First of all allow me some comments:
Your program is not compiled and linked by Eclipse.
Compiling is done by the compiler (gcc using option -c):
make all
Building file: ../zip.c
Invoking: GCC C Compiler
gcc -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"zip.d" -MT"zip.d" -o "zip.o" "../zip.c"
Finished building: ../zip.c
Linking is done by the linker (via the compiler using option -o):
Invoking: GCC C Linker
gcc -o "unzipper" ./zip.o
./main.o: In function `zip':
/home/alk/workspace/unzipper/Debug/../zip.c:20: undefined reference to `zip_open'
/home/alk/workspace/unzipper/Debug/../zip.c:27: undefined reference to `zip_get_num_files'
/home/alk/workspace/unzipper/Debug/../zip.c:33: undefined reference to `zip_fopen_index'
/home/alk/workspace/unzipper/Debug/../zip.c:35: undefined reference to `zip_fread'
/home/alk/workspace/unzipper/Debug/../zip.c:38: undefined reference to `zip_fclose'
/home/alk/workspace/unzipper/Debug/../zip.c:43: undefined reference to `zip_close'
collect2: ld returned 1 exit status
Eclipse provides a framework helping you in managing all sources and their references as also spawing compiler and linker tasks and setting their options.
When the linker told you there where undefined references to the zip_*function during the build of your program, the cause for this was, you were missing to tell the linker (via the compiler, via Eclipse) where those zip_* functions could be found.
Those zip_* functions are located in a library, namely libzip.
So what you as the programmer need to tell the linker (via the compiler, via Eclipse) is to link those functions against what the compiler compiled from your sources.
As the result the linker is able to create a runnable program from your compiled sources together with all libraries needed. Certain libraries are know to Eclipse (and therfore to the linker) by default, for example the one containing the C standard functions, namely libc.
To get things going:
1 Remove the source files you pulled from the libzip librarie's sources from your project. Those sources had been compiled into the library libzip, which you will use in your project.
2 Tell the linker (via Eclipse) to use libzip for your project.
Do so by following the steps below:
open the project's properties
click 'C/C++ General'
click 'Path and Symbols', on the left select the 'Libraries' tab, there click 'Add' and enter zip
finally click 'OK'
3 Then try to build your program:
Building target: unzipper
Invoking: GCC C Linker
gcc -o "unzipper" ./zip.o -lzip
Finished building target: unzipper
(Please note additional option -lzip!)
If the developement version of 'libzip' had been installed properly before, you should be fine.
PS: unzipper was the name I used for the Eclispe project to produce the examples.
PSS: I used Eclipse Juno SR1
Answer from alk on Stack OverflowFirst of all allow me some comments:
Your program is not compiled and linked by Eclipse.
Compiling is done by the compiler (gcc using option -c):
make all
Building file: ../zip.c
Invoking: GCC C Compiler
gcc -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"zip.d" -MT"zip.d" -o "zip.o" "../zip.c"
Finished building: ../zip.c
Linking is done by the linker (via the compiler using option -o):
Invoking: GCC C Linker
gcc -o "unzipper" ./zip.o
./main.o: In function `zip':
/home/alk/workspace/unzipper/Debug/../zip.c:20: undefined reference to `zip_open'
/home/alk/workspace/unzipper/Debug/../zip.c:27: undefined reference to `zip_get_num_files'
/home/alk/workspace/unzipper/Debug/../zip.c:33: undefined reference to `zip_fopen_index'
/home/alk/workspace/unzipper/Debug/../zip.c:35: undefined reference to `zip_fread'
/home/alk/workspace/unzipper/Debug/../zip.c:38: undefined reference to `zip_fclose'
/home/alk/workspace/unzipper/Debug/../zip.c:43: undefined reference to `zip_close'
collect2: ld returned 1 exit status
Eclipse provides a framework helping you in managing all sources and their references as also spawing compiler and linker tasks and setting their options.
When the linker told you there where undefined references to the zip_*function during the build of your program, the cause for this was, you were missing to tell the linker (via the compiler, via Eclipse) where those zip_* functions could be found.
Those zip_* functions are located in a library, namely libzip.
So what you as the programmer need to tell the linker (via the compiler, via Eclipse) is to link those functions against what the compiler compiled from your sources.
As the result the linker is able to create a runnable program from your compiled sources together with all libraries needed. Certain libraries are know to Eclipse (and therfore to the linker) by default, for example the one containing the C standard functions, namely libc.
To get things going:
1 Remove the source files you pulled from the libzip librarie's sources from your project. Those sources had been compiled into the library libzip, which you will use in your project.
2 Tell the linker (via Eclipse) to use libzip for your project.
Do so by following the steps below:
open the project's properties
click 'C/C++ General'
click 'Path and Symbols', on the left select the 'Libraries' tab, there click 'Add' and enter zip
finally click 'OK'
3 Then try to build your program:
Building target: unzipper
Invoking: GCC C Linker
gcc -o "unzipper" ./zip.o -lzip
Finished building target: unzipper
(Please note additional option -lzip!)
If the developement version of 'libzip' had been installed properly before, you should be fine.
PS: unzipper was the name I used for the Eclispe project to produce the examples.
PSS: I used Eclipse Juno SR1
Answer from alk on Stack Overflowzlib handles the deflate compression/decompression algorithm, but there is more than that in a ZIP file.
You can try libzip. It is free, portable and easy to use.
