Operations

P3 handles most changes to the world and its elements through operations. An operation is a 20 bytes wide struct, where the first u32 denotes the operation's type, and the following 16 bytes contain the operation's arguments.

Scheduling

While the game executes operation handlers directly sometimes, usually operations are scheduled by inserting them into the pending operations queue in the static operations struct at 0x006DF2F0:

00000000 operations      struc ; (sizeof=0x948, mappedto_126)
[...]
00000048 field_48_pending_operations operation_switch_input_container ?
0000046C field_46C       dd ?
00000470 field_470_pending_operations_in_use dd ?
00000474 field_474_current_operations operation_switch_input_container ?
[...]

The operation_switch_input_container struct contains an array of 53 operations. The function schedule_operation at 0x00543F10 inserts an operation at the next free position, creating a new operation_switch_input_container and appending it to the last full one if necessary.

Execution

The function execute_operations at 0x00546870 removes up to 53 operations from operations and executes them.

Debugging

The following IDC script adds scripted breakpoints to the executing and scheduling functions, allowing the investigation of P3's operation behavior:

static handle_operation_switch() {
    auto ptr = GetRegValue("esi");
    auto operationSwitchInput = OperationSwitchInput(ptr);
    // Ignore noisy operations
    if (operationSwitchInput.opcode() == 0x94) {
        return 0;
    }
    if (operationSwitchInput.opcode() == 0x24) {
        return 0;
    }
    if (operationSwitchInput.opcode() == 0x7B) {
        return 0;
    }
    
    Message(operationSwitchInput.toString());

    return 0;
}

static handle_insert_into_pending_operations_wrapper() {
    auto ptr = GetRegValue("eax");
    auto operationSwitchInput = OperationSwitchInput(ptr);
    // Ignore noisy operations
    if (operationSwitchInput.opcode() == 0x94) {
        return 0; // weird thing
    }

    Message("handle_insert_into_pending_operations_wrapper %s", operationSwitchInput.toString());

    return 0;
}

static main() {
    auto bp = AddBpt(0x0053576B);
    SetBptCnd(0x0053576B, "handle_operation_switch()");
    auto bp2 = AddBpt(0x0054AABD);
    SetBptCnd(0x0054AABD, "handle_insert_into_pending_operations_wrapper()");
}

Identified Operations

The following operations have been identified: