Question

I was making a code and I had like 5 include files in there, I was defining functions in this file and then realized why should not I just make separate header files for all the functions and then just include them in a file at last. But, I have seen that this is not done usually. Why not? Is there a particular disadvantage of doing this?

Answer 1

This is not a real answer, because the question has a wrong assumption:

But, I have seen that this is not done usually.

This is not true. This is a common practice. A good example is ffmpeg.h. The header is a front-end to an extensive library.

The argument of long compilation times is bogus. Today the systems are very fast. This is only important for really huge systems, but I really don’t think that you work with them. I never encountered such systems myself.

And compilation times aren’t execution times. This is another misconception.

For your convenience the whole code of ffmpeg.h:

#ifndef _INCLUDE_FFMPEG_H_
#define _INCLUDE_FFMPEG_H_

#ifdef HAVE_FFMPEG
#include <avformat.h>
#endif

#include <stdio.h>
#include <stdarg.h>

/* Define a codec name/identifier for timelapse videos, so that we can
 * differentiate between normal mpeg1 videos and timelapse videos.
 */
#define TIMELAPSE_CODEC "mpeg1_tl"

struct ffmpeg {
#ifdef HAVE_FFMPEG
    AVFormatContext *oc;
    AVStream *video_st;
    AVCodecContext *c;

    AVFrame *picture;       /* contains default image pointers */
    uint8_t *video_outbuf;
    int video_outbuf_size;

    void *udata;            /* U & V planes for greyscale images */
    int vbr;                /* variable bitrate setting */
    char codec[20];         /* codec name */
#else
    int dummy;
#endif
};

/* Initialize FFmpeg stuff. Needs to be called before ffmpeg_open. */
void ffmpeg_init(void);

/* Open an mpeg file. This is a generic interface for opening either an mpeg1 or
 * an mpeg4 video. If non-standard mpeg1 isn't supported (FFmpeg build > 4680), 
 * calling this function with "mpeg1" as codec results in an error. To create a
 * timelapse video, use TIMELAPSE_CODEC as codec name.
 */
struct ffmpeg *ffmpeg_open(
    char *ffmpeg_video_codec, 
    char *filename, 
    unsigned char *y,    /* YUV420 Y plane */
    unsigned char *u,    /* YUV420 U plane */
    unsigned char *v,    /* YUV420 V plane */
    int width,
    int height, 
    int rate,            /* framerate, fps */
    int bps,             /* bitrate; bits per second */
    int vbr              /* variable bitrate */
    );

/* Puts the image pointed to by the picture member of struct ffmpeg. */
void ffmpeg_put_image(struct ffmpeg *);

/* Puts the image defined by u, y and v (YUV420 format). */
void ffmpeg_put_other_image(
    struct ffmpeg *ffmpeg, 
    unsigned char *y, 
    unsigned char *u, 
    unsigned char *v
    );

/* Closes the mpeg file. */
void ffmpeg_close(struct ffmpeg *);

/*Deinterlace the image. */
void ffmpeg_deinterlace(unsigned char *, int, int);

/*Setup an avcodec log handler. */
void ffmpeg_avcodec_log(void *, int, const char *, va_list);

#endif /* _INCLUDE_FFMPEG_H_ */