townengine/src/util.h

#ifndef UTIL_H
#define UTIL_H


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

#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <math.h>
#include <stdnoreturn.h>


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

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()))


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


/* for when there's absolutely no way to continue */
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 */
void *cmalloc(size_t size);
void *crealloc(void *ptr, size_t size);
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

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

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


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


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

/* 32-bit color data */
typedef struct color {
    uint8_t r;
    uint8_t g;
    uint8_t b;
    uint8_t a;
} t_color;


/* a point in some space (integer) */
typedef struct vec2 {
    int x, y;
} t_vec2;


/* a point in some space (floating point) */
typedef struct fvec2 {
    float x, y;
} t_fvec2;


/* a point in some three dimension space (floating point) */
/* y goes up, x goes to the right */
typedef struct fvec3 {
    float x, y, z;
} t_fvec3;


/* a point in some space (short) */
typedef struct shvec2 {
    short x, y;
} t_shvec2;


/* a rectangle with the origin at the upper left (integer) */
typedef struct rect {
    int x, y;
    int w, h;
} t_rect;


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


bool intersect_rect(const t_rect *a, const t_rect *b, t_rect *result);

bool intersect_frect(const t_frect *a, const t_frect *b, t_frect *result);

/* TODO: generics and specials (see m_to_fvec2() for an example)*/
t_frect to_frect(t_rect rect);

t_fvec2 frect_center(t_frect rect);


/* aren't macros to prevent double evaluation with side effects */
/* maybe could be inlined? i hope LTO will resolve this */
t_fvec2 fvec2_from_vec2(t_vec2 vec);
t_fvec2 fvec2_from_shvec2(t_shvec2 vec);

#define m_to_fvec2(p_any_vec2) (_Generic((p_any_vec2),          \
                                    t_vec2:   fvec2_from_vec2,  \
                                    t_shvec2: fvec2_from_shvec2 \
                                )(p_any_vec2))


/* 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);
 */
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 */
void tick_ftimer(float *value);

/* same as `tick_ftimer` but instead of clamping it repeats */
/* returns true if value was cycled */
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 t_fvec2 fast_cossine(float a) {
    const float s = sinf(a);
    return (t_fvec2){
        .x = fast_sqrt(1.0f - s * s) * (a >= (float)M_PI_2 && a < (float)(M_PI + M_PI_2) ? -1 : 1),
        .y = s
    };
}


#endif