2005

## zzip/memdisk

zip cache for mmapped views

> These routines are fully independent from the traditional zzip implementation. They build on top of zzip/mmapped that uses a readonly mmapped sharedmem block. These functions add additional hints how to parse extension blocks and how to cache the zip central directory entries which does furthermore allow to convert them to any host-local format as required.

### zzip disk handle

Other than with the fseeko alternative interface there is no need to have an actual disk handle to the zip archive. Instead you can use a bytewise copy of a file or even use a mmapped view of a file. This is generally the fastest way to get to the data contained in a zipped file. All it requires is enough of virtual memory space but a desktop computer with a a modern operating system will easily take care of that.

The zzipmmapped library provides a number of calls to create a disk handle representing a zip archive in virtual memory. Per default we use the sys/mmap.h (or MappedView) functionality of the operating system. See for more details in the zzip/mmapped descriptions.

The zzip/memdisk extensions of zzip/mmapped are made to have a very similar call API - therefore you will find again open and close functions for filenames or filehandles. However the direct mmap interface is not re-exported under the zzip_mem_disk prefix (of the underlying zzip_disk prefix). The "_mem_" part hints that the central directory of the underlying zzip_disk is preparsed to a separate memory block.

      ZZIP_MEM_DISK*  zzip_mem_disk_open(char* filename);
      ZZIP_MEM_DISK*  zzip_mem_disk_fdopen(int fd);
      void            zzip_mem_disk_close(ZZIP_MEM_DISK* disk);

      int  zzip_mem_disk_load (ZZIP_MEM_DISK* dir, ZZIP_DISK* disk);
      void zzip_mem_disk_unload (ZZIP_MEM_DISK* dir);

The last two functions export some parts of the underlying interface. It is possible to bind an existing ZZIP_MEM_DISK handle with an arbitrary ZZIP_DISK handle. Upon calling "load" the central directory will be loaded from the underlying zip disk content and parsed to an internal mem block. The corresponding "unload" function will trash that central directory cache but it leaves the handles intact.

### reading the central directory

All other zzip_mem_disk functions are simply re-exporting the underlying zzip_disk functions. Note that the first field in the ZZIP_MEM_DISK is a "ZZIP_DISK* disk" - the header file zzip/memdisk.h will simply export inline functions where there is no special zzip_mem_disk function. Therefore, whenever a function call on a ZZIP_DISK handle is appropriate one can also use its cousin for a ZZIP_MEM_DISK handle without any penalties but future compatibility for extra functionality in zzip/memdisk layer of the zzip/mmapped library.

Note: by default the re-exports are done with the help of the C precompiler as precompiler macros. Using USE_INLINE will force to make them real inlines. In the future that may change in favor of a better autodetection for inline capabilities of the compiler and/or using a standard cpp-define that enables the C/C++ inline functions. The inline functions do have the added value of having strongtyped arguments provoking more readable warning messages in user application code.

         inline ZZIP_DISK_ENTRY*
    zzip_mem_disk_findfirst(ZZIP_MEM_DISK* dir);
         inline ZZIP_DISK_ENTRY*
    zzip_mem_disk_findnext(ZZIP_MEM_DISK* dir, ZZIP_DISK_ENTRY* entry);
         inline char* _zzip_restrict
    zzip_mem_disk_entry_strdup_name(ZZIP_MEM_DISK* dir,
                                    ZZIP_DISK_ENTRY* entry);
         inline struct zzip_file_header*
    zzip_mem_disk_entry_to_file_header(ZZIP_MEM_DISK* dir,
    				   ZZIP_DISK_ENTRY* entry);
         inline char*
    zzip_mem_disk_entry_to_data(ZZIP_MEM_DISK* dir, ZZIP_DISK_ENTRY* entry);
         inline ZZIP_DISK_ENTRY*
    zzip_mem_disk_findfile(ZZIP_MEM_DISK* dir,
                           char* filename, ZZIP_DISK_ENTRY* after,
    		       zzip_strcmp_fn_t compare);
         inline ZZIP_DISK_ENTRY*
    zzip_mem_disk_findmatch(ZZIP_MEM_DISK* dir,
                            char* filespec, ZZIP_DISK_ENTRY* after,
    			zzip_fnmatch_fn_t compare, int flags);
         inline ZZIP_DISK_FILE* _zzip_restrict
    zzip_mem_disk_entry_fopen (ZZIP_MEM_DISK* dir, ZZIP_DISK_ENTRY* entry);
         inline ZZIP_DISK_FILE* _zzip_restrict
    zzip_mem_disk_fopen (ZZIP_MEM_DISK* dir, char* filename);
         inline _zzip_size_t
    zzip_mem_disk_fread (void* ptr, _zzip_size_t size, _zzip_size_t nmemb,
                         ZZIP_DISK_FILE* file);
         inline int
    zzip_mem_disk_fclose (ZZIP_DISK_FILE* file);
         inline int
    zzip_mem_disk_feof (ZZIP_DISK_FILE* file);