dir_forest.c

[詳解]

/*++
/* NAME
/*  dir_forest 3
/* SUMMARY
/*  file name to directory forest
/* SYNOPSIS
/*  #include <dir_forest.h>
/*
/*  char    *dir_forest(buf, path, depth)
/*  VSTRING *buf;
/*  const char *path;
/*  int depth;
/* DESCRIPTION
/*  This module implements support for directory forests: a file
/*  organization that introduces one or more levels of intermediate
/*  subdirectories in order to reduce the number of files per directory.
/*
/*  dir_forest() maps a file basename to a directory forest and
/*  returns the resulting string: file name "abcd" becomes "a/b/"
/*  and so on. The number of subdirectory levels is adjustable.
/*
/*  Arguments:
/* .IP buf
/*  A buffer that is overwritten with the result. The result
/*  ends in "/" and is null terminated. If a null pointer is
/*  specified, the result is written to a private buffer that
/*  is overwritten upon each call.
/* .IP path
/*  A null-terminated string of printable characters. Characters
/*  special to the file system are not permitted.
/*  The first subdirectory is named after the first character
/*  in \fIpath\fR, and so on. When the path is shorter than the
/*  desired number of subdirectory levels, directory names
/*  of '_' (underscore) are used as replacement.
/* .IP depth
/*  The desired number of subdirectory levels.
/* DIAGNOSTICS
/*  Panic: interface violations. Fatal error: out of memory.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <ctype.h>

/* Utility library. */

#include "msg.h"
#include "dir_forest.h"

/* dir_forest - translate base name to directory forest */

char   *dir_forest(VSTRING *buf, const char *path, int depth)
{
    const char *myname = "dir_forest";
    static VSTRING *private_buf = 0;
    int     n;
    const char *cp;
    int     ch;

    /*
     * Sanity checks.
     */
    if (*path == 0)
    msg_panic("%s: empty path", myname);
    if (depth < 1)
    msg_panic("%s: depth %d", myname, depth);

    /*
     * Your buffer or mine?
     */
    if (buf == 0) {
    if (private_buf == 0)
        private_buf = vstring_alloc(1);
    buf = private_buf;
    }

    /*
     * Generate one or more subdirectory levels, depending on the pathname
     * contents. When the pathname is short, use underscores instead.
     * Disallow non-printable characters or characters that are special to
     * the file system.
     */
    VSTRING_RESET(buf);
    for (cp = path, n = 0; n < depth; n++) {
    if ((ch = *cp) == 0) {
        ch = '_';
    } else {
        if (!ISPRINT(ch) || ch == '.' || ch == '/')
        msg_panic("%s: invalid pathname: %s", myname, path);
        cp++;
    }
    VSTRING_ADDCH(buf, ch);
    VSTRING_ADDCH(buf, '/');
    }
    VSTRING_TERMINATE(buf);

    if (msg_verbose > 1)
    msg_info("%s: %s -> %s", myname, path, vstring_str(buf));
    return (vstring_str(buf));
}