, unsigned nbFiles);
 int UTIL_getFileStat(const char* infilename, stat_t* statbuf);
-int UTIL_setFileStat(const char* filename, stat_t* statbuf);
+int UTIL_setFileStat(const char* filename, const stat_t* statbuf);
 int UTIL_getDirectoryStat(const char* infilename, stat_t* statbuf);
 int UTIL_chmod(char const* filename, mode_t permissions);   /*< like chmod, but avoid changing permission of /dev/null */
 int UTIL_compareStr(const void *p1, const void *p2);

From b6e24bc4dc633d9596a06fc86e55dc3ff93b110e Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 00:40:16 -0400
Subject: [PATCH 05/14] Rename UTIL_getFileStat() -> UTIL_statFile() and
 UTIL_getDirectoryStat() -> UTIL_statDir()

I want to introduce versions of many of these functions that take pre-
populated `stat_t` objects and use those rather than doing their own redundant
`stat()` internally. These functions will have `...Stat()` suffixes. So this
commit renames these existing functions into the active voice, to avoid
confusion.
---
 programs/fileio.c |  4 ++--
 programs/util.c   | 10 +++++-----
 programs/util.h   |  4 ++--
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/programs/fileio.c b/programs/fileio.c
index b8183d89f..e818614b2 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -1478,7 +1478,7 @@ static int FIO_compressFilename_dstFile(FIO_prefs_t* const prefs,
         addHandler(dstFileName);
 
         if ( strcmp (srcFileName, stdinmark)
-          && UTIL_getFileStat(srcFileName, &statbuf))
+          && UTIL_statFile(srcFileName, &statbuf))
             transfer_permissions = 1;
     }
 
@@ -2344,7 +2344,7 @@ static int FIO_decompressDstFile(FIO_prefs_t* const prefs,
         addHandler(dstFileName);
 
         if ( strcmp(srcFileName, stdinmark)   /* special case : don't transfer permissions from stdin */
-          && UTIL_getFileStat(srcFileName, &statbuf) )
+          && UTIL_statFile(srcFileName, &statbuf) )
             transfer_permissions = 1;
     }
 
diff --git a/programs/util.c b/programs/util.c
index 785a37535..3f91adeb5 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -119,10 +119,10 @@ int UTIL_fileExist(const char* filename)
 int UTIL_isRegularFile(const char* infilename)
 {
     stat_t statbuf;
-    return UTIL_getFileStat(infilename, &statbuf); /* Only need to know whether it is a regular file */
+    return UTIL_statFile(infilename, &statbuf); /* Only need to know whether it is a regular file */
 }
 
-int UTIL_getFileStat(const char* infilename, stat_t *statbuf)
+int UTIL_statFile(const char* infilename, stat_t *statbuf)
 {
     const int r = UTIL_stat(infilename, statbuf);
 #if defined(_MSC_VER)
@@ -132,7 +132,7 @@ int UTIL_getFileStat(const char* infilename, stat_t *statbuf)
 #endif
 }
 
-int UTIL_getDirectoryStat(const char* infilename, stat_t *statbuf)
+int UTIL_statDir(const char* infilename, stat_t *statbuf)
 {
     const int r = UTIL_stat(infilename, statbuf);
 #if defined(_MSC_VER)
@@ -190,7 +190,7 @@ int UTIL_setFileStat(const char *filename, const stat_t *statbuf)
 int UTIL_isDirectory(const char* infilename)
 {
     stat_t statbuf;
-    return UTIL_getDirectoryStat(infilename, &statbuf);
+    return UTIL_statDir(infilename, &statbuf);
 }
 
 int UTIL_compareStr(const void *p1, const void *p2) {
@@ -647,7 +647,7 @@ static int isFileNameValidForMirroredOutput(const char *filename)
 static mode_t getDirMode(const char *dirName)
 {
     stat_t st;
-    int ret = UTIL_getDirectoryStat(dirName, &st);
+    int ret = UTIL_statDir(dirName, &st);
     if (!ret) {
         UTIL_DISPLAY("zstd: failed to get DIR stats %s: %s\n", dirName, strerror(errno));
         return DIR_DEFAULT_MODE;
diff --git a/programs/util.h b/programs/util.h
index 7618e2489..ed3bd09ec 100644
--- a/programs/util.h
+++ b/programs/util.h
@@ -120,6 +120,8 @@ extern int g_utilDisplayLevel;
  * Returns success (1) or failure (0).
  */
 int UTIL_stat(const char* filename, stat_t* statbuf);
+int UTIL_statFile(const char* infilename, stat_t* statbuf); /* also check it's a file */
+int UTIL_statDir(const char* infilename, stat_t* statbuf); /* also check it's a directory */
 int UTIL_fileExist(const char* filename);
 int UTIL_isRegularFile(const char* infilename);
 int UTIL_isDirectory(const char* infilename);
@@ -131,9 +133,7 @@ int UTIL_isFIFO(const char* infilename);
 #define UTIL_FILESIZE_UNKNOWN  ((U64)(-1))
 U64 UTIL_getFileSize(const char* infilename);
 U64 UTIL_getTotalFileSize(const char* const * fileNamesTable, unsigned nbFiles);
-int UTIL_getFileStat(const char* infilename, stat_t* statbuf);
 int UTIL_setFileStat(const char* filename, const stat_t* statbuf);
-int UTIL_getDirectoryStat(const char* infilename, stat_t* statbuf);
 int UTIL_chmod(char const* filename, mode_t permissions);   /*< like chmod, but avoid changing permission of /dev/null */
 int UTIL_compareStr(const void *p1, const void *p2);
 const char* UTIL_getFileExtension(const char* infilename);

