// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- 
// vim: ts=8 sw=2 smarttab
/*
 * Ceph - scalable distributed file system
 *
 * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
 *
 * This is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 2.1, as published by the Free Software 
 * Foundation.  See file COPYING.
 * 
 */
#ifndef CEPH_ENCODING_H
#define CEPH_ENCODING_H

#include "include/int_types.h"

#include "include/memory.h"

#include "byteorder.h"
#include "buffer.h"
#include "assert.h"

using namespace ceph;

/*
 * Notes on feature encoding:
 *
 * - The default encode() methods have a features argument with a default parameter
 *   (which goes to zero).
 * - Normal classes will use WRITE_CLASS_ENCODER, with that features=0 default.
 * - Classes that _require_ features will use WRITE_CLASS_ENCODER_FEATURES, which
 *   does not define the default.  Any caller must explicitly pass it in.
 * - STL container macros have two encode variants: one with a features arg, and one
 *   without.
 *
 * The result:
 * - A feature encode() method will fail to compile if a value is not
 *   passed in.
 * - The feature varianet of the STL templates will be used when the feature arg is
 *   provided.  It will be passed through to any template arg types, but it will be
 *   ignored when not needed.
 */

// --------------------------------------
// base types

template<class T>
inline void encode_raw(const T& t, bufferlist& bl)
{
  bl.append((char*)&t, sizeof(t));
}
template<class T>
inline void decode_raw(T& t, bufferlist::iterator &p)
{
  p.copy(sizeof(t), (char*)&t);
}

#define WRITE_RAW_ENCODER(type)						\
  inline void encode(const type &v, bufferlist& bl, uint64_t features=0) { encode_raw(v, bl); } \
  inline void decode(type &v, bufferlist::iterator& p) { __ASSERT_FUNCTION decode_raw(v, p); }

WRITE_RAW_ENCODER(__u8)
#ifndef _CHAR_IS_SIGNED
WRITE_RAW_ENCODER(__s8)
#endif
WRITE_RAW_ENCODER(char)
WRITE_RAW_ENCODER(ceph_le64)
WRITE_RAW_ENCODER(ceph_le32)
WRITE_RAW_ENCODER(ceph_le16)

// FIXME: we need to choose some portable floating point encoding here
WRITE_RAW_ENCODER(float)
WRITE_RAW_ENCODER(double)

inline void encode(const bool &v, bufferlist& bl) {
  __u8 vv = v;
  encode_raw(vv, bl);
}
inline void decode(bool &v, bufferlist::iterator& p) {
  __u8 vv;
  decode_raw(vv, p);
  v = vv;
}


// -----------------------------------
// int types

#define WRITE_INTTYPE_ENCODER(type, etype)				\
  inline void encode(type v, bufferlist& bl, uint64_t features=0) {	\
    ceph_##etype e;					                \
    e = v;                                                              \
    encode_raw(e, bl);							\
  }									\
  inline void decode(type &v, bufferlist::iterator& p) {		\
    ceph_##etype e;							\
    decode_raw(e, p);							\
    v = e;								\
  }

WRITE_INTTYPE_ENCODER(uint64_t, le64)
WRITE_INTTYPE_ENCODER(int64_t, le64)
WRITE_INTTYPE_ENCODER(uint32_t, le32)
WRITE_INTTYPE_ENCODER(int32_t, le32)
WRITE_INTTYPE_ENCODER(uint16_t, le16)
WRITE_INTTYPE_ENCODER(int16_t, le16)

#ifdef ENCODE_DUMP
# include <stdio.h>
# include <sys/types.h>
# include <sys/stat.h>
# include <fcntl.h>

