sim: Refactor the serialization base class

Objects that are can be serialized are supposed to inherit from the
Serializable class. This class is meant to provide a unified API for
such objects. However, so far it has mainly been used by SimObjects
due to some fundamental design limitations. This changeset redesigns
to the serialization interface to make it more generic and hide the
underlying checkpoint storage. Specifically:

  * Add a set of APIs to serialize into a subsection of the current
    object. Previously, objects that needed this functionality would
    use ad-hoc solutions using nameOut() and section name
    generation. In the new world, an object that implements the
    interface has the methods serializeSection() and
    unserializeSection() that serialize into a named /subsection/ of
    the current object. Calling serialize() serializes an object into
    the current section.

  * Move the name() method from Serializable to SimObject as it is no
    longer needed for serialization. The fully qualified section name
    is generated by the main serialization code on the fly as objects
    serialize sub-objects.

  * Add a scoped ScopedCheckpointSection helper class. Some objects
    need to serialize data structures, that are not deriving from
    Serializable, into subsections. Previously, this was done using
    nameOut() and manual section name generation. To simplify this,
    this changeset introduces a ScopedCheckpointSection() helper
    class. When this class is instantiated, it adds a new /subsection/
    and subsequent serialization calls during the lifetime of this
    helper class happen inside this section (or a subsection in case
    of nested sections).

  * The serialize() call is now const which prevents accidental state
    manipulation during serialization. Objects that rely on modifying
    state can use the serializeOld() call instead. The default
    implementation simply calls serialize(). Note: The old-style calls
    need to be explicitly called using the
    serializeOld()/serializeSectionOld() style APIs. These are used by
    default when serializing SimObjects.

  * Both the input and output checkpoints now use their own named
    types. This hides underlying checkpoint implementation from
    objects that need checkpointing and makes it easier to change the
    underlying checkpoint storage code.

1 files changed, 156 insertions, 114 deletions

diff --git a/src/sim/serialize.cc b/src/sim/serialize.cc
index 99426b5a6..a7c1834cf 100644
--- a/src/sim/serialize.cc
+++ b/src/sim/serialize.cc
@@ -1,4 +1,16 @@
 /*
+ * Copyright (c) 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
  * Copyright (c) 2002-2005 The Regents of The University of Michigan
  * Copyright (c) 2013 Advanced Micro Devices, Inc.
  * Copyright (c) 2013 Mark D. Hill and David A. Wood
@@ -30,6 +42,7 @@
  * Authors: Nathan Binkert
  *          Erik Hallnor
  *          Steve Reinhardt
+ *          Andreas Sandberg
  */
 
 #include <sys/stat.h>
@@ -47,6 +60,7 @@
 #include "base/output.hh"
 #include "base/str.hh"
 #include "base/trace.hh"
+#include "debug/Checkpoint.hh"
 #include "sim/eventq.hh"
 #include "sim/serialize.hh"
 #include "sim/sim_events.hh"
@@ -71,7 +85,7 @@ parseParam(const string &s, T &value)
 
 template <class T>
 void
-showParam(ostream &os, const T &value)
+showParam(CheckpointOut &os, const T &value)
 {
     os << value;
 }
@@ -87,7 +101,7 @@ showParam(ostream &os, const T &value)
 // Treat 8-bit ints (chars) as ints on output, not as chars
 template <>
 void
-showParam(ostream &os, const char &value)
+showParam(CheckpointOut &os, const char &value)
 {
     os << (int)value;
 }
@@ -95,7 +109,7 @@ showParam(ostream &os, const char &value)
 
 template <>
 void
-showParam(ostream &os, const signed char &value)
+showParam(CheckpointOut &os, const signed char &value)
 {
     os << (int)value;
 }
@@ -103,7 +117,7 @@ showParam(ostream &os, const signed char &value)
 
