Rewrite sdn-view AWK core in C++

sdn-view is still slower than I'd like it to be,
just no longer ridiculously so.

CMakeLists.txt

@@ -26,10 +26,17 @@ target_compile_features (${PROJECT_NAME} PUBLIC cxx_std_14)
 target_compile_definitions (${PROJECT_NAME} PUBLIC
 	-DPROJECT_NAME=\"${PROJECT_NAME}\" -DPROJECT_VERSION=\"${PROJECT_VERSION}\")
 
+add_executable (${PROJECT_NAME}-mc-ext ${PROJECT_NAME}-mc-ext.cpp)
+target_compile_features (${PROJECT_NAME}-mc-ext PUBLIC cxx_std_17)
+
 include (GNUInstallDirs)
-install (TARGETS ${PROJECT_NAME} DESTINATION ${CMAKE_INSTALL_BINDIR})
-install (PROGRAMS ${PROJECT_NAME}-install DESTINATION ${CMAKE_INSTALL_BINDIR})
-install (FILES sdn.1 sdn-install.1 DESTINATION ${CMAKE_INSTALL_MANDIR}/man1)
+# sdn-mc-ext should be in libexec, but we prefer it in PATH.
+install (TARGETS sdn sdn-mc-ext
+	DESTINATION ${CMAKE_INSTALL_BINDIR})
+install (PROGRAMS sdn-install sdn-view
+	DESTINATION ${CMAKE_INSTALL_BINDIR})
+install (FILES sdn.1 sdn-install.1 sdn-view.1
+	DESTINATION ${CMAKE_INSTALL_MANDIR}/man1)
 install (FILES LICENSE DESTINATION ${CMAKE_INSTALL_DOCDIR})
 
 set (CPACK_PACKAGE_DESCRIPTION_SUMMARY "Directory navigator")

NEWS

@@ -1,3 +1,11 @@
+Unreleased
+
+ * Added an sdn-view script that can process Midnight Commander mc.ext.ini files
+   and apply matching filters; this script has been made the default F3 binding,
+   while the original direct pager invocation has been moved to F13 (which also
+   reflects Midnight Commander)
+
+
 1.0.0 (2024-12-21)
 
  * Initial release

README.adoc

@@ -25,7 +25,7 @@ or as a https://git.janouch.name/p/nixexprs[Nix derivation].
 
 Building
 --------
-Build dependencies: CMake and/or make, a C++14 compiler, pkg-config +
+Build dependencies: CMake and/or make, a C++17 compiler, pkg-config +
 Runtime dependencies: ncursesw, libacl (on Linux)
 
 // Working around libasciidoc's missing support for escaping it like \++

sdn-install.1

@@ -1,6 +1,6 @@
 .Dd October 27, 2020
 .Dt SDN-INSTALL 1
-.Os Linux
+.Os
 .Sh NAME
 .Nm sdn-install
 .Nd integrate sdn with the shell