# define ENCODE_STR(x) #x
# define ENCODE_STRINGIFY(x) ENCODE_STR(x)

# define ENCODE_DUMP_PRE()			\
  unsigned pre_off = bl.length()

// NOTE: This is almost an exponential backoff, but because we count
// bits we get a better sample of things we encode later on.
# define ENCODE_DUMP_POST(cl)						\
  do {									\
    static int i = 0;							\
    i++;								\
    int bits = 0;							\
    for (unsigned t = i; t; bits++)					\
      t &= t - 1;							\
    if (bits > 2)							\
      break;								\
    char fn[200];							\
    snprintf(fn, sizeof(fn), ENCODE_STRINGIFY(ENCODE_DUMP) "/%s__%d.%x", #cl, getpid(), i++); \
    int fd = ::open(fn, O_WRONLY|O_TRUNC|O_CREAT, 0644);		\
    if (fd >= 0) {							\
      bufferlist sub;							\
      sub.substr_of(bl, pre_off, bl.length() - pre_off);		\
      sub.write_fd(fd);							\
      ::close(fd);							\
    }									\
  } while (0)
#else
# define ENCODE_DUMP_PRE()
# define ENCODE_DUMP_POST(cl)
#endif

#define WRITE_CLASS_ENCODER(cl)						\
  inline void encode(const cl &c, bufferlist &bl, uint64_t features=0) { \
    ENCODE_DUMP_PRE(); c.encode(bl); ENCODE_DUMP_POST(cl); }		\
  inline void decode(cl &c, bufferlist::iterator &p) { c.decode(p); }

#define WRITE_CLASS_MEMBER_ENCODER(cl)					\
  inline void encode(const cl &c, bufferlist &bl) const {		\
    ENCODE_DUMP_PRE(); c.encode(bl); ENCODE_DUMP_POST(cl); }		\
  inline void decode(cl &c, bufferlist::iterator &p) { c.decode(p); }

#define WRITE_CLASS_ENCODER_FEATURES(cl)				\
  inline void encode(const cl &c, bufferlist &bl, uint64_t features) {	\
    ENCODE_DUMP_PRE(); c.encode(bl, features); ENCODE_DUMP_POST(cl); }	\
  inline void decode(cl &c, bufferlist::iterator &p) { c.decode(p); }


// string
inline void encode(const std::string& s, bufferlist& bl, uint64_t features=0)
{
  __u32 len = s.length();
  encode(len, bl);
  if (len)
    bl.append(s.data(), len);
}
inline void decode(std::string& s, bufferlist::iterator& p)
{
  __u32 len;
  decode(len, p);
  s.clear();
  p.copy(len, s);
}

inline void encode_nohead(const std::string& s, bufferlist& bl)
{
  bl.append(s.data(), s.length());
}
inline void decode_nohead(int len, std::string& s, bufferlist::iterator& p)
{
  s.clear();
  p.copy(len, s);
}

// const char* (encode only, string compatible)
inline void encode(const char *s, bufferlist& bl) 
{
  __u32 len = strlen(s);
  encode(len, bl);
  if (len)
    bl.append(s, len);
}


// array
template<class A>
inline void encode_array_nohead(const A a[], int n, bufferlist &bl)
{
  for (int i=0; i<n; i++)
    encode(a[i], bl);
}
template<class A>
inline void decode_array_nohead(A a[], int n, bufferlist::iterator &p)
{
  for (int i=0; i<n; i++)
    decode(a[i], p);
}



// -----------------------------
// buffers

// bufferptr (encapsulated)
inline void encode(const buffer::ptr& bp, bufferlist& bl) 
{
  __u32 len = bp.length();
  encode(len, bl);
  if (len)
    bl.append(bp);
}
inline void decode(buffer::ptr& bp, bufferlist::iterator& p)
{
  __u32 len;
  decode(len, p);

  bufferlist s;
  p.copy(len, s);

  if (len) {
    if (s.get_num_buffers() == 1)
      bp = s.front();
    else
      bp = buffer::copy(s.c_str(), s.length());
  }
}

// bufferlist (encapsulated)
inline void encode(const bufferlist& s, bufferlist& bl) 
{
  __u32 len = s.length();
  encode(len, bl);
  bl.append(s);
}
inline void encode_destructively(bufferlist& s, bufferlist& bl) 
{
  __u32 len = s.length();
  encode(len, bl);
  bl.claim_append(s);
}
inline void decode(bufferlist& s, bufferlist::iterator& p)
{
  __u32 len;
  decode(len, p);
  s.clear();
  p.copy(len, s);
}

inline void encode_nohead(const bufferlist& s, bufferlist& bl) 
{
  bl.append(s);
}
inline void decode_nohead(int len, bufferlist& s, bufferlist::iterator& p)
{
  s.clear();
  p.copy(len, s);
}


