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guile/ice-9/ftw.scm
Marius Vollmer 7d81830dd2 The FSF has a new address.
2005-05-23 20:15:36 +00:00

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;;;; ftw.scm --- filesystem tree walk
;;;; Copyright (C) 2002, 2003 Free Software Foundation, Inc.
;;;;
;;;; This program is free software; you can redistribute it and/or modify
;;;; it under the terms of the GNU General Public License as published by
;;;; the Free Software Foundation; either version 2, or (at your option)
;;;; any later version.
;;;;
;;;; This program is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;;; GNU General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU General Public License
;;;; along with this software; see the file COPYING. If not, write to
;;;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;;;; Boston, MA 02110-1301 USA
;;;;
;;;; As a special exception, the Free Software Foundation gives permission
;;;; for additional uses of the text contained in its release of GUILE.
;;;;
;;;; The exception is that, if you link the GUILE library with other files
;;;; to produce an executable, this does not by itself cause the
;;;; resulting executable to be covered by the GNU General Public License.
;;;; Your use of that executable is in no way restricted on account of
;;;; linking the GUILE library code into it.
;;;;
;;;; This exception does not however invalidate any other reasons why
;;;; the executable file might be covered by the GNU General Public License.
;;;;
;;;; This exception applies only to the code released by the
;;;; Free Software Foundation under the name GUILE. If you copy
;;;; code from other Free Software Foundation releases into a copy of
;;;; GUILE, as the General Public License permits, the exception does
;;;; not apply to the code that you add in this way. To avoid misleading
;;;; anyone as to the status of such modified files, you must delete
;;;; this exception notice from them.
;;;;
;;;; If you write modifications of your own for GUILE, it is your choice
;;;; whether to permit this exception to apply to your modifications.
;;;; If you do not wish that, delete this exception notice.
;;; Author: Thien-Thi Nguyen <ttn@gnu.org>
;;; Commentary:
;; Two procedures are provided: `ftw' and `nftw'.
;; NOTE: The following description was adapted from the GNU libc info page, w/
;; significant modifications for a more "Schemey" interface. Most noticible
;; are the inlining of `struct FTW *' parameters `base' and `level' and the
;; omission of `descriptors' parameters.
;; * Types
;;
;; The X/Open specification defines two procedures to process whole
;; hierarchies of directories and the contained files. Both procedures
;; of this `ftw' family take as one of the arguments a callback procedure
;; which must be of these types.
;;
;; - Data Type: __ftw_proc_t
;; (lambda (filename statinfo flag) ...) => status
;;
;; Type for callback procedures given to the `ftw' procedure. The
;; first parameter is a filename, the second parameter is the
;; vector value as returned by calling `stat' on FILENAME.
;;
;; The last parameter is a symbol giving more information about
;; FILENAM. It can have one of the following values:
;;
;; `regular'
;; The current item is a normal file or files which do not fit
;; into one of the following categories. This means
;; especially special files, sockets etc.
;;
;; `directory'
;; The current item is a directory.
;;
;; `invalid-stat'
;; The `stat' call to fill the object pointed to by the second
;; parameter failed and so the information is invalid.
;;
;; `directory-not-readable'
;; The item is a directory which cannot be read.
;;
;; `symlink'
;; The item is a symbolic link. Since symbolic links are
;; normally followed seeing this value in a `ftw' callback
;; procedure means the referenced file does not exist. The
;; situation for `nftw' is different.
;;
;; - Data Type: __nftw_proc_t
;; (lambda (filename statinfo flag base level) ...) => status
;;
;; The first three arguments have the same as for the
;; `__ftw_proc_t' type. A difference is that for the third
;; argument some additional values are defined to allow finer
;; differentiation:
;;
;; `directory-processed'
;; The current item is a directory and all subdirectories have
;; already been visited and reported. This flag is returned
;; instead of `directory' if the `depth' flag is given to
;; `nftw' (see below).
;;
;; `stale-symlink'
;; The current item is a stale symbolic link. The file it
;; points to does not exist.
;;
;; The last two parameters are described below. They contain
;; information to help interpret FILENAME and give some information
;; about current state of the traversal of the directory hierarchy.
;;
;; `base'
;; The value specifies which part of the filename argument
;; given in the first parameter to the callback procedure is
;; the name of the file. The rest of the string is the path
;; to locate the file. This information is especially
;; important if the `chdir' flag for `nftw' was set since then
;; the current directory is the one the current item is found
;; in.
;;
;; `level'
;; While processing the directory the procedures tracks how
;; many directories have been examined to find the current
;; item. This nesting level is 0 for the item given starting
;; item (file or directory) and is incremented by one for each
;; entered directory.
;;
;; * Procedure: (ftw filename proc . options)
;; Do a filesystem tree walk starting at FILENAME using PROC.
;;
;; The `ftw' procedure calls the callback procedure given in the
;; parameter PROC for every item which is found in the directory
;; specified by FILENAME and all directories below. The procedure
;; follows symbolic links if necessary but does not process an item
;; twice. If FILENAME names no directory this item is the only
;; object reported by calling the callback procedure.
;;
;; The filename given to the callback procedure is constructed by
;; taking the FILENAME parameter and appending the names of all
;; passed directories and then the local file name. So the
;; callback procedure can use this parameter to access the file.
;; Before the callback procedure is called `ftw' calls `stat' for
;; this file and passes the information up to the callback
;; procedure. If this `stat' call was not successful the failure is
;; indicated by setting the flag argument of the callback procedure
;; to `invalid-stat'. Otherwise the flag is set according to the
;; description given in the description of `__ftw_proc_t' above.
;;
;; The callback procedure is expected to return non-#f to indicate
;; that no error occurred and the processing should be continued.
;; If an error occurred in the callback procedure or the call to
;; `ftw' shall return immediately the callback procedure can return
;; #f. This is the only correct way to stop the procedure. The
;; program must not use `throw' or similar techniques to continue
;; the program in another place. [Can we relax this? --ttn]
;;
;; The return value of the `ftw' procedure is #t if all callback
;; procedure calls returned #t and all actions performed by the
;; `ftw' succeeded. If some procedure call failed (other than
;; calling `stat' on an item) the procedure returns #f. If a
;; callback procedure returns a value other than #t this value is
;; returned as the return value of `ftw'.
;;
;; * Procedure: (nftw filename proc . control-flags)
;; Do a new-style filesystem tree walk starting at FILENAME using PROC.
;; Various optional CONTROL-FLAGS alter the default behavior.
;;
;; The `nftw' procedures works like the `ftw' procedures. It calls
;; the callback procedure PROC for all items it finds in the
;; directory FILENAME and below.
;;
;; The differences are that for one the callback procedure is of a
;; different type. It takes also `base' and `level' parameters as
;; described above.
;;
;; The second difference is that `nftw' takes additional optional
;; arguments which are zero or more of the following symbols:
;;
;; physical'
;; While traversing the directory symbolic links are not
;; followed. I.e., if this flag is given symbolic links are
;; reported using the `symlink' value for the type parameter
;; to the callback procedure. Please note that if this flag is
;; used the appearance of `symlink' in a callback procedure
;; does not mean the referenced file does not exist. To
;; indicate this the extra value `stale-symlink' exists.
;;
;; mount'
;; The callback procedure is only called for items which are on
;; the same mounted filesystem as the directory given as the
;; FILENAME parameter to `nftw'.
;;
;; chdir'
;; If this flag is given the current working directory is
;; changed to the directory containing the reported object
;; before the callback procedure is called.
;;
;; depth'
;; If this option is given the procedure visits first all files
;; and subdirectories before the callback procedure is called
;; for the directory itself (depth-first processing). This
;; also means the type flag given to the callback procedure is
;; `directory-processed' and not `directory'.
;;
;; The return value is computed in the same way as for `ftw'.
;; `nftw' returns #t if no failure occurred in `nftw' and all
;; callback procedure call return values are also #t. For internal
;; errors such as memory problems the error `ftw-error' is thrown.
;; If the return value of a callback invocation is not #t this
;; very same value is returned.
;;; Code:
(define-module (ice-9 ftw)
:export (ftw nftw))
(define (directory-files dir)
(let ((dir-stream (opendir dir)))
(let loop ((new (readdir dir-stream))
(acc '()))
(if (eof-object? new)
(begin
(closedir dir-stream)
acc)
(loop (readdir dir-stream)
(if (or (string=? "." new) ;;; ignore
(string=? ".." new)) ;;; ignore
acc
(cons new acc)))))))
(define (pathify . nodes)
(let loop ((nodes nodes)
(result ""))
(if (null? nodes)
(or (and (string=? "" result) "")
(substring result 1 (string-length result)))
(loop (cdr nodes) (string-append result "/" (car nodes))))))
(define (abs? filename)
(char=? #\/ (string-ref filename 0)))
(define (visited?-proc size)
(let ((visited (make-hash-table size)))
(lambda (s)
(and s (let ((ino (stat:ino s)))
(or (hash-ref visited ino)
(begin
(hash-set! visited ino #t)
#f)))))))
(define (stat-dir-readable?-proc uid gid)
(let ((uid (getuid))
(gid (getgid)))
(lambda (s)
(let* ((perms (stat:perms s))
(perms-bit-set? (lambda (mask)
(not (= 0 (logand mask perms))))))
(or (and (= uid (stat:uid s))
(perms-bit-set? #o400))
(and (= gid (stat:gid s))
(perms-bit-set? #o040))
(perms-bit-set? #o004))))))
(define (stat&flag-proc dir-readable? . control-flags)
(let* ((directory-flag (if (memq 'depth control-flags)
'directory-processed
'directory))
(stale-symlink-flag (if (memq 'nftw-style control-flags)
'stale-symlink
'symlink))
(physical? (memq 'physical control-flags))
(easy-flag (lambda (s)
(let ((type (stat:type s)))
(if (eq? 'directory type)
(if (dir-readable? s)
directory-flag
'directory-not-readable)
'regular)))))
(lambda (name)
(let ((s (false-if-exception (lstat name))))
(cond ((not s)
(values s 'invalid-stat))
((eq? 'symlink (stat:type s))
(let ((s-follow (false-if-exception (stat name))))
(cond ((not s-follow)
(values s stale-symlink-flag))
((and s-follow physical?)
(values s 'symlink))
((and s-follow (not physical?))
(values s-follow (easy-flag s-follow))))))
(else (values s (easy-flag s))))))))
(define (clean name)
(let ((last-char-index (1- (string-length name))))
(if (char=? #\/ (string-ref name last-char-index))
(substring name 0 last-char-index)
name)))
(define (ftw filename proc . options)
(let* ((visited? (visited?-proc (cond ((memq 'hash-size options) => cadr)
(else 211))))
(stat&flag (stat&flag-proc
(stat-dir-readable?-proc (getuid) (getgid)))))
(letrec ((go (lambda (fullname)
(call-with-values (lambda () (stat&flag fullname))
(lambda (s flag)
(or (visited? s)
(let ((ret (proc fullname s flag))) ; callback
(or (eq? #t ret)
(throw 'ftw-early-exit ret))
(and (eq? 'directory flag)
(for-each
(lambda (child)
(go (pathify fullname child)))
(directory-files fullname)))
#t)))))))
(catch 'ftw-early-exit
(lambda () (go (clean filename)))
(lambda (key val) val)))))
(define (nftw filename proc . control-flags)
(let* ((od (getcwd)) ; orig dir
(odev (let ((s (false-if-exception (lstat filename))))
(if s (stat:dev s) -1)))
(same-dev? (if (memq 'mount control-flags)
(lambda (s) (= (stat:dev s) odev))
(lambda (s) #t)))
(base-sub (lambda (name base) (substring name 0 base)))
(maybe-cd (if (memq 'chdir control-flags)
(if (abs? filename)
(lambda (fullname base)
(or (= 0 base)
(chdir (base-sub fullname base))))
(lambda (fullname base)
(chdir
(pathify od (base-sub fullname base)))))
(lambda (fullname base) #t)))
(maybe-cd-back (if (memq 'chdir control-flags)
(lambda () (chdir od))
(lambda () #t)))
(depth-first? (memq 'depth control-flags))
(visited? (visited?-proc
(cond ((memq 'hash-size control-flags) => cadr)
(else 211))))
(has-kids? (if depth-first?
(lambda (flag) (eq? flag 'directory-processed))
(lambda (flag) (eq? flag 'directory))))
(stat&flag (apply stat&flag-proc
(stat-dir-readable?-proc (getuid) (getgid))
(cons 'nftw-style control-flags))))
(letrec ((go (lambda (fullname base level)
(call-with-values (lambda () (stat&flag fullname))
(lambda (s flag)
(letrec ((self (lambda ()
(maybe-cd fullname base)
;; the callback
(let ((ret (proc fullname s flag
base level)))
(maybe-cd-back)
(or (eq? #t ret)
(throw 'nftw-early-exit ret)))))
(kids (lambda ()
(and (has-kids? flag)
(for-each
(lambda (child)
(go (pathify fullname child)
(1+ (string-length
fullname))
(1+ level)))
(directory-files fullname))))))
(or (visited? s)
(not (same-dev? s))
(if depth-first?
(begin (kids) (self))
(begin (self) (kids)))))))
#t)))
(let ((ret (catch 'nftw-early-exit
(lambda () (go (clean filename) 0 0))
(lambda (key val) val))))
(chdir od)
ret))))
;;; ftw.scm ends here
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