allegro5

folder_checksum.c

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <zlib.h>   // for the adler-32 checksum

#include <allegro5/allegro.h>

//required by fmtime
#include <sys/types.h>
#include <sys/stat.h>
#ifndef WIN32          // linking -lmingw32 will be required
#include <unistd.h>
#endif
#ifdef WIN32
#define stat _stat
#endif


/* 
Get file modification time (stackoverflow.com/a/40504396/5496529)
*/
uint32_t fmtime(const char* filename) {
    if(stat(filename, &fmtime_result)==0) {
        return fmtime_result.st_mtime;
    }
    
   return 0;
}


/* 
Get the extension of a file
*/
const char* get_file_ext(const char* fspec) {
    char *e = strrchr (fspec, '.');
    if (e == NULL) {
        e = "";
    } else {
        ++e;
    }
    
    return e;
}


/* 
Iterate over each .png file at a folder and calculate an adler-32 checksum by feeding it the name and modification time of files only
(based on code from allegro.cc/forums/thread/606721/908205#target)
*/
int getDirectoryItems(const char* path) {
    // name of each file during iteration
    char *name;

    // modification date of each file during iteration
    uint32_t fmtime_v;

    // running Adler-32 checksum
    long unsigned int adler = adler32(0L, Z_NULL, 0);

    ALLEGRO_FS_ENTRY* dir = al_create_fs_entry(path);
    if(al_open_directory(dir)) {
        ALLEGRO_FS_ENTRY* file;
        while((file = al_read_directory(dir))) {
            name = (char*)al_get_fs_entry_name(file);
            if (!strcmp(get_file_ext(name), "png")) {                
                // adler consider bytes [0..len-1], so we pass the full length of a string
                adler = adler32(adler, (const unsigned char*) name, sizeof(name));
                fmtime_v = fmtime(name);
                // adler consider bytes [0..len-1], so we pass the length of the number + 1
                adler = adler32(adler, (const unsigned char*) &fmtime_v, sizeof(fmtime_v) + 1);
            }
            al_destroy_fs_entry(file);
        }
    }
    printf("adler32 %lu\n", adler); // e.g.: 3391961898
    al_destroy_fs_entry(dir);

    return 0;
}