// full bl decoder
template<class T>
inline void decode(T &o, bufferlist& bl)
{
  bufferlist::iterator p = bl.begin();
  decode(o, p);
  assert(p.end());
}


// -----------------------------
// STL container types

#include <set>
#include <map>
#include <deque>
#include <vector>
#include <string>
#include <boost/optional/optional_io.hpp>
#include <boost/tuple/tuple.hpp>

#ifndef _BACKWARD_BACKWARD_WARNING_H
#define _BACKWARD_BACKWARD_WARNING_H   // make gcc 4.3 shut up about hash_*
#endif
#include "include/unordered_map.h"
#include "include/unordered_set.h"


// boost optional
template<typename T>
inline void encode(const boost::optional<T> &p, bufferlist &bl)
{
  __u8 present = static_cast<bool>(p);
  ::encode(present, bl);
  if (p)
    encode(p.get(), bl);
}

#pragma GCC diagnostic ignored "-Wpragmas"
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wuninitialized"
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
template<typename T>
inline void decode(boost::optional<T> &p, bufferlist::iterator &bp)
{
  __u8 present;
  ::decode(present, bp);
  if (present) {
    T t;
    p = t;
    decode(p.get(), bp);
  }
}
#pragma GCC diagnostic pop
#pragma GCC diagnostic warning "-Wpragmas"

//triple tuple
template<class A, class B, class C>
inline void encode(const boost::tuple<A, B, C> &t, bufferlist& bl)
{
  encode(boost::get<0>(t), bl);
  encode(boost::get<1>(t), bl);
  encode(boost::get<2>(t), bl);
}
template<class A, class B, class C>
inline void decode(boost::tuple<A, B, C> &t, bufferlist::iterator &bp)
{
  decode(boost::get<0>(t), bp);
  decode(boost::get<1>(t), bp);
  decode(boost::get<2>(t), bp);
}

// pair
template<class A, class B>
inline void encode(const std::pair<A,B> &p, bufferlist &bl, uint64_t features)
{
  encode(p.first, bl, features);
  encode(p.second, bl, features);
}
template<class A, class B>
inline void encode(const std::pair<A,B> &p, bufferlist &bl)
{
  encode(p.first, bl);
  encode(p.second, bl);
}
template<class A, class B>
inline void decode(std::pair<A,B> &pa, bufferlist::iterator &p)
{
  decode(pa.first, p);
  decode(pa.second, p);
}

// list
template<class T>
inline void encode(const std::list<T>& ls, bufferlist& bl)
{
  __u32 n = (__u32)(ls.size());  // c++11 std::list::size() is O(1)
  encode(n, bl);
  for (typename std::list<T>::const_iterator p = ls.begin(); p != ls.end(); ++p)
    encode(*p, bl);
}
template<class T>
inline void decode(std::list<T>& ls, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  ls.clear();
  while (n--) {
    T v;
    decode(v, p);
    ls.push_back(v);
  }
}

template<class T>
inline void encode(const std::list<ceph::shared_ptr<T> >& ls, bufferlist& bl)
{
  __u32 n = (__u32)(ls.size());  // c++11 std::list::size() is O(1)
  encode(n, bl);
  for (typename std::list<ceph::shared_ptr<T> >::const_iterator p = ls.begin(); p != ls.end(); ++p)
    encode(**p, bl);
}
template<class T>
inline void encode(const std::list<ceph::shared_ptr<T> >& ls, bufferlist& bl, uint64_t features)
{
  __u32 n = (__u32)(ls.size());  // c++11 std::list::size() is O(1)
  encode(n, bl);
  for (typename std::list<ceph::shared_ptr<T> >::const_iterator p = ls.begin(); p != ls.end(); ++p)
    encode(**p, bl, features);
}
template<class T>
inline void decode(std::list<ceph::shared_ptr<T> >& ls, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  ls.clear();
  while (n--) {
    ceph::shared_ptr<T> v(std::make_shared<T>());
    decode(*v, p);
    ls.push_back(v);
  }
}

