M-OSCAR

Erlang :
send_integer(Int) ->
    Size = erlang:system_info(wordsize) * 8,
    Data = <<Int:Size/integer-little>>,
    Port ! {self(), {command, Data}},
    ....

CPP :
static void output(ErlDrvData handle, char* buff, int bufflen){
    int *num = (int *)buff
    ....

#include 
#include "erl_driver.h"
using namespace std;

struct data{
    ErlDrvPort port;
};

//PORT打开时执行
static ErlDrvData start(ErlDrvPort port, char *buff){
    data* d = (data*)driver_alloc(sizeof(data));
    d->port = port;
    return (ErlDrvData)d;
}

//PORT关闭时执行
static void stop(ErlDrvData handle){
    driver_free((char*)handle);
}

//ERLANG发送来信息时执行
static void output(ErlDrvData handle, char *buff, int bufflen){
    cout << buff << endl;
    char rs[] = "ok";
    data* d = (data*)handle;
    driver_output(d->port, rs, 2);
}

ErlDrvEntry driver_entry = {
    NULL,    //F_PTR init N/A
    start,   //L_PTR PORT打开时执行此函数
    stop,    //F_PTR PORT关闭时执行此函数
    output,  //F_PTR ERLANG发来信息时执行
    NULL,    //F_PTR ready_input, called when input descriptor ready to read
    NULL,    //F_PTR ready_output
    "test",  //DRIVER名，OPEN_PORT函数的参数
    NULL,    //F_PTR finish, called when unloaded
    NULL,    //F_PTR control, port_command callback
    NULL,    //F_PTR timeout, reserved
    NULL     //F_PTR outputv, reserved
};

extern "C"{
    DRIVER_INIT(test){
        return &driver_entry;
    }
}

-module(test).
-compile(export_all).

start() ->
    ok = erl_ddll:load_driver(".", "test"),
    Port = open_port({spawn, "test"}, [{packet, 2}]),
    Port ! {self(), {command, "woo just a test"}},
    receive
        {Port, {data, Data}} ->
            ok = io:format("[~p/~p] ~p\n", [?MODULE, self(), Data])
    end,
    Port ! {self(), close}.

首先試試將字符串轉換為Json Object：
1> JsonBin = <<"{ 
1> \"username\":\"Oscar Tong\",
1> \"password\":\"123456\",
1> \"male\":true,
1> \"age\":23
1> }">>.
<<"{\n\"username\":\"Oscar Tong\",\n\"password\":\"123456\",\n\"male\":true,\n\"age\":23\n}">>
2> {ok, {obj, JsonObj}, _Rest} = rfc4627:decode(JsonBin).
{ok,{obj,[{"username",<<"Oscar Tong">>},
          {"password",<<"123456">>},
          {"male",true},
          {"age",23}]},
    []}

再轉換為JSON格式的字符串：
3> rfc4627:encode({obj,JsonObj}).
"{\"username\":\"Oscar Tong\",\"password\":\"123456\",\"male\":true,\"age\":23}"

....
{ok, Sock} = gen_tcp:accept(Listener),
Pid = spawn(SomeOtherNode, Mod, Fun, Arg),
ok = gen_tcp:controlling_process(Sock, Pid),
....

...
wait_for_reply() ->
    receive
        {reply, Reply} -> handle(Reply);
        _Other -> wait_for_reply()
    end.

出錯前：
myfun(params1) -> .... ;
myfun(params2) -> .... .

這樣就會提示錯誤了：
myfun(params1) -> .... ;
new_fun_here(params) -> .... .
myfun(params2) -> .... .

> l(my_module).
{module, my_module)

io:format("Erlang is running ....\n").
code:add_patha("."),
code:add_pathz("/home/m/bin").

$ erl
Erlang (BEAM) emulator version 5.6.5 [source] [smp:2] [async-threads:0] [hipe] [kernel-poll:false]

Erlang is running ....
Eshell V5.6.5  (abort with ^G)
1>

1> init:get_argument(home).
{ok,[["/home/m"]]}

code:get_path().
["ebin",".","/usr/local/lib/erlang/lib/kernel-2.12.5/ebin",
 "/usr/local/lib/erlang/lib/stdlib-1.15.5/ebin",
 "/usr/local/lib/erlang/lib/xmerl-1.1.10/ebin",
 "/usr/local/lib/erlang/lib/webtool-0.8.3.2/ebin",
 "/usr/local/lib/erlang/lib/typer-0.1.5/ebin",
 "/usr/local/lib/erlang/lib/tv-2.1.4.2/ebin",
 "/usr/local/lib/erlang/lib/tools-2.6.2/ebin",
 "/usr/local/lib/erlang/lib/toolbar-1.3.0.1/ebin",
 "/usr/local/lib/erlang/lib/test_server-3.2.4/ebin",
 "/usr/local/lib/erlang/lib/syntax_tools-1.5.6/ebin",
 "/usr/local/lib/erlang/lib/ssl-3.10/ebin",
 "/usr/local/lib/erlang/lib/ssh-1.0.2/ebin",
 [...]|...]

