song/StringFilter: support regular expressions with "=~" and "!~"

This feature requires `libpcre`.

NEWS

@@ -1,4 +1,6 @@
 ver 0.21.2 (not yet released)
+* protocol
+  - operator "=~" matches a regular expression
 * decoder
   - ffmpeg: require FFmpeg 3.1 or later
   - ffmpeg: fix broken sound with certain codecs

doc/protocol.rst

@@ -157,6 +157,11 @@ of:
   and are case-sensitive; the `search`
   commands specify a sub string and ignore case.
 
+- ``(TAG =~ 'VALUE')`` and ``(TAG !~ 'VALUE')`` use a Perl-compatible
+  regular expression instead of doing a simple string comparison.
+  (This feature is only available if :program:`MPD` was compiled with
+  :file:`libpcre`)
+
 - ``(file == 'VALUE')``: match the full song URI
   (relative to the music directory).
 

doc/user.rst

@@ -67,6 +67,7 @@ For example, the following installs a fairly complete list of build dependencies
 .. code-block:: none
 
     apt install g++ \
+      libpcre3-dev \
       libmad0-dev libmpg123-dev libid3tag0-dev \
       libflac-dev libvorbis-dev libopus-dev \
       libadplug-dev libaudiofile-dev libsndfile1-dev libfaad-dev \

meson.build

@@ -315,6 +315,7 @@ subdir('src/lib/gcrypt')
 subdir('src/lib/wrap')
 subdir('src/lib/nfs')
 subdir('src/lib/oss')
+subdir('src/lib/pcre')
 subdir('src/lib/pulse')
 subdir('src/lib/sndio')
 subdir('src/lib/sqlite')

meson_options.txt

@@ -176,6 +176,7 @@ option('expat', type: 'feature', description: 'Expat XML support')
 option('icu', type: 'feature', description: 'Use libicu for Unicode')
 option('iconv', type: 'feature', description: 'Use iconv() for character set conversion')
 option('libwrap', type: 'feature', description: 'libwrap support')
+option('pcre', type: 'feature', description: 'Enable regular expression support (using libpcre)')
 option('sqlite', type: 'feature', description: 'SQLite database support (for stickers)')
 option('yajl', type: 'feature', description: 'libyajl for YAML support')
 option('zlib', type: 'feature', description: 'zlib support (for database compression)')

src/lib/pcre/RegexPointer.hxx

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2007-2018 Content Management AG
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef REGEX_POINTER_HXX
+#define REGEX_POINTER_HXX
+
+#include "util/StringView.hxx"
+#include "util/Compiler.h"
+
+#include <pcre.h>
+
+#include <array>
+
+class RegexPointer {
+protected:
+	pcre *re = nullptr;
+	pcre_extra *extra = nullptr;
+
+	unsigned n_capture = 0;
+
+public:
+	constexpr bool IsDefined() const noexcept {
+		return re != nullptr;
+	}
+
+	gcc_pure
+	bool Match(StringView s) const noexcept {
+		/* we don't need the data written to ovector, but PCRE can
+		   omit internal allocations if we pass a buffer to
+		   pcre_exec() */
+		std::array<int, 16> ovector;
+		return pcre_exec(re, extra, s.data, s.size,
+				 0, 0, &ovector.front(), ovector.size()) >= 0;
+	}
+};
+
+#endif

src/lib/pcre/UniqueRegex.cxx

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2007-2018 Content Management AG
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "UniqueRegex.hxx"
+#include "util/RuntimeError.hxx"
+
+void
+UniqueRegex::Compile(const char *pattern, bool anchored, bool capture,
+		     bool caseless)
+{
+	constexpr int default_options = PCRE_DOTALL|PCRE_NO_AUTO_CAPTURE|PCRE_UTF8;
+
+	int options = default_options;
+	if (anchored)
+		options |= PCRE_ANCHORED;
+	if (capture)
+		options &= ~PCRE_NO_AUTO_CAPTURE;
+	if (caseless)
+		options |= PCRE_CASELESS;
+
+	const char *error_string;
+	int error_offset;
+	re = pcre_compile(pattern, options, &error_string, &error_offset, nullptr);
+	if (re == nullptr)
+		throw FormatRuntimeError("Error in regex at offset %d: %s",
+					 error_offset, error_string);
+
+	int study_options = 0;
+#ifdef PCRE_CONFIG_JIT
+	study_options |= PCRE_STUDY_JIT_COMPILE;
+#endif
+	extra = pcre_study(re, study_options, &error_string);
+	if (extra == nullptr && error_string != nullptr) {
+		pcre_free(re);
+		re = nullptr;
+		throw FormatRuntimeError("Regex study error: %s", error_string);
+	}
+
+	int n;
+	if (capture && pcre_fullinfo(re, extra, PCRE_INFO_CAPTURECOUNT, &n) == 0)
+		n_capture = n;
+}

