BlueAmulet's PhysBodySetTransform body function

PhysBodySetTransform.cpp

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <iterator>

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <dbghelp.h>

extern "C" {
#include <lua.h>
#include <lauxlib.h>
}

namespace {

struct Node {
    // std::map implementation detail
    void* left;
    void* parent;
    void* right;
    char color;
    char isnil;

    int component_id;
    void* component_ptr;
};

struct CompIt {
    Node* ptr;
    CompIt() {}
    bool operator==(const CompIt& other) { return ptr == other.ptr; }
    bool operator!=(const CompIt& other) { return !(*this == other); }
};

typedef CompIt (__stdcall* fnkGetComponent)(const int&);
fnkGetComponent getComponent = nullptr;

const std::uint8_t get_comp_search[] = {
    0x8b, 0xd6, 0x8b, 0x46, 0x04, 0x80, 0x78, 0x0d, 0x00, 0x75, 0x2b, 0x8b, 0x4d, 0x0c, 0x8b, 0x09,
    0x8d, 0x9b, 0x00, 0x00, 0x00, 0x00, 0x39, 0x48, 0x10, 0x73, 0x05, 0x8b, 0x40, 0x08, 0xeb, 0x04,
    0x8b, 0xd0, 0x8b, 0x00, 0x80, 0x78, 0x0d, 0x00, 0x74, 0xec, 0x3b, 0xd6, 0x74, 0x08, 0x89, 0x55,
    0x0c, 0x3b, 0x4a, 0x10, 0x73, 0x03, 0x89, 0x75, 0x0c, 0x8b, 0x45, 0x08, 0x8d, 0x4d, 0x0c, 0x8b,
    0x09, 0x5e, 0x89, 0x08, 0x5d, 0xc2, 0x08, 0x00
};
const std::ptrdiff_t function_offset = -10;

fnkGetComponent find_get_component()
{
    void* exe_location = GetModuleHandleA(nullptr);
    IMAGE_NT_HEADERS* header = ImageNtHeader(exe_location);

    auto section_byte_start = (char*)&header->OptionalHeader + header->FileHeader.SizeOfOptionalHeader;
    auto section_begin = (IMAGE_SECTION_HEADER*)section_byte_start;
    auto section_end = section_begin + header->FileHeader.NumberOfSections;

    auto text_section = std::find_if(section_begin, section_end,
        [](IMAGE_SECTION_HEADER& section) { return std::strcmp((char*)section.Name, ".text") == 0; });

    auto text_start = (std::uint8_t*)exe_location + text_section->VirtualAddress;
    auto text_end = text_start + text_section->SizeOfRawData;

    // The Steam noita(_dev).exe files have two occurrences of the search text,
    // for both of them it's the last occurrence that is the get component by id
    // function. (That's why it's using std::find_end instead of std::search)
    auto search_result = std::find_end(
        text_start, text_end,
        std::begin(get_comp_search), std::end(get_comp_search));

    if (search_result == text_end)
        return nullptr;

    return (fnkGetComponent)(search_result + function_offset);
}

}

// Check 8DE910 (b2Body::Dump()) for offsets
int PhysBodySetTransform(lua_State* L) {
    if (getComponent == nullptr) {
        getComponent = find_get_component();
    }

    int componentId = luaL_checkinteger(L, 1);
    double x = luaL_checknumber(L, 2);
    double y = luaL_checknumber(L, 3);
    double r = luaL_checknumber(L, 4);
    double vx = luaL_checknumber(L, 5);
    double vy = luaL_checknumber(L, 6);
    double av = luaL_checknumber(L, 7);

    CompIt comp_it = getComponent(componentId);
    if (comp_it == getComponent(-943857)) {
        return 0;
    }
    char* physBody = (char*)comp_it.ptr->component_ptr;
    int b2Body = *(int*)(physBody + 0x48);
    if (b2Body == 0) {
        return 0;
    }
    *(double*)(b2Body + 0x58) = x;
    *(double*)(b2Body + 0x60) = y;
    *(double*)(b2Body + 0x70) = r;
    *(double*)(b2Body + 0x80) = vx;
    *(double*)(b2Body + 0x88) = vy;
    *(double*)(b2Body + 0x90) = av;
    return 0;
}