sdn-mc-ext.cpp

@@ -0,0 +1,222 @@
+//
+// sdn-mc-ext: Midnight Commander extension file processor
+//
+// Copyright (c) 2024, Přemysl Eric Janouch <p@janouch.name>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+
+#include <cstdlib>
+#include <cctype>
+#include <iostream>
+#include <regex>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+// Trailing return types make C++ syntax suck considerably less
+#define fun static auto
+
+using namespace std;
+
+// It is completely fine if this only modifies ASCII letters.
+fun tolower (const string &s) -> string {
+    string result;
+	for (auto c : s) result += tolower (c);
+    return result;
+}
+
+fun shell_escape (const string &v) -> string {
+    return "'" + regex_replace (v, regex {"'"}, "'\\''") + "'";
+}
+
+string arg_type, arg_path, arg_basename, arg_dirname, arg_verb;
+unordered_map<string, unordered_map<string, string>> sections;
+
+fun expand_command (string command) -> pair<string, string> {
+	regex re_sequence {R"(%(%|[[:alpha:]]*\{([^}]*)\}|[[:alpha:]]+))"};
+	regex re_name {R"([^{}]*)"};
+	regex re_parameter {R"([^,]+")"};
+	string kind, out, pipe; smatch m;
+	while (regex_search (command, m, re_sequence)) {
+		out.append (m.prefix ());
+		auto seq = m.str (1);
+		command = m.suffix ();
+
+		string argument = m.str (2);
+		if (regex_search (seq, m, re_name))
+			seq = m.str ();
+
+		if (seq == "%") {
+			out += "%";
+		} else if (seq == "p") {
+			out += shell_escape (arg_basename);
+		} else if (seq == "f") {
+			out += shell_escape (arg_path);
+		} else if (seq == "d") {
+			out += shell_escape (arg_dirname);
+		} else if (seq == "var") {
+			string value;
+			if (auto colon = argument.find (':'); colon == argument.npos) {
+				if (auto v = getenv (argument.c_str ()))
+					value = v;
+			} else {
+				value = argument.substr (colon + 1);
+				if (auto v = getenv (argument.substr (0, colon).c_str ()))
+					value = v;
+			}
+			out += shell_escape (value);
+		} else if (seq == "cd") {
+			kind = seq;
+			command = regex_replace (command, regex {"^ +"}, "");
+		} else if (seq == "view") {
+			kind = seq;
+			command = regex_replace (command, regex {"^ +"}, "");
+
+			sregex_token_iterator it (argument.begin (), argument.end (),
+				re_parameter, 0), end;
+			for (; it != end; it++) {
+				if (*it == "hex")
+					pipe.append (" | od -t x1");
+
+				// more(1) and less(1) either ignore or display this:
+				//if (*it == "nroff")
+				//	pipe.append (" | col -b");
+			}
+		} else if (seq == "") {
+			cerr << "sdn-mc-ext: prompting not supported" << endl;
+			return {};
+		} else {
+			cerr << "sdn-mc-ext: unsupported: %" << seq << endl;
+			return {};
+		}
+	}
+	return {kind,
+		pipe.empty () ? out.append (command) : "(" + out + ")" + pipe};
+}
+
+fun print_command (string cmd) {
+	auto command = expand_command (cmd);
+	cout << get<0> (command) << endl << get<1> (command) << endl;
+}
+
+fun section_matches (const unordered_map<string, string> &section) -> bool {
+	if (section.count ("Directory"))
+		return false;
+
+	// The configuration went through some funky changes;
+	// unescape \\ but leave other escapes alone.
+	auto filter_re = [](const string &s) {
+		string result;
+		for (size_t i = 0; i < s.length (); ) {
+			auto c = s[i++];
+			if (c == '\\' && i < s.length ())
+				if (c = s[i++]; c != '\\')
+					result += '\\';
+			result += c;
+		}
+		return result;
+	};
+	auto is_true = [&](const string &name) {
+		auto value = section.find (name);
+		return value != section.end () && value->second == "true";
+	};
+	if (auto kv = section.find ("Type"); kv != section.end ()) {
+		auto flags = std::regex::ECMAScript;
+		if (is_true ("TypeIgnoreCase"))
+			flags |= regex_constants::icase;
+		if (!regex_search (arg_type, regex {filter_re (kv->second), flags}))
+			return false;
+	}
+	auto basename = arg_basename;
+	if (auto kv = section.find ("Regex"); kv != section.end ()) {
+		auto flags = std::regex::ECMAScript;
+		if (is_true ("RegexIgnoreCase"))
+			flags |= regex_constants::icase;
+		return regex_search (basename, regex {filter_re (kv->second), flags});
+	}
+	if (auto kv = section.find ("Shell"); kv != section.end ()) {
+		auto value = kv->second;
+		if (is_true ("ShellIgnoreCase")) {
+			value = tolower (value);
+			basename = tolower (arg_basename);
+		}
+		if (value.empty () || value[0] != '.')
+			return value == basename;
+		return basename.length () >= value.length () &&
+			basename.substr (basename.length () - value.length ()) == value;
+	}
+	return !arg_type.empty ();
+}
+
+fun process (const string &section) -> bool {
+	auto full = sections.at (section);
+	if (auto include = full.find ("Include"); include != full.end ()) {
+		full.erase ("Open");
+		full.erase ("View");
+		full.erase ("Edit");
+
+		if (auto included = sections.find ("Include/" + include->second);
+			included != sections.end ()) {
+			for (const auto &kv : included->second)
+				full[kv.first] = kv.second;
+		}
+	}
+	if (getenv ("SDN_MC_EXT_DEBUG")) {
+		cerr << "[" << section << "]" << endl;
+		for (const auto &kv : full)
+			cerr << "  " << kv.first << ": " << kv.second << endl;
+	}
+	if (full.count (arg_verb) && section_matches (full)) {
+		print_command (full[arg_verb]);
+		return true;
+	}
+	return false;
+}
+
+int main (int argc, char *argv[]) {
+	if (argc != 6) {
+		cerr << "Usage: " << argv[0]
+			<< " TYPE PATH BASENAME DIRNAME VERB < mc.ext.ini" << endl;
+		return 2;
+	}
+
+	arg_type = argv[1];
+	arg_path = argv[2], arg_basename = argv[3], arg_dirname = argv[4];
+	arg_verb = argv[5];
+
+	string line, section;
+	vector<string> order;
+	regex re_entry {R"(^([-\w]+) *= *(.*)$)"};
+	smatch m;
+	while (getline (cin, line)) {
+		if (line.empty () || line[0] == '#') {
+			continue;
+		} else if (auto length = line.length();
+			line.find_last_of ('[') == 0 &&
+			line.find_first_of (']') == length - 1) {
+			order.push_back ((section = line.substr (1, length - 2)));
+		} else if (regex_match (line, m, re_entry)) {
+			sections[section][m[1]] = m[2];
+		}
+	}
+	for (const auto &section : order) {
+		if (section == "mc.ext.ini" ||
+			section == "Default" ||
+			section.substr (0, 8) == "Include/")
+			continue;
+		if (process (section))
+			return 0;
+	}
+	print_command (sections["Default"][arg_verb]);
+	return 0;
+}