From 44fa052599d36b87c0e42219f05d0119d2726a5a Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 01:00:06 -0400
Subject: [PATCH 06/14] Introduce Variants of Various UTIL Functions that Take
 Pre-Populated stat_t Structs

Instead of calling `stat()`, these functions accept the result of a previous
`stat()` call on the file in question, which will allow us to make multiple
decisions around a file without redundant `stat()` calls.
---
 programs/util.c | 61 ++++++++++++++++++++++++++++++++++---------------
 programs/util.h | 10 ++++++--
 2 files changed, 50 insertions(+), 21 deletions(-)

diff --git a/programs/util.c b/programs/util.c
index 3f91adeb5..c81587b47 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -122,24 +122,23 @@ int UTIL_isRegularFile(const char* infilename)
     return UTIL_statFile(infilename, &statbuf); /* Only need to know whether it is a regular file */
 }
 
+int UTIL_isRegularFileStat(const stat_t* statbuf)
+{
+#if defined(_MSC_VER)
+    return (statbuf->st_mode & S_IFREG) != 0;
+#else
+    return S_ISREG(statbuf->st_mode) != 0;
+#endif
+}
+
 int UTIL_statFile(const char* infilename, stat_t *statbuf)
 {
-    const int r = UTIL_stat(infilename, statbuf);
-#if defined(_MSC_VER)
-    return r && (statbuf->st_mode & S_IFREG);
-#else
-    return r && S_ISREG(statbuf->st_mode);
-#endif
+    return UTIL_stat(infilename, statbuf) && UTIL_isRegularFileStat(statbuf);
 }
 
 int UTIL_statDir(const char* infilename, stat_t *statbuf)
 {
-    const int r = UTIL_stat(infilename, statbuf);
-#if defined(_MSC_VER)
-    return r && (statbuf->st_mode & _S_IFDIR);
-#else
-    return r && S_ISDIR(statbuf->st_mode);
-#endif
+    return UTIL_stat(infilename, statbuf) && UTIL_isDirectoryStat(statbuf);
 }
 
 /* like chmod, but avoid changing permission of /dev/null */
@@ -193,6 +192,15 @@ int UTIL_isDirectory(const char* infilename)
     return UTIL_statDir(infilename, &statbuf);
 }
 
+int UTIL_isDirectoryStat(const stat_t* statbuf)
+{
+#if defined(_MSC_VER)
+    return (statbuf->st_mode & _S_IFDIR) != 0;
+#else
+    return S_ISDIR(statbuf->st_mode) != 0;
+#endif
+}
+
 int UTIL_compareStr(const void *p1, const void *p2) {
     return strcmp(* (char * const *) p1, * (char * const *) p2);
 }
@@ -223,13 +231,23 @@ int UTIL_isFIFO(const char* infilename)
 /* macro guards, as defined in : https://linux.die.net/man/2/lstat */
 #if PLATFORM_POSIX_VERSION >= 200112L
     stat_t statbuf;
-    int const r = UTIL_stat(infilename, &statbuf);
-    if (r && S_ISFIFO(statbuf.st_mode)) return 1;
+    if (UTIL_stat(infilename, &statbuf) && UTIL_isFIFOStat(&statbuf)) return 1;
 #endif
     (void)infilename;
     return 0;
 }
 