src/lib/pcre/UniqueRegex.hxx

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2007-2018 Content Management AG
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef UNIQUE_REGEX_HXX
+#define UNIQUE_REGEX_HXX
+
+#include "RegexPointer.hxx"
+#include "util/StringView.hxx"
+
+#include <algorithm>
+
+#include <pcre.h>
+
+class UniqueRegex : public RegexPointer {
+public:
+	UniqueRegex() = default;
+
+	UniqueRegex(const char *pattern, bool anchored, bool capture,
+		    bool caseless) {
+		Compile(pattern, anchored, capture, caseless);
+	}
+
+	UniqueRegex(UniqueRegex &&src) noexcept:RegexPointer(src) {
+		src.re = nullptr;
+		src.extra = nullptr;
+	}
+
+	~UniqueRegex() noexcept {
+		pcre_free(re);
+#ifdef PCRE_CONFIG_JIT
+		pcre_free_study(extra);
+#else
+		pcre_free(extra);
+#endif
+	}
+
+	UniqueRegex &operator=(UniqueRegex &&src) {
+		using std::swap;
+		swap<RegexPointer>(*this, src);
+		return *this;
+	}
+
+	/**
+	 * Throws std::runtime_error on error.
+	 */
+	void Compile(const char *pattern, bool anchored, bool capture,
+		     bool caseless);
+};
+
+#endif

src/lib/pcre/meson.build

@@ -0,0 +1,21 @@
+pcre_dep = dependency('libpcre', required: get_option('pcre'))
+conf.set('HAVE_PCRE', pcre_dep.found())
+if not pcre_dep.found()
+  subdir_done()
+endif
+
+pcre = static_library(
+  'pcre',
+  'UniqueRegex.cxx',
+  include_directories: inc,
+  dependencies: [
+    pcre_dep,
+  ],
+)
+
+pcre_dep = declare_dependency(
+  link_with: pcre,
+  dependencies: [
+    pcre_dep,
+  ],
+)

src/song/Filter.cxx

@@ -207,6 +207,20 @@ static StringFilter
 ParseStringFilter(const char *&s, bool fold_case)
 {
 	bool negated = false;
+
+#ifdef HAVE_PCRE
+	if ((s[0] == '!' || s[0] == '=') && s[1] == '~') {
+		negated = s[0] == '!';
+		s = StripLeft(s + 2);
+		auto value = ExpectQuoted(s);
+		StringFilter f(std::move(value), fold_case, false, negated);
+		f.SetRegex(std::make_shared<UniqueRegex>(f.GetValue().c_str(),
+							 false, false,
+							 fold_case));
+		return f;
+	}
+#endif
+
 	if (s[0] == '!' && s[1] == '=')
 		negated = true;
 	else if (s[0] != '=' || s[1] != '=')

src/song/StringFilter.cxx

@@ -31,6 +31,11 @@ StringFilter::MatchWithoutNegation(const char *s) const noexcept
 	assert(s != nullptr);
 #endif
 
+#ifdef HAVE_PCRE
+	if (regex)
+		return regex->Match(s);
+#endif
+
 	if (fold_case) {
 		return substring
 			? fold_case.IsIn(s)

src/song/StringFilter.hxx

@@ -23,7 +23,12 @@
 #include "lib/icu/Compare.hxx"
 #include "util/Compiler.h"
 
+#ifdef HAVE_PCRE
+#include "lib/pcre/UniqueRegex.hxx"
+#endif
+
 #include <string>
+#include <memory>
 
 class StringFilter {
 	std::string value;
@@ -33,6 +38,10 @@ class StringFilter {
 	 */
 	IcuCompare fold_case;
 
+#ifdef HAVE_PCRE
+	std::shared_ptr<UniqueRegex> regex;
+#endif
+
 	/**
 	 * Search for substrings instead of matching the whole string?
 	 */
@@ -53,6 +62,21 @@ public:
 		return value.empty();
 	}
 
+	bool IsRegex() const noexcept {
+#ifdef HAVE_PCRE
+		return !!regex;
+#else
+		return false;
+#endif
+	}
+
+#ifdef HAVE_PCRE
+	template<typename R>
+	void SetRegex(R &&_regex) noexcept {
+		regex = std::forward<R>(_regex);
+	}
+#endif
+
 	const auto &GetValue() const noexcept {
 		return value;
 	}
@@ -70,7 +94,9 @@ public:
 	}
 
 	const char *GetOperator() const noexcept {
-		return negated ? "!=" : "==";
+		return IsRegex()
+			? (negated ? "!~" : "=~")
+			: (negated ? "!=" : "==");
 	}
 
 	gcc_pure

src/song/meson.build

@@ -19,6 +19,7 @@ song_dep = declare_dependency(
   link_with: song,
   dependencies: [
     icu_dep,
+    pcre_dep,
     tag_dep,
     util_dep,
   ],