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1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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4 | */
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5 |
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6 | #include "libbb.h"
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7 | #include "unarchive.h" /* for external decl of check_header_gzip_or_die */
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8 |
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9 | void check_header_gzip_or_die(int src_fd)
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10 | {
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11 | union {
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12 | unsigned char raw[8];
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13 | struct {
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14 | unsigned char method;
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15 | unsigned char flags;
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16 | unsigned int mtime;
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17 | unsigned char xtra_flags;
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18 | unsigned char os_flags;
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19 | } formatted;
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20 | } header;
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21 |
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22 | xread(src_fd, header.raw, 8);
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23 |
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24 | /* Check the compression method */
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25 | if (header.formatted.method != 8) {
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26 | bb_error_msg_and_die("unknown compression method %d",
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27 | header.formatted.method);
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28 | }
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29 |
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30 | if (header.formatted.flags & 0x04) {
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31 | /* bit 2 set: extra field present */
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32 | unsigned extra_short;
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33 |
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34 | extra_short = xread_char(src_fd) + (xread_char(src_fd) << 8);
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35 | while (extra_short > 0) {
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36 | /* Ignore extra field */
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37 | xread_char(src_fd);
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38 | extra_short--;
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39 | }
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40 | }
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41 |
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42 | /* Discard original name if any */
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43 | if (header.formatted.flags & 0x08) {
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44 | /* bit 