 template <>
 void
-showParam(ostream &os, const unsigned char &value)
+showParam(CheckpointOut &os, const unsigned char &value)
 {
     os << (unsigned int)value;
 }
@@ -133,7 +147,7 @@ parseParam(const string &s, bool &value)
 // Display bools as strings
 template <>
 void
-showParam(ostream &os, const bool &value)
+showParam(CheckpointOut &os, const bool &value)
 {
     os << (value ? "true" : "false");
 }
@@ -151,22 +165,11 @@ parseParam(const string &s, string &value)
 int Serializable::ckptMaxCount = 0;
 int Serializable::ckptCount = 0;
 int Serializable::ckptPrevCount = -1;
-
-void
-Serializable::nameOut(ostream &os)
-{
-    os << "\n[" << name() << "]\n";
-}
-
-void
-Serializable::nameOut(ostream &os, const string &_name)
-{
-    os << "\n[" << _name << "]\n";
-}
+std::stack<std::string> Serializable::path;
 
 template <class T>
 void
-paramOut(ostream &os, const string &name, const T &param)
+paramOut(CheckpointOut &os, const string &name, const T &param)
 {
     os << name << "=";
     showParam(os, param);
@@ -175,7 +178,7 @@ paramOut(ostream &os, const string &name, const T &param)
 
 template <class T>
 void
-arrayParamOut(ostream &os, const string &name, const vector<T> &param)
+arrayParamOut(CheckpointOut &os, const string &name, const vector<T> &param)
 {
     typename vector<T>::size_type size = param.size();
     os << name << "=";
@@ -190,7 +193,7 @@ arrayParamOut(ostream &os, const string &name, const vector<T> &param)
 
 template <class T>
 void
-arrayParamOut(ostream &os, const string &name, const list<T> &param)
+arrayParamOut(CheckpointOut &os, const string &name, const list<T> &param)
 {
     typename list<T>::const_iterator it = param.begin();
 
@@ -208,20 +211,22 @@ arrayParamOut(ostream &os, const string &name, const list<T> &param)
 
 template <class T>
 void
-paramIn(Checkpoint *cp, const string &section, const string &name, T &param)
+paramIn(CheckpointIn &cp, const string &name, T &param)
 {
+    const string &section(Serializable::currentSection());
     string str;
-    if (!cp->find(section, name, str) || !parseParam(str, param)) {
+    if (!cp.find(section, name, str) || !parseParam(str, param)) {
         fatal("Can't unserialize '%s:%s'\n", section, name);
     }
 }
 
 template <class T>
 bool
-optParamIn(Checkpoint *cp, const string &section, const string &name, T &param)
+optParamIn(CheckpointIn &cp, const string &name, T &param)
 {
+    const string &section(Serializable::currentSection());
     string str;
-    if (!cp->find(section, name, str) || !parseParam(str, param)) {
+    if (!cp.find(section, name, str) || !parseParam(str, param)) {
         warn("optional parameter %s:%s not present\n", section, name);
         return false;
     } else {
@@ -231,7 +236,8 @@ optParamIn(Checkpoint *cp, const string &section, const string &name, T &param)
 
 template <class T>
 void
-arrayParamOut(ostream &os, const string &name, const T *param, unsigned size)
+arrayParamOut(CheckpointOut &os, const string &name,
+              const T *param, unsigned size)
 {
     os << name << "=";
     if (size > 0)
@@ -246,11 +252,11 @@ arrayParamOut(ostream &os, const string &name, const T *param, unsigned size)
 
 template <class T>
 void
-arrayParamIn(Checkpoint *cp, const string &section, const string &name,
-             T *param, unsigned size)
+arrayParamIn(CheckpointIn &cp, const string &name, T *param, unsigned size)
 {
+    const string &section(Serializable::currentSection());
     string str;
-    if (!cp->find(section, name, str)) {
+    if (!cp.find(section, name, str)) {
         fatal("Can't unserialize '%s:%s'\n", section, name);
     }
 
@@ -273,7 +279,7 @@ arrayParamIn(Checkpoint *cp, const string &section, const string &name,
         // for which operator[] returns a special reference class
         // that's not the same as 'bool&', (since it's a packed
         // vector)
-        T scalar_value = 0;
+        T scalar_value;
         if (!parseParam(tokens[i], scalar_value)) {
             string err("could not parse \"");
 
@@ -290,11 +296,11 @@ arrayParamIn(Checkpoint *cp, const string &section, const string &name,
 
 template <class T>
 void
-arrayParamIn(Checkpoint *cp, const string &section,
-             const string &name, vector<T> &param)
+arrayParamIn(CheckpointIn &cp, const string &name, vector<T> &param)
 {
+    const string &section(Serializable::currentSection());
     string str;
-    if (!cp->find(section, name, str)) {
+    if (!cp.find(section, name, str)) {
         fatal("Can't unserialize '%s:%s'\n", section, name);
     }
 
