terminal: teach git how to save/restore the console

Add two functions to push/pop the terminal state as needed, and refactor the current users around it. This will be used in a future patch to protect git from a cooked console because of a broken child process. Signed-off-by: Carlo Marcelo Arenas Belón <[email protected]>
carenas · Sep 30, 2021 · d60439f · d60439f
1 parent 225bc32
commit d60439f
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Showing 2 changed files with 62 additions and 13 deletions.
diff --git a/compat/terminal.c b/compat/terminal.c
@@ -25,25 +25,38 @@ static void restore_term_on_signal(int sig)
 static int term_fd = -1;
 static struct termios old_term;
 
-static void restore_term(void)
+void pop_term(void)
 {
 	if (term_fd < 0)
 		return;
 
 	tcsetattr(term_fd, TCSAFLUSH, &old_term);
+}
+
+static void restore_term(void)
+{
+	pop_term();
+
 	close(term_fd);
 	term_fd = -1;
 }
 
+int push_term(int full_duplex)
+{
+	if (term_fd < 0)
+		term_fd = open("/dev/tty", O_RDWR);
+
+	return (term_fd < 0) ? -1 : tcgetattr(term_fd, &old_term);
+}
+
 static int disable_bits(tcflag_t bits)
 {
 	struct termios t;
 
-	term_fd = open("/dev/tty", O_RDWR);
-	if (tcgetattr(term_fd, &t) < 0)
+	if (push_term(0) < 0)
 		goto error;
 
-	old_term = t;
+	t = old_term;
 	sigchain_push_common(restore_term_on_signal);
 
 	t.c_lflag &= ~bits;
@@ -75,7 +88,22 @@ static int enable_non_canonical(void)
 static int use_stty = 1;
 static struct string_list stty_restore = STRING_LIST_INIT_DUP;
 static HANDLE hconin = INVALID_HANDLE_VALUE;
-static DWORD cmode;
+static HANDLE hconout = INVALID_HANDLE_VALUE;
+static DWORD cmodein, cmodeout;
+
+void pop_term(void)
+{
+	if (hconin == INVALID_HANDLE_VALUE)
+		return;
+
+	SetConsoleMode(hconin, cmodein);
+	CloseHandle(hconin);
+	if (cmodeout) {
+		assert(hconout != INVALID_HANDLE_VALUE);
+		SetConsoleMode(hconout, cmodeout);
+		CloseHandle(hconout);
+	}
+}
 
 static void restore_term(void)
 {
@@ -94,12 +122,34 @@ static void restore_term(void)
 		return;
 	}
 
+	pop_term();
+	hconin = hconout = INVALID_HANDLE_VALUE;
+}
+
+int push_term(int full_duplex)
+{
+	hconin = CreateFileA("CONIN$", GENERIC_READ | GENERIC_WRITE,
+	    FILE_SHARE_READ, NULL, OPEN_EXISTING,
+	    FILE_ATTRIBUTE_NORMAL, NULL);
 	if (hconin == INVALID_HANDLE_VALUE)
-		return;
+		return -1;
+
+	if (full_duplex) {
+		hconout = CreateFileA("CONOUT$", GENERIC_READ | GENERIC_WRITE,
+			FILE_SHARE_WRITE, NULL, OPEN_EXISTING,
+			FILE_ATTRIBUTE_NORMAL, NULL);
+		if (hconout == INVALID_HANDLE_VALUE)
+			goto error;
 
-	SetConsoleMode(hconin, cmode);
+		GetConsoleMode(hconout, &cmodeout);
+	}
+
+	GetConsoleMode(hconin, &cmodein);
+	return 0;
+error:
 	CloseHandle(hconin);
 	hconin = INVALID_HANDLE_VALUE;
+	return -1;
 }
 
 static int disable_bits(DWORD bits)
@@ -135,15 +185,11 @@ static int disable_bits(DWORD bits)
 		use_stty = 0;
 	}
 
-	hconin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
-	    FILE_SHARE_READ, NULL, OPEN_EXISTING,
-	    FILE_ATTRIBUTE_NORMAL, NULL);
-	if (hconin == INVALID_HANDLE_VALUE)
+	if (push_term(0) < 0)
 		return -1;
 
-	GetConsoleMode(hconin, &cmode);
 	sigchain_push_common(restore_term_on_signal);
-	if (!SetConsoleMode(hconin, cmode & ~bits)) {
+	if (!SetConsoleMode(hconin, cmodein & ~bits)) {
 		CloseHandle(hconin);
 		hconin = INVALID_HANDLE_VALUE;
 		return -1;

diff --git a/compat/terminal.h b/compat/terminal.h
@@ -1,6 +1,9 @@
 #ifndef COMPAT_TERMINAL_H
 #define COMPAT_TERMINAL_H
 
+int push_term(int full_duplex);
+void pop_term(void);
+
 char *git_terminal_prompt(const char *prompt, int echo);
 
 /* Read a single keystroke, without echoing it to the terminal */