OpenEuphoria

Re: Help me wrap PahoMQTT

• Posted by ghaberek (admin) Apr 22, 2019
• 2721 views

Don't do this:

atom hndl = allocate(4) 
atom ret = peek4u(hndl) 

Do this instead:

atom hndl = allocate_data( sizeof(C_POINTER) ) 
atom ret = peek_pointer( hndl ) 

Define structures like this:

ifdef BITS64 then 
 
constant 
    MQTTClient_willOptions__struct_id       =  0, -- char[4] 
    MQTTClient_willOptions__struct_version  =  4, -- int 
    MQTTClient_willOptions__topicName       =  8, -- const char* 
    MQTTClient_willOptions__message         = 16, -- const char* 
    MQTTClient_willOptions__retained        = 24, -- int 
    MQTTClient_willOptions__qos             = 28, -- int 
    MQTTClient_willOptions__payload_len     = 32, -- int 
    MQTTClient_willOptions__payload_data    = 40, -- const void* 
    SIZEOF_MQTTClient_willOptions           = 48, 
$ 
 
elsedef 
 
constant 
    MQTTClient_willOptions__struct_id       =  0, -- char[4] 
    MQTTClient_willOptions__struct_version  =  4, -- int 
    MQTTClient_willOptions__topicName       =  8, -- const char* 
    MQTTClient_willOptions__message         = 12, -- const char* 
    MQTTClient_willOptions__retained        = 16, -- int 
    MQTTClient_willOptions__qos             = 20, -- int 
    MQTTClient_willOptions__payload_len     = 24, -- int 
    MQTTClient_willOptions__payload_data    = 28, -- const void* 
    SIZEOF_MQTTClient_willOptions           = 32, 
$ 
 
end ifdef 

And if you need to use them frequently, create wrapper functions to peek/poke your structure members safely:

-- peek a string pointer and return the string or "" if the ptr is NULL 
function peek_str( atom ptr ) 
     
    ptr = peek_pointer( ptr ) 
     
    if ptr = NULL then 
        return "" 
    end if 
     
    return peek_string( ptr ) 
end function 
 
function peek_MQTTClient_willOptions( atom ptr ) 
     
    sequence struct_id  =    peek({ ptr + MQTTClient_willOptions__struct_id, 4 }) 
    atom struct_version =   peek4s( ptr + MQTTClient_willOptions__struct_version ) 
    sequence topicName  = peek_str( ptr + MQTTClient_willOptions__topicName ) 
    sequence message    = peek_str( ptr + MQTTClient_willOptions__message ) 
    atom retained       =   peek4s( ptr + MQTTClient_willOptions__retained ) 
    atom qos            =   peek4s( ptr + MQTTClient_willOptions__qos ) 
    atom payload_len    =   peek4s( ptr + MQTTClient_willOptions__payload_len ) 
    object payload_data =   peek4s( ptr + MQTTClient_willOptions__payload_data ) 
     
    if payload_len != 0 and payload_data != NULL then 
        -- actually peek the data if it's present 
        payload_data = peek({ payload_data, payload_len }) 
    end if 
     
    return { 
        struct_id, 
        struct_version, 
        topicName, 
        message, 
        retained, 
        qos, 
        payload_len, 
        payload_data 
    } 
end function 

Tips and tricks:

• Invert your current ifdef's; use ifdef BITS64 and then else for 32-bit.
• Use sizeof() to determine the size of C types.
• Use allocate_data() unless you explicitly need executable memory.
• Ensure the correct peek/poke variants for your structures.
• Define separate 32/64 bit structures where necessary.

-Greg