using lzo library in c++ application

Question

I got lzo library to use in our application. The version was provided is 1.07. They have given me .lib along with some header file and some .c source files.

I have setup test environment as per specs. I am able to see lzo routine functions in my application.

Here is my test application

#include "stdafx.h"
#include "lzoconf.h"
#include "lzo1z.h"
#include <stdlib.h>


int _tmain(int argc, _TCHAR* argv[])
{
    FILE * pFile;
    long lSize;
    unsigned char *i_buff;
    unsigned char *o_buff;

    int i_len,e = 0;
    unsigned int o_len;

    size_t result;

    //data.txt have a single compressed packet 
    pFile = fopen("data.txt","rb");

    if (pFile==NULL) 
        return -1;

    // obtain file size:
    fseek (pFile , 0 , SEEK_END);
    lSize = ftell (pFile);
    rewind (pFile);

    // allocate memory to contain the whole file:
    i_buff = (unsigned char*) malloc (sizeof(char)*lSize);
    if (i_buff == NULL) 
        return -1;

    // copy the file into the buffer:
    result = fread (i_buff,1,lSize,pFile);
    if (result != lSize) 
        return -1;

    i_len = lSize;
    o_len = 512;

    // allocate memory for output buffer
    o_buff = (unsigned char*) malloc(sizeof(char)*o_len);

    if (o_buff == NULL) 
        return -1;
     lzo_memset(o_buff,0,o_len);    
    lzo1z_decompress(i_buff,i_len,o_buff,&o_len,NULL);

    return 0;   
}

It gives access violation on last line.

lzo1z_decompress(i_buff,i_len,o_buff,&o_len,NULL);

in provided library signature for above functiion is

lzo1z_decompress        ( const lzo_byte *src, lzo_uint  src_len,
                                lzo_byte *dst, lzo_uint *dst_len,
                                lzo_voidp wrkmem /* NOT USED */ );

What is wrong?

Answer 1

Are you sure 512 bytes is big enough for the decompressed data? You shouldn't be using an arbitrary value, but rather you should have stowed away the original size somewhere as a header when your file was compressed:

http://stackoverflow.com/questions/773962/lzo-decompression-buffer-size

You should probably make your data types match the interface spec (e.g. o_len should be a lzo_uint...you're passing an address so the actual underlying type matters).

Beyond that, it's open source. So why don't you build lzo with debug info and step into it to see where the problem is?

http://www.oberhumer.com/opensource/lzo/

Answer 2

Thans everyone for suggestion and comments.

The problem was with data. I have successfully decomressed it.