XNul32.dll - Null Interface Analysis

Decompilation analysis of the EDIABAS Null/Dummy interface driver.

Overview

Purpose: Stub/dummy interface that returns simulated responses without actual hardware communication.

Use Case: Testing, development, offline simulation.

Size: ~5.7K lines of decompiled code

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Exported Functions

Export	Ordinal	Description
dllStartupIFH	6	Initialize interface
dllShutdownIFH	5	Shutdown interface
dllCheckIFH	2	Check interface capability
dllCallIFH	1	Execute IFH command

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Function Analysis

dllStartupIFH

uint dllStartupIFH(undefined4 unused, char* ifh_name) {
    // Copy IFH name to global buffer (max ~256 bytes)
    size_t len = strlen(ifh_name);
    memcpy(&global_ifh_name, ifh_name, len);
    
    // Return success (high word = 0)
    return 0;
}

Parameters:

• unused - Not used
• ifh_name - Interface name string

Returns: 0 on success

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dllShutdownIFH

void dllShutdownIFH(void) {
    // No-op - nothing to clean up
    return;
}

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dllCheckIFH

byte dllCheckIFH(short cmd) {
    // Only command 6 (GET_INFO) returns 0 (supported)
    // All others return 0x1D (29 = not supported)
    if (cmd == 6) {
        return 0;
    }
    return 0x1D;
}

Commands:

Code	Supported	Description
6	Yes	Get interface info
Other	No	Returns error 0x1D

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dllCallIFH

Main command dispatcher. Handles IFH commands 2-51.

uint dllCallIFH(short* request, short* response) {
    short cmd;
    
    // Validate request
    uint result = validate_request(&request, response);
    if (result != 0) {
        return result;  // Error in high word cleared
    }
    
    cmd = *request;
    
    // Dispatch based on command (2-51 range)
    if (cmd - 2 >= 50) {
        return 0;  // Out of range - ignore
    }
    
    switch (cmd) {
        case 2:  // IFH_INIT
            result = handle_init();
            response[1] = 0;
            // Copy interface name to response
            strcpy((char*)&response[2], global_ifh_name);
            break;
            
        case 3:  // IFH_END
            break;
            
        case 4:  // IFH_CONNECT
            // Return success
            response[1] = 0;
            break;
            
        case 5:  // IFH_DISCONNECT
            break;
            
        case 6:  // IFH_SYSINFO
            // Return interface info
            response[1] = 0;
            response[2] = 0x0001;  // Version
            break;
            
        case 0x16:  // IFH_SEND
            // Simulate send - always succeeds
            break;
            
        case 0x17:  // IFH_RECEIVE
            // Return empty response
            response[1] = 0;  // No data
            break;
            
        case 0x1E:  // IFH_GETERROR
            // Return no error
            response[1] = 0;
            break;
            
        case 0x22:  // IFH_SETPARAMETER
            // Accept any parameters
            break;
            
        case 0x23:  // IFH_GETPARAMETER
            // Return empty
            response[1] = 0;
            break;
            
        default:
            // Unsupported command
            break;
    }
    
    return 0;
}

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IFH Command Codes

Code	Hex	Name	Description
2	0x02	IFH_INIT	Initialize interface
3	0x03	IFH_END	Terminate interface
4	0x04	IFH_CONNECT	Connect to ECU
5	0x05	IFH_DISCONNECT	Disconnect from ECU
6	0x06	IFH_SYSINFO	Get system info
22	0x16	IFH_SEND	Send telegram
23	0x17	IFH_RECEIVE	Receive telegram
30	0x1E	IFH_GETERROR	Get last error
34	0x22	IFH_SETPARAMETER	Set parameters
35	0x23	IFH_GETPARAMETER	Get parameters

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Global Variables

Address	Name	Purpose
DAT_10009e3c	global_ifh_name	Stored interface name
DAT_10009d00	work_buffer	Temporary work buffer

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Error Codes

Code	Hex	Description
0	0x00	Success
29	0x1D	Command not supported

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Notes

1. No Hardware: This interface performs no actual I/O
2. Simulation: All operations succeed without side effects
3. Testing: Useful for unit tests and SGBD validation
4. Minimal: Only implements essential IFH commands