// set
template<class T>
inline void encode(const std::set<T>& s, bufferlist& bl)
{
  __u32 n = (__u32)(s.size());
  encode(n, bl);
  for (typename std::set<T>::const_iterator p = s.begin(); p != s.end(); ++p)
    encode(*p, bl);
}
template<class T>
inline void decode(std::set<T>& s, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  s.clear();
  while (n--) {
    T v;
    decode(v, p);
    s.insert(v);
  }
}

template<class T, class C>
inline void encode(const std::set<T, C>& s, bufferlist& bl)
{
  __u32 n = (__u32)(s.size());
  encode(n, bl);
  for (typename std::set<T, C>::const_iterator p = s.begin(); p != s.end(); ++p)
    encode(*p, bl);
}
template<class T, class C>
inline void decode(std::set<T, C>& s, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  s.clear();
  while (n--) {
    T v;
    decode(v, p);
    s.insert(v);
  }
}

template<class T>
inline void encode_nohead(const std::set<T>& s, bufferlist& bl)
{
  for (typename std::set<T>::const_iterator p = s.begin(); p != s.end(); ++p)
    encode(*p, bl);
}
template<class T>
inline void decode_nohead(int len, std::set<T>& s, bufferlist::iterator& p)
{
  for (int i=0; i<len; i++) {
    T v;
    decode(v, p);
    s.insert(v);
  }
}

// multiset
template<class T>
inline void encode(const std::multiset<T>& s, bufferlist& bl)
{
  __u32 n = (__u32)(s.size());
  encode(n, bl);
  for (typename std::multiset<T>::const_iterator p = s.begin(); p != s.end(); ++p)
    encode(*p, bl);
}
template<class T>
inline void decode(std::multiset<T>& s, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  s.clear();
  while (n--) {
    T v;
    decode(v, p);
    s.insert(v);
  }
}

// vector (pointers)
/*template<class T>
inline void encode(const std::vector<T*>& v, bufferlist& bl)
{
  __u32 n = v.size();
  encode(n, bl);
  for (typename std::vector<T*>::const_iterator p = v.begin(); p != v.end(); ++p)
    encode(**p, bl);
}
template<class T>
inline void decode(std::vector<T*>& v, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  v.resize(n);
  for (__u32 i=0; i<n; i++) 
    v[i] = new T(p);
}
*/
// vector
template<class T>
inline void encode(const std::vector<T>& v, bufferlist& bl, uint64_t features)
{
  __u32 n = (__u32)(v.size());
  encode(n, bl);
  for (typename std::vector<T>::const_iterator p = v.begin(); p != v.end(); ++p)
    encode(*p, bl, features);
}
template<class T>
inline void encode(const std::vector<T>& v, bufferlist& bl)
{
  __u32 n = (__u32)(v.size());
  encode(n, bl);
  for (typename std::vector<T>::const_iterator p = v.begin(); p != v.end(); ++p)
    encode(*p, bl);
}
template<class T>
inline void decode(std::vector<T>& v, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  v.resize(n);
  for (__u32 i=0; i<n; i++) 
    decode(v[i], p);
}

template<class T>
inline void encode_nohead(const std::vector<T>& v, bufferlist& bl)
{
  for (typename std::vector<T>::const_iterator p = v.begin(); p != v.end(); ++p)
    encode(*p, bl);
}
template<class T>
inline void decode_nohead(int len, std::vector<T>& v, bufferlist::iterator& p)
{
  v.resize(len);
  for (__u32 i=0; i<v.size(); i++) 
    decode(v[i], p);
}

// vector (shared_ptr)
template<class T>
inline void encode(const std::vector<ceph::shared_ptr<T> >& v, bufferlist& bl)
{
  __u32 n = (__u32)(v.size());
  encode(n, bl);
  for (typename std::vector<ceph::shared_ptr<T> >::const_iterator p = v.begin(); p != v.end(); ++p)
    if (*p)
      encode(**p, bl);
    else
      encode(T(), bl);
}
template<class T>
inline void decode(std::vector<ceph::shared_ptr<T> >& v, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  v.resize(n);
  for (__u32 i=0; i<n; i++) {
    v[i] = std::make_shared<T>();
    decode(*v[i], p);
  }
}

