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jwatte's picture

MD5 hex digests in Erlang

June 10, 2010 - 08:41 — jwatte

In various web APIs, there is some confusion between the representation of a hash value.
There exists APIs where a password is validated as, say, MD5(challenge + MD5(salt + password)).
Let's leave aside the fact that MD5 is not a secure algorithm anymore (you can procedurally generate an input that generates any MD5 hash value you want in cheap-to-compute time).

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A simple approach to native network marshalling

January 18, 2010 - 22:30 — jwatte

I used to do serialization using all kinds of fancy templates and macros. You can create pretty elegant systems that way. However, at some point, simplicity should win out. Here's a system that might work just fine for you:

A simple packet class, which really is all you need:

class packet {
public:
  packet() : pos_(0) {}
  void append(void const *data, size_t size) {

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How to structure a reusable game networking library

September 3, 2009 - 19:21 — jwatte

I recently have answered several questions about how to structure a networking library such that it can be easy to use for users of the library and/or when expanding the game you're writing. Here are some thoughts on that. (Code examples in C++)

Networking generally ends up needing to do three things:

1) Mirror state updates from one object to another.
2) Request remote services ("RPC").

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main.cpp

July 22, 2009 - 19:59 — jwatte 

#include "etwork/etwork.h"
#include "etwork/buffer.h"
#include "etwork/errors.h"
#include "etwork/notify.h"
#include "etwork/marshal.h"
 
#include <assert.h>
#include <stdio.h>
#include <string>
#include <math.h>
 
#if defined( NDEBUG )
#pragma warning( disable: 4101 )  //  unreferenced local variable
#endif
 
 
void TestEtworkCreate()
{
  EtworkSettings es;

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tester

July 22, 2009 - 19:58 — jwatte

A simple command-line program that exercises parts of the Etwork API and asserts if something fails. Think of it as an API acceptance test.

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sockimpl.h

July 22, 2009 - 19:57 — jwatte 

#if !defined( etwork_sockimpl_h )
#define etwork_sockimpl_h
 
#include "etwork/etwork.h"
#include "etwork/locker.h"
#include "etwork/buffer.h"
#include "etwork/timer.h"
#include "etwork/errors.h"
#include "etwork/notify.h"
 
#if defined( WIN32 )
#include <windows.h>
#endif
 
#include <stdio.h>  //  for _snprintf
#include <math.h>
 
#include <string>
#include <map>

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socketbase.cpp

July 22, 2009 - 19:42 — jwatte 

#include "sockimpl.h"
 
using namespace etwork;
using namespace etwork::impl;
 
 
SocketManager::SocketManager()
{
  listening_ = INVALID_SOCKET;
  maxNumSocks_ = FD_SETSIZE;
  numSocks_ = 0;
  maxSock_ = 0;
  allSet_ = (fd_set *)::operator new( sizeof(fd_set) );
  FD_ZERO( allSet_ );
  readSet_ = (fd_set *)::operator new( sizeof(fd_set) );
  FD_ZERO( readSet_ );

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marshal.cpp

July 22, 2009 - 19:42 — jwatte 

#include <assert.h>
#include <string>
#include <math.h>
#include <map>
 
#include "etwork/marshal.h"
 
namespace marshaller {
 
inline std::string operator+( std::string const & left, int right ) {
  char buf[24];
  sprintf( buf, "%d", right );
  return left + std::string( buf );
}
 
inline std::string operator+( std::string const & left, size_t right ) {
  char buf[24];

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errors.cpp

July 22, 2009 - 19:41 — jwatte 

#include "sockimpl.h"
#include <stdarg.h>
 
using namespace etwork;
using namespace etwork::impl;
 
#if !defined( NDEBUG )
bool etwork::impl::gDebugging = true;
#else
bool etwork::impl::gDebugging = false;
#endif
 
bool etwork::impl::wsOpen = false;
 
Lock etwork::impl::gethostLock; //!< gethostbyname is not thread safe
 
IErrorNotify * etwork::impl::gErrorNotify;

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buffer.cpp

July 22, 2009 - 19:40 — jwatte 

#include "etwork/buffer.h"
 
#include <string.h>
#include <deque>
#include <assert.h>
 
using namespace etwork;
 
//! The framing protocol for etwork::Buffer is simple: each packet is 
//! preceded by a two-byte length, in network-endian order.
//! If random data is received, this may result in arbitrary packet

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