mingw: accommodate for BusyBox' assumptions about isatty()

On Windows, isatty(fd) determines whether the file descriptor refers to
a character device.

The thing is: even NUL or a printer is a character device. BusyBox
thinks, however, that isatty() only returns non-zero for an interactive
terminal.

So let's shadow isatty() by a version that answers the question BusyBox
wants to have answered.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Ron Yorston <rmy@pobox.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/win32/winansi.c b/win32/winansi.c
index 7c7e1a626..8fffc5a00 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -733,3 +733,30 @@ int winansi_getc(FILE *stream)
 
         return rv;
 }
+
+/* Ensure that isatty(fd) returns 0 for the NUL device */
+int mingw_isatty(int fd)
+{
+        int result = _isatty(fd);
+
+        if (result) {
+                HANDLE handle = (HANDLE) _get_osfhandle(fd);
+                CONSOLE_SCREEN_BUFFER_INFO sbi;
+                DWORD mode;
+
+                if (handle == INVALID_HANDLE_VALUE)
+                        return 0;
+
+                /* check if its a device (i.e. console, printer, serial port) */
+                if (GetFileType(handle) != FILE_TYPE_CHAR)
+                        return 0;
+
+                if (!fd) {
+                        if (!GetConsoleMode(handle, &mode))
+                                return 0;
+                } else if (!GetConsoleScreenBufferInfo(handle, &sbi))
+                        return 0;
+        }
+
+        return result;
+}