source: MondoRescue/branches/3.2/mindi-busybox/libbb/uuencode.c@ 3232

/* vi: set sw=4 ts=4: */
/*
 * Copyright 2003, Glenn McGrath
 * Copyright 2006, Rob Landley <rob@landley.net>
 * Copyright 2010, Denys Vlasenko
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"

/* Conversion table.  for base 64 */
const char bb_uuenc_tbl_base64[65 + 1] ALIGN1 = {
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
    'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
    'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
    'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
    'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
    'w', 'x', 'y', 'z', '0', '1', '2', '3',
    '4', '5', '6', '7', '8', '9', '+', '/',
    '=' /* termination character */,
    '\0' /* needed for uudecode.c only */
};

const char bb_uuenc_tbl_std[65] ALIGN1 = {
    '`', '!', '"', '#', '$', '%', '&', '\'',
    '(', ')', '*', '+', ',', '-', '.', '/',
    '0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', ':', ';', '<', '=', '>', '?',
    '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
    'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
    'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
    'X', 'Y', 'Z', '[', '\\', ']', '^', '_',
    '`' /* termination character */
};

/*
 * Encode bytes at S of length LENGTH to uuencode or base64 format and place it
 * to STORE.  STORE will be 0-terminated, and must point to a writable
 * buffer of at least 1+BASE64_LENGTH(length) bytes.
 * where BASE64_LENGTH(len) = (4 * ((LENGTH + 2) / 3))
 */
void FAST_FUNC bb_uuencode(char *p, const void *src, int length, const char *tbl)
{
    const unsigned char *s = src;

    /* Transform the 3x8 bits to 4x6 bits */
    while (length > 0) {
        unsigned s1, s2;

        /* Are s[1], s[2] valid or should be assumed 0? */
        s1 = s2 = 0;
        length -= 3; /* can be >=0, -1, -2 */
        if (length >= -1) {
            s1 = s[1];
            if (length >= 0)
                s2 = s[2];
        }
        *p++ = tbl[s[0] >> 2];
        *p++ = tbl[((s[0] & 3) << 4) + (s1 >> 4)];
        *p++ = tbl[((s1 & 0xf) << 2) + (s2 >> 6)];
        *p++ = tbl[s2 & 0x3f];
        s += 3;
    }
    /* Zero-terminate */
    *p = '\0';
    /* If length is -2 or -1, pad last char or two */
    while (length) {
        *--p = tbl[64];
        length++;
    }
}

/*
 * Decode base64 encoded string. Stops on '\0'.
 *
 * Returns: pointer to the undecoded part of source.
 * If points to '\0', then the source was fully decoded.
 * (*pp_dst): advanced past the last written byte.
 */
const char* FAST_FUNC decode_base64(char **pp_dst, const char *src)
{
    char *dst = *pp_dst;
    const char *src_tail;

    while (1) {
        unsigned char six_bit[4];
        int count = 0;

        /* Fetch up to four 6-bit values */
        src_tail = src;
        while (count < 4) {
            char *table_ptr;
            int ch;

            /* Get next _valid_ character.
             * bb_uuenc_tbl_base64[] contains this string:
             *  0         1         2         3         4         5         6
             *  01234567890123456789012345678901234567890123456789012345678901234
             * "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
             */
            do {
                ch = *src;
                if (ch == '\0') {
                    if (count == 0) {
                        /* Example:
                         * If we decode "QUJD <NUL>", we want
                         * to return ptr to NUL, not to ' ',
                         * because we did fully decode
                         * the string (to "ABC").
                         */
                        src_tail = src;
                    }
                    goto ret;
                }
                src++;
                table_ptr = strchr(bb_uuenc_tbl_base64, ch);
//TODO: add BASE64_FLAG_foo to die on bad char?
            } while (!table_ptr);

            /* Convert encoded character to decimal */
            ch = table_ptr - bb_uuenc_tbl_base64;

            /* ch is 64 if char was '=', otherwise 0..63 */
            if (ch == 64)
                break;
            six_bit[count] = ch;
            count++;
        }

        /* Transform 6-bit values to 8-bit ones.
         * count can be < 4 when we decode the tail:
         * "eQ==" -> "y", not "y NUL NUL".
         * Note that (count > 1) is always true,
         * "x===" encoding is not valid:
         * even a single zero byte encodes as "AA==".
         * However, with current logic we come here with count == 1
         * when we decode "==" tail.
         */
        if (count > 1)
            *dst++ = six_bit[0] << 2 | six_bit[1] >> 4;
        if (count > 2)
            *dst++ = six_bit[1] << 4 | six_bit[2] >> 2;
        if (count > 3)
            *dst++ = six_bit[2] << 6 | six_bit[3];
        /* Note that if we decode "AA==" and ate first '=',
         * we just decoded one char (count == 2) and now we'll
         * do the loop once more to decode second '='.
         */
    } /* while (1) */
 ret:
    *pp_dst = dst;
    return src_tail;
}

/*
 * Decode base64 encoded stream.
 * Can stop on EOF, specified char, or on uuencode-style "====" line:
 * flags argument controls it.
 */
void FAST_FUNC read_base64(FILE *src_stream, FILE *dst_stream, int flags)
{
/* Note that EOF _can_ be passed as exit_char too */
#define exit_char    ((int)(signed char)flags)
#define uu_style_end (flags & BASE64_FLAG_UU_STOP)

    /* uuencoded files have 61 byte lines. Use 64 byte buffer
     * to process line at a time.
     */
    enum { BUFFER_SIZE = 64 };

    char in_buf[BUFFER_SIZE + 2];
    char out_buf[BUFFER_SIZE / 4 * 3 + 2];
    char *out_tail;
    const char *in_tail;
    int term_seen = 0;
    int in_count = 0;

    while (1) {
        while (in_count < BUFFER_SIZE) {
            int ch = fgetc(src_stream);
            if (ch == exit_char) {
                if (in_count == 0)
                    return;
                term_seen = 1;
                break;
            }
            if (ch == EOF) {
                term_seen = 1;
                break;
            }
            /* Prevent "====" line to be split: stop if we see '\n'.
             * We can also skip other whitespace and skirt the problem
             * of files with NULs by stopping on any control char or space:
             */
            if (ch <= ' ')
                break;
            in_buf[in_count++] = ch;
        }
        in_buf[in_count] = '\0';

        /* Did we encounter "====" line? */
        if (uu_style_end && strcmp(in_buf, "====") == 0)
            return;

        out_tail = out_buf;
        in_tail = decode_base64(&out_tail, in_buf);

        fwrite(out_buf, (out_tail - out_buf), 1, dst_stream);

        if (term_seen) {
            /* Did we consume ALL characters? */
            if (*in_tail == '\0')
                return;
            /* No */
            bb_error_msg_and_die("truncated base64 input");
        }

        /* It was partial decode */
        in_count = strlen(in_tail);
        memmove(in_buf, in_tail, in_count);
    }
}