so I'm using the zlib package on Ubuntu. I'm trying to figure out how to use gzopen and gzread correctly, this is what I have so far
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <zlib.h>
#define NUM_BUFFERS 8
#define BUFFER_LENGTH 1024
char buf[BUFFER_LENGTH];
int main(int argc, const char* argv[])
{
int status;
gzFile file;
file = gzopen("beowulf.txt", "w");
int counter = 0; /*when the counter reachers BUFFERS_FULL, stop*/
if(file == NULL)
{
printf("COULD NOT OPEN FILE\n");
return 1;
}
while(counter < NUM_BUFFERS)
{
status = gzread(file, buf, BUFFER_LENGTH - 2);
printf("STATUS: %d\n", status);
buf[BUFFER_LENGTH - 1] = "\0";
printf("%s\n", buf);
counter++;
}
gzclose(file);
printf("STATUS: %d\n", status);
return 0;
}
The gzread("STATUS: %d\n",status); returns -2, and I have no clue why. Any help would be appreciated.
3 Answers
Mode "w" indicates that you are preparing to create a new archive:
file = gzopen("beowulf.txt", "w");
You've just truncated the file to zero length.
Also, you should use the binary mode flag: "wb" or "rb".
Also, it's a bit weird that your supposed .gz-archive has an extension .txt.
Read the docs, docs rule. :)
Log the error type using function gzerror(). Since it is -2, it won't be an end-of-file error. Possibly any of the following errors.
Z_DATA_ERROR
A CRC error occurred when reading data; the file is corrupt.
Z_STREAM_ERROR
The stream is invalid, or is in an invalid state.
Z_NEED_DICT
A dictionary is needed (see inflateSetDictionary()).
Z_MEM_ERROR
Insufficient memory available to decompress.
From :
- If the return is positive it is the number of bytes read, you can use that to put the NULL terminator in the right place.
- You can use
gzerrorif the return code is<0to work out what the error is.