// map (pointers)
/*
template<class T, class U>
inline void encode(const std::map<T,U*>& m, bufferlist& bl)
{
  __u32 n = m.size();
  encode(n, bl);
  for (typename std::map<T,U*>::const_iterator p = m.begin(); p != m.end(); ++p) {
    encode(p->first, bl);
    encode(*p->second, bl);
  }
}
template<class T, class U>
inline void decode(std::map<T,U*>& m, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  m.clear();
  while (n--) {
    T k;
    decode(k, p);
    m[k] = new U(p);
  }
  }*/

// map
template<class T, class U>
inline void encode(const std::map<T,U>& m, bufferlist& bl)
{
  __u32 n = (__u32)(m.size());
  encode(n, bl);
  for (typename std::map<T,U>::const_iterator p = m.begin(); p != m.end(); ++p) {
    encode(p->first, bl);
    encode(p->second, bl);
  }
}
template<class T, class U, class C>
inline void encode(const std::map<T,U,C>& m, bufferlist& bl)
{
  __u32 n = (__u32)(m.size());
  encode(n, bl);
  for (typename std::map<T,U,C>::const_iterator p = m.begin(); p != m.end(); ++p) {
    encode(p->first, bl);
    encode(p->second, bl);
  }
}
template<class T, class U>
inline void encode(const std::map<T,U>& m, bufferlist& bl, uint64_t features)
{
  __u32 n = (__u32)(m.size());
  encode(n, bl);
  for (typename std::map<T,U>::const_iterator p = m.begin(); p != m.end(); ++p) {
    encode(p->first, bl, features);
    encode(p->second, bl, features);
  }
}
template<class T, class U>
inline void decode(std::map<T,U>& m, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  m.clear();
  while (n--) {
    T k;
    decode(k, p);
    decode(m[k], p);
  }
}
template<class T, class U, class C>
inline void decode(std::map<T,U,C>& m, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  m.clear();
  while (n--) {
    T k;
    decode(k, p);
    decode(m[k], p);
  }
}
template<class T, class U, class C>
inline void decode_noclear(std::map<T,U,C>& m, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  while (n--) {
    T k;
    decode(k, p);
    decode(m[k], p);
  }
}
template<class T, class U>
inline void decode_noclear(std::map<T,U>& m, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  while (n--) {
    T k;
    decode(k, p);
    decode(m[k], p);
  }
}
template<class T, class U>
inline void encode_nohead(const std::map<T,U>& m, bufferlist& bl)
{
  for (typename std::map<T,U>::const_iterator p = m.begin(); p != m.end(); ++p) {
    encode(p->first, bl);
    encode(p->second, bl);
  }
}
template<class T, class U>
inline void encode_nohead(const std::map<T,U>& m, bufferlist& bl, uint64_t features)
{
  for (typename std::map<T,U>::const_iterator p = m.begin(); p != m.end(); ++p) {
    encode(p->first, bl, features);
    encode(p->second, bl, features);
  }
}
template<class T, class U>
inline void decode_nohead(int n, std::map<T,U>& m, bufferlist::iterator& p)
{
  m.clear();
  while (n--) {
    T k;
    decode(k, p);
    decode(m[k], p);
  }
}

// multimap
template<class T, class U>
inline void encode(const std::multimap<T,U>& m, bufferlist& bl)
{
  __u32 n = (__u32)(m.size());
  encode(n, bl);
  for (typename std::multimap<T,U>::const_iterator p = m.begin(); p != m.end(); ++p) {
    encode(p->first, bl);
    encode(p->second, bl);
  }
}
template<class T, class U>
inline void decode(std::multimap<T,U>& m, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  m.clear();
  while (n--) {
    typename std::pair<T,U> tu = std::pair<T,U>();
    decode(tu.first, p);
    typename std::multimap<T,U>::iterator it = m.insert(tu);
    decode(it->second, p);
  }
}

