[PATCH v2 5/9] terminal: add a new function to read a single keystroke
From: Johannes Schindelin via GitGitGadget <hidden>
Date: 2019-12-25 11:57:17
Subsystem:
the rest · Maintainer:
Linus Torvalds
From: Johannes Schindelin <redacted> Typically, input on the command-line is line-based. It is actually not really easy to get single characters (or better put: keystrokes). We provide two implementations here: - One that handles `/dev/tty` based systems as well as native Windows. The former uses the `tcsetattr()` function to put the terminal into "raw mode", which allows us to read individual keystrokes, one by one. The latter uses `stty.exe` to do the same, falling back to direct Win32 Console access. Thanks to the refactoring leading up to this commit, this is a single function, with the platform-specific details hidden away in conditionally-compiled code blocks. - A fall-back which simply punts and reads back an entire line. Note that the function writes the keystroke into an `strbuf` rather than a `char`, in preparation for reading Escape sequences (e.g. when the user hit an arrow key). This is also required for UTF-8 sequences in case the keystroke corresponds to a non-ASCII letter. Signed-off-by: Johannes Schindelin <redacted> --- compat/terminal.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++ compat/terminal.h | 3 +++ 2 files changed, 58 insertions(+)
diff --git a/compat/terminal.c b/compat/terminal.c
index 16e9949da1..1b2564042a 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c@@ -60,6 +60,11 @@ static int disable_echo(void) return disable_bits(ECHO); } +static int enable_non_canonical(void) +{ + return disable_bits(ICANON | ECHO); +} + #elif defined(GIT_WINDOWS_NATIVE) #define INPUT_PATH "CONIN$"
@@ -151,6 +156,10 @@ static int disable_echo(void) return disable_bits(ENABLE_ECHO_INPUT); } +static int enable_non_canonical(void) +{ + return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT); +} #endif
@@ -198,6 +207,33 @@ char *git_terminal_prompt(const char *prompt, int echo) return buf.buf; } +int read_key_without_echo(struct strbuf *buf) +{ + static int warning_displayed; + int ch; + + if (warning_displayed || enable_non_canonical() < 0) { + if (!warning_displayed) { + warning("reading single keystrokes not supported on " + "this platform; reading line instead"); + warning_displayed = 1; + } + + return strbuf_getline(buf, stdin); + } + + strbuf_reset(buf); + ch = getchar(); + if (ch == EOF) { + restore_term(); + return EOF; + } + + strbuf_addch(buf, ch); + restore_term(); + return 0; +} + #else char *git_terminal_prompt(const char *prompt, int echo)
@@ -205,4 +241,23 @@ char *git_terminal_prompt(const char *prompt, int echo) return getpass(prompt); } +int read_key_without_echo(struct strbuf *buf) +{ + static int warning_displayed; + const char *res; + + if (!warning_displayed) { + warning("reading single keystrokes not supported on this " + "platform; reading line instead"); + warning_displayed = 1; + } + + res = getpass(""); + strbuf_reset(buf); + if (!res) + return EOF; + strbuf_addstr(buf, res); + return 0; +} + #endif
diff --git a/compat/terminal.h b/compat/terminal.h
index 97db7cd69d..a9d52b8464 100644
--- a/compat/terminal.h
+++ b/compat/terminal.h@@ -3,4 +3,7 @@ char *git_terminal_prompt(const char *prompt, int echo); +/* Read a single keystroke, without echoing it to the terminal */ +int read_key_without_echo(struct strbuf *buf); + #endif /* COMPAT_TERMINAL_H */
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