#include "master.hpp"

namespace factor {

typedef unsigned char UBYTE;

const UBYTE UNW_FLAG_EHANDLER = 0x1;

struct UNWIND_INFO {
    UBYTE Version:3;
    UBYTE Flags:5;
    UBYTE SizeOfProlog;
    UBYTE CountOfCodes;
    UBYTE FrameRegister:4;
    UBYTE FrameOffset:4;
    ULONG ExceptionHandler;
    ULONG ExceptionData[1];
};

struct seh_data {
    UNWIND_INFO unwind_info;
    RUNTIME_FUNCTION func;
    UBYTE handler[32];
};

void factor_vm::c_to_factor_toplevel(cell quot)
{
    /* The annoying thing about Win64 SEH is that the offsets in
     * function tables are 32-bit integers, and the exception handler
     * itself must reside between the start and end pointers, so
     * we stick everything at the beginning of the code heap and
     * generate a small trampoline that jumps to the real
     * exception handler. */

    seh_data *seh_area = (seh_data *)code->seh_area;
    cell base = code->seg->start;

    /* Should look at generating this with the Factor assembler */

    /* mov rax,0 */
    seh_area->handler[0] = 0x48;
    seh_area->handler[1] = 0xb8;
    seh_area->handler[2] = 0x0;
    seh_area->handler[3] = 0x0;
    seh_area->handler[4] = 0x0;
    seh_area->handler[5] = 0x0;
    seh_area->handler[6] = 0x0;
    seh_area->handler[7] = 0x0;
    seh_area->handler[8] = 0x0;
    seh_area->handler[9] = 0x0;

    /* jmp rax */
    seh_area->handler[10] = 0x48;
    seh_area->handler[11] = 0xff;
    seh_area->handler[12] = 0xe0;

    /* Store address of exception handler in the operand of the 'mov' */
    cell handler = (cell)&factor::exception_handler;
    memcpy(&seh_area->handler[2],&handler,sizeof(cell));

    UNWIND_INFO *unwind_info = &seh_area->unwind_info;
    unwind_info->Version = 1;
    unwind_info->Flags = UNW_FLAG_EHANDLER;
    unwind_info->SizeOfProlog = 0;
    unwind_info->CountOfCodes = 0;
    unwind_info->FrameRegister = 0;
    unwind_info->FrameOffset = 0;
    unwind_info->ExceptionHandler = (DWORD)((cell)&seh_area->handler[0] - base);
    unwind_info->ExceptionData[0] = 0;

    RUNTIME_FUNCTION *func = &seh_area->func;
    func->BeginAddress = 0;
    func->EndAddress = (DWORD)(code->seg->end - base);
    func->UnwindData = (DWORD)((cell)&seh_area->unwind_info - base);

    if(!RtlAddFunctionTable(func,1,base))
        fatal_error("RtlAddFunctionTable() failed",0);

    c_to_factor(quot);

    if(!RtlDeleteFunctionTable(func))
        fatal_error("RtlDeleteFunctionTable() failed",0);
}

}