@@ -315,7 +321,7 @@ arrayParamIn(Checkpoint *cp, const string &section,
         // for which operator[] returns a special reference class
         // that's not the same as 'bool&', (since it's a packed
         // vector)
-        T scalar_value = 0;
+        T scalar_value;
         if (!parseParam(tokens[i], scalar_value)) {
             string err("could not parse \"");
 
@@ -332,11 +338,11 @@ arrayParamIn(Checkpoint *cp, const string &section,
 
 template <class T>
 void
-arrayParamIn(Checkpoint *cp, const string &section,
-             const string &name, list<T> &param)
+arrayParamIn(CheckpointIn &cp, const string &name, list<T> &param)
 {
+    const string &section(Serializable::currentSection());
     string str;
-    if (!cp->find(section, name, str)) {
+    if (!cp.find(section, name, str)) {
         fatal("Can't unserialize '%s:%s'\n", section, name);
     }
     param.clear();
@@ -345,7 +351,7 @@ arrayParamIn(Checkpoint *cp, const string &section,
     tokenize(tokens, str, ' ');
 
     for (vector<string>::size_type i = 0; i < tokens.size(); i++) {
-        T scalar_value = 0;
+        T scalar_value;
         if (!parseParam(tokens[i], scalar_value)) {
             string err("could not parse \"");
 
@@ -362,42 +368,40 @@ arrayParamIn(Checkpoint *cp, const string &section,
 
 
 void
-objParamIn(Checkpoint *cp, const string &section,
-           const string &name, SimObject * &param)
+objParamIn(CheckpointIn &cp, const string &name, SimObject * &param)
 {
-    if (!cp->findObj(section, name, param)) {
+    const string &section(Serializable::currentSection());
+    if (!cp.findObj(section, name, param)) {
         fatal("Can't unserialize '%s:%s'\n", section, name);
     }
 }
 
 
 #define INSTANTIATE_PARAM_TEMPLATES(type)                               \
-template void                                                           \
-paramOut(ostream &os, const string &name, type const &param);           \
-template void                                                           \
-paramIn(Checkpoint *cp, const string &section,                          \
-        const string &name, type & param);                              \
-template bool                                                           \
-optParamIn(Checkpoint *cp, const string &section,                       \
-        const string &name, type & param);                              \
-template void                                                           \
-arrayParamOut(ostream &os, const string &name,                          \
-              type const *param, unsigned size);                        \
-template void                                                           \
-arrayParamIn(Checkpoint *cp, const string &section,                     \
-             const string &name, type *param, unsigned size);           \
-template void                                                           \
-arrayParamOut(ostream &os, const string &name,                          \
-              const vector<type> &param);                               \
-template void                                                           \
-arrayParamIn(Checkpoint *cp, const string &section,                     \
-             const string &name, vector<type> &param);                  \
-template void                                                           \
-arrayParamOut(ostream &os, const string &name,                          \
-              const list<type> &param);                                 \
-template void                                                           \
-arrayParamIn(Checkpoint *cp, const string &section,                     \
-             const string &name, list<type> &param);
+    template void                                                       \
+    paramOut(CheckpointOut &os, const string &name, type const &param); \
+    template void                                                       \
+    paramIn(CheckpointIn &cp, const string &name, type & param);        \
+    template bool                                                       \
+    optParamIn(CheckpointIn &cp, const string &name, type & param);     \
+    template void                                                       \
+    arrayParamOut(CheckpointOut &os, const string &name,                \
+                  type const *param, unsigned size);                    \
+    template void                                                       \
+    arrayParamIn(CheckpointIn &cp, const string &name,                  \
+                 type *param, unsigned size);                           \
+    template void                                                       \
+    arrayParamOut(CheckpointOut &os, const string &name,                \
+                  const vector<type> &param);                           \
+    template void                                                       \
+    arrayParamIn(CheckpointIn &cp, const string &name,                  \
+                 vector<type> &param);                                  \
+    template void                                                       \
+    arrayParamOut(CheckpointOut &os, const string &name,                \
+                  const list<type> &param);                             \
+    template void                                                       \
+    arrayParamIn(CheckpointIn &cp, const string &name,                  \
+                 list<type> &param);
 
