zip_source_seek_write —
set write offset in zip source
#include <zip.h>
int
  
  zip_source_seek_write(zip_source_t
    *source, zip_int64_t
    offset, int
    whence);
The function zip_source_seek_write() sets the current
  write offset for source. Just like in
  fseek(3), depending on the
  whence argument, the offset is
  counted relative from:
Upon successful completion 0 is returned. Otherwise, -1 is returned and the
  error information in source is set to indicate the
  error.
zip_source_seek_write() was added in libzip 1.0.