sdn-view

@@ -0,0 +1,54 @@
+#!/bin/sh -e
+# sdn-view: a viewer for sdn that makes use of Midnight Commander configuration
+# to make more kinds of files directly viewable
+
+if [ "$#" -ne 1 ]
+then
+	echo "Usage: $0 FILE" >&2
+	exit 2
+fi
+
+# This handles both MC_DATADIR and odd installation locations.
+datadir=
+if command -v mc >/dev/null
+then datadir=$(mc --datadir | sed 's/ (.*)$//')
+fi
+
+config=
+for dir in "$HOME"/.config/mc "$datadir" /etc/mc
+do
+	if [ -n "$dir" -a -f "$dir/mc.ext.ini" ]
+	then
+		config=$dir/mc.ext.ini
+		break
+	fi
+done
+
+# This is often used in %env{} expansion, so let's be on the same page.
+export PAGER=${PAGER:-less}
+
+export MC_EXT_FILENAME=$(realpath "$1")
+export MC_EXT_BASENAME=$(basename "$1")
+export MC_EXT_CURRENTDIR=$(dirname "$MC_EXT_FILENAME")
+output=$(sdn-mc-ext <"$config" "$(file -Lbz "$1")" \
+	"$MC_EXT_FILENAME" "$MC_EXT_BASENAME" "$MC_EXT_CURRENTDIR" View || :)
+kind=$(echo "$output" | sed -n 1p)
+command=$(echo "$output" | sed -n 2p)
+
+case "$kind" in
+view)
+	if [ -n "$command" ]
+	then eval "$command" | "$PAGER"
+	else "$PAGER" -- "$MC_EXT_FILENAME"
+	fi
+	;;
+'')
+	if [ -n "$command" ]
+	then eval "$command"
+	else "$PAGER" -- "$MC_EXT_FILENAME"
+	fi
+	;;
+*)
+	echo "Unsupported: $kind" >&2
+	exit 1
+esac

sdn-view.1

@@ -0,0 +1,23 @@
+.Dd December 28, 2024
+.Dt SDN-VIEW 1
+.Os
+.Sh NAME
+.Nm sdn-view
+.Nd run Midnight Commander view configuration externally
+.Sh SYNOPSIS
+.Nm sdn-view
+.Ar path
+.Sh DESCRIPTION
+.Nm
+invokes
+.Ev PAGER
+or a fallback pager on the passed filename.
+.Pp
+If it succeeds in finding a
+.Xr mc 1
+.Pa mc.ext.ini
+file, it will first process it, and apply any matching filter.
+.Sh REPORTING BUGS
+Use
+.Lk https://git.janouch.name/p/sdn
+to report bugs, request features, or submit pull requests.

