Zipping of files

rajesh_b · 10-20-2004, 05:28 AM

Hi

I am writing a c program which will zip the files in the directories. It will read the directory names that have to be zipped from an xml file. For this i m using libxml parser. What i want to do is that "How to zip the files". Is there any libraries/Header files available under linux so that i can call the appropriate functions to zip the files. I want to do this with out using system function. Any one have ideas about this.

Thankx in advance,
rajesh.

CroMagnon · 10-20-2004, 06:31 AM

I think you want zlib.

barisdemiray · 10-20-2004, 06:34 AM

Quote:

Originally posted by rajesh_b
[B
..
Is there any libraries/Header files available under linux so that i can call the appropriate functions to zip the files. I want to do this with out using system function. Any one have ideas about this.

Thankx in advance,
rajesh. [/B]

Hello, you can use the zlib library for this purpose. Here is an example code.. this is used for gzipping log files if they're oversized:

Code:

int ns_compress_file(char *file_path)
{
	FILE   *in_file;		/* file that will be compressed */
	gzFile  gz_file;		/* gzip file descriptor */
	char   *gz_file_path;		/* file name that will be created */
	char   *in_file_buffer;		/* buffer that will hold input file */
	unsigned long in_file_size;	/* input file's size in byte(s) */

	if ( !(in_file = fopen(file_path, "r")) )	{
		ns_log_event("Input file cannot be opened for compressing", LOG_ERR);
		return -1;
	}

	/* add the extension's (.gz) length */
	gz_file_path = (char *)malloc(strlen(file_path) + 4);
	sprintf(gz_file_path, "%s.gz", file_path);
	printf("DEBUG: output file will be %s\n", gz_file_path);

	if ( !(gz_file = gzopen(gz_file_path, "wb")) )	{
		ns_log_event("gzip file cannot be opened for writing", LOG_ERR);
		fclose(in_file);
		free(gz_file_path);
		return -1;
	}

	in_file_size = ns_get_file_size_path(file_path);
	in_file_buffer = (char *)malloc(in_file_size * BYTE);
	if ( (fread(in_file_buffer, BYTE, in_file_size, in_file)) < in_file_size )	{
		ns_log_event("Read error in input file at ns_compress_file()", LOG_ERR);
		goto fire_exit;
	}

	/* write out the compressed file */
	if ( !(gzwrite(gz_file, in_file_buffer, in_file_size)) )	{
		ns_log_event("Error writing compressed file at ns_compressed_file()", \
					 LOG_ERR);
		goto fire_exit;
	} else {	/* everything must be OK here */
		free(gz_file_path);
		free(in_file_buffer);
		gzclose(gz_file);
		/* 
		 * remove the source file after creating compressed one
		 */
		unlink(file_path);
		fclose(in_file);
		return 0;
	}

	/* 
	 * Here is an advantage of goto statement:
	 * if you don't like goto statement, write this 
	 * cleanup code 3 or 4 times after each if statement.
	 * Lost of readability? No!
	 * i love goto :-)
	 */
  fire_exit:
	free(gz_file_path);
	free(in_file_buffer);
	gzclose(gz_file);
	fclose(in_file);
	return -1;
}

Don't forget to include zlib.h header.

rajesh_b · 10-20-2004, 07:05 AM

Hai barisdemiray,
Thanx for u reply. I tried the code given by u. But i m getting errors when i am trying to compile it. the errrors are

/tmp/ccSDyhwf.o(.text+0x2d): In function `ns_compress_file':
: undefined reference to `ns_log_event'
/tmp/ccSDyhwf.o(.text+0x92): In function `ns_compress_file':
: undefined reference to `gzopen'
/tmp/ccSDyhwf.o(.text+0xad): In function `ns_compress_file':
: undefined reference to `ns_log_event'
/tmp/ccSDyhwf.o(.text+0xe3): In function `ns_compress_file':
: undefined reference to `ns_get_file_size_path'
/tmp/ccSDyhwf.o(.text+0x124): In function `ns_compress_file':
: undefined reference to `ns_log_event'
similarly there are other errors . But i have zlib.h file in "/usr/include" directory. I dont know why i am getting these errors.
Please help me.

barisdemiray · 10-20-2004, 11:02 AM

Ooops! Sorry about that.

As i _don't_ said, this code fragment is part of my current project named NetSentinel and the functions beginning with ns_* is implemented in my source tree. So it's normal to getting these errors. I will also copy the ns_get_file_size_path() function. ns_log_event calls could be replaced with perror("Aiiii! Some error occured") calls and then link the zlib library (like gcc -o code -lz code.c). Finally, there should be no problem anymore.

Here is the ns_get_file_size_path() function:

Code:

/*
 * Returns the file size in bytes
 * @param file_path Full path of the file
 */
unsigned long ns_get_file_size_path(char *file_path)
{
	FILE *fp;
	unsigned long file_size = 0L;

	if ( !(fp = fopen(file_path, "r")) )	{
		ns_log_event("Cannot open file", LOG_ERR);
		return 0;
	}

	fseek(fp, 0L, SEEK_END);
	file_size = ftell(fp);
	fclose(fp);

	return file_size;
}

rajesh_b · 10-27-2004, 06:02 AM

Thanx for u r help
It worked out.

Rajesh.