output/recorder: dynamic file name

Makefile.am

@@ -399,6 +399,7 @@ libutil_a_SOURCES = \
 	src/util/OptionParser.cxx src/util/OptionParser.hxx \
 	src/util/OptionDef.hxx \
 	src/util/ByteReverse.cxx src/util/ByteReverse.hxx \
+	src/util/format.c src/util/format.h \
 	src/util/bit_reverse.c src/util/bit_reverse.h
 
 # Multi-threading library
@@ -797,6 +798,7 @@ libtag_a_SOURCES =\
 	src/tag/TagPool.cxx src/tag/TagPool.hxx \
 	src/tag/TagTable.cxx src/tag/TagTable.hxx \
 	src/tag/Set.cxx src/tag/Set.hxx \
+	src/tag/Format.cxx src/tag/Format.hxx \
 	src/tag/VorbisComment.cxx src/tag/VorbisComment.hxx \
 	src/tag/ReplayGain.cxx src/tag/ReplayGain.hxx \
 	src/tag/MixRamp.cxx src/tag/MixRamp.hxx \

NEWS

@@ -15,6 +15,7 @@ ver 0.20 (not yet released)
   - jack: reduce CPU usage
   - pulse: set channel map to WAVE-EX
   - recorder: record tags
+  - recorder: allow dynamic file names
 * mixer
   - null: new plugin
 * reset song priority on playback

doc/user.xml

@@ -3091,6 +3091,50 @@ buffer_size: 16384</programlisting>
                   Write to this file.
                 </entry>
               </row>
+
+              <row>
+                <entry>
+                  <varname>format_path</varname>
+                  <parameter>P</parameter>
+                </entry>
+                <entry>
+                  <para>
+                    An alternative to <varname>path</varname> which
+                    provides a format string referring to tag values.
+                    Every time a new song starts or a new tag gets
+                    received from a radio station, a new file is
+                    opened.  If the format does not render a file
+                    name, nothing is recorded.
+                  </para>
+
+                  <para>
+                    A tag name enclosed in percent signs ('%') is
+                    replaced with the tag value.  Example:
+                    <parameter>~/.mpd/recorder/%artist% -
+                    %title%.ogg</parameter>
+                  </para>
+
+                  <para>
+                    Square brackets can be used to group a substring.
+                    If none of the tags referred in the group can be
+                    found, the whole group is omitted.  Example:
+                    <parameter>[~/.mpd/recorder/[%artist% -
+                    ]%title%.ogg]</parameter> (this omits the dash
+                    when no artist tag exists; if title also doesn't
+                    exist, no file is written)
+                  </para>
+
+                  <para>
+                    The operators "|" (logical "or") and "&amp;"
+                    (logical "and") can be used to select portions of
+                    the format string depending on the existing tag
+                    values.  Example:
+                    <parameter>~/.mpd/recorder/[%title|%name%].ogg</parameter>
+                    (use the "name" tag if no title exists)
+                  </para>
+                </entry>
+              </row>
+
               <row>
                 <entry>
                   <varname>encoder</varname>

src/output/plugins/RecorderOutputPlugin.cxx

@@ -21,17 +21,23 @@
 #include "RecorderOutputPlugin.hxx"
 #include "../OutputAPI.hxx"
 #include "../Wrapper.hxx"
+#include "tag/Format.hxx"
 #include "encoder/ToOutputStream.hxx"
 #include "encoder/EncoderInterface.hxx"
 #include "encoder/EncoderPlugin.hxx"
 #include "encoder/EncoderList.hxx"
 #include "config/ConfigError.hxx"
+#include "config/ConfigPath.hxx"
 #include "Log.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "fs/io/FileOutputStream.hxx"
 #include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
+#include <stdlib.h>
+
+static constexpr Domain recorder_domain("recorder");
 
 class RecorderOutput {
 	friend struct AudioOutputWrapper<RecorderOutput>;
@@ -48,6 +54,18 @@ class RecorderOutput {
 	 */
 	AllocatedPath path;
 
+	/**
+	 * A string that will be used with FormatTag() to build the
+	 * destination path.
+	 */
+	std::string format_path;
+
+	/**
+	 * The #AudioFormat that is currently active.  This is used
+	 * for switching to another file.
+	 */
+	AudioFormat effective_audio_format;
+
 	/**
 	 * The destination file.
 	 */
@@ -84,10 +102,18 @@ class RecorderOutput {
 	size_t Play(const void *chunk, size_t size, Error &error);
 
 private:
+	gcc_pure
+	bool HasDynamicPath() const {
+		return !format_path.empty();
+	}
+
 	/**
 	 * Finish the encoder and commit the file.
 	 */
 	bool Commit(Error &error);
+
+	void FinishFormat();
+	bool ReopenFormat(AllocatedPath &&new_path, Error &error);
 };
 
