From 0ecfaa6df91f7c37510f370295f593b9c0b88b98 Mon Sep 17 00:00:00 2001 From: Jia Tan Date: Thu, 23 Nov 2023 22:04:35 +0800 Subject: [PATCH] xz: Create separate is_tty() function. The new is_tty() will report if a file descriptor is a terminal or not. On POSIX systems, it is a wrapper around isatty(). However, the native Windows implementation of isatty() will return true for all character devices, not just terminals. So is_tty() has a special case for Windows so it can use alternative Windows API functions to determine if a file descriptor is a terminal. This fixes a bug with MSVC and MinGW-w64 builds that refused to read from or write to non-terminal character devices because xz thought it was a terminal. For instance: xz foo -c > /dev/null would fail because /dev/null was assumed to be a terminal. --- src/xz/util.c | 25 +++++++++++++++++++++++-- src/xz/util.h | 14 ++++++++++++++ 2 files changed, 37 insertions(+), 2 deletions(-) diff --git a/src/xz/util.c b/src/xz/util.c index 6ab4c2d7..f3816ae5 100644 --- a/src/xz/util.c +++ b/src/xz/util.c @@ -261,10 +261,31 @@ my_snprintf(char **pos, size_t *left, const char *fmt, ...) } +extern bool +is_tty(int fd) +{ +#if defined(_WIN32) && !defined(__CYGWIN__) + // There is no need to check if handle == INVALID_HANDLE_VALUE + // because it will return false anyway when used in GetConsoleMode(). + // The resulting HANDLE is owned by the file descriptor. + // The HANDLE must not be closed here. + intptr_t handle = _get_osfhandle(fd); + DWORD mode; + + // GetConsoleMode() is an easy way to tell if the HANDLE is a + // console or not. We do not care about the value of mode since we + // do not plan to use any further Windows console functions. + return GetConsoleMode((HANDLE)handle, &mode); +#else + return isatty(fd); +#endif +} + + extern bool is_tty_stdin(void) { - const bool ret = isatty(STDIN_FILENO); + const bool ret = is_tty(STDIN_FILENO); if (ret) message_error(_("Compressed data cannot be read from " @@ -277,7 +298,7 @@ is_tty_stdin(void) extern bool is_tty_stdout(void) { - const bool ret = isatty(STDOUT_FILENO); + const bool ret = is_tty(STDOUT_FILENO); if (ret) message_error(_("Compressed data cannot be written to " diff --git a/src/xz/util.h b/src/xz/util.h index 6d7e1481..1da40371 100644 --- a/src/xz/util.h +++ b/src/xz/util.h @@ -105,6 +105,20 @@ lzma_attribute((__format__(__printf__, 3, 4))) extern void my_snprintf(char **pos, size_t *left, const char *fmt, ...); +/// \brief Test if file descriptor is a terminal +/// +/// For POSIX systems, this is a simple wrapper around isatty(). However on +/// Windows, isatty() returns true for all character devices, not just +/// terminals. +/// +/// \param fd File descriptor to test +/// +/// \return bool: +/// - true if file descriptor is a terminal +/// - false otherwise +extern bool is_tty(int fd); + + /// \brief Test if stdin is a terminal /// /// If stdin is a terminal, an error message is printed and exit status set