// ceph::unordered_map
template<class T, class U>
inline void encode(const unordered_map<T,U>& m, bufferlist& bl)
{
  __u32 n = (__u32)(m.size());
  encode(n, bl);
  for (typename unordered_map<T,U>::const_iterator p = m.begin(); p != m.end(); ++p) {
    encode(p->first, bl);
    encode(p->second, bl);
  }
}
template<class T, class U>
inline void decode(unordered_map<T,U>& m, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  m.clear();
  while (n--) {
    T k;
    decode(k, p);
    decode(m[k], p);
  }
}

// ceph::unordered_set
template<class T>
inline void encode(const ceph::unordered_set<T>& m, bufferlist& bl)
{
  __u32 n = (__u32)(m.size());
  encode(n, bl);
  for (typename ceph::unordered_set<T>::const_iterator p = m.begin(); p != m.end(); ++p)
    encode(*p, bl);
}
template<class T>
inline void decode(ceph::unordered_set<T>& m, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  m.clear();
  while (n--) {
    T k;
    decode(k, p);
    m.insert(k);
  }
}

// deque
template<class T>
inline void encode(const std::deque<T>& ls, bufferlist& bl)
{
  __u32 n = ls.size();
  encode(n, bl);
  for (typename std::deque<T>::const_iterator p = ls.begin(); p != ls.end(); ++p)
    encode(*p, bl);
}
template<class T>
inline void decode(std::deque<T>& ls, bufferlist::iterator& p)
{
  __u32 n;
  decode(n, p);
  ls.clear();
  while (n--) {
    T v;
    decode(v, p);
    ls.push_back(v);
  }
}


/*
 * guards
 */

/**
 * start encoding block
 *
 * @param v current (code) version of the encoding
 * @param compat oldest code version that can decode it
 * @param bl bufferlist to encode to
 */
#define ENCODE_START(v, compat, bl)			     \
  __u8 struct_v = v, struct_compat = compat;		     \
  ::encode(struct_v, (bl));				     \
  ::encode(struct_compat, (bl));			     \
  buffer::list::iterator struct_compat_it = (bl).end();	     \
  struct_compat_it.advance(-1);				     \
  ceph_le32 struct_len;				             \
  struct_len = 0;                                            \
  ::encode(struct_len, (bl));				     \
  buffer::list::iterator struct_len_it = (bl).end();	     \
  struct_len_it.advance(-4);				     \
  do {

/**
 * finish encoding block
 *
 * @param bl bufferlist we were encoding to
 * @param new_struct_compat struct-compat value to use
 */
#define ENCODE_FINISH_NEW_COMPAT(bl, new_struct_compat)			\
  } while (false);							\
  struct_len = (bl).length() - struct_len_it.get_off() - sizeof(struct_len); \
  struct_len_it.copy_in(4, (char *)&struct_len);			\
  if (new_struct_compat) {						\
    struct_compat = new_struct_compat;					\
    struct_compat_it.copy_in(1, (char *)&struct_compat);		\
  }

#define ENCODE_FINISH(bl) ENCODE_FINISH_NEW_COMPAT(bl, 0)

#define DECODE_ERR_VERSION(func, v)			\
  (std::string(func) + " unknown encoding version > " #v)

#define DECODE_ERR_OLDVERSION(func, v)			\
  (std::string(func) + " no longer understand old encoding version < " #v)

#define DECODE_ERR_PAST(func) \
  (std::string(func) + " decode past end of struct encoding")

/**
 * check for very old encoding
 *
 * If the encoded data is older than oldestv, raise an exception.
 *
 * @param oldestv oldest version of the code we can successfully decode.
 */
#define DECODE_OLDEST(oldestv)						\
  if (struct_v < oldestv)						\
    throw buffer::malformed_input(DECODE_ERR_OLDVERSION(__PRETTY_FUNCTION__, v)); 