 inline bool
@@ -105,9 +131,20 @@ RecorderOutput::Configure(const config_param &param, Error &error)
 	}
 
 	path = param.GetBlockPath("path", error);
-	if (path.IsNull()) {
-		if (!error.IsDefined())
-			error.Set(config_domain, "'path' not configured");
+	if (error.IsDefined())
+		return false;
+
+	const char *fmt = param.GetBlockValue("format_path", nullptr);
+	if (fmt != nullptr)
+		format_path = fmt;
+
+	if (path.IsNull() && fmt == nullptr) {
+		error.Set(config_domain, "'path' not configured");
+		return false;
+	}
+
+	if (!path.IsNull() && fmt != nullptr) {
+		error.Set(config_domain, "Cannot have both 'path' and 'format_path'");
 		return false;
 	}
 
@@ -152,9 +189,19 @@ RecorderOutput::Open(AudioFormat &audio_format, Error &error)
 {
 	/* create the output file */
 
-	file = FileOutputStream::Create(path, error);
-	if (file == nullptr)
-		return false;
+	if (!HasDynamicPath()) {
+		assert(!path.IsNull());
+
+		file = FileOutputStream::Create(path, error);
+		if (file == nullptr)
+			return false;
+	} else {
+		/* don't open the file just yet; wait until we have
+		   a tag that we can use to build the path */
+		assert(path.IsNull());
+
+		file = nullptr;
+	}
 
 	/* open the encoder */
 
@@ -163,10 +210,19 @@ RecorderOutput::Open(AudioFormat &audio_format, Error &error)
 		return false;
 	}
 
-	if (!EncoderToFile(error)) {
+	if (!HasDynamicPath()) {
+		if (!EncoderToFile(error)) {
+			encoder->Close();
+			delete file;
+			return false;
+		}
+	} else {
+		/* remember the AudioFormat for ReopenFormat() */
+		effective_audio_format = audio_format;
+
+		/* close the encoder for now; it will be opened as
+		   soon as we have received a tag */
 		encoder->Close();
-		delete file;
-		return false;
 	}
 
 	return true;
@@ -175,6 +231,8 @@ RecorderOutput::Open(AudioFormat &audio_format, Error &error)
 inline bool
 RecorderOutput::Commit(Error &error)
 {
+	assert(!path.IsNull());
+
 	/* flush the encoder and write the rest to the file */
 
 	bool success = encoder_end(encoder, error) &&
@@ -195,14 +253,108 @@ RecorderOutput::Commit(Error &error)
 inline void
 RecorderOutput::Close()
 {
+	if (file == nullptr) {
+		/* not currently encoding to a file; nothing needs to
+		   be done now */
+		assert(HasDynamicPath());
+		assert(path.IsNull());
+		return;
+	}
+
 	Error error;
 	if (!Commit(error))
 		LogError(error);
+
+	if (HasDynamicPath()) {
+		assert(!path.IsNull());
+		path.SetNull();
+	}
+}
+
+void
+RecorderOutput::FinishFormat()
+{
+	assert(HasDynamicPath());
+
+	if (file == nullptr)
+		return;
+
+	Error error;
+	if (!Commit(error))
+		LogError(error);
+
+	file = nullptr;
+	path.SetNull();
+}
+
+inline bool
+RecorderOutput::ReopenFormat(AllocatedPath &&new_path, Error &error)
+{
+	assert(HasDynamicPath());
+	assert(path.IsNull());
+	assert(file == nullptr);
+
+	FileOutputStream *new_file =
+		FileOutputStream::Create(new_path, error);
+	if (new_file == nullptr)
+		return false;
+
+	AudioFormat new_audio_format = effective_audio_format;
+	if (!encoder->Open(new_audio_format, error)) {
+		delete new_file;
+		return false;
+	}
+
+	/* reopening the encoder must always result in the same
+	   AudioFormat as before */
+	assert(new_audio_format == effective_audio_format);
+
+	if (!EncoderToOutputStream(*new_file, *encoder, error)) {
+		encoder->Close();
+		delete new_file;
+		return false;
+	}
+
+	path = std::move(new_path);
+	file = new_file;
+
+	FormatDebug(recorder_domain, "Recording to \"%s\"", path.c_str());
+
+	return true;
 }
 
