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From: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Johannes Schindelin <johannes.schindelin@gmx.de>,
	Junio C Hamano <gitster@pobox.com>,
	Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: [PATCH v2 8/9] built-in add -p: handle Escape sequences more efficiently
Date: Wed, 25 Dec 2019 11:56:59 +0000	[thread overview]
Message-ID: <703719ffce4e69fa1d22fd2b740ddfaa0ef7283d.1577275020.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.175.v2.git.1577275020.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

When `interactive.singlekey = true`, we react immediately to keystrokes,
even to Escape sequences (e.g. when pressing a cursor key).

The problem with Escape sequences is that we do not really know when
they are done, and as a heuristic we poll standard input for half a
second to make sure that we got all of it.

While waiting half a second is not asking for a whole lot, it can become
quite annoying over time, therefore with this patch, we read the
terminal capabilities (if available) and extract known Escape sequences
from there, then stop polling immediately when we detected that the user
pressed a key that generated such a known sequence.

This recapitulates the remaining part of b5cc003253c8 (add -i: ignore
terminal escape sequences, 2011-05-17).

Note: We do *not* query the terminal capabilities directly. That would
either require a lot of platform-specific code, or it would require
linking to a library such as ncurses.

Linking to a library in the built-ins is something we try very hard to
avoid (we even kicked the libcurl dependency to a non-built-in remote
helper, just to shave off a tiny fraction of a second from Git's startup
time). And the platform-specific code would be a maintenance nightmare.

Even worse: in Git for Windows' case, we would need to query MSYS2
pseudo terminals, which `git.exe` simply cannot do (because it is
intentionally *not* an MSYS2 program).

To address this, we simply spawn `infocmp -L -1` and parse its output
(which works even in Git for Windows, because that helper is included in
the end-user facing installations).

This is done only once, as in the Perl version, but it is done only when
the first Escape sequence is encountered, not upon startup of `git add
-i`; This saves on startup time, yet makes reacting to the first Escape
sequence slightly more sluggish. But it allows us to keep the
terminal-related code encapsulated in the `compat/terminal.c` file.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 compat/terminal.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index b7f58d1781..35bca03d14 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c
@@ -4,6 +4,7 @@
 #include "strbuf.h"
 #include "run-command.h"
 #include "string-list.h"
+#include "hashmap.h"
 
 #if defined(HAVE_DEV_TTY) || defined(GIT_WINDOWS_NATIVE)
 
@@ -238,6 +239,71 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+/*
+ * The `is_known_escape_sequence()` function returns 1 if the passed string
+ * corresponds to an Escape sequence that the terminal capabilities contains.
+ *
+ * To avoid depending on ncurses or other platform-specific libraries, we rely
+ * on the presence of the `infocmp` executable to do the job for us (failing
+ * silently if the program is not available or refused to run).
+ */
+struct escape_sequence_entry {
+	struct hashmap_entry entry;
+	char sequence[FLEX_ARRAY];
+};
+
+static int sequence_entry_cmp(const void *hashmap_cmp_fn_data,
+			      const struct escape_sequence_entry *e1,
+			      const struct escape_sequence_entry *e2,
+			      const void *keydata)
+{
+	return strcmp(e1->sequence, keydata ? keydata : e2->sequence);
+}
+
+static int is_known_escape_sequence(const char *sequence)
+{
+	static struct hashmap sequences;
+	static int initialized;
+
+	if (!initialized) {
+		struct child_process cp = CHILD_PROCESS_INIT;
+		struct strbuf buf = STRBUF_INIT;
+		char *p, *eol;
+
+		hashmap_init(&sequences, (hashmap_cmp_fn)sequence_entry_cmp,
+			     NULL, 0);
+
+		argv_array_pushl(&cp.args, "infocmp", "-L", "-1", NULL);
+		if (pipe_command(&cp, NULL, 0, &buf, 0, NULL, 0))
+			strbuf_setlen(&buf, 0);
+
+		for (eol = p = buf.buf; *p; p = eol + 1) {
+			p = strchr(p, '=');
+			if (!p)
+				break;
+			p++;
+			eol = strchrnul(p, '\n');
+
+			if (starts_with(p, "\\E")) {
+				char *comma = memchr(p, ',', eol - p);
+				struct escape_sequence_entry *e;
+
+				p[0] = '^';
+				p[1] = '[';
+				FLEX_ALLOC_MEM(e, sequence, p, comma - p);
+				hashmap_entry_init(&e->entry,
+						   strhash(e->sequence));
+				hashmap_add(&sequences, &e->entry);
+			}
+			if (!*eol)
+				break;
+		}
+		initialized = 1;
+	}
+
+	return !!hashmap_get_from_hash(&sequences, strhash(sequence), sequence);
+}
+
 int read_key_without_echo(struct strbuf *buf)
 {
 	static int warning_displayed;
@@ -271,7 +337,12 @@ int read_key_without_echo(struct strbuf *buf)
 		 * Start by replacing the Escape byte with ^[ */
 		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
 