+/* UTIL_isFIFO : distinguish named pipes */
+int UTIL_isFIFOStat(const stat_t* statbuf)
+{
+/* macro guards, as defined in : https://linux.die.net/man/2/lstat */
+#if PLATFORM_POSIX_VERSION >= 200112L
+    if (S_ISFIFO(statbuf->st_mode)) return 1;
+#endif
+    (void)statbuf;
+    return 0;
+}
+
 int UTIL_isLink(const char* infilename)
 {
 /* macro guards, as defined in : https://linux.die.net/man/2/lstat */
@@ -246,15 +264,20 @@ U64 UTIL_getFileSize(const char* infilename)
 {
     stat_t statbuf;
     if (!UTIL_stat(infilename, &statbuf)) return UTIL_FILESIZE_UNKNOWN;
-    if (!UTIL_isRegularFile(infilename)) return UTIL_FILESIZE_UNKNOWN;
+    return UTIL_getFileSizeStat(&statbuf);
+}
+
+U64 UTIL_getFileSizeStat(const stat_t* statbuf)
+{
+    if (!UTIL_isRegularFileStat(statbuf)) return UTIL_FILESIZE_UNKNOWN;
 #if defined(_MSC_VER)
-    if (!(statbuf.st_mode & S_IFREG)) return UTIL_FILESIZE_UNKNOWN;
+    if (!(statbuf->st_mode & S_IFREG)) return UTIL_FILESIZE_UNKNOWN;
 #elif defined(__MINGW32__) && defined (__MSVCRT__)
-    if (!(statbuf.st_mode & S_IFREG)) return UTIL_FILESIZE_UNKNOWN;
+    if (!(statbuf->st_mode & S_IFREG)) return UTIL_FILESIZE_UNKNOWN;
 #else
-    if (!S_ISREG(statbuf.st_mode)) return UTIL_FILESIZE_UNKNOWN;
+    if (!S_ISREG(statbuf->st_mode)) return UTIL_FILESIZE_UNKNOWN;
 #endif
-    return (U64)statbuf.st_size;
+    return (U64)statbuf->st_size;
 }
 
 
diff --git a/programs/util.h b/programs/util.h
index ed3bd09ec..0a3be31cb 100644
--- a/programs/util.h
+++ b/programs/util.h
@@ -120,18 +120,24 @@ extern int g_utilDisplayLevel;
  * Returns success (1) or failure (0).
  */
 int UTIL_stat(const char* filename, stat_t* statbuf);
-int UTIL_statFile(const char* infilename, stat_t* statbuf); /* also check it's a file */
-int UTIL_statDir(const char* infilename, stat_t* statbuf); /* also check it's a directory */
+/** Also checks that the target is a regular file. */
+int UTIL_statFile(const char* infilename, stat_t* statbuf);
+/** Also checks that the target is a directory. */
+int UTIL_statDir(const char* infilename, stat_t* statbuf);
 int UTIL_fileExist(const char* filename);
 int UTIL_isRegularFile(const char* infilename);
+int UTIL_isRegularFileStat(const stat_t* statbuf); /* same but takes existing statbuf */
 int UTIL_isDirectory(const char* infilename);
+int UTIL_isDirectoryStat(const stat_t* statbuf); /* same but takes existing statbuf */
 int UTIL_isSameFile(const char* file1, const char* file2);
 int UTIL_isCompressedFile(const char* infilename, const char *extensionList[]);
 int UTIL_isLink(const char* infilename);
 int UTIL_isFIFO(const char* infilename);
+int UTIL_isFIFOStat(const stat_t* statbuf); /* same but takes existing statbuf */
 
 #define UTIL_FILESIZE_UNKNOWN  ((U64)(-1))
 U64 UTIL_getFileSize(const char* infilename);
+U64 UTIL_getFileSizeStat(const stat_t* statbuf);
 U64 UTIL_getTotalFileSize(const char* const * fileNamesTable, unsigned nbFiles);
 int UTIL_setFileStat(const char* filename, const stat_t* statbuf);
 int UTIL_chmod(char const* filename, mode_t permissions);   /*< like chmod, but avoid changing permission of /dev/null */

From 7238cca1a1f00b27570b721b852317dfcfbffa72 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 01:08:34 -0400
Subject: [PATCH 07/14] Deduplicate Some Low-Hanging Fruit of Redundant Stat
 Calls

---
 programs/fileio.c | 7 ++++---
 programs/util.c   | 5 +++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/programs/fileio.c b/programs/fileio.c
index e818614b2..0633d39df 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -519,6 +519,7 @@ static int FIO_remove(const char* path)
  * @result : FILE* to `srcFileName`, or NULL if it fails */
 static FILE* FIO_openSrcFile(const char* srcFileName)
 {
+    stat_t statbuf;
     assert(srcFileName != NULL);
     if (!strcmp (srcFileName, stdinmark)) {
         DISPLAYLEVEL(4,"Using stdin for input \n");
@@ -526,14 +527,14 @@ static FILE* FIO_openSrcFile(const char* srcFileName)
         return stdin;
     }
 
