slice.c

// slice file to pieces of selected size
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>

#define SLICESIZE 5000
#define MAXNAME 50
#define MAXEXTENSION 10

// routines
char *itoa(long int val, int base);
void removeaddextension(char *filename, int flag);
int fetchsizetype(char *argument);
void arrangeslicefilename(int chapter);
void showusage();
void diskwritefailure();

// constants & variables
char *myname;
const char *sizetypes[]={ "BY", "KB", "MB" };
char sourcefilename[MAXNAME+MAXEXTENSION], filenameextension[MAXEXTENSION];
char slicefilename[MAXNAME+MAXEXTENSION+24];
int disregardextention=1, sizetype=0; // 0 bytes, 1 kbytes, 2 mbytes
int sizetypesmultiplication[3]={ 1, 1024, 1024*1024 };

int main(int argc, char *argv[])
{
  int i, cc, charcount=0, currentchapter=1;
  unsigned long slicesize=SLICESIZE; // 5000 bytes is default size
  char buf[1], ttype[MAXNAME];
  size_t nread, nwrite;
  int infile, outfile;
  strcpy((myname=malloc(sizeof(argv[0]))), argv[0]);

    // parse command line options
    while ((cc = getopt(argc, argv, ":ef:")) != -1)
     switch (cc) {
      case 'e':
       disregardextention=0;
      break;
      case 'f':
       strcpy(ttype, optarg);
       if ((i=fetchsizetype(ttype)))
        slicesize=i;
      break;
      case '?':
       showusage();
      break;
      default:
       abort();
    break; }
    if (optind==argc || argc<2)
     showusage();
    slicesize*=sizetypesmultiplication[sizetype];

   // slice files
   for (i=optind;i<argc;i++, currentchapter=1) {
    // source filename and extension
    strcpy(sourcefilename, argv[i]);
    if ((infile=open(sourcefilename, O_RDONLY))==-1)
     showusage();
    if (disregardextention)
     removeaddextension(sourcefilename, 2);
    // open outfile and break into pieces
    arrangeslicefilename(currentchapter);
    if ((outfile=open(slicefilename, O_WRONLY| O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR))==-1)
     diskwritefailure();
    while (1) {
     if (!(nread=read(infile, buf, sizeof(buf))))
      break;
     if ((nwrite=write(outfile, buf, nread))==-1)
      diskwritefailure();
     ++charcount;
     if (charcount==slicesize) {
      charcount=0;
      ++currentchapter;
      close(outfile);
      arrangeslicefilename(currentchapter);
    outfile=open(slicefilename, O_WRONLY| O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR); } }
    close(infile);
   close(outfile); }

 return 0;
}

// filename extension add/remove
void removeaddextension(char *filename, int flag) // 0 remove, 1 add extension, 2 read extension
{
  int i, n=0;

  switch (flag) {
   case 0:
    i=strlen(filename);
    while (i)
     if (filename[i--]=='.')
    filename[i+1]='\0';
   break;
   case 1:
    removeaddextension(filename, 0);
    strcat(filename, filenameextension);
   break;
   case 2:
    i=strlen(filename);
    while (filename[i]!='.' && i)
     i--;
    if (i)
     for (;i<strlen(filename);i++)
      filenameextension[n++]=filename[i];
    filenameextension[n]='\0';
  break; }
}

// fetch sizetype
int fetchsizetype(char *argument)
{
  int i=strlen(argument), endpoint, n=0;
  char tsizetype[3];

   while (!isdigit(argument[i]) && i>-1)
    --i;
   if (i==-1)
    return 0;
   endpoint=++i;
   for (;i<strlen(argument);i++)
    tsizetype[n++]=toupper(argument[i]);
   tsizetype[n]='\0';
   argument[endpoint]='\0'; // remove sizetype letters
   for (i=0;i<3;i++)
    if (!strcmp(tsizetype, sizetypes[i]))
     break;
   if (i==3)
    return 0;
   sizetype=i;

 return atoi(argument);
}

// arrange slicefilename
void arrangeslicefilename(int chapter)
{
  strcpy(slicefilename, sourcefilename);
  if (disregardextention)
   removeaddextension(slicefilename, 0);
  strcat(slicefilename, "_");
  strcat(slicefilename, itoa(chapter, 10));
  if (disregardextention)
   removeaddextension(slicefilename, 1);
}

// integer to string
char *itoa(long int val, int base)
{
    static char buf[32] = {0};
    int sign_flag=0, v = 30;
    buf[31]='\0';

    if (!val) {
     buf[v]='0';
    return &buf[v]; }
    if (val<0) {
     val*=-1;
    sign_flag=1; }

    for(; val && v ; --v, val /= base)
     buf[v] = "0123456789abcdef"[val % base];
    if (sign_flag) {
     buf[v]='-';
    return &buf[v]; }
    else
     return &buf[v+1];
}

// show usage
void showusage()
{
  printf("%s [-e disregard extension] [-f <slice size (BY, KB, MB)>] [files ...]\n", myname);

 exit(EXIT_FAILURE);
}

// error writing to disk
void diskwritefailure()
{
  printf("error writing to disk!\n");

 exit(EXIT_FAILURE);
}