-		for (;;) {
+		/*
+		 * Query the terminal capabilities once about all the Escape
+		 * sequences it knows about, so that we can avoid waiting for
+		 * half a second when we know that the sequence is complete.
+		 */
+		while (!is_known_escape_sequence(buf->buf)) {
 			struct pollfd pfd = { .fd = 0, .events = POLLIN };
 
 			if (poll(&pfd, 1, 500) < 1)
-- 
gitgitgadget


  parent reply	other threads:[~2019-12-25 11:57 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-21 22:41 [PATCH 0/9] built-in add -p: add support for the same config settings as the Perl version Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 1/9] built-in add -p: support interactive.diffFilter Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 2/9] built-in add -p: handle diff.algorithm Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 3/9] terminal: make the code of disable_echo() reusable Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 4/9] terminal: accommodate Git for Windows' default terminal Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 5/9] terminal: add a new function to read a single keystroke Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 6/9] built-in add -p: respect the `interactive.singlekey` config setting Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 7/9] built-in add -p: handle Escape sequences in interactive.singlekey mode Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 8/9] built-in add -p: handle Escape sequences more efficiently Johannes Schindelin via GitGitGadget
2019-12-21 22:42 ` [PATCH 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job Johannes Schindelin via GitGitGadget
2019-12-21 22:53   ` SZEDER Gábor
2019-12-25 11:56     ` Johannes Schindelin
2019-12-22  0:11   ` Junio C Hamano
2019-12-25 11:57     ` Johannes Schindelin
2019-12-24 18:23 ` [PATCH 0/9] built-in add -p: add support for the same config settings as the Perl version Junio C Hamano
2019-12-24 18:39   ` Junio C Hamano
2019-12-25  8:46     ` Simon Ruderich
2019-12-25 12:09     ` Johannes Schindelin
2019-12-25 12:02   ` Johannes Schindelin
2019-12-25 11:56 ` [PATCH v2 " Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 1/9] built-in add -p: support interactive.diffFilter Johannes Schindelin via GitGitGadget
2020-01-07 22:57     ` SZEDER Gábor
2020-01-13  6:47       ` Johannes Schindelin
2019-12-25 11:56   ` [PATCH v2 2/9] built-in add -p: handle diff.algorithm Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 3/9] terminal: make the code of disable_echo() reusable Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 4/9] terminal: accommodate Git for Windows' default terminal Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 5/9] terminal: add a new function to read a single keystroke Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 6/9] built-in add -p: respect the `interactive.singlekey` config setting Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 7/9] built-in add -p: handle Escape sequences in interactive.singlekey mode Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` Johannes Schindelin via GitGitGadget [this message]
2019-12-25 11:57   ` [PATCH v2 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job Johannes Schindelin via GitGitGadget
2019-12-26 20:48     ` Derrick Stolee
2020-01-01 22:10       ` Johannes Schindelin
2019-12-26 20:45   ` [PATCH v2 0/9] built-in add -p: add support for the same config settings as the Perl version Junio C Hamano
2020-01-13  8:29   ` [PATCH v3 00/10] " Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 01/10] built-in add -i/-p: treat SIGPIPE as EOF Johannes Schindelin via GitGitGadget
2020-01-13 17:04       ` SZEDER Gábor
2020-01-13 18:33         ` Jeff King
2020-01-15 18:32           ` Junio C Hamano
2020-01-15 19:03             ` Jeff King
2020-01-14 12:47         ` Johannes Schindelin
2020-01-17 14:32         ` SZEDER Gábor
2020-01-17 18:58           ` Jeff King
2020-01-13  8:29     ` [PATCH v3 02/10] built-in add -p: support interactive.diffFilter Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 03/10] built-in add -p: handle diff.algorithm Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 04/10] terminal: make the code of disable_echo() reusable Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 05/10] terminal: accommodate Git for Windows' default terminal Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 06/10] terminal: add a new function to read a single keystroke Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 07/10] built-in add -p: respect the `interactive.singlekey` config setting Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 08/10] built-in add -p: handle Escape sequences in interactive.singlekey mode Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 09/10] built-in add -p: handle Escape sequences more efficiently Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 10/10] ci: include the built-in `git add -i` in the `linux-gcc` job Johannes Schindelin via GitGitGadget
2020-01-14 18:43     ` [PATCH v4 00/10] built-in add -p: add support for the same config settings as the Perl version Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 01/10] t3701: adjust difffilter test Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 02/10] built-in add -p: support interactive.diffFilter Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 03/10] built-in add -p: handle diff.algorithm Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 04/10] terminal: make the code of disable_echo() reusable Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 05/10] terminal: accommodate Git for Windows' default terminal Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 06/10] terminal: add a new function to read a single keystroke Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 07/10] built-in add -p: respect the `interactive.singlekey` config setting Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 08/10] built-in add -p: handle Escape sequences in interactive.singlekey mode Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 09/10] built-in add -p: handle Escape sequences more efficiently Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 10/10] ci: include the built-in `git add -i` in the `linux-gcc` job Johannes Schindelin via GitGitGadget

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