From: "bubble" <bubble@bubble.d2g.com>
Subject: how to declare a accss type in ada as C's generic pointer
Date: Thu, 9 Dec 2004 14:29:58 +0800
Date: 2004-12-09T14:29:58+08:00 [thread overview]
Message-ID: <cp8s17$u2$1@netnews.hinet.net> (raw)
dear all:
I got a problem work with C's generic pointer(void *).
in general case,I declare access type with convention pragma as C's pointer
define.
It work fine.
my question is I don't know how to define a access type as C's generic
pointer.
now,I use System.address as C's generic point,is it correct?
for example.
in C,I got a C's .H file.
enum message_type{singer_name=6,music_size=7,playTime=11}
int querySongStatus(int message_type,char * message ,int
max_message_length,int * message_length,void * Num);
in Ada.I rewrite it and import it to ada. such as
package work is
pragma Liner_Options("-lmymusic32");
type message_type is (singer_name,music_size,play_time);
subtype myString is string(1..300);
type mystring_access is access all mystring;
type integer_access is access all integer;
function query_Song_Status(
msg_type:message_type;
message:mystring;
max_message_length:integer;
message_length:integer_access;
Num:System.address);
pragma Conversion(C,mystring);
pragma COnversion(C,integer_access);
pragma import(Stdcall,query_Song_Status,"querySongStatus");
private
for message_Type use (
singer_name=>6;
music_size=>7;
playTime=>11);
end work;
in C,if I want to query singer name then
char * name = (char *)malloc (sizeof(char) * 300);
int length=0;
//I must pass a char pointer to querySongStatus..
querySongStatus(singer_name,name,300,&length,null);
else if I want to query song's disk size then
int diskByte=0;
//I must pass a integer pointer to last parameter
querySongStatus(music_size,null,0,null,&diskByte);
else if I want to query a song's play time then
float totalTime;
//I must pass float pointer to last parameter
querySongStatus(playTime,null,0,0,&totalTime);
the last parameter is generic pointer,
the C's function will cast the generic pointer to another type pointer
according to what the first parameter is?
in Ada.
I don't know how to declare the access type correct?
can anybody tell me how to do?
thanks.
next reply other threads:[~2004-12-09 6:29 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-09 6:29 bubble [this message]
2004-12-10 1:02 ` how to declare a accss type in ada as C's generic pointer Jeffrey Carter
2004-12-15 13:48 ` David Botton
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