 inline void
 RecorderOutput::SendTag(const Tag &tag)
 {
+	if (HasDynamicPath()) {
+		char *p = FormatTag(tag, format_path.c_str());
+		if (p == nullptr || *p == 0) {
+			/* no path could be composed with this tag:
+			   don't write a file */
+			free(p);
+			FinishFormat();
+			return;
+		}
+
+		Error error;
+		AllocatedPath new_path = ParsePath(p, error);
+		free(p);
+		if (new_path.IsNull()) {
+			LogError(error);
+			FinishFormat();
+			return;
+		}
+
+		if (new_path != path) {
+			FinishFormat();
+
+			if (!ReopenFormat(std::move(new_path), error)) {
+				LogError(error);
+				return;
+			}
+		}
+	}
+
 	Error error;
 	if (!encoder_pre_tag(encoder, error) ||
 	    !EncoderToFile(error) ||
@@ -213,6 +365,14 @@ RecorderOutput::SendTag(const Tag &tag)
 inline size_t
 RecorderOutput::Play(const void *chunk, size_t size, Error &error)
 {
+	if (file == nullptr) {
+		/* not currently encoding to a file; discard incoming
+		   data */
+		assert(HasDynamicPath());
+		assert(path.IsNull());
+		return size;
+	}
+
 	return encoder_write(encoder, chunk, size, error) &&
 		EncoderToFile(error)
 		? size : 0;

src/tag/Format.cxx

@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2003-2015 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Format.hxx"
+#include "Tag.hxx"
+#include "util/format.h"
+#include "util/StringUtil.hxx"
+
+#include <algorithm>
+
+#include <string.h>
+
+struct FormatTagContext {
+	const Tag &tag;
+
+	char buffer[256];
+
+	explicit FormatTagContext(const Tag &_tag):tag(_tag) {}
+};
+
+/**
+ * Is this a character unsafe to use in a path name segment?
+ */
+static constexpr bool
+IsUnsafeChar(char ch)
+{
+	return
+		/* disallow characters illegal in file names on
+		   Windows (Linux allows almost anything) */
+		ch == '\\' || ch == '/' || ch == ':' || ch == '*' ||
+		ch == '?' || ch == '<' || ch == '>' || ch == '|' ||
+		/* allow space, but disallow all other whitespace */
+		(unsigned char)ch < 0x20;
+}
+
+gcc_pure
+static bool
+HasUnsafeChar(const char *s)
+{
+	for (; *s; ++s)
+		if (IsUnsafeChar(*s))
+			return true;
+
+	return false;
+}
+
+static const char *
+SanitizeString(const char *s, char *buffer, size_t buffer_size)
+{
+	/* skip leading dots to avoid generating "../" sequences */
+	while (*s == '.')
+		++s;
+
+	if (!HasUnsafeChar(s))
+		return s;
+
+	char *end = CopyString(buffer, s, buffer_size);
+	std::replace_if(buffer, end, IsUnsafeChar, ' ');
+	return buffer;
+}
+
+gcc_pure gcc_nonnull_all
+static const char *
+TagGetter(const void *object, const char *name)
+{
+	const auto &_ctx = *(const FormatTagContext *)object;
+	auto &ctx = const_cast<FormatTagContext &>(_ctx);
+	const Tag &tag = ctx.tag;
+
+	TagType tag_type = tag_name_parse_i(name);
+	if (tag_type == TAG_NUM_OF_ITEM_TYPES)
+		/* unknown tag name */
+		return nullptr;
+
+	const char *value = tag.GetValue(tag_type);
+	if (value == nullptr)
+		/* known tag name, but not present in this object */
+		value = "";
+
+	// TODO: handle multiple tag values
+	return SanitizeString(value, ctx.buffer, sizeof(ctx.buffer));
+}
+
+char *
+FormatTag(const Tag &tag, const char *format)
+{
+	FormatTagContext ctx(tag);
+	return format_object(format, &ctx, TagGetter);
+}

src/tag/Format.hxx

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2003-2015 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_TAG_FORMAT_HXX
+#define MPD_TAG_FORMAT_HXX
+
+#include "check.h"
+#include "Compiler.h"
+
+struct Tag;
+
+gcc_malloc gcc_nonnull_all
+char *
+FormatTag(const Tag &tag, const char *format);
+
+#endif

