Fix to allow the flac command to parse piped WAV input with

WAVEFORMATEXTENSIBLE format.

MinGW's fseeko() doesn't return error for the attempt to seek on non
seekable file (same behavior as MSVC).
The simplest solution would be to change #ifdef _MSC_VER to #ifdef
_WIN32 here.
Instead, this patch tests file with fstat(), and use fseeko() only when
it is a regular file.
This is confirmed to work properly both on MSVC and MinGW, can seek if
stdin is a redirected regular file, and doesn't require #ifdef.

Signed-off-by: Erik de Castro Lopo <erikd@mega-nerd.com>

1 files changed, 11 insertions, 21 deletions

diff --git a/src/flac/encode.c b/src/flac/encode.c
index b3f36706..eeea08aa 100644
--- a/src/flac/encode.c
+++ b/src/flac/encode.c
@@ -26,6 +26,7 @@
 #include <stdio.h> /* for FILE etc. */
 #include <stdlib.h> /* for malloc */
 #include <string.h> /* for strcmp(), strerror() */
+#include <sys/stat.h>
 #include "FLAC/all.h"
 #include "share/alloc.h"
 #include "share/grabbag.h"
@@ -2799,29 +2800,18 @@ FLAC__bool read_sane_extended(FILE *f, FLAC__uint32 *val, const char *fn)
 FLAC__bool fskip_ahead(FILE *f, FLAC__uint64 offset)
 {
 	static unsigned char dump[8192];
+	struct stat stb;
 
-#ifdef _MSC_VER
-	if(f == stdin) {
-		/* MS' stdio impl can't even seek forward on stdin, have to use pure non-fseek() version: */
-		while(offset > 0) {
-			const long need = (long)min(offset, sizeof(dump));
-			if((long)fread(dump, 1, need, f) < need)
-				return false;
-			offset -= need;
-		}
-	}
-	else
-#endif
+	if(fstat(fileno(f), &stb) == 0 && (stb.st_mode & S_IFMT) == S_IFREG)
 	{
-		while(offset > 0) {
-			long need = (long)min(offset, LONG_MAX);
-			if(fseeko(f, need, SEEK_CUR) < 0) {
-				need = (long)min(offset, sizeof(dump));
-				if((long)fread(dump, 1, need, f) < need)
-					return false;
-			}
-			offset -= need;
-		}
+		if(fseeko(f, offset, SEEK_CUR) == 0)
+			return true;
+	}
+	while(offset > 0) {
+		const long need = (long)min(offset, sizeof(dump));
+		if((long)fread(dump, 1, need, f) < need)
+			return false;
+		offset -= need;
 	}
 	return true;
 }