 INSTANTIATE_PARAM_TEMPLATES(char)
 INSTANTIATE_PARAM_TEMPLATES(signed char)
@@ -423,45 +427,31 @@ INSTANTIATE_PARAM_TEMPLATES(string)
 class Globals : public Serializable
 {
   public:
-    const string name() const;
-    void serialize(ostream &os);
-    void unserialize(Checkpoint *cp, const std::string &section);
+    Globals()
+        : unserializedCurTick(0) {}
+
+    void serialize(CheckpointOut &cp) const M5_ATTR_OVERRIDE;
+    void unserialize(CheckpointIn &cp) M5_ATTR_OVERRIDE;
+
+    Tick unserializedCurTick;
 };
 
 /// The one and only instance of the Globals class.
 Globals globals;
 
-const string
-Globals::name() const
-{
-    return "Globals";
-}
-
 void
-Globals::serialize(ostream &os)
+Globals::serialize(CheckpointOut &cp) const
 {
-    nameOut(os);
-    paramOut(os, "curTick", curTick());
+    paramOut(cp, "curTick", curTick());
+    paramOut(cp, "numMainEventQueues", numMainEventQueues);
 
-    paramOut(os, "numMainEventQueues", numMainEventQueues);
-
-    for (uint32_t i = 0; i < numMainEventQueues; ++i) {
-        nameOut(os, "MainEventQueue");
-        mainEventQueue[i]->serialize(os);
-    }
 }
 
 void
-Globals::unserialize(Checkpoint *cp, const std::string &section)
+Globals::unserialize(CheckpointIn &cp)
 {
-    Tick tick;
-    paramIn(cp, section, "curTick", tick);
-    paramIn(cp, section, "numMainEventQueues", numMainEventQueues);
-
-    for (uint32_t i = 0; i < numMainEventQueues; ++i) {
-        mainEventQueue[i]->setCurTick(tick);
-        mainEventQueue[i]->unserialize(cp, "MainEventQueue");
-    }
+    paramIn(cp, "curTick", unserializedCurTick);
+    paramIn(cp, "numMainEventQueues", numMainEventQueues);
 }
 
 Serializable::Serializable()
@@ -473,37 +463,82 @@ Serializable::~Serializable()
 }
 
 void
-Serializable::serialize(ostream &os)
+Serializable::serializeSection(CheckpointOut &cp, const char *name) const
 {
+    Serializable::ScopedCheckpointSection sec(cp, name);
+    serialize(cp);
 }
 
 void
-Serializable::unserialize(Checkpoint *cp, const string &section)
+Serializable::serializeSectionOld(CheckpointOut &cp, const char *name)
 {
+    Serializable::ScopedCheckpointSection sec(cp, name);
+    serializeOld(cp);
+}
+
+void
+Serializable::unserializeSection(CheckpointIn &cp, const char *name)
+{
+    Serializable::ScopedCheckpointSection sec(cp, name);
+    unserialize(cp);
 }
 
 void
 Serializable::serializeAll(const string &cpt_dir)
 {
-    string dir = Checkpoint::setDir(cpt_dir);
+    string dir = CheckpointIn::setDir(cpt_dir);
     if (mkdir(dir.c_str(), 0775) == -1 && errno != EEXIST)
             fatal("couldn't mkdir %s\n", dir);
 
-    string cpt_file = dir + Checkpoint::baseFilename;
+    string cpt_file = dir + CheckpointIn::baseFilename;
     ofstream outstream(cpt_file.c_str());
     time_t t = time(NULL);
     if (!outstream.is_open())
         fatal("Unable to open file %s for writing\n", cpt_file.c_str());
     outstream << "## checkpoint generated: " << ctime(&t);
 