-    if (!UTIL_fileExist(srcFileName)) {
+    if (!UTIL_stat(srcFileName, &statbuf)) {
         DISPLAYLEVEL(1, "zstd: can't stat %s : %s -- ignored \n",
                         srcFileName, strerror(errno));
         return NULL;
     }
 
-    if (!UTIL_isRegularFile(srcFileName)
-     && !UTIL_isFIFO(srcFileName)
+    if (!UTIL_isRegularFileStat(&statbuf)
+     && !UTIL_isFIFOStat(&statbuf)
     ) {
         DISPLAYLEVEL(1, "zstd: %s is not a regular file -- ignored \n",
                         srcFileName);
diff --git a/programs/util.c b/programs/util.c
index c81587b47..69b93b8d9 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -354,11 +354,12 @@ UTIL_createFileNamesTable_fromFileName(const char* inputFileName)
     char* buf;
     size_t bufSize;
     size_t pos = 0;
+    stat_t statbuf;
 
-    if (!UTIL_fileExist(inputFileName) || !UTIL_isRegularFile(inputFileName))
+    if (!UTIL_stat(inputFileName, &statbuf) || !UTIL_isRegularFileStat(&statbuf))
         return NULL;
 
-    {   U64 const inputFileSize = UTIL_getFileSize(inputFileName);
+    {   U64 const inputFileSize = UTIL_getFileSizeStat(&statbuf);
         if(inputFileSize > MAX_FILE_OF_FILE_NAMES_SIZE)
             return NULL;
         bufSize = (size_t)(inputFileSize + 1); /* (+1) to add '\0' at the end of last filename */

From 0a8aacb4db881e43b41e7043605fcf82f45836c1 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 12:00:12 -0400
Subject: [PATCH 08/14] Use stat() to Check that File Should be chmod()-ed

Rather than special-casing a check for `/dev/null`, this uses `stat()` to
avoid `chmod()`-ing any non-regular file. I believe this is the desirable
behavior. `UTIL_chmod()` is never called on directories at the moment, only
output files.
---
 programs/fileio.c |  4 ++--
 programs/util.c   | 11 ++++++++---
 programs/util.h   |  7 ++++++-
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/programs/fileio.c b/programs/fileio.c
index 0633d39df..7d58a11e7 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -509,7 +509,7 @@ static int FIO_remove(const char* path)
 #if defined(_WIN32) || defined(WIN32)
     /* windows doesn't allow remove read-only files,
      * so try to make it writable first */
-    UTIL_chmod(path, _S_IWRITE);
+    UTIL_chmod(path, NULL, _S_IWRITE);
 #endif
     return remove(path);
 }
@@ -619,7 +619,7 @@ FIO_openDstFile(FIO_prefs_t* const prefs,
                && strcmp (srcFileName, stdinmark)
                && strcmp(dstFileName, nulmark) ) {
             /* reduce rights on newly created dst file while compression is ongoing */
-            UTIL_chmod(dstFileName, 00600);
+            UTIL_chmod(dstFileName, NULL, 00600);
         }
         return f;
     }
diff --git a/programs/util.c b/programs/util.c
index 69b93b8d9..fd4d7a604 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -142,9 +142,14 @@ int UTIL_statDir(const char* infilename, stat_t *statbuf)
 }
 
 /* like chmod, but avoid changing permission of /dev/null */
-int UTIL_chmod(char const* filename, mode_t permissions)
+int UTIL_chmod(char const* filename, const stat_t* statbuf, mode_t permissions)
 {
-    if (!strcmp(filename, "/dev/null")) return 0;   /* pretend success, but don't change anything */
+    stat_t localStatBuf;
+    if (statbuf == NULL) {
+        if (!UTIL_stat(filename, &localStatBuf)) return 0;
+        statbuf = &localStatBuf;
+    }
+    if (!UTIL_isRegularFileStat(statbuf)) return 0; /* pretend success, but don't change anything */
     return chmod(filename, permissions);
 }
 
@@ -180,7 +185,7 @@ int UTIL_setFileStat(const char *filename, const stat_t *statbuf)
     res += chown(filename, statbuf->st_uid, statbuf->st_gid);  /* Copy ownership */
 #endif
 