{Modules, Options}

openssl genrsa -des3 -out privkey.pem 2048
生成一個長2048 bit的私鑰，并用密碼以DES算法加密該私鑰，最后輸出為名為privkey.pem的文件。
如果加密了該私鑰，則每次使用的時候都需要提供密碼，如果不需要密碼保謢，去掉-des3參數就可以了～～

openssl req -new -x509 -key privkey.pem -out cert.pem -days 1020
生成一個自簽的測試用證書，輸出為文件cert.pem，有效期為1020天。

-module(test).
-export([start/0, connect/0]).


%啟動SSL服務
start() ->
    application:start(ssl),
    ssl:seed("seed-every-time"),
    {ok, spawn(fun() -> start_server() end)}.


%運行SSL SOCKET SERVER
start_server() ->
    
    %創建socket server
    {ok, ListenSocket} = ssl:listen(51020, [
        binary, {active, true},
        {keyfile, "privkey.pem"},
        {certfile, "cert.pem"}]),
    io:format("SSL socket server is ready\n", []),

    %接受客戶端連接
    {ok, Sock} = ssl:transport_accept(ListenSocket),
    ok = ssl:ssl_accept(Sock),
    io:format("New ssl client is connected\n", []),
    loop_client(Sock).


%處理來自客戶端的信息
loop_client(Sock) ->
    receive
        {ssl, Sock, Data} ->
            io:format("Receive : ~p\n", [Data]),
            ssl:send(Sock, Data),
            loop_client(Sock);
        {ssl_closed, Sock} -> io:format("Client ~p is discionnected\n", [Sock]);
        {ssl_errlr, Sock, Reason} -> io:format("ERROR : ~p\n", [Reason])
    end.


%客戶端進行連接
connect() ->
    {ok, Sock} = ssl:connect("localhost", 51020, [bianry]),
    io:format("connected\n", []),
    ssl:send(Sock, "this is just a test"),
    receive
        Any ->
            io:format("client receive : ~p\n", [Any])
    end,
    ssl:close(Sock),
    io:format("client closed\n", []).

== 等于
/= 不等于
=< 小于或等于
<  小于
>= 大于或等于
>  大于
=:= 完全等于
=/= 完全不等于

keysearch(Key, N, TupleList) -> {value, Tuple} | false
    Key = term()
    N = 1..tuple_size(Tuple)
    TupleList = [Tuple]
        Tuple = tuple()

> Attributes = [{to, "jojo@verse.com"},
                {from, "oscar@verse.com/school"},
                {type, "chat"},
                {'xml:lang', "en"}].

> lists:keysearch(from, 1, Attributes).
{value, {from, "oscar@verse.com/school"}}

若指定Key不存在则返回false
> lists:keysearch(not_exist, 2, Attributes).
false

-module(test).
-export([start/0]).
-include_lib("stdlib/include/qlc.hrl").

start() ->
    QH1 = qlc:q([{X, Y} || X <- [8,3,6,2], Y <- [b,a,c]]),
    %以第一个值作为key进行排序
    QH2 = qlc:keysort(1, QH1, [{order, ascending}]),
    QC = qlc:cursor(QH2),
    %获取前两条记录
    qlc:next_answers(QC, 2),
    %获取剩余的其他记录
    qlc:next_answers(QC, all_remainning).

=ERROR REPORT==== 11-Apr-2009::01:51:47 ===
** Generic server test terminating 
** Last message in was error
** When Server state == []
** Reason for termination == 
** error
gen_server test is started （test重启时所输出的信息）
** exception exit: {error,{gen_server,call,[test,error]}}
    in function  gen_server:call/2
13> 
=ERROR REPORT==== 11-Apr-2009::01:51:47 ===
** Generic server sup terminating 
** Last message in was {'EXIT',<0.54.0>,
    {{error,{gen_server,call,[test,error]}},

shell
    eval_loop
        sup

{ok, Pid} = supervisor:start_link({local, sup}, sup, []),
unlink(Pid).

首先启动新节点上面的mnesia
> rpc:call(Node, mnesia, start, []).
添加新节点
> {ok, _} = mnesia:change_config(extra_db_nodes, [Node]).
修改新节点上的schema表的类型
> {atomic, ok} = mnesia:change_table_copy_type(schema, Node, disc_copies).

首先关闭该节点上的mnesia
> rpc:call(Node, mnesia, stop, []).
删掉该节点上的schema表
> {atomic, ok} = mnesia:del_table_copy(schema, Node).
> ok = mnesia:delete_schema([Node]).