[thin_dump] --format custom=<shared lib>

Allow people to use their own emitters held in a shared library.

Put a trivial emitter in contrib/ as an example.

Makefile.in

@@ -91,6 +91,7 @@ SOURCE=\
 	thin-provisioning/restore_emitter.cc \
 	thin-provisioning/rmap_visitor.cc \
 	thin-provisioning/superblock.cc \
+	thin-provisioning/shared_library_emitter.cc \
 	thin-provisioning/thin_check.cc \
 	thin-provisioning/thin_delta.cc \
 	thin-provisioning/thin_dump.cc \
@@ -123,9 +124,9 @@ STRIP:=@STRIP@
 OBJECTS:=$(subst .cc,.o,$(SOURCE))
 TOP_DIR:=@top_srcdir@
 TOP_BUILDDIR:=@top_builddir@
-CFLAGS+=-g -Wall -O3
+CFLAGS+=-g -Wall -O3 -fPIC
 CFLAGS+=@LFS_FLAGS@
-CXXFLAGS+=-g -Wall -fno-strict-aliasing -std=c++11
+CXXFLAGS+=-g -Wall -fPIC -fno-strict-aliasing -std=c++11
 
 ifeq ("@DEVTOOLS@", "yes")
 CXXFLAGS+=-DDEV_TOOLS
@@ -260,6 +261,7 @@ endif
 
 ifeq ("@TESTING@", "yes")
 include unit-tests/Makefile
+include contrib/Makefile
 
 .PHONEY: features
 

configure.ac

@@ -188,6 +188,7 @@ dnl -- First and last lines should not contain files to generate in order to
 dnl -- keep utility scripts running properly
 AC_CONFIG_FILES([
 Makefile
+contrib/Makefile
 unit-tests/Makefile
 version.h
 ])

contrib/Makefile.in

@@ -0,0 +1,7 @@
+contrib: contrib/thin_sexp_emitter.so
+
+contrib/thin_sexp_emitter.so: contrib/thin_sexp_emitter.o
+	$(V)echo "    [LD] $@"
+	$(V)$(CC) -shared -Wl,-soname,thin_sexp_emitter.so -o contrib/thin_sexp_emitter.so contrib/thin_sexp_emitter.o
+
+

contrib/thin_sexp_emitter.cc

@@ -0,0 +1,120 @@
+#include "base/indented_stream.h"
+#include "thin-provisioning/emitter.h"
+
+using namespace std;
+using namespace thin_provisioning;
+
+//----------------------------------------------------------------
+
+namespace {
+	class sexp_emitter : public emitter {
+	public:
+		sexp_emitter(ostream &out)
+		: out_(out) {
+		}
+
+		virtual void begin_superblock(std::string const &uuid,
+					      uint64_t time,
+					      uint64_t trans_id,
+					      boost::optional<uint32_t> flags,
+					      boost::optional<uint32_t> version,
+					      uint32_t data_block_size,
+					      uint64_t nr_data_blocks,
+					      boost::optional<uint64_t> metadata_snap) {
+			open("superblock");
+			out_.indent();
+			out_ << "((uuid \"" << uuid << "\")\n";
+			kv("time", time);
+			kv("trans_id", trans_id);
+			kv("flags", flags);
+			kv("version", version);
+			kv("data_block_size", data_block_size);
+			kv("nr_data_blocks", nr_data_blocks);
+			kv("metadata_snap", metadata_snap);
+			out_.indent();
+			out_ << ")\n";
+		}
+
+		virtual void end_superblock() {
+			close();
+		}
+
+		virtual void begin_device(uint32_t dev_id,
+					  uint64_t mapped_blocks,
+					  uint64_t trans_id,
+					  uint64_t creation_time,
+					  uint64_t snap_time) {
+			open("device");
+			out_.indent();
+			out_ << "((dev_id " << dev_id << ")\n";
+			kv("mapped_blocks", mapped_blocks);
+			kv("trans_id", trans_id);
+			kv("creation_time", creation_time);
+			kv("snap_time", snap_time);
+			out_.indent();
+			out_ << ")\n";
+		}
+
+		virtual void end_device() {
+			close();
+		}
+
+		virtual void begin_named_mapping(std::string const &name) {
+
+		}
+
+		virtual void end_named_mapping() {
+
+		}
+
+		virtual void identifier(std::string const &name) {
+
+		}
+
+		virtual void range_map(uint64_t origin_begin, uint64_t data_begin, uint32_t time, uint64_t len) {
+			out_.indent();
+			out_ << "(range (origin_begin " << origin_begin
+			     << ") (data_begin " << data_begin
+			     << ") (time " << time
+			     << ") (len " << len << "))\n";
+		}
+
+		virtual void single_map(uint64_t origin_block, uint64_t data_block, uint32_t time) {
+			out_.indent();
+			out_ << "(single (origin_block " << origin_block
+			     << ") (data_block " << data_block
+			     << ") (time " << time << "))\n";
+		}
+
+	private:
+		void open(char const *tag) {
+			out_.indent();
+			out_ << "(" << tag << "\n";
+			out_.inc();
+		}
+
+		void close() {
+			out_.dec();
+			out_.indent();
+			out_ << ")\n";
+		}
+
+		template <typename T>
+		void kv(char const *k, T const &v) {
+			out_.indent();
+			out_ << " (" << k << " " << v << ")\n";
+		}
+
+		indented_stream out_;
+	};
+}
+
+//----------------------------------------------------------------
+
+extern "C" {
+	emitter::ptr create_emitter(ostream &out) {
+		return emitter::ptr(new sexp_emitter(out));
+	}
+}
+
+//----------------------------------------------------------------