src/util/format.c

@@ -0,0 +1,252 @@
+/*
+ * music player command (mpc)
+ * Copyright (C) 2003-2015 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "format.h"
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+/**
+ * Reallocate the given string and append the source string.
+ */
+gcc_malloc
+static char *
+string_append(char *dest, const char *src, size_t len)
+{
+	size_t destlen = dest != NULL
+		? strlen(dest)
+		: 0;
+
+	dest = realloc(dest, destlen + len + 1);
+	memcpy(dest + destlen, src, len);
+	dest[destlen + len] = '\0';
+
+	return dest;
+}
+
+/**
+ * Skip the format string until the current group is closed by either
+ * '&', '|' or ']' (supports nesting).
+ */
+gcc_pure
+static const char *
+skip_format(const char *p)
+{
+	unsigned stack = 0;
+
+	while (*p != '\0') {
+		if (*p == '[')
+			stack++;
+		else if (*p == '#' && p[1] != '\0')
+			/* skip escaped stuff */
+			++p;
+		else if (stack > 0) {
+			if (*p == ']')
+				--stack;
+		} else if (*p == '&' || *p == '|' || *p == ']')
+			break;
+
+		++p;
+	}
+
+	return p;
+}
+
+static char *
+format_object2(const char *format, const char **last, const void *object,
+	       const char *(*getter)(const void *object, const char *name))
+{
+	char *ret = NULL;
+	const char *p;
+	bool found = false;
+
+	for (p = format; *p != '\0';) {
+		switch (p[0]) {
+		case '|':
+			++p;
+			if (!found) {
+				/* nothing found yet: try the next
+				   section */
+				free(ret);
+				ret = NULL;
+			} else
+				/* already found a value: skip the
+				   next section */
+				p = skip_format(p);
+			break;
+
+		case '&':
+			++p;
+			if (!found)
+				/* nothing found yet, so skip this
+				   section */
+				p = skip_format(p);
+			else
+				/* we found something yet, but it will
+				   only be used if the next section
+				   also found something, so reset the
+				   flag */
+				found = false;
+			break;
+
+		case '[': {
+			char *t = format_object2(p + 1, &p, object, getter);
+			if (t != NULL) {
+				ret = string_append(ret, t, strlen(t));
+				free(t);
+				found = true;
+			}
+		}
+			break;
+
+		case ']':
+			if (last != NULL)
+				*last = p + 1;
+			if (!found) {
+				free(ret);
+				ret = NULL;
+			}
+			return ret;
+
+		case '\\': {
+			/* take care of escape sequences */
+			char ltemp;
+			switch (p[1]) {
+			case 'a':
+				ltemp = '\a';
+				break;
+
+			case 'b':
+				ltemp = '\b';
+				break;
+
+			case 't':
+				ltemp = '\t';
+				break;
+
+			case 'n':
+				ltemp = '\n';
+				break;
+
+			case 'v':
+				ltemp = '\v';
+				break;
+
+			case 'f':
+				ltemp = '\f';
+				break;
+
+			case 'r':
+				ltemp = '\r';
+				break;
+
+			case '[':
+			case ']':
+				ltemp = p[1];
+				break;
+
+			default:
+				/* unknown escape: copy the
+				   backslash */
+				ltemp = p[0];
+				--p;
+				break;
+			}
+
+			ret = string_append(ret, &ltemp, 1);
+			p += 2;
+		}
+			break;
+
+		case '%': {
+			/* find the extent of this format specifier
+			   (stop at \0, ' ', or esc) */
+			const char *end = p + 1;
+			while (*end >= 'a' && *end <= 'z')
+				++end;
+
+			const size_t length = end - p + 1;
+
+			if (*end != '%') {
+				ret = string_append(ret, p, length - 1);
+				p = end;
+				continue;
+			}
+
+			char name[32];
+			if (length > (int)sizeof(name)) {
+				ret = string_append(ret, p, length);
+				p = end + 1;
+				continue;
+			}
+
+			memcpy(name, p + 1, length - 2);
+			name[length - 2] = 0;
+
+			const char *value = getter(object, name);
+			size_t value_length;
+			if (value != NULL) {
+				if (*value != 0)
+					found = true;
+				value_length = strlen(value);
+			} else {
+				/* unknown variable: copy verbatim
+				   from format string */
+				value = p;
+				value_length = length;
+			}
+
+			ret = string_append(ret, value, value_length);
+
+			/* advance past the specifier */
+			p = end + 1;
+		}
+			break;
+
+		case '#':
+			/* let the escape character escape itself */
+			if (p[1] != '\0') {
+				ret = string_append(ret, p + 1, 1);
+				p += 2;
+				break;
+			}
+
+			/* fall through */
+
+		default:
+			/* pass-through non-escaped portions of the format string */
+			ret = string_append(ret, p, 1);
+			++p;
+		}
+	}
+
+	if (last != NULL)
+		*last = p;
+	return ret;
+}
+
+char *
+format_object(const char *format, const void *object,
+	      const char *(*getter)(const void *object, const char *name))
+{
+	return format_object2(format, NULL, object, getter);
+}

src/util/format.h

@@ -0,0 +1,51 @@
+/*
+ * music player command (mpc)
+ * Copyright (C) 2003-2015 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPC_FORMAT_H
+#define MPC_FORMAT_H
+
+#include "Compiler.h"
+
+struct mpd_song;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Pretty-print an object into a string using the given format
+ * specification.
+ *
+ * @param format the format string
+ * @param object the object
+ * @param getter a getter function that extracts a value from the object
+ * @return the resulting string to be freed by free(); NULL if
+ * no format string group produced any output
+ */
+gcc_malloc
+char *
+format_object(const char *format, const void *object,
+	      const char *(*getter)(const void *object, const char *name));
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif