NAME

zipfs - Mount and work with ZIP files within Tcl

SYNOPSIS

package require tcl::zipfs ?1.0?

zipfs canonical ?mntpnt? filename ?ZIPFS?
zipfs exists filename
zipfs find directoryName
zipfs info filename
zipfs list ?(-glob|-regexp)? ?pattern?
zipfs lmkimg outfile inlist ?password infile?
zipfs lmkzip outfile inlist ?password?
zipfs mkimg outfile indir ?strip? ?password? ?infile?
zipfs mkkey password
zipfs mkzip outfile indir ?strip? ?password?
zipfs mount ?mountpoint? ?zipfile? ?password?
zipfs root
zipfs unmount mountpoint

DESCRIPTION

The zipfs command (the sole public command provided by the built-in package with the same name) provides Tcl with the ability to mount the contents of a ZIP archive file as a virtual file system. ZIP archives support simple encryption, sufficient to prevent casual inspection of their contents but not able to prevent access by even a moderately determined attacker.

zipfs canonical ?mountpoint? filename ?inZipfs?: This takes the name of a file, filename, and produces where it would be mapped into a zipfs mount as its result. If specified, mountpoint says within which mount the mapping will be done; if omitted, the main root of the zipfs system is used. The inZipfs argument is a an optional boolean which controls whether to fully canonicalise the name; it defaults to true.
zipfs exists filename: Return 1 if the given filename exists in the mounted zipfs and 0 if it does not.
zipfs find directoryName: Recursively lists files including and below the directory directoryName. The result list consists of relative path names starting from the given directory. This command is also used by the zipfs mkzip and zipfs mkimg commands.
zipfs info file: Return information about the given file in the mounted zipfs. The information consists of:

(1): the name of the ZIP archive file that contains the file,
(2): the size of the file after decompressions,
(3): the compressed size of the file, and
(4): the offset of the compressed data in the ZIP archive file.

Note: querying the mount point gives the start of the zip data as the offset in (4), which can be used to truncate the zip information from an executable.

zipfs list ?(-glob|-regexp)? ?pattern?: Return a list of all files in the mounted zipfs, or just those matching pattern (optionally controlled by the option parameters). The order of the names in the list is arbitrary.
zipfs mount ?mountpoint? ?zipfile? ?password?: The zipfs mount command mounts a ZIP archive file as a Tcl virtual filesystem at mountpoint. After this command executes, files contained in zipfile will appear to Tcl to be regular files at the mount point.

With no zipfile, returns the zipfile mounted at mountpoint. With no mountpoint, return all zipfile/mount pairs. If mountpoint is specified as an empty string, mount on file path.

NB: because the current working directory is a concept maintained by the operating system, using cd into a mounted archive will only work in the current process, and then not entirely consistently (e.g., if a shared library uses direct access to the OS rather than through Tcl's filesystem API, it will not see the current directory as being inside the mount and will not be able to access the files inside the mount).

zipfs root: Returns a constant string which indicates the mount point for zipfs volumes for the current platform. On Windows, this value is “zipfs:/”. On Unix, this value is “//zipfs:/”.
zipfs unmount mountpoint: Unmounts a previously mounted ZIP archive mounted to mountpoint.

ZIP CREATION COMMANDS

This package also provides several commands to aid the creation of ZIP archives as Tcl applications.

zipfs mkzip outfile indir ?strip? ?password?: Creates a ZIP archive file named outfile from the contents of the input directory indir (contained regular files only) with optional ZIP password password. While processing the files below indir the optional file name prefix given in strip is stripped off the beginning of the respective file name. When stripping, it is common to remove either the whole source directory name or the name of its parent directory.

Caution: the choice of the indir parameter (less the optional stripped prefix) determines the later root name of the archive's content.

zipfs mkimg outfile indir ?strip? ?password? ?infile?: Creates an image (potentially a new executable file) similar to zipfs mkzip; see that command for a description of most parameters to this command, as they behave identically here.

If the infile parameter is specified, this file is prepended in front of the ZIP archive, otherwise the file returned by info nameofexecutable (i.e., the executable file of the running process) is used. If the password parameter is not empty, an obfuscated version of that password (see zipfs mkkey) is placed between the image and ZIP chunks of the output file and the contents of the ZIP chunk are protected with that password. If the starting image has a ZIP archive already attached to it, it is removed from the copy in outfile before the new ZIP archive is added.

If there is a file, main.tcl, in the root directory of the resulting archive and the image file that the archive is attached to is a tclsh (or wish) instance (true by default, but depends on your configuration), then the resulting image is an executable that will source the script in that main.tcl after mounting the ZIP archive, and will exit once that script has been executed.

Caution: highly experimental, not usable on Android, only partially tested on Linux and Windows.

zipfs mkkey password: Given the clear text password argument, an obfuscated string version is returned with the same format used in the zipfs mkimg command.
zipfs lmkimg outfile inlist ?password infile?: This command is like zipfs mkimg, but instead of an input directory, inlist must be a Tcl list where the odd elements are the names of files to be copied into the archive in the image, and the even elements are their respective names within that archive.
zipfs lmkzip outfile inlist ?password?: This command is like zipfs mkzip, but instead of an input directory, inlist must be a Tcl list where the odd elements are the names of files to be copied into the archive, and the even elements are their respective names within that archive.

EXAMPLES

Mounting an ZIP archive as an application directory and running code out of it before unmounting it again:

set zip myApp.zip
set base [file join [zipfs root] myApp]
zipfs mount $base $zip
# $base now has the contents of myApp.zip
source [file join $base app.tcl]
# use the contents, load libraries from it, etc...
zipfs unmount $zip

Creating a ZIP archive, given that a directory exists containing the content to put in the archive. Note that the source directory is given twice, in order to strip the exterior directory name from each filename in the archive.

set sourceDirectory [file normalize myApp]
set targetZip myApp.zip
zipfs mkzip $targetZip $sourceDirectory $sourceDirectory

Encryption can be applied to ZIP archives by providing a password when building the ZIP and when mounting it.

set zip myApp.zip
set sourceDir [file normalize myApp]
set password "hunter2"
set base [file join [zipfs root] myApp]
# Create with password
zipfs mkzip $targetZip $sourceDir $sourceDir $password
# Mount with password
zipfs mount $base $zip $password

When creating an executable image with a password, the password is placed within the executable in a shrouded form so that the application can read files inside the embedded ZIP archive yet casual inspection cannot read it.

set appDir [file normalize myApp]
set img "myApp.bin"
set password "hunter2"
# Create some simple content to define a basic application
file mkdir $appDir
set f [open $appDir/main.tcl]
puts $f {
    puts "Hi. This is [info script]"
}
close $f
# Create the executable
zipfs mkimg $img $appDir $appDir $password
# Launch the executable, printing its output to stdout
exec $img >@stdout
#    prints: Hi. This is //zipfs:/app/main.tcl

KEYWORDS