#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/mman.h>
#include <sys/stat.h>

extern const char *__progname;

static int file_fd;
static const char *filename;
static const unsigned char *file;
static unsigned int filesize;

static unsigned int moov_at = 0;
static unsigned int moov_len = 0;
static unsigned int mdat_at = 0;
static unsigned int mdat_len = 0;

#define FOURCHAR(a,b,c,d) ( ((a) * 0x01000000) +	\
			    ((b) *   0x010000) +	\
			    ((c) *     0x0100) +	\
			    ((d) *       0x01) )

static void usage(void)
{
 fprintf(stderr,"Usage: %s filename\n",__progname);
 exit(1);
}

static void map_file(const char *name)
{
 struct stat stb;
 void *mmrv;

 filename = name;
 file_fd = open(name,O_RDONLY,0);
 if (file_fd < 0)
  { fprintf(stderr,"%s: %s: %s\n",__progname,name,strerror(errno));
    exit(1);
  }
 fstat(file_fd,&stb);
 filesize = stb.st_size;
 if (filesize != stb.st_size)
  { fprintf(stderr,"%s: %s: too large\n",__progname,name);
    exit(1);
  }
 mmrv = mmap(0,stb.st_size,PROT_READ,MAP_FILE|MAP_SHARED,file_fd,0);
 if (mmrv == MAP_FAILED)
  { fprintf(stderr,"%s: mmap %s: %s\n",__progname,name,strerror(errno));
    exit(1);
  }
 file = mmrv;
}

static unsigned int get4be(unsigned int o)
{
 return( (file[o  ] * 0x01000000) +
	 (file[o+1] *   0x010000) +
	 (file[o+2] *     0x0100) +
	 (file[o+3] *       0x01) );
}

static void print_4_vis(FILE *to, const unsigned char *d)
{
 int i;

 for (i=4;i>0;i--)
  { if (*d < 32)
     { fprintf(to,"^%c",64+*d);
     }
    else if (*d < 127)
     { putc(*d,to);
     }
    else if (*d == 127)
     { fprintf(to,"^?");
     }
    else if (*d < 160)
     { fprintf(to,"^%c",64+*d);
     }
    else
     { putc(*d,to);
     }
    d ++;
  }
}

static void scan_chunks(unsigned int start, unsigned int len, void (*chunk)(const unsigned char [4], unsigned int, unsigned int))
{
 unsigned int o;
 unsigned int l;

 o = 0;
 while (1)
  { if (o == len) break;
    if (o+8 > len)
     { printf("chunk overrun 1 (%u+8 > %u)\n",o,len);
       exit(1);
     }
    l = get4be(start+o);
    if (l == 1)
     { printf("64-bit chunk length at %u+%u\n",start,o);
       exit(1);
     }
    if (l < 8)
     { printf("runt chunk (%u) at %u+%u\n",l,start,o);
       exit(1);
     }
    printf("%08x+%08x: chunk len=%x type=",start,o,l);
    print_4_vis(stdout,file+start+o+4);
    printf("\n");
    if (o+l > len)
     { printf("chunk overrun 2 (%u+%u > %u)\n",o,l,len);
       exit(1);
     }
    (*chunk)(file+start+o+4,start+o+8,l-8);
    o += l;
  }
}

static void file_chunk(const unsigned char type[4], unsigned int data, unsigned int len)
{
 int i;

 switch (FOURCHAR(type[0],type[1],type[2],type[3]))
  { default:
       printf("skipping unknown chunk\n");
       return;
    case FOURCHAR('f','t','y','p'):
       if (len < 8)
	{ printf("ftyp chunk too small (%u)\n",len);
	  return;
	}
       if (len % 4)
	{ printf("ftyp chunk length (%u) isn't a multiple of 4\n",len);
	  return;
	}
       printf("ftyp: major `");
       print_4_vis(stdout,file+data);
       printf("' minor %08x compat:",get4be(data+4));
       for (i=8;i<len;i+=4)
	{ printf(" ");
	  print_4_vis(stdout,file+data+i);
	}
       printf("\n");
       break;
    case FOURCHAR('m','o','o','v'):
       moov_at = data;
       moov_len = len;
       break;
    case FOURCHAR('m','d','a','t'):
       mdat_at = data;
       mdat_len = len;
       break;
    case FOURCHAR('f','r','e','e'):
       break;
  }
}

int main(int, char **);
int main(int ac, char **av)
{
 if (ac != 2) usage();
 map_file(av[1]);
 scan_chunks(0,filesize,&file_chunk);
 return(0);
}