townengine/include/twn_util.h

#ifndef UTIL_H
#define UTIL_H

#include "twn_vec.h"
#include "twn_engine_api.h"

#include <SDL2/SDL.h>
#include <physfs.h>

#include <stdint.h>
#include <stdbool.h>


/*                   */
/* GENERAL UTILITIES */
/*                   */

TWN_API void cry_impl(const char *file, const int line, const char *title, const char *text);
#define CRY(title, text) cry_impl(__FILE__, __LINE__, title, text)
#define CRY_SDL(title) cry_impl(__FILE__, __LINE__, title, SDL_GetError())
#define CRY_PHYSFS(title)                                               \
cry_impl(__FILE__, __LINE__, title, PHYSFS_getErrorByCode(PHYSFS_getLastErrorCode()))


TWN_API void log_info(const char *restrict format, ...);
TWN_API void log_critical(const char *restrict format, ...);
TWN_API void log_warn(const char *restrict format, ...);


/* for when there's absolutely no way to continue */
TWN_API _Noreturn void die_abruptly(void);


/* "critical" allocation functions which will log and abort() on failure. */
/* if it is reasonable to handle this gracefully, use the standard versions. */
/* the stb implementations will be configured to use these */
TWN_API void *cmalloc(size_t size);
TWN_API void *crealloc(void *ptr, size_t size);
TWN_API void *ccalloc(size_t num, size_t size);


/* DON'T FORGET ABOUT DOUBLE EVALUATION */
/* YOU THINK YOU WON'T, AND THEN YOU DO */
/* C23's typeof could fix it, so i will */
/* leave them as macros to be replaced. */
/* use the macro in tgmath.h for floats */
#define MAX SDL_max
#define MIN SDL_min

#ifndef M_PI
#define M_PI 3.14159265358979323846264338327950288   /**< pi */
#endif

/* multiply by these to convert degrees <---> radians */
#define DEG2RAD (M_PI / 180)
#define RAD2DEG (180 / M_PI)

/* TODO: this is why generics were invented. sorry, i'm tired today */
TWN_API double clamp(double d, double min, double max);
TWN_API float clampf(float f, float min, float max);
TWN_API int clampi(int i, int min, int max);

/* sets buf_out to a pointer to a byte buffer which must be freed. */
/* returns the size of this buffer. */
TWN_API int64_t file_to_bytes(const char *path, unsigned char **buf_out);

/* returns a pointer to a string which must be freed */
TWN_API char *file_to_str(const char *path);

/* returns true if the file exists in the filesystem */
TWN_API bool file_exists(const char *path);

/* saves all texture atlases as BMP files in the write directory */
TWN_API void textures_dump_atlases(void);


/* returns true if str ends with suffix */
TWN_API TWN_API bool strends(const char *str, const char *suffix);


/*                      */
/* GAME LOGIC UTILITIES */
/*                      */

/* 32-bit color data */
typedef struct Color {
_Alignas(4)
    uint8_t r;
    uint8_t g;
    uint8_t b;
    uint8_t a;
} Color;


/* a rectangle with the origin at the upper left (integer) */
typedef struct Recti {
_Alignas(16)
    int32_t x;
    int32_t y;
    int32_t w;
    int32_t h;
} Recti;


/* a rectangle with the origin at the upper left (floating point) */
typedef struct Rect {
_Alignas(16)
    float x;
    float y;
    float w;
    float h;
} Rect;


/* calculates the overlap of two rectangles and places it in result. */
/* result may be NULL. if this is the case, it will simply be ignored. */
/* returns true if the rectangles are indeed intersecting. */
TWN_API bool overlap_rect(const Recti *a, const Recti *b, Recti *result);
TWN_API bool overlap_frect(const Rect *a, const Rect *b, Rect *result);

/* returns true if two rectangles are intersecting */
TWN_API bool intersect_rect(const Recti *a, const Recti *b);
TWN_API bool intersect_frect(const Rect *a, const Rect *b);

/* TODO: generics and specials (see m_vec2_from() for an example)*/
TWN_API Rect to_frect(Recti rect);

TWN_API Vec2 frect_center(Rect rect);


typedef struct Matrix4 {
    Vec4 row[4];
} Matrix4;


/* decrements an lvalue (which should be an int), stopping at 0 */
/* meant for tick-based timers in game logic */
/*
 * example:
 * tick_timer(&player->jump_air_timer);
 */
TWN_API void tick_timer(int *value);

/* decrements a floating point second-based timer, stopping at 0.0 */
/* meant for poll based real time logic in game logic */
/* note that it should be decremented only on the next tick after its creation */
TWN_API void tick_ftimer(float *value);

/* same as `tick_ftimer` but instead of clamping it repeats */
/* returns true if value was cycled */
TWN_API bool repeat_ftimer(float *value, float at);

/* http://www.azillionmonkeys.com/qed/sqroot.html */
static inline float fast_sqrt(float x)
{
    union {
        float f;
        uint32_t u;
    } pun = {.f = x};

    pun.u += 127 << 23;
    pun.u >>= 1;

    return pun.f;
}


static inline Vec2 fast_cossine(float a) {
    const float s = sinf(a);
    return (Vec2){
        .x = fast_sqrt(1.0f - s * s) * (a >= (float)M_PI_2 && a < (float)(M_PI + M_PI_2) ? -1 : 1),
        .y = s
    };
}

static inline bool is_power_of_two(int x)
{
    return (x != 0) && ((x & (x - 1)) == 0);
}

#endif