Simple way to unzip a .zip file using zlib [duplicate]

Question

Is there a simple example of how to unzip a .zip file and extract the files to a directory? I am currently using zlib, and while I understand that zlib does not directly deal with zip files, there seems to be several additional things in zlibs's "contrib" library. I noticed and read about "minizip", and after reading some documents and looking at some of the code, I do not see a simple example of how to unzip a .zip file and extract the files to a directory.

I would like to find a platform independent way of doing so, but if that is not possible then I need to find a way for windows and mac.

Answer 1

zlib 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:

#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; } 

Answer 2

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.

// 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:

contrib/minizip/$ gcc -I../.. -o unzip uzip.c unzip.c ioapi.c ../../libz.a contrib/minizip/$ ./unzip.exe /j/zlib-125.zip