// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
//
//  Copyright (c) 2001-2003, Haiku
//
//  This software is part of the Haiku distribution and is covered
//  by the MIT License.
//
//
//  File:        unchop.c
//  Author:      Daniel Reinhold (danielre@users.sf.net)
//  Description: recreates a file previously split with chop
//
// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

#include <OS.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>


void  append_file (int, int);
void  do_unchop   (char *, char *);
void  replace     (char *, char *);
char *temp_file   (void);
void  usage       (void);
bool  valid_file  (char *);


// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// globals

#define BLOCKSIZE 64 * 1024     // file data is read in BLOCKSIZE blocks
static char Block[BLOCKSIZE];   // and stored in the global Block array

static int Errors = 0;



void
usage()
{
	printf("Usage: unchop file\n");
	printf("Concatenates files named file00, file01... into file\n");
}


int
main(int argc, char *argv[])
{
	if (argc != 2) {
		usage();
		return 0;
	}
	else {
		char *origfile = argv[1];
		char *tmpfile  = origfile;
		bool  needs_replace = false;
	
		if (valid_file(origfile)) {
			// output file already exists -- write to temp file
			tmpfile = temp_file();
			needs_replace = true;
		}
		
		do_unchop(tmpfile, origfile);
		
		if (needs_replace) {
			if (Errors == 0)
				replace(origfile, tmpfile);
			else
				remove(tmpfile);
		}
	}
	
	return Errors;
}


void
do_unchop(char *outfile, char *basename)
{
	int fdout = open(outfile, O_WRONLY|O_CREAT|O_APPEND);
	if (fdout < 0)
		fprintf(stderr, "can't open '%s': %s\n", outfile, strerror(errno));
	
	else {
		int  i;
		char fnameN[256];
		
		for (i = 0; i < 999999; ++i) {
			sprintf(fnameN,  "%s%02d", basename, i);
			
			if (valid_file(fnameN)) {
				int fdin = open(fnameN, O_RDONLY);
				if (fdin < 0) {
					fprintf(stderr, "can't open '%s': %s\n", fnameN, strerror(errno));
					++Errors;
				} else {
					append_file(fdin, fdout);
					close(fdin);
				}
			} else {
				if (i == 0)
					printf("No chunk files present (%s)", fnameN);
				break;
			}
		}
		close(fdout);
	}
}


void
append_file(int fdin, int fdout)
{
	// appends the entire contents of the input file
	// to the output file
	
	ssize_t got;
	
	for (;;) {
		got = read(fdin, Block, BLOCKSIZE);
		if (got <= 0)
			break;
		
		write(fdout, Block, got);
	}
}


bool
valid_file(char *fname)
{
	// for this program, a valid file is one that:
	//   a) exists (that always helps)
	//   b) is a regular file (not a directory, link, etc.)
	
	struct stat e;
		
	if (stat(fname, &e) == -1) {
		// no such file
		return false;
	}

	return (S_ISREG(e.st_mode));
}


void
replace(char *origfile, char *newfile)
{
	// replace the contents of the original file
	// with the contents of the new file
	
	char buf[1000];
	
	// delete the original file
	remove(origfile);
	
	// rename the new file to the original file name
	sprintf(buf, "mv \"%s\" \"%s\"", newfile, origfile);
	system(buf);
}


char *
temp_file(void)
{
	// creates a new, temporary file and returns its name
	
	char *tmp = tmpnam(NULL);
	
	FILE *fp = fopen(tmp, "w");
	fclose(fp);
	
	return tmp;
}