sdn.1

@@ -1,7 +1,7 @@
 \" https://mandoc.bsd.lv/man/roff.7.html#Sentence_Spacing
 .Dd October 27, 2020
 .Dt SDN 1
-.Os Linux
+.Os
 .Sh NAME
 .Nm sdn
 .Nd directory navigator
@@ -68,8 +68,8 @@ and you can use the
 .Xr dircolors 1
 utility to initialize this variable.
 .It Ev PAGER
-The viewer program to be launched by the F3 key binding as well as to show
-the internal help message.
+The viewer program to be launched by the F3 and F13 key bindings as well as
+to show the internal help message.
 If none is set, it defaults to
 .Xr less 1 .
 .It Ev VISUAL , Ev EDITOR

sdn.cpp

@@ -428,7 +428,8 @@ enum { ALT = 1 << 24, SYM = 1 << 25 };  // Outside the range of Unicode
 #define CTRL(char) ((char) == '?' ? 0x7f : (char) & 0x1f)
 
 #define ACTIONS(XX) XX(NONE) XX(HELP) XX(QUIT) XX(QUIT_NO_CHDIR) \
-	XX(CHOOSE) XX(CHOOSE_FULL) XX(VIEW) XX(EDIT) XX(SORT_LEFT) XX(SORT_RIGHT) \
+	XX(CHOOSE) XX(CHOOSE_FULL) XX(VIEW_RAW) XX(VIEW) XX(EDIT) \
+	XX(SORT_LEFT) XX(SORT_RIGHT) \
 	XX(UP) XX(DOWN) XX(TOP) XX(BOTTOM) XX(HIGH) XX(MIDDLE) XX(LOW) \
 	XX(PAGE_PREVIOUS) XX(PAGE_NEXT) XX(SCROLL_UP) XX(SCROLL_DOWN) XX(CENTER) \
 	XX(CHDIR) XX(PARENT) XX(GO_START) XX(GO_HOME) \
@@ -451,7 +452,8 @@ static map<wint_t, action> g_normal_actions {
 	{ALT | '\r', ACTION_CHOOSE_FULL}, {ALT | KEY (ENTER), ACTION_CHOOSE_FULL},
 	{'\r', ACTION_CHOOSE}, {KEY (ENTER), ACTION_CHOOSE},
 	{KEY (F (1)), ACTION_HELP}, {'h', ACTION_HELP},
-	{KEY (F (3)), ACTION_VIEW}, {KEY (F (4)), ACTION_EDIT},
+	{KEY (F (3)), ACTION_VIEW}, {KEY (F (13)), ACTION_VIEW_RAW},
+	{KEY (F (4)), ACTION_EDIT},
 	{'q', ACTION_QUIT}, {ALT | 'q', ACTION_QUIT_NO_CHDIR},
 	// M-o ought to be the same shortcut the navigator is launched with
 	{ALT | 'o', ACTION_QUIT},
@@ -1015,12 +1017,17 @@ fun run_program (initializer_list<const char *> list, const string &filename) {
 	update ();
 }
 
-fun view (const string &filename) {
+fun view_raw (const string &filename) {
 	// XXX: we cannot realistically detect that the pager hasn't made a pause
 	// at the end of the file, so we can't ensure all contents have been seen
 	run_program ({(const char *) getenv ("PAGER"), "less", "cat"}, filename);
 }
 
+fun view (const string &filename) {
+	run_program ({(const char *) getenv ("SDN_VIEWER"), "sdn-view",
+		(const char *) getenv ("PAGER"), "less", "cat"}, filename);
+}
+
 fun edit (const string &filename) {
 	run_program ({(const char *) getenv ("VISUAL"),
 		(const char *) getenv ("EDITOR"), "vi"}, filename);
@@ -1445,8 +1452,11 @@ fun handle (wint_t c) -> bool {
 	case ACTION_CHOOSE:
 		choose (current);
 		break;
-	case ACTION_VIEW:
+	case ACTION_VIEW_RAW:
 		// Mimic mc, it does not seem sensible to page directories
+		(is_directory ? change_dir : view_raw) (current.filename);
+		break;
+	case ACTION_VIEW:
 		(is_directory ? change_dir : view) (current.filename);
 		break;
 	case ACTION_EDIT: