Versione delle 18:46, 3 lug 2017

La libreria 'libzip consente di gestire file compressi .zip.

Per poter fruire in gambas delle risorse della libreria libzip, è necessario installare e richiamare la libreria dinamica condivisa: libzip.so.2.1.0

Mostriamo un esempio pratico per estrarre uno o più file contenuti in un file compresso .zip:

Public Struct zip_stat
  valid As Long
  name As Pointer
  index As Long
  size As Long
  comp_size As Long
  mtime As Long
  crc As Integer
  comp_method As Short
  encryption_method As Short
  flags As Integer
End Struct


Library "libzip:2.1.0"

' struct zip *zip_open(const char *, int, int *)
' Open zip archive.
Private Extern zip_open(path As String, flags As Integer, errorp As Pointer) As Pointer

' zip_int64_t zip_get_num_entries(zip_t *, zip_flags_t)
' Get number of files in archive.
Private Extern zip_get_num_entries(archive As Pointer, flags As Integer) As Long

' int zip_stat_index(struct zip *, int, int, struct zip_stat *)
' Get information about file by index.
Private Extern zip_stat_index(archive As Pointer, index As Integer, flags As Integer, sb As Zip_stat) As Integer

' struct zip_file * zip_fopen_index(struct zip *, int, int)
' Open file in zip archive for reading by index
Private Extern zip_fopen_index(archive As Pointer, index As Integer, flags As Integer) As Pointer

' zip_int64_t zip_fread(struct zip_file *, void *, zip_uint64_t)
' Read from file.
Private Extern zip_fread(zfile As Pointer, buf As Byte[], nbytes As Long) As Long

' int zip_fclose(struct zip_file *)
' Close file in zip archive.
Private Extern zip_fclose(zfile As Pointer)

' int zip_close(struct zip archive)
' Close zip archive.
Private Extern zip_close(archive As Pointer)


Public Sub Main()
 
 Dim percorsoZip, decompresso As String
 Dim z, zf As Pointer
 Dim i, lun As Integer
 Dim zs As New Zip_stat
 Dim l As Long
 Dim fl As File
 Dim buf As New Byte[64]
 
  percorsoZip = "/percorso/del/file.zip"
  decompresso = "/percorso/ove/saranno/estratti/i/file"
  
  z = zip_open(percorsoZip, 0, 0)
  If IsNull(z) Then Error.Raise("Impossibile aprire un file '.zip' !")
  
  For i = 0 To zip_get_num_entries(z, 0) - 1
     
    If zip_stat_index(z, i, 0, zs) = 0 Then
      lun = Len(String@(zs.name))
      Print "Nome:       "; String@(zs.name)
      Print "Dimensione: "; zs.size
      Print "mtime:      "; zs.mtime
      If Right(String@(zs.name), 1) = "/" Then
        Continue
      Else
        zf = zip_fopen_index(z, i, 0)
        If IsNull(zf) Then Error.Raise("Errore alla funzione 'zip_fopen_index()' !")
        fl = Open decompresso &/ File.Name(String@(zs.name)) For Create
        While l < zs.size
          lun = zip_fread(zf, buf, 64)
          If lun < 0 Then Error.Raise("Errore nella lettura del file !")
          buf.Write(fl, 0, lun)
          l += lun
        Wend
        fl.Close
        zip_fclose(zf)
      Endif
    Endif
          
  Next
  
  zip_close(z)
  
End

Riferimenti

• http://www.nih.at/libzip
• http://sourcecodebrowser.com/libzip/0.9/index.html
• https://linux.die.net/man/3/libzip