-    globals.serialize(outstream);
+    globals.serializeSection(outstream, "Globals");
+    for (uint32_t i = 0; i < numMainEventQueues; ++i)
+        mainEventQueue[i]->serializeSection(outstream, "MainEventQueue");
+
     SimObject::serializeAll(outstream);
 }
 
 void
-Serializable::unserializeGlobals(Checkpoint *cp)
+Serializable::unserializeGlobals(CheckpointIn &cp)
+{
+    globals.unserializeSection(cp, "Globals");
+
+    for (uint32_t i = 0; i < numMainEventQueues; ++i) {
+        mainEventQueue[i]->setCurTick(globals.unserializedCurTick);
+        mainEventQueue[i]->unserializeSection(cp, "MainEventQueue");
+    }
+}
+
+Serializable::ScopedCheckpointSection::~ScopedCheckpointSection()
+{
+    assert(!path.empty());
+    DPRINTF(Checkpoint, "Popping: %s\n", path.top());
+    path.pop();
+}
+
+void
+Serializable::ScopedCheckpointSection::pushName(const char *obj_name)
 {
-  globals.unserialize(cp, globals.name());
+    if (path.empty()) {
+        path.push(obj_name);
+    } else {
+        path.push(csprintf("%s.%s", path.top(), obj_name));
+    }
+    DPRINTF(Checkpoint, "ScopedCheckpointSection::pushName: %s\n", obj_name);
+}
+
+void
+Serializable::ScopedCheckpointSection::nameOut(CheckpointOut &cp)
+{
+    DPRINTF(Checkpoint, "ScopedCheckpointSection::nameOut: %s\n",
+            Serializable::currentSection());
+    cp << "\n[" << Serializable::currentSection() << "]\n";
 }
 
 void
@@ -542,11 +577,11 @@ SerializableClass::SerializableClass(const string &className,
 //
 //
 Serializable *
-SerializableClass::createObject(Checkpoint *cp, const string &section)
+SerializableClass::createObject(CheckpointIn &cp, const string &section)
 {
     string className;
 
-    if (!cp->find(section, "type", className)) {
+    if (!cp.find(section, "type", className)) {
         fatal("Serializable::create: no 'type' entry in section '%s'.\n",
               section);
     }
@@ -565,22 +600,29 @@ SerializableClass::createObject(Checkpoint *cp, const string &section)
     return object;
 }
 
+const std::string &
+Serializable::currentSection()
+{
+    assert(!path.empty());
+
+    return path.top();
+}
 
 Serializable *
-Serializable::create(Checkpoint *cp, const string &section)
+Serializable::create(CheckpointIn &cp, const string &section)
 {
     Serializable *object = SerializableClass::createObject(cp, section);
-    object->unserialize(cp, section);
+    object->unserializeSection(cp, section);
     return object;
 }
 
 
-const char *Checkpoint::baseFilename = "m5.cpt";
+const char *CheckpointIn::baseFilename = "m5.cpt";
 
-string Checkpoint::currentDirectory;
+string CheckpointIn::currentDirectory;
 
 string
-Checkpoint::setDir(const string &name)
+CheckpointIn::setDir(const string &name)
 {
     // use csprintf to insert curTick() into directory name if it
     // appears to have a format placeholder in it.
@@ -592,35 +634,35 @@ Checkpoint::setDir(const string &name)
 }
 
 string
-Checkpoint::dir()
+CheckpointIn::dir()
 {
     return currentDirectory;
 }
 
 
-Checkpoint::Checkpoint(const string &cpt_dir, SimObjectResolver &resolver)
+CheckpointIn::CheckpointIn(const string &cpt_dir, SimObjectResolver &resolver)
     : db(new IniFile), objNameResolver(resolver), cptDir(setDir(cpt_dir))
 {
-    string filename = cptDir + "/" + Checkpoint::baseFilename;
+    string filename = cptDir + "/" + CheckpointIn::baseFilename;
     if (!db->load(filename)) {
         fatal("Can't load checkpoint file '%s'\n", filename);
     }
 }
 
-Checkpoint::~Checkpoint()
+CheckpointIn::~CheckpointIn()
 {
     delete db;
 }
 
 bool
-Checkpoint::find(const string &section, const string &entry, string &value)
+CheckpointIn::find(const string &section, const string &entry, string &value)
 {
     return db->find(section, entry, value);
 }
 
 
 bool
-Checkpoint::findObj(const string &section, const string &entry,
+CheckpointIn::findObj(const string &section, const string &entry,
                     SimObject *&value)
 {
     string path;
@@ -634,7 +676,7 @@ Checkpoint::findObj(const string &section, const string &entry,
 
 
 bool
-Checkpoint::sectionExists(const string &section)
+CheckpointIn::sectionExists(const string &section)
 {
     return db->sectionExists(section);
 }