unescape.c

[詳解]

/*++
/* NAME
/*  unescape 3
/* SUMMARY
/*  translate C-like escape sequences
/* SYNOPSIS
/*  #include <stringops.h>
/*
/*  VSTRING *unescape(result, input)
/*  VSTRING *result;
/*  const char *input;
/*
/*  VSTRING *escape(result, input, len)
/*  VSTRING *result;
/*  const char *input;
/*  ssize_t len;
/* DESCRIPTION
/*  unescape() translates C-like escape sequences in the null-terminated
/*  string \fIinput\fR and places the result in \fIresult\fR. The result
/*  is null-terminated, and is the function result value.
/*
/*  escape() does the reverse transformation.
/*
/*  Escape sequences and their translations:
/* .IP \ea
/*  Bell character.
/* .IP \eb
/*  Backspace character.
/* .IP \ef
/*  formfeed character.
/* .IP \en
/*  newline character
/* .IP \er
/*  Carriage-return character.
/* .IP \et
/*  Horizontal tab character.
/* .IP \ev
/*  Vertical tab character.
/* .IP \e\e
/*  Backslash character.
/* .IP \e\fInum\fR
/*  8-bit character whose ASCII value is the 1..3 digit
/*  octal number \fInum\fR.
/* .IP \e\fIother\fR
/*  The backslash character is discarded.
/* 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 <vstring.h>
#include <stringops.h>

/* unescape - process escape sequences */

VSTRING *unescape(VSTRING *result, const char *data)
{
    int     ch;
    int     oval;
    int     i;

#define UCHAR(cp)   ((unsigned char *) (cp))
#define ISOCTAL(ch) (ISDIGIT(ch) && (ch) != '8' && (ch) != '9')

    VSTRING_RESET(result);

    while ((ch = *UCHAR(data++)) != 0) {
    if (ch == '\\') {
        if ((ch = *UCHAR(data++)) == 0)
        break;
        switch (ch) {
        case 'a':               /* \a -> audible bell */
        ch = '\a';
        break;
        case 'b':               /* \b -> backspace */
        ch = '\b';
        break;
        case 'f':               /* \f -> formfeed */
        ch = '\f';
        break;
        case 'n':               /* \n -> newline */
        ch = '\n';
        break;
        case 'r':               /* \r -> carriagereturn */
        ch = '\r';
        break;
        case 't':               /* \t -> horizontal tab */
        ch = '\t';
        break;
        case 'v':               /* \v -> vertical tab */
        ch = '\v';
        break;
        case '0':               /* \nnn -> ASCII value */
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        for (oval = ch - '0', i = 0;
             i < 2 && (ch = *UCHAR(data)) != 0 && ISOCTAL(ch);
             i++, data++) {
            oval = (oval << 3) | (ch - '0');
        }
        ch = oval;
        break;
        default:                /* \any -> any */
        break;
        }
    }
    VSTRING_ADDCH(result, ch);
    }
    VSTRING_TERMINATE(result);
    return (result);
}

/* escape - reverse transformation */

VSTRING *escape(VSTRING *result, const char *data, ssize_t len)
{
    int     ch;

    VSTRING_RESET(result);
    while (len-- > 0) {
    ch = *UCHAR(data++);
    if (ISASCII(ch)) {
        if (ISPRINT(ch)) {
        if (ch == '\\')
            VSTRING_ADDCH(result, ch);
        VSTRING_ADDCH(result, ch);
        continue;
        } else if (ch == '\a') {        /* \a -> audible bell */
        vstring_strcat(result, "\\a");
        continue;
        } else if (ch == '\b') {        /* \b -> backspace */
        vstring_strcat(result, "\\b");
        continue;
        } else if (ch == '\f') {        /* \f -> formfeed */
        vstring_strcat(result, "\\f");
        continue;
        } else if (ch == '\n') {        /* \n -> newline */
        vstring_strcat(result, "\\n");
        continue;
        } else if (ch == '\r') {        /* \r -> carriagereturn */
        vstring_strcat(result, "\\r");
        continue;
        } else if (ch == '\t') {        /* \t -> horizontal tab */
        vstring_strcat(result, "\\t");
        continue;
        } else if (ch == '\v') {        /* \v -> vertical tab */
        vstring_strcat(result, "\\v");
        continue;
        }
    }
    vstring_sprintf_append(result, "\\%03o", ch);
    }
    VSTRING_TERMINATE(result);
    return (result);
}

#ifdef TEST

#include <stdlib.h>
#include <string.h>
#include <msg.h>
#include <vstring_vstream.h>

int     main(int argc, char **argv)
{
    VSTRING *in = vstring_alloc(10);
    VSTRING *out = vstring_alloc(10);
    int     un_escape = 1;

    if (argc > 2 || (argc > 1 && (un_escape = strcmp(argv[1], "-e"))) != 0)
    msg_fatal("usage: %s [-e (escape)]", argv[0]);

    if (un_escape) {
    while (vstring_fgets_nonl(in, VSTREAM_IN)) {
        unescape(out, vstring_str(in));
        vstream_fwrite(VSTREAM_OUT, vstring_str(out), VSTRING_LEN(out));
        VSTREAM_PUTC('\n', VSTREAM_OUT);
    }
    } else {
    while (vstring_fgets_nonl(in, VSTREAM_IN)) {
        escape(out, vstring_str(in), VSTRING_LEN(in));
        vstream_fwrite(VSTREAM_OUT, vstring_str(out), VSTRING_LEN(out));
        VSTREAM_PUTC('\n', VSTREAM_OUT);
    }
    }
    vstream_fflush(VSTREAM_OUT);
    exit(0);
}

#endif