I've struggled with at p/invoke problem for some time now. Keep getting "Attempted to read or write protected memory." all the time, and I suspect my marshaling is a bit off.
Here is the c signature:
long ft_show( /* show file-attributes */
const struct ft_admission *admis, /* I: transfer admission */
const struct ft_shwpar *par, /* IO: parameter-list */
struct ft_fileinfo *info, /* O: requested information */
struct ft_err *errorinfo, /* O: error information */
void *options /* I: options */
);
and here are the related structures (in c)
struct ft_admission
{
char *remsys;
char *remadmis;
char *remaccount;
char *rempasswd;
};
struct ft_shwpar
{
int shwparvers;
char *fn;
char *mgmtpasswd;
char *fud;
int fudlen;
};
struct ft_fileinfo
{
int ftshowivers;
char fn[INFO_FN_LEN];
enum ft_ftype filetype;
enum ft_charset charset;
enum ft_rform recordform;
long recsize;
enum ft_available availability;
int access;
char account[ACC_LEN];
long size;
long maxsize;
char legalqual[LQ_LEN];
char cre_user[USER_LEN];
long cre_date;
char mod_user[USER_LEN];
long mod_date;
char rea_user[USER_LEN];
long rea_date;
char atm_user[USER_LEN];
long atm_date;
long long fsize;
long long fmaxsize;
};
struct ft_err
{
long main;
long detail;
long additional;
};
struct ft_options
{
int ftoptsvers;
int ftapivers;
};
I've tried to create c# structs and calls like this:
[DllImport("ftapi.dll", EntryPoint = "ft_showdir")]
private static extern long ft_showdir(ft_admission admis, ref ft_shwpar par, ft_fileinfo[] buf, int bufsize, ref ft_err errorinfo, ft_options options);
public struct ft_admission
{
public String remsys;
public String remadmis;
public String remaccount;
public String rempasswd;
};
public struct ft_shwpar
{
public int shwparvers;
public String fn;
public String mgmtpasswd;
public IntPtr fud;
public int fudlen;
};
[StructLayout(LayoutKind.Sequential, Size = 1464, CharSet = CharSet.Ansi), Serializable]
public struct ft_fileinfo
{
public int ftshowivers;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 257)]
public String fn;
public ft_ftype filetype;
public ft_charset charset;
public ft_rform recordform;
public long recsize;
public ft_available availability;
public int access;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 65)]
public String account;
public long size;
public long maxsize;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 81)]
public String legalqual;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 68)]
public String cre_user;
public long cre_date;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 68)]
public String mod_user;
public long mod_date;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 68)]
public String rea_user;
public long rea_date;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 68)]
public String atm_user;
public long atm_date;
public long fsize;
public long fmaxsize;
};
public struct ft_err
{
public long main;
public long detail;
public long additional;
}
public struct ft_options
{
public int ftoptsvers;
public int ftapivers;
};
I've already used the ft_err and ft_options structs successfully in another call, so I think those are marshaled correctly.
I think the problem is the ft_fileinfo structure. I want to use StringBuilder in there, but there is a bug in the framework preventing correct marshaling of StringBuilder inside structs. I've tried the workarounds described here: http://support.microsoft.com/kb/327109 but no success.
Here's the code snippet provided in the documentation of the api I try to access (some code has been removed as it's only used for printing info to the screen):
/* sample3.c File management requests */
/*************************************************************/
static const char Sccsid[] = "@(#)sample3.c 2.33 2009/03/25";
/*************************************************************
Program call: sample3 <directory>
*************************************************************/
/* Include Files */
/*************************************************************/
#include <stdio.h> /* printf() */
#include <stdlib.h> /* exit() */
#include <string.h> /* strcat(), strcpy() */
#include <ftapi.h>
/*************************************************************/
/* Local Constants and Macros */
/*************************************************************/
#define BUFSIZE 200 /* number of ft_fileinfo structures */
/* in output buffer */
/*************************************************************/
/* Local Functions Declarations */
/*************************************************************/
static void error_print(struct ft_err *, char *);
static void printinfo(struct ft_fileinfo *info);
int main (int argc, char *argv[])
{
int i; /* Some local counter */
int count; /* Number of files */
char remotesys[201]; /* Address of remote systems */
char remoteadm[68]; /* Transfer admission */
char fud[STAT_FUD_LEN]; /* Further details */
struct ft_err errorinfo; /* Error information */
struct ft_admission admis; /* Admission parameters */
struct ft_shwpar par; /* Show directory parameters */
struct ft_options opt; /* Options */
struct ft_fileinfo buf[BUFSIZE]; /* Output buffer */
/* Check program arguments */
if (argc != 2)
{
printf("Call: %s <directory>\n", argv[0]);
exit(EXIT_FAILURE);
}
/* Initialize ft_transpar structure */
memset(&par, 0, sizeof(par));
/* Set version of the parameter list */
par.shwparvers = FT_SPARV2;
/* Set the name of the remote directory */
par.fn = argv[1];
/* Set buffer and buffer length for the further details */
par.fud = fud;
par.fudlen = sizeof(fud);
/* Set version of the ft_fileinfo structure in the */
/* output buffer. The version in the first structure */
/* is valid for all structtures in the output buffer. */
buf[0].ftshowivers = FT_SHOWIV2;
/* Get the name/address of the remote system and the */
/* transfer admission */
printf("Enter name of remote system: ");
scanf("%s", remotesys);
printf("Input transfer admission to remote system: ");
scanf("%s", remoteadm);
admis.remsys = remotesys;
admis.remadmis = remoteadm;
admis.remaccount = NULL;
admis.rempasswd = NULL;
/* Prepare the options structure */
opt.ftoptsvers = FT_OPTSV1;
opt.ftapivers = FT_APIV2;
/* Read the contents of the remote directory */
count = ft_showdir(&admis, &par, buf, BUFSIZE, &errorinfo,
&opt);
if (count == -1)
{
/* Error */
error_print(&errorinfo, par.fud);
}
/* Display result of request */
printf("There are %d entries in remote directory %s\n",
count, argv[1]);
/* If the output range was not large enough for all */
/* the information, only the data in the buffer is */
/* displayed */
if (count > BUFSIZE)
count = BUFSIZE;
for (i = 0; i < count; i++)
printinfo(&buf[i]);
return(0);
}
Can someone help me achieve the same in C#? And even explain why it have to be that way, so we all can learn something from this :)
Thanks!
Ok, I figured it out.
When looking at the c declaration of the function we can see that all of the parameters are sent in by reference or via pointers. So I just altered the pinvoke declaration so that all parameters where ref.
[DllImport("ftapi.dll", EntryPoint = "ft_showdir", CallingConvention = CallingConvention.Cdecl)]
private static extern Int32 ft_showdir(ref ft_admission admis, ref ft_shwpar par, ref ft_fileinfo[] buf, int bufsize, ref ft_err errorinfo, ref ft_options options);