-    res += UTIL_chmod(filename, statbuf->st_mode & 07777);  /* Copy file permissions */
+    res += UTIL_chmod(filename, NULL, statbuf->st_mode & 07777);  /* Copy file permissions */
 
     errno = 0;
     return -res; /* number of errors is returned */
diff --git a/programs/util.h b/programs/util.h
index 0a3be31cb..f75bca042 100644
--- a/programs/util.h
+++ b/programs/util.h
@@ -140,7 +140,12 @@ U64 UTIL_getFileSize(const char* infilename);
 U64 UTIL_getFileSizeStat(const stat_t* statbuf);
 U64 UTIL_getTotalFileSize(const char* const * fileNamesTable, unsigned nbFiles);
 int UTIL_setFileStat(const char* filename, const stat_t* statbuf);
-int UTIL_chmod(char const* filename, mode_t permissions);   /*< like chmod, but avoid changing permission of /dev/null */
+/**
+ * Like chmod, but only modifies regular files. Provided statbuf may be NULL,
+ * in which case this function will stat() the file internally, in order to
+ * check that it should be modified.
+ */
+int UTIL_chmod(char const* filename, const stat_t* statbuf, mode_t permissions);
 int UTIL_compareStr(const void *p1, const void *p2);
 const char* UTIL_getFileExtension(const char* infilename);
 void  UTIL_mirrorSourceFilesDirectories(const char** fileNamesTable, unsigned int nbFiles, const char *outDirName);

From c1449143c5502367ca1277f01d28416880d37e9b Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Wed, 5 Aug 2020 12:10:42 -0400
Subject: [PATCH 09/14] Share stat() Calls in Uses of UTIL_chmod()

---
 programs/fileio.c | 13 ++++++++++---
 programs/util.c   |  5 +++--
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/programs/fileio.c b/programs/fileio.c
index 7d58a11e7..e289f9abf 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -502,14 +502,21 @@ void FIO_setContentSize(FIO_prefs_t* const prefs, int value)
  * @result : Unlink `fileName`, even if it's read-only */
 static int FIO_remove(const char* path)
 {
-    if (!UTIL_isRegularFile(path)) {
-        DISPLAYLEVEL(2, "zstd: Refusing to remove non-regular file %s \n", path);
+    stat_t statbuf;
+    if (!UTIL_stat(path, &statbuf)) {
+        DISPLAYLEVEL(2, "zstd: Failed to stat %s while trying to remove it\n", path);
+        return 0;
+    }
+    if (!UTIL_isRegularFileStat(&statbuf)) {
+        DISPLAYLEVEL(2, "zstd: Refusing to remove non-regular file %s\n", path);
         return 0;
     }
 #if defined(_WIN32) || defined(WIN32)
     /* windows doesn't allow remove read-only files,
      * so try to make it writable first */
-    UTIL_chmod(path, NULL, _S_IWRITE);
+    if (!(statbuf.mode & _S_IWRITE)) {
+        UTIL_chmod(path, &statbuf, _S_IWRITE);
+    }
 #endif
     return remove(path);
 }
diff --git a/programs/util.c b/programs/util.c
index fd4d7a604..9f9f45d2b 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -157,7 +157,8 @@ int UTIL_setFileStat(const char *filename, const stat_t *statbuf)
 {
     int res = 0;
 
-    if (!UTIL_isRegularFile(filename))
+    stat_t curStatBuf;
+    if (!UTIL_stat(filename, &curStatBuf) || !UTIL_isRegularFileStat(&curStatBuf))
         return -1;
 
     /* set access and modification times */
@@ -185,7 +186,7 @@ int UTIL_setFileStat(const char *filename, const stat_t *statbuf)
     res += chown(filename, statbuf->st_uid, statbuf->st_gid);  /* Copy ownership */
 #endif
 
-    res += UTIL_chmod(filename, NULL, statbuf->st_mode & 07777);  /* Copy file permissions */
+    res += UTIL_chmod(filename, &curStatBuf, statbuf->st_mode & 07777);  /* Copy file permissions */
 
     errno = 0;
     return -res; /* number of errors is returned */

From 76878697a4e4a902f2b4617b71b0ad6f2c71bf9e Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Mon, 10 Aug 2020 15:16:14 -0400
Subject: [PATCH 10/14] Re-Organize and Document Prototypes in util.h