man8/thin_dump.8

@@ -26,8 +26,13 @@ in order to put it back onto a metadata
 
 This tool cannot be run on live metadata unless the \fB\-\-metadata\-snap\fP option is used.
 
-.IP "\fB\-f, \-\-format\fP \fI{xml|human_readable}\fP".
+.IP "\fB\-f, \-\-format\fP \fI{xml|human_readable|custom}\fP".
-Print output in XML or human readable format.
+
+Print output in XML or human readable format.  Custom formats are
+supported via shared library plugins.  They should be specified as in
+this example:
+.sp
+.B thin_dump --format custom=mylib.so /dev/sda
 
 .IP "\fB\-r, \-\-repair\fP".
 Repair the metadata whilst dumping it.

thin-provisioning/shared_library_emitter.cc

@@ -0,0 +1,29 @@
+#include "thin-provisioning/shared_library_emitter.h"
+
+#include <dlfcn.h>
+#include <stdexcept>
+
+using namespace std;
+using namespace thin_provisioning;
+
+//----------------------------------------------------------------
+
+emitter::ptr
+thin_provisioning::create_custom_emitter(string const &shared_lib, ostream &out)
+{
+	emitter::ptr (*create_fn)(ostream &out);
+	void *handle = dlopen(shared_lib.c_str(), RTLD_LAZY);
+	if (!handle)
+		throw runtime_error(dlerror());
+
+	dlerror();    // Clear any existing error
+	create_fn = reinterpret_cast<emitter::ptr (*)(ostream &)>(dlsym(handle, "create_emitter"));
+
+	char *error = dlerror();
+	if (error)
+		throw runtime_error(error);
+
+	return create_fn(out);
+}
+
+//----------------------------------------------------------------

thin-provisioning/shared_library_emitter.h

@@ -0,0 +1,14 @@
+#ifndef THIN_PROVISIONING_SHARED_LIBRARY_EMITTER_H
+#define THIN_PROVISIONING_SHARED_LIBRARY_EMITTER_H
+
+#include "thin-provisioning/emitter.h"
+
+//----------------------------------------------------------------
+
+namespace thin_provisioning {
+	emitter::ptr create_custom_emitter(std::string const &shared_lib, std::ostream &out);
+}
+
+//----------------------------------------------------------------
+
+#endif

thin-provisioning/thin_dump.cc

@@ -21,13 +21,14 @@
 #include <getopt.h>
 #include <libgen.h>
 
-#include "human_readable_format.h"
-#include "metadata_dumper.h"
-#include "metadata.h"
-#include "xml_format.h"
-#include "version.h"
-#include "thin-provisioning/commands.h"
 #include "persistent-data/file_utils.h"
+#include "thin-provisioning/commands.h"
+#include "thin-provisioning/human_readable_format.h"
+#include "thin-provisioning/metadata.h"
+#include "thin-provisioning/metadata_dumper.h"
+#include "thin-provisioning/shared_library_emitter.h"
+#include "thin-provisioning/xml_format.h"
+#include "version.h"
 
 using namespace boost;
 using namespace persistent_data;
@@ -56,6 +57,10 @@ namespace {
 		return md;
 	}
 
+	bool begins_with(string const &str, string const &prefix) {
+		return str.substr(0, prefix.length()) == prefix;
+	}
+
 	emitter::ptr create_emitter(string const &format, ostream &out) {
 		emitter::ptr e;
 
@@ -65,9 +70,13 @@ namespace {
 		else if (format == "human_readable")
 			e = create_human_readable_emitter(out);
 
+		else if (begins_with(format, "custom="))
+			e = create_custom_emitter(format.substr(7), out);
+
 		else {
-			cerr << "unknown format '" << format << "'" << endl;
+			ostringstream msg;
-			exit(1);
+			msg << "unknown format '" << format << "'";
+			throw runtime_error(msg.str());
 		}
 
 		return e;