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

@@ -26,9 +26,14 @@ 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})
+# sdn-mc-ext should be in libexec, but we prefer it in PATH.
-install (PROGRAMS ${PROJECT_NAME}-install ${PROJECT_NAME}-view
+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)

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-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

@@ -14,198 +14,41 @@ if command -v mc >/dev/null
 then datadir=$(mc --datadir | sed 's/ (.*)$//')
 fi
 
-export SDN_VIEW_CONFIG=
+config=
 for dir in "$HOME"/.config/mc "$datadir" /etc/mc
 do
 	if [ -n "$dir" -a -f "$dir/mc.ext.ini" ]
 	then
-		SDN_VIEW_CONFIG=$dir/mc.ext.ini
+		config=$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 "$1")
+export MC_EXT_CURRENTDIR=$(dirname "$MC_EXT_FILENAME")
-export SDN_VIEW_TYPE=$(file -bz "$1")
+output=$(sdn-mc-ext <"$config" "$(file -Lbz "$1")" \
-process() (awk -f - <<'EOF'
+	"$MC_EXT_FILENAME" "$MC_EXT_BASENAME" "$MC_EXT_CURRENTDIR" View || :)
-BEGIN {
+kind=$(echo "$output" | sed -n 1p)
-	if (!(Config = ENVIRON["SDN_VIEW_CONFIG"]))
+command=$(echo "$output" | sed -n 2p)
-		exit
 