UPDATE: Here I attach quick'n'dirty example of libzip, with all the error controls ommited:
Copy#include <zip.h>
int main()
{
//Open the ZIP archive
int err = 0;
zip *z = zip_open("foo.zip", 0, &err);
//Search for the file of given name
const char *name = "file.txt";
struct zip_stat st;
zip_stat_init(&st);
zip_stat(z, name, 0, &st);
//Alloc memory for its uncompressed contents
char *contents = new char[st.size];
//Read the compressed file
zip_file *f = zip_fopen(z, name, 0);
zip_fread(f, contents, st.size);
zip_fclose(f);
//And close the archive
zip_close(z);
//Do something with the contents
//delete allocated memory
delete[] contents;
}
Minizip does have an example programs to demonstrate its usage - the files are called minizip.c and miniunz.c.
Update: I had a few minutes so I whipped up this quick, bare bones example for you. It's very smelly C, and I wouldn't use it without major improvements. Hopefully it's enough to get you going for now.
Copy// uzip.c - Simple example of using the minizip API.
// Do not use this code as is! It is educational only, and probably
// riddled with errors and leaks!
#include <stdio.h>
#include <string.h>
#include "unzip.h"
#define dir_delimter '/'
#define MAX_FILENAME 512
#define READ_SIZE 8192
int main( int argc, char **argv )
{
if ( argc < 2 )
{
printf( "usage:\n%s {file to unzip}\n", argv[ 0 ] );
return -1;
}
// Open the zip file
unzFile *zipfile = unzOpen( argv[ 1 ] );
if ( zipfile == NULL )
{
printf( "%s: not found\n" );
return -1;
}
// Get info about the zip file
unz_global_info global_info;
if ( unzGetGlobalInfo( zipfile, &global_info ) != UNZ_OK )
{
printf( "could not read file global info\n" );
unzClose( zipfile );
return -1;
}
// Buffer to hold data read from the zip file.
char read_buffer[ READ_SIZE ];
// Loop to extract all files
uLong i;
for ( i = 0; i < global_info.number_entry; ++i )
{
// Get info about current file.
unz_file_info file_info;
char filename[ MAX_FILENAME ];
if ( unzGetCurrentFileInfo(
zipfile,
&file_info,
filename,
MAX_FILENAME,
NULL, 0, NULL, 0 ) != UNZ_OK )
{
printf( "could not read file info\n" );
unzClose( zipfile );
return -1;
}
// Check if this entry is a directory or file.
const size_t filename_length = strlen( filename );
if ( filename[ filename_length-1 ] == dir_delimter )
{
// Entry is a directory, so create it.
printf( "dir:%s\n", filename );
mkdir( filename );
}
else
{
// Entry is a file, so extract it.
printf( "file:%s\n", filename );
if ( unzOpenCurrentFile( zipfile ) != UNZ_OK )
{
printf( "could not open file\n" );
unzClose( zipfile );
return -1;
}
// Open a file to write out the data.
FILE *out = fopen( filename, "wb" );
if ( out == NULL )
{
printf( "could not open destination file\n" );
unzCloseCurrentFile( zipfile );
unzClose( zipfile );
return -1;
}
int error = UNZ_OK;
do
{
error = unzReadCurrentFile( zipfile, read_buffer, READ_SIZE );
if ( error < 0 )
{
printf( "error %d\n", error );
unzCloseCurrentFile( zipfile );
unzClose( zipfile );
return -1;
}
// Write data to file.
if ( error > 0 )
{
fwrite( read_buffer, error, 1, out ); // You should check return of fwrite...
}
} while ( error > 0 );
fclose( out );
}
unzCloseCurrentFile( zipfile );
// Go the the next entry listed in the zip file.
if ( ( i+1 ) < global_info.number_entry )
{
if ( unzGoToNextFile( zipfile ) != UNZ_OK )
{
printf( "cound not read next file\n" );
unzClose( zipfile );
return -1;
}
}
}
unzClose( zipfile );
return 0;
}
I built and tested it with MinGW/MSYS on Windows like this:
Copycontrib/minizip/$ gcc -I../.. -o unzip uzip.c unzip.c ioapi.c ../../libz.a
contrib/minizip/$ ./unzip.exe /j/zlib-125.zip
You can try using zip_stat to get file size.
http://linux.die.net/man/3/zip_stat
I haven't used the libzip interface but from what you write it seems to look very similar to a file interface: once you got a handle to the stream you keep calling zip_fread() until this function return an error (ir, possibly, less than requested bytes). The buffer you pass in us just a reasonably size temporary buffer where the data is communicated.
Personally I would probably create a stream buffer for this so once the file in the zip archive is set up it can be read using the conventional I/O stream methods. This would look something like this:
struct zipbuf: std::streambuf {
zipbuf(???): file_(???) {}
private:
zip_file* file_;
enum { s_size = 8196 };
char buffer_[s_size];
int underflow() {
int rc(zip_fread(this->file_, this->buffer_, s_size));
this->setg(this->buffer_, this->buffer_,
this->buffer_ + std::max(0, rc));
return this->gptr() == this->egptr()
? traits_type::eof()
: traits_type::to_int_type(*this->gptr());
}
};
With this stream buffer you should be able to create an std::istream and read the file into whatever structure you need:
zipbuf buf(???);
std::istream in(&buf);
...
Obviously, this code isn't tested or compiled. However, when you replace the ??? with whatever is needed to open the zip file, I'd think this should pretty much work.