void glTexSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLsizei width, GLsizei height, GLenum format, GLenum type, const GLvoid* pixels){
    texture_unit* tex_unit = &texture_units[server_texture_unit];
    int texture2d_idx = tex_unit->tex_id;
    texture* target_texture = &tex_unit->textures[texture2d_idx];
    SceGxmTextureFormat tex_format = sceGxmTextureGetFormat(&target_texture->gxm_tex);
    uint8_t bpp = tex_format_to_bytespp(tex_format);
    uint32_t stride = ((sceGxmTextureGetWidth(&target_texture->gxm_tex) + 7) & ~7) * bpp;
    uint8_t* ptr = (uint8_t*)sceGxmTextureGetData(&target_texture->gxm_tex) + xoffset * bpp + yoffset * stride * bpp;
    uint8_t* ptr_line = ptr;
    int i,j;
    switch (target){
        case GL_TEXTURE_2D:
            switch (format){
                case GL_RGB:
                    switch (type){
                        case GL_UNSIGNED_BYTE:
                            switch (tex_format){
                                case SCE_GXM_TEXTURE_FORMAT_U8U8U8U8_ABGR:
                                    for (i=0;i<height;i++){
                                        for (j=0;j<width;j++){
                                            memcpy(ptr, pixels, 3);
                                            ptr[3] = 0xFF;
                                            pixels += 3;
                                            ptr += bpp;
                                        }
                                        ptr = ptr_line + stride;
                                        ptr_line = ptr;
                                    }
                                    break;
                                default:
                                    error = GL_INVALID_ENUM;
                                    break;
                            }
                        default:
                            error = GL_INVALID_ENUM;
                            break;
                    }
                    break;
                case GL_RGBA:
                    switch (type){
                        case GL_UNSIGNED_BYTE:
                            switch (tex_format){
                                case SCE_GXM_TEXTURE_FORMAT_U8U8U8U8_ABGR:
                                    for (i=0;i<height;i++){
                                        memcpy(ptr, pixels, width * bpp);
                                        pixels += width * bpp;
                                        ptr += stride;
                                    }
                                    break;
                                default:
                                    error = GL_INVALID_ENUM;
                                    break;
                            }
                        default:
                            error = GL_INVALID_ENUM;
                            break;
                    }
                    break;
                case GL_LUMINANCE:
                    switch (type){
                        case GL_UNSIGNED_BYTE:
                            switch (tex_format){
                                case SCE_GXM_TEXTURE_FORMAT_L8:
                                    for (i=0;i<height;i++){
                                        memcpy(ptr, pixels, width * bpp);
                                        pixels += width * bpp;
                                        ptr += stride;
                                    }
                                    break;
                                case SCE_GXM_TEXTURE_FORMAT_U8U8U8U8_ABGR:
                                    for (i=0;i<height;i++){
                                        for (j=0;j<width;j++){
                                            ptr[0] = ((uint8_t*)pixels)[0];
                                            ptr[1] = ((uint8_t*)pixels)[0];
                                            ptr[2] = ((uint8_t*)pixels)[0];
                                            ptr[3] = 0xFF;
                                            pixels += 1;
                                            ptr += bpp;
                                        }
                                        ptr = ptr_line + stride;
                                        ptr_line = ptr;
                                    }
                                    break;
                                default:
                                    error = GL_INVALID_ENUM;
                                    break;
                            }
                        default:
                            error = GL_INVALID_ENUM;
                            break;
                    }
                    break;
                default:
                    error = GL_INVALID_ENUM;
                    break;
            }
            break;
        default:
            error = GL_INVALID_ENUM;
            break;
    }
}