/* vi: set sw=4 ts=4: */
/*
 *  Copyright 2003, Glenn McGrath
 *
 *  Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 *
 *  Based on specification from
 *  http://www.opengroup.org/onlinepubs/007904975/utilities/uuencode.html
 *
 *  Bugs: the spec doesn't mention anything about "`\n`\n" prior to the
 *        "end" line
 */


#include "libbb.h"

static void read_stduu(FILE *src_stream, FILE *dst_stream)
{
        char *line;

        while ((line = xmalloc_fgetline(src_stream)) != NULL) {
                int encoded_len, str_len;
                char *line_ptr, *dst;

                if (strcmp(line, "end") == 0) {
                        return; /* the only non-error exit */
                }

                line_ptr = line;
                while (*line_ptr) {
                        *line_ptr = (*line_ptr - 0x20) & 0x3f;
                        line_ptr++;
                }
                str_len = line_ptr - line;

                encoded_len = line[0] * 4 / 3;
                /* Check that line is not too short. (we tolerate
                 * overly _long_ line to accomodate possible extra '`').
                 * Empty line case is also caught here. */
                if (str_len <= encoded_len) {
                        break; /* go to bb_error_msg_and_die("short file"); */
                }
                if (encoded_len <= 0) {
                        /* Ignore the "`\n" line, why is it even in the encode file ? */
                        free(line);
                        continue;
                }
                if (encoded_len > 60) {
                        bb_error_msg_and_die("line too long");
                }

                dst = line;
                line_ptr = line + 1;
                do {
                        /* Merge four 6 bit chars to three 8 bit chars */
                        *dst++ = line_ptr[0] << 2 | line_ptr[1] >> 4;
                        encoded_len--;
                        if (encoded_len == 0) {
                                break;
                        }

                        *dst++ = line_ptr[1] << 4 | line_ptr[2] >> 2;
                        encoded_len--;
                        if (encoded_len == 0) {
                                break;
                        }

                        *dst++ = line_ptr[2] << 6 | line_ptr[3];
                        line_ptr += 4;
                        encoded_len -= 2;
                } while (encoded_len > 0);
                fwrite(line, 1, dst - line, dst_stream);
                free(line);
        }
        bb_error_msg_and_die("short file");
}

static void read_base64(FILE *src_stream, FILE *dst_stream)
{
        int term_count = 1;

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

                while (count < 4) {
                        char *table_ptr;
                        int ch;

                        /* Get next _valid_ character.
                         * global vector bb_uuenc_tbl_base64[] contains this string:
                         * "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=\n"
                         */
                        do {
                                ch = fgetc(src_stream);
                                if (ch == EOF) {
                                        bb_error_msg_and_die("short file");
                                }
                                table_ptr = strchr(bb_uuenc_tbl_base64, ch);
                        } while (table_ptr == NULL);

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

                        if (*table_ptr == '=') {
                                if (term_count == 0) {
                                        translated[count] = '\0';
                                        break;
                                }
                                term_count++;
                        } else if (*table_ptr == '\n') {
                                /* Check for terminating line */
                                if (term_count == 5) {
                                        return;
                                }
                                term_count = 1;
                                continue;
                        } else {
                                translated[count] = ch;
                                count++;
                                term_count = 0;
                        }
                }

                /* Merge 6 bit chars to 8 bit */
                if (count > 1) {
                        fputc(translated[0] << 2 | translated[1] >> 4, dst_stream);
                }
                if (count > 2) {
                        fputc(translated[1] << 4 | translated[2] >> 2, dst_stream);
                }
                if (count > 3) {
                        fputc(translated[2] << 6 | translated[3], dst_stream);
                }
        }
}

int uudecode_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int uudecode_main(int argc UNUSED_PARAM, char **argv)
{
        FILE *src_stream;
        char *outname = NULL;
        char *line;

        opt_complementary = "?1"; /* 1 argument max */
        getopt32(argv, "o:", &outname);
        argv += optind;

        if (!*argv)
                *--argv = (char*)"-";
        src_stream = xfopen_stdin(*argv);

        /* Search for the start of the encoding */
        while ((line = xmalloc_fgetline(src_stream)) != NULL) {
                void (*decode_fn_ptr)(FILE *src, FILE *dst);
                char *line_ptr;
                FILE *dst_stream;
                int mode;

                if (strncmp(line, "begin-base64 ", 13) == 0) {
                        line_ptr = line + 13;
                        decode_fn_ptr = read_base64;
                } else if (strncmp(line, "begin ", 6) == 0) {
                        line_ptr = line + 6;
                        decode_fn_ptr = read_stduu;
                } else {
                        free(line);
                        continue;
                }

                /* begin line found. decode and exit */
                mode = bb_strtou(line_ptr, NULL, 8);
                if (outname == NULL) {
                        outname = strchr(line_ptr, ' ');
                        if ((outname == NULL) || (*outname == '\0')) {
                                break;
                        }
                        outname++;
                }
                dst_stream = stdout;
                if (NOT_LONE_DASH(outname)) {
                        dst_stream = xfopen_for_write(outname);
                        fchmod(fileno(dst_stream), mode & (S_IRWXU | S_IRWXG | S_IRWXO));
                }
                free(line);
                decode_fn_ptr(src_stream, dst_stream);
                /* fclose_if_not_stdin(src_stream); - redundant */
                return EXIT_SUCCESS;
        }
        bb_error_msg_and_die("no 'begin' line");
}

/* Test script.
Put this into an empty dir with busybox binary, an run.

#!/bin/sh
test -x busybox || { echo "No ./busybox?"; exit; }
ln -sf busybox uudecode
ln -sf busybox uuencode
>A_null
echo -n A >A
echo -n AB >AB
echo -n ABC >ABC
echo -n ABCD >ABCD
echo -n ABCDE >ABCDE
echo -n ABCDEF >ABCDEF
cat busybox >A_bbox
for f in A*; do
    echo uuencode $f
    ./uuencode    $f <$f >u_$f
    ./uuencode -m $f <$f >m_$f
done
mkdir unpk_u unpk_m 2>/dev/null
for f in u_*; do
    ./uudecode <$f -o unpk_u/${f:2}
    diff -a ${f:2} unpk_u/${f:2} >/dev/null 2>&1
    echo uudecode $f: $?
done
for f in m_*; do
    ./uudecode <$f -o unpk_m/${f:2}
    diff -a ${f:2} unpk_m/${f:2} >/dev/null 2>&1
    echo uudecode $f: $?
done
*/