---
 programs/util.h | 43 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 11 deletions(-)

diff --git a/programs/util.h b/programs/util.h
index f75bca042..57cdc6058 100644
--- a/programs/util.h
+++ b/programs/util.h
@@ -124,28 +124,49 @@ int UTIL_stat(const char* filename, stat_t* statbuf);
 int UTIL_statFile(const char* infilename, stat_t* statbuf);
 /** Also checks that the target is a directory. */
 int UTIL_statDir(const char* infilename, stat_t* statbuf);
+
+/**
+ * Instead of getting a file's stats, this updates them with the info in the
+ * provided stat_t. Currently sets owner, group, atime, and mtime. Will only
+ * update this info for regular files.
+ */
+int UTIL_setFileStat(const char* filename, const stat_t* statbuf);
+
+/*
+ * These helpers operate on a pre-populated stat_t, i.e., the result of
+ * calling one of the above functions.
+ */
+
+int UTIL_isRegularFileStat(const stat_t* statbuf);
+int UTIL_isDirectoryStat(const stat_t* statbuf);
+int UTIL_isFIFOStat(const stat_t* statbuf);
+U64 UTIL_getFileSizeStat(const stat_t* statbuf);
+
+/**
+ * Like chmod(), but only modifies regular files. Provided statbuf may be NULL,
+ * in which case this function will stat() the file internally, in order to
+ * check whether it should be modified.
+ */
+int UTIL_chmod(char const* filename, const stat_t* statbuf, mode_t permissions);
+
+/*
+ * In the absence of a pre-existing stat result on the file in question, these
+ * functions will do a stat() call internally and then use that result to
+ * compute the needed information.
+ */
+
 int UTIL_fileExist(const char* filename);
 int UTIL_isRegularFile(const char* infilename);
-int UTIL_isRegularFileStat(const stat_t* statbuf); /* same but takes existing statbuf */
 int UTIL_isDirectory(const char* infilename);
-int UTIL_isDirectoryStat(const stat_t* statbuf); /* same but takes existing statbuf */
 int UTIL_isSameFile(const char* file1, const char* file2);
 int UTIL_isCompressedFile(const char* infilename, const char *extensionList[]);
 int UTIL_isLink(const char* infilename);
 int UTIL_isFIFO(const char* infilename);
-int UTIL_isFIFOStat(const stat_t* statbuf); /* same but takes existing statbuf */
 
 #define UTIL_FILESIZE_UNKNOWN  ((U64)(-1))
 U64 UTIL_getFileSize(const char* infilename);
-U64 UTIL_getFileSizeStat(const stat_t* statbuf);
 U64 UTIL_getTotalFileSize(const char* const * fileNamesTable, unsigned nbFiles);
-int UTIL_setFileStat(const char* filename, const stat_t* statbuf);
-/**
- * Like chmod, but only modifies regular files. Provided statbuf may be NULL,
- * in which case this function will stat() the file internally, in order to
- * check that it should be modified.
- */
-int UTIL_chmod(char const* filename, const stat_t* statbuf, mode_t permissions);
+
 int UTIL_compareStr(const void *p1, const void *p2);
 const char* UTIL_getFileExtension(const char* infilename);
 void  UTIL_mirrorSourceFilesDirectories(const char** fileNamesTable, unsigned int nbFiles, const char *outDirName);

From 93dda988c85b6bbd688cba44a6c21233aa7e78ea Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Mon, 10 Aug 2020 15:22:29 -0400
Subject: [PATCH 11/14] Remove Unused Function UTIL_fileExist()

---
 programs/util.c | 6 ------
 programs/util.h | 1 -
 2 files changed, 7 deletions(-)

diff --git a/programs/util.c b/programs/util.c
index 9f9f45d2b..420d6aa70 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -110,12 +110,6 @@ int UTIL_stat(const char* filename, stat_t* statbuf)
 #endif
 }
 
-int UTIL_fileExist(const char* filename)
-{
-    stat_t statbuf;
-    return UTIL_stat(filename, &statbuf);
-}
-
 int UTIL_isRegularFile(const char* infilename)
 {
     stat_t statbuf;
diff --git a/programs/util.h b/programs/util.h
index 57cdc6058..f903ccb13 100644
--- a/programs/util.h
+++ b/programs/util.h
@@ -155,7 +155,6 @@ int UTIL_chmod(char const* filename, const stat_t* statbuf, mode_t permissions);
  * compute the needed information.
  */
 
-int UTIL_fileExist(const char* filename);
 int UTIL_isRegularFile(const char* infilename);
 int UTIL_isDirectory(const char* infilename);
 int UTIL_isSameFile(const char* file1, const char* file2);

From 51ac0207afb1477a65c0b7a4ed407970cf63b243 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Mon, 10 Aug 2020 15:28:02 -0400
Subject: [PATCH 12/14] Remove UTIL_statFile() and UTIL_statDir(); Decompose
 Former Call-Sites