-	Verb = "View"
+case "$kind" in
-	Section = ""
+view)
-	while ((getline < Config) > 0) {
+	if [ -n "$command" ]
-		if (/^\s*(#.*)?$/) {
+	then eval "$command" | "$PAGER"
-			# Skip.
+	else "$PAGER" -- "$MC_EXT_FILENAME"
-		} else if (/^\[[^]]+\]$/) {
+	fi
-			Sections[++SectionsLen] = Section = substr($0, 2, length($0) - 2)
+	;;
-		} else if (/^[^=]+=[^=]*$/) {
+'')
-			split($0, kv, "=")
+	if [ -n "$command" ]
-			Keys[Section, kv[1]] = kv[2]
+	then eval "$command"
-		}
+	else "$PAGER" -- "$MC_EXT_FILENAME"
-	}
+	fi
-
+	;;
-	Type     = ENVIRON["SDN_VIEW_TYPE"]
+*)
-	Path     = ENVIRON["MC_EXT_FILENAME"]
+	echo "Unsupported: $kind" >&2
-	Basename = ENVIRON["MC_EXT_BASENAME"]
+	exit 1
-	Dirname  = ENVIRON["MC_EXT_CURRENTDIR"]
+esac
-
-	for (i = 1; i <= SectionsLen; i++) {
-		if (Sections[i] == "mc.ext.ini" ||
-			Sections[i] == "Default" ||
-			Sections[i] ~ /^Include[\/]/)
-			continue
-		try(Sections[i])
-	}
-
-	# Not attempting any inclusions here.
-	print expand_command(Keys["Default", Verb])
-}
-
-function try(section,    pair, a, key, full, include) {
-	for (pair in Keys) {
-		split(pair, a, SUBSEP)
-		if (a[1] == section)
-			full[a[2]] = Keys[pair]
-	}
-	if ("Include" in full) {
-		delete full["Open"]
-		delete full["View"]
-		delete full["Edit"]
-		include = "Include/" full["Include"]
-		for (pair in Keys) {
-			split(pair, a, SUBSEP)
-			if (a[1] == include)
-				full[a[2]] = Keys[pair]
-		}
-	}
-	if (ENVIRON["SDN_VIEW_DEBUG"]) {
-		print "[" section "]" > "/dev/stderr"
-		for (key in full)
-			print "  " key ": " full[key] > "/dev/stderr"
-	}
-	if (Verb in full && section_matches(full, Type, Basename)) {
-		print expand_command(full[Verb])
-		exit
-	}
-}
-
-function shell_escape(string) {
-	gsub(/'/, "'\\''", string)
-	return "'" string "'"
-}
-
-function expand_command(cmd,    toview, out, seq, argument, value, a, pipe) {
-	out = ""
-	while (match(cmd, /%[a-zA-Z]*\{[^}]*\}|%[a-zA-Z]+|%%/)) {
-		out = out substr(cmd, 1, RSTART - 1)
-		seq = substr(cmd, RSTART + 1, RLENGTH - 1)
-		cmd = substr(cmd, RSTART + RLENGTH)
-
-		argument = ""
-		if (match(seq, /\{.*\}$/)) {
-			argument = substr(seq, RSTART + 1, RLENGTH - 2)
-			seq = substr(seq, 1, RSTART - 1)
-		}
-
-		if (seq == "%") {
-			out = out "%"
-		} else if (seq == "p") {
-			out = out shell_escape(Basename)
-		} else if (seq == "f") {
-			out = out shell_escape(Path)
-		} else if (seq == "d") {
-			out = out shell_escape(Dirname)
-		} else if (seq == "view") {
-			toview = 1
-
-			sub(/^ +/, "", cmd)
-			split(argument, a, /,/)
-			for (value in a) {
-				if (a[value] == "hex")
-					pipe = pipe " | od -t x1"
-
-				# more(1) and less(1) either ignore or display this:
-				#if (a[value] == "nroff")
-				#	pipe = pipe " | col -b"
-			}
-		} else if (seq == "var") {
-			value = ""
-			if (!match(argument, /:.*/)) {
-				if (argument in ENVIRON)
-					value = ENVIRON[argument]
-			} else {
-				value = substr(argument, RSTART + 1)
-				argument = substr(argument, 1, RSTART - 1)
-				if (argument in ENVIRON)
-					value = ENVIRON[argument]
-			}
-			out = out shell_escape(value)
-		} else if (seq == "") {
-			print Config ": prompting not supported" > "/dev/stderr"
-			return
-		} else {
-			print Config ": unsupported: %" seq > "/dev/stderr"
-			return
-		}
-	}
-	out = out cmd pipe
-
-	# While the processing is mostly generic for all verbs,
-	# we'd have to distinguish non-view commands in this AWK script's output.
-	if (!toview)
-		return
-
-	# In the case of out == "", we should just explicitly pass it to the pager,
-	# however it currently mixes with the case of "we can't use this View=".
-	return out
-}
-
-function section_matches(section, type, basename,    value) {
-	if ("Directory" in section)
-		return 0
-
-	if ("Type" in section) {
-		value = section["Type"]
-		if ("TypeIgnoreCase" in section &&
-			section["TypeIgnoreCase"] == "true") {
-			type = tolower(type)
-			value = tolower(value)
-		}
-		gsub(/\\\\/, "\\", value)
-		gsub(/\\ /, " ", value)
-		if (type !~ value)
-			return 0
-	}
-	if ("Regex" in section) {
-		value = section["Regex"]
-		if ("RegexIgnoreCase" in section &&
-			section["RegexIgnoreCase"] == "true") {
-			basename = tolower(basename)
-			value = tolower(value)
-		}
-		gsub(/\\\\/, "\\", value)
-		return basename ~ value
-	} else if ("Shell" in section) {
-		value = section["Shell"]
-		if ("RegexIgnoreCase" in section &&
-			section["ShellIgnoreCase"] == "true") {
-			basename = tolower(basename)
-			value = tolower(value)
-		}
-		if (value !~ /^[.]/)
-			return value == basename
-		return length(basename) >= length(value) &&
-			substr(basename, length(basename) - length(value) + 1) == value
-	}
-	return type != ""
-}
-EOF
-)
-command=$(process)
-if [ -z "$command" ]
-then "$PAGER" -- "$MC_EXT_FILENAME"
-else eval "$command" | "$PAGER"
-fi