/**
 * start a decoding block
 *
 * @param v current version of the encoding that the code supports/encodes
 * @param bl bufferlist::iterator for the encoded data
 */
#define DECODE_START(v, bl)						\
  __u8 struct_v, struct_compat;						\
  ::decode(struct_v, bl);						\
  ::decode(struct_compat, bl);						\
  if (v < struct_compat)						\
    throw buffer::malformed_input(DECODE_ERR_VERSION(__PRETTY_FUNCTION__, v)); \
  __u32 struct_len;							\
  ::decode(struct_len, bl);						\
  if (struct_len > bl.get_remaining())					\
    throw buffer::malformed_input(DECODE_ERR_PAST(__PRETTY_FUNCTION__)); \
  unsigned struct_end = bl.get_off() + struct_len;			\
  do {

#define __DECODE_START_LEGACY_COMPAT_LEN(v, compatv, lenv, skip_v, bl)	\
  __u8 struct_v;							\
  ::decode(struct_v, bl);						\
  if (struct_v >= compatv) {						\
    __u8 struct_compat;							\
    ::decode(struct_compat, bl);					\
    if (v < struct_compat)						\
      throw buffer::malformed_input(DECODE_ERR_VERSION(__PRETTY_FUNCTION__, v)); \
  } else if (skip_v) {							\
    if ((int)bl.get_remaining() < skip_v)				\
      throw buffer::malformed_input(DECODE_ERR_PAST(__PRETTY_FUNCTION__)); \
    bl.advance(skip_v);							\
  }									\
  unsigned struct_end = 0;						\
  if (struct_v >= lenv) {						\
    __u32 struct_len;							\
    ::decode(struct_len, bl);						\
    if (struct_len > bl.get_remaining())				\
      throw buffer::malformed_input(DECODE_ERR_PAST(__PRETTY_FUNCTION__)); \
    struct_end = bl.get_off() + struct_len;				\
  }									\
  do {

/**
 * start a decoding block with legacy support for older encoding schemes
 *
 * The old encoding schemes has a __u8 struct_v only, or lacked either
 * the compat version or length.  Skip those fields conditionally.
 *
 * Most of the time, v, compatv, and lenv will all match the version
 * where the structure was switched over to the new macros.
 *
 * @param v current version of the encoding that the code supports/encodes
 * @param compatv oldest version that includes a __u8 compat version field
 * @param lenv oldest version that includes a __u32 length wrapper
 * @param bl bufferlist::iterator containing the encoded data
 */
#define DECODE_START_LEGACY_COMPAT_LEN(v, compatv, lenv, bl)		\
  __DECODE_START_LEGACY_COMPAT_LEN(v, compatv, lenv, 0, bl)

/**
 * start a decoding block with legacy support for older encoding schemes
 *
 * This version of the macro assumes the legacy encoding had a 32 bit
 * version
 *
 * The old encoding schemes has a __u8 struct_v only, or lacked either
 * the compat version or length.  Skip those fields conditionally.
 *
 * Most of the time, v, compatv, and lenv will all match the version
 * where the structure was switched over to the new macros.
 *
 * @param v current version of the encoding that the code supports/encodes
 * @param compatv oldest version that includes a __u8 compat version field
 * @param lenv oldest version that includes a __u32 length wrapper
 * @param bl bufferlist::iterator containing the encoded data
 */
#define DECODE_START_LEGACY_COMPAT_LEN_32(v, compatv, lenv, bl)		\
  __DECODE_START_LEGACY_COMPAT_LEN(v, compatv, lenv, 3, bl)

#define DECODE_START_LEGACY_COMPAT_LEN_16(v, compatv, lenv, bl)		\
  __DECODE_START_LEGACY_COMPAT_LEN(v, compatv, lenv, 1, bl)

/**
 * finish decode block
 *
 * @param bl bufferlist::iterator we were decoding from
 */
#define DECODE_FINISH(bl)						\
  } while (false);							\
  if (struct_end) {							\
    if (bl.get_off() > struct_end)					\
      throw buffer::malformed_input(DECODE_ERR_PAST(__PRETTY_FUNCTION__)); \
    if (bl.get_off() < struct_end)					\
      bl.advance(struct_end - bl.get_off());				\
  }

#endif