---
 programs/fileio.c |  6 ++++--
 programs/util.c   | 21 +++++++--------------
 programs/util.h   |  4 ----
 3 files changed, 11 insertions(+), 20 deletions(-)

diff --git a/programs/fileio.c b/programs/fileio.c
index e289f9abf..b6d8fb5aa 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -1486,7 +1486,8 @@ static int FIO_compressFilename_dstFile(FIO_prefs_t* const prefs,
         addHandler(dstFileName);
 
         if ( strcmp (srcFileName, stdinmark)
-          && UTIL_statFile(srcFileName, &statbuf))
+          && UTIL_stat(srcFileName, &statbuf)
+          && UTIL_isRegularFileStat(&statbuf) )
             transfer_permissions = 1;
     }
 
@@ -2352,7 +2353,8 @@ static int FIO_decompressDstFile(FIO_prefs_t* const prefs,
         addHandler(dstFileName);
 
         if ( strcmp(srcFileName, stdinmark)   /* special case : don't transfer permissions from stdin */
-          && UTIL_statFile(srcFileName, &statbuf) )
+          && UTIL_stat(srcFileName, &statbuf)
+          && UTIL_isRegularFileStat(&statbuf) )
             transfer_permissions = 1;
     }
 
diff --git a/programs/util.c b/programs/util.c
index 420d6aa70..fc88ab35c 100644
--- a/programs/util.c
+++ b/programs/util.c
@@ -113,7 +113,7 @@ int UTIL_stat(const char* filename, stat_t* statbuf)
 int UTIL_isRegularFile(const char* infilename)
 {
     stat_t statbuf;
-    return UTIL_statFile(infilename, &statbuf); /* Only need to know whether it is a regular file */
+    return UTIL_stat(infilename, &statbuf) && UTIL_isRegularFileStat(&statbuf);
 }
 
 int UTIL_isRegularFileStat(const stat_t* statbuf)
@@ -125,16 +125,6 @@ int UTIL_isRegularFileStat(const stat_t* statbuf)
 #endif
 }
 
-int UTIL_statFile(const char* infilename, stat_t *statbuf)
-{
-    return UTIL_stat(infilename, statbuf) && UTIL_isRegularFileStat(statbuf);
-}
-
-int UTIL_statDir(const char* infilename, stat_t *statbuf)
-{
-    return UTIL_stat(infilename, statbuf) && UTIL_isDirectoryStat(statbuf);
-}
-
 /* like chmod, but avoid changing permission of /dev/null */
 int UTIL_chmod(char const* filename, const stat_t* statbuf, mode_t permissions)
 {
@@ -189,7 +179,7 @@ int UTIL_setFileStat(const char *filename, const stat_t *statbuf)
 int UTIL_isDirectory(const char* infilename)
 {
     stat_t statbuf;
-    return UTIL_statDir(infilename, &statbuf);
+    return UTIL_stat(infilename, &statbuf) && UTIL_isDirectoryStat(&statbuf);
 }
 
 int UTIL_isDirectoryStat(const stat_t* statbuf)
@@ -671,11 +661,14 @@ static int isFileNameValidForMirroredOutput(const char *filename)
 static mode_t getDirMode(const char *dirName)
 {
     stat_t st;
-    int ret = UTIL_statDir(dirName, &st);
-    if (!ret) {
+    if (!UTIL_stat(dirName, &st)) {
         UTIL_DISPLAY("zstd: failed to get DIR stats %s: %s\n", dirName, strerror(errno));
         return DIR_DEFAULT_MODE;
     }
+    if (!UTIL_isDirectoryStat(&st)) {
+        UTIL_DISPLAY("zstd: expected directory: %s\n", dirName);
+        return DIR_DEFAULT_MODE;
+    }
     return st.st_mode;
 }
 
diff --git a/programs/util.h b/programs/util.h
index f903ccb13..f8eee86ad 100644
--- a/programs/util.h
+++ b/programs/util.h
@@ -120,10 +120,6 @@ extern int g_utilDisplayLevel;
  * Returns success (1) or failure (0).
  */
 int UTIL_stat(const char* filename, stat_t* statbuf);
-/** Also checks that the target is a regular file. */
-int UTIL_statFile(const char* infilename, stat_t* statbuf);
-/** Also checks that the target is a directory. */
-int UTIL_statDir(const char* infilename, stat_t* statbuf);
 
 /**
  * Instead of getting a file's stats, this updates them with the info in the

From b02cdf63b0a14ce79d9129629f4eddf171fdadd9 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Mon, 10 Aug 2020 15:39:14 -0400
Subject: [PATCH 13/14] Clean Up Redundant Checks, Rename FIO_remove() ->
 FIO_removeFile()

