lib/libcodex/code-rot13.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 2003-2011 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                 Eclipse Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                A copy of the License is available at                 *
*          http://www.eclipse.org/org/documents/epl-v10.html           *
*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                   Phong Vo <kpv@research.att.com>                    *
*                                                                      *
***********************************************************************/
#pragma prototyped

/*
 * rot13 decoder/encoder
 */

#include <codex.h>

typedef struct State_s
{
    unsigned char   rot[256];

    unsigned char*  buf;
    size_t      bufsiz;
} State_t;

static const char   rot[] = "abcdefghijklmnopqrstuvwxyz";
static const char   ROT[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

static int
rot13_open(Codex_t* p, char* const args[], Codexnum_t flags)
{
    register State_t*   state;
    register int        i;

    if (!(state = newof(0, State_t, 1, 0)))
    {
        if (p->disc->errorf)
            (*p->disc->errorf)(NiL, p->disc, 2, "out of space");
        return -1;
    }
    for (i = 0; i < sizeof(state->rot); i++)
        state->rot[i] = i;
    for (i = 0; i < sizeof(rot); i++)
        state->rot[rot[i]] = rot[(i + 13) % 26];
    for (i = 0; i < sizeof(ROT); i++)
        state->rot[ROT[i]] = ROT[(i + 13) % 26];
    p->data = state;
    return 0;
}

static int
rot13_close(Codex_t* p)
{
    State_t*    state = (State_t*)p->data;

    if (!state)
        return -1;
    if (state->buf)
        free(state->buf);
    free(state);
    return 0;
}

static ssize_t
rot13_read(Sfio_t* sp, void* buf, size_t n, Sfdisc_t* disc)
{
    register State_t*   state = (State_t*)CODEX(disc)->data;
    register unsigned char* s;
    register unsigned char* e;
    ssize_t         r;

    if ((r = sfrd(sp, buf, n, disc)) > 0)
        for (e = (s = (unsigned char*)buf) + r; s < e; s++)
            *s = state->rot[*s];
    return r;
}

static ssize_t
rot13_write(Sfio_t* sp, const void* buf, size_t n, Sfdisc_t* disc)
{
    register State_t*   state = (State_t*)CODEX(disc)->data;
    register unsigned char* s;
    register unsigned char* e;
    register unsigned char* b;

    if (n > state->bufsiz)
    {
        state->bufsiz = roundof(n, 1024);
        if (!(state->buf = newof(state->buf, unsigned char, state->bufsiz, 0)))
        {
            if (CODEX(disc)->disc->errorf)
                (*CODEX(disc)->disc->errorf)(NiL, CODEX(disc)->disc, 2, "out of space");
            return -1;
        }
    }
    for (b = state->buf, e = (s = (unsigned char*)buf) + n; s < e; s++)
        *b++ = state->rot[*s];
    return sfwr(sp, state->buf, n, disc);
}

Codexmeth_t codex_rot13 =
{
    "rot13",
    "rot13 self-inverting encoding.",
    "[+(version)?codex-rot13 (AT&T Research) 2003-12-11]"
    "[+(author)?Glenn Fowler <gsf@research.att.com>]",
    CODEX_DECODE|CODEX_ENCODE|CODEX_UU,
    0,
    0,
    rot13_open,
    rot13_close,
    0,
    0,
    rot13_read,
    rot13_write,
    0,
    0,
    0,
    0,
    0,
    CODEXNEXT(rot13)
};

CODEXLIB(rot13)