source: MondoRescue/branches/2.2.2/mindi-busybox/coreutils/uudecode.c@ 1247

/*
 *  Copyright 2003, Glenn McGrath <bug1@iinet.net.au>
 *
 *  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 <stdio.h>
#include <errno.h>
#include <getopt.h> /* optind */
#include <string.h>
#include <stdlib.h>
#include "busybox.h"

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

    while ((line = bb_get_chomped_line_from_file(src_stream)) != NULL) {
        int length;
        char *line_ptr = line;

        if (strcmp(line, "end") == 0) {
            return(EXIT_SUCCESS);
        }
        length = ((*line_ptr - 0x20) & 0x3f)* 4 / 3;

        if (length <= 0) {
            /* Ignore the "`\n" line, why is it even in the encode file ? */
            continue;
        }
        if (length > 60) {
            bb_error_msg_and_die("Line too long");
        }

        line_ptr++;
        /* Tolerate an overly long line to acomadate a possible exta '`' */
        if (strlen(line_ptr) < (size_t)length) {
            bb_error_msg_and_die("Short file");
        }

        while (length > 0) {
            /* Merge four 6 bit chars to three 8 bit chars */
            fputc(((line_ptr[0] - 0x20) & 077) << 2 | ((line_ptr[1] - 0x20) & 077) >> 4, dst_stream);
            line_ptr++;
            length--;
            if (length == 0) {
                break;
            }

            fputc(((line_ptr[0] - 0x20) & 077) << 4 | ((line_ptr[1] - 0x20) & 077) >> 2, dst_stream);
            line_ptr++;
            length--;
            if (length == 0) {
                break;
            }

            fputc(((line_ptr[0] - 0x20) & 077) << 6 | ((line_ptr[1] - 0x20) & 077), dst_stream);
            line_ptr += 2;
            length -= 2;
        }
        free(line);
    }
    bb_error_msg_and_die("Short file");
}

static int read_base64(FILE *src_stream, FILE *dst_stream)
{
    static const char base64_table[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=\n";
    char term_count = 0;

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

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

            /* Get next _valid_ character */
            do {
                ch = fgetc(src_stream);
                if (ch == EOF) {
                    bb_error_msg_and_die("Short file");
                }
            } while ((table_ptr = strchr(base64_table, ch)) == NULL);

            /* Convert encoded charcter to decimal */
            ch = table_ptr - base64_table;

            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(EXIT_SUCCESS);
                }
                term_count = 1;
                continue;
            } else {
                translated[count] = ch;
                count++;
                term_count = 0;
            }
        }

        /* Merge 6 bit chars to 8 bit */
        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)
{
    int (*decode_fn_ptr) (FILE * src, FILE * dst);
    FILE *src_stream;
    char *outname = NULL;
    char *line;
    int opt;

    opt = bb_getopt_ulflags(argc, argv, "o:", &outname);

    if (optind == argc) {
        src_stream = stdin;
    } else if (optind + 1 == argc) {
        src_stream = bb_xfopen(argv[optind], "r");
    } else {
        bb_show_usage();
    }

    /* Search for the start of the encoding */
    while ((line = bb_get_chomped_line_from_file(src_stream)) != NULL) {
        char *line_ptr = NULL;

        if (line == NULL) {
            break;
        } else 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;
        }

        if (line_ptr) {
            FILE *dst_stream;
            int mode;
            int ret;

            mode = strtoul(line_ptr, NULL, 8);
            if (outname == NULL) {
                outname = strchr(line_ptr, ' ');
                if ((outname == NULL) || (*outname == '\0')) {
                    break;
                }
                outname++;
            }
            if (strcmp(outname, "-") == 0) {
                dst_stream = stdout;
            } else {
                dst_stream = bb_xfopen(outname, "w");
                chmod(outname, mode & (S_IRWXU | S_IRWXG | S_IRWXO));
            }
            free(line);
            ret = decode_fn_ptr(src_stream, dst_stream);
            bb_fclose_nonstdin(src_stream);
            return(ret);
        }
        free(line);
    }
    bb_error_msg_and_die("No `begin' line");
}