---
 programs/fileio.c | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/programs/fileio.c b/programs/fileio.c
index b6d8fb5aa..2c0d2772d 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -498,9 +498,9 @@ void FIO_setContentSize(FIO_prefs_t* const prefs, int value)
 /*-*************************************
 *  Functions
 ***************************************/
-/** FIO_remove() :
+/** FIO_removeFile() :
  * @result : Unlink `fileName`, even if it's read-only */
-static int FIO_remove(const char* path)
+static int FIO_removeFile(const char* path)
 {
     stat_t statbuf;
     if (!UTIL_stat(path, &statbuf)) {
@@ -616,7 +616,7 @@ FIO_openDstFile(FIO_prefs_t* const prefs,
                     while ((ch!=EOF) && (ch!='\n')) ch = getchar();
             }   }
             /* need to unlink */
-            FIO_remove(dstFileName);
+            FIO_removeFile(dstFileName);
     }   }
 
     {   FILE* const f = fopen( dstFileName, "wb" );
@@ -1505,13 +1505,10 @@ static int FIO_compressFilename_dstFile(FIO_prefs_t* const prefs,
             result=1;
         }
         if ( (result != 0)  /* operation failure */
-          && strcmp(dstFileName, nulmark)     /* special case : don't remove() /dev/null */
           && strcmp(dstFileName, stdoutmark)  /* special case : don't remove() stdout */
           ) {
-            FIO_remove(dstFileName); /* remove compression artefact; note don't do anything special if remove() fails */
-        } else if ( strcmp(dstFileName, stdoutmark)
-                 && strcmp(dstFileName, nulmark)
-                 && transfer_permissions) {
+            FIO_removeFile(dstFileName); /* remove compression artefact; note don't do anything special if remove() fails */
+        } else if (transfer_permissions) {
             DISPLAYLEVEL(6, "FIO_compressFilename_dstFile: transferring permissions into dst: %s \n", dstFileName);
             UTIL_setFileStat(dstFileName, &statbuf);
         } else {
@@ -1588,7 +1585,7 @@ FIO_compressFilename_srcFile(FIO_prefs_t* const prefs,
          * delete both the source and destination files.
          */
         clearHandler();
-        if (FIO_remove(srcFileName))
+        if (FIO_removeFile(srcFileName))
             EXM_THROW(1, "zstd: %s: %s", srcFileName, strerror(errno));
     }
     return result;
@@ -2370,15 +2367,11 @@ static int FIO_decompressDstFile(FIO_prefs_t* const prefs,
         }
 
         if ( (result != 0)  /* operation failure */
-          && strcmp(dstFileName, nulmark)     /* special case : don't remove() /dev/null (#316) */
           && strcmp(dstFileName, stdoutmark)  /* special case : don't remove() stdout */
           ) {
-            FIO_remove(dstFileName);  /* remove decompression artefact; note: don't do anything special if remove() fails */
-        } else {  /* operation success */
-            if ( strcmp(dstFileName, stdoutmark) /* special case : don't chmod stdout */
-              && strcmp(dstFileName, nulmark)    /* special case : don't chmod /dev/null */
-              && transfer_permissions )          /* file permissions correctly extracted from src */
-                UTIL_setFileStat(dstFileName, &statbuf);  /* transfer file permissions from src into dst */
+            FIO_removeFile(dstFileName);  /* remove decompression artefact; note: don't do anything special if remove() fails */
+        } else if ( transfer_permissions /* file permissions correctly extracted from src */ ) {
+            UTIL_setFileStat(dstFileName, &statbuf);  /* transfer file permissions from src into dst */
         }
     }
 
@@ -2419,7 +2412,7 @@ static int FIO_decompressSrcFile(FIO_prefs_t* const prefs, dRess_t ress, const c
          * delete both the source and destination files.
          */
         clearHandler();
-        if (FIO_remove(srcFileName)) {
+        if (FIO_removeFile(srcFileName)) {
             /* failed to remove src file */
             DISPLAYLEVEL(1, "zstd: %s: %s \n", srcFileName, strerror(errno));
             return 1;

From 953f0a072ac02773fd16f6ab1df037670bc3ae74 Mon Sep 17 00:00:00 2001
From: "W. Felix Handte" <w@felixhandte.com>
Date: Mon, 10 Aug 2020 17:28:34 -0400
Subject: [PATCH 14/14] Fix MS Build

---
 programs/fileio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/programs/fileio.c b/programs/fileio.c
index 2c0d2772d..d5b8a7d14 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -514,7 +514,7 @@ static int FIO_removeFile(const char* path)
 #if defined(_WIN32) || defined(WIN32)
     /* windows doesn't allow remove read-only files,
      * so try to make it writable first */
-    if (!(statbuf.mode & _S_IWRITE)) {
+    if (!(statbuf.st_mode & _S_IWRITE)) {
         UTIL_chmod(path, &statbuf, _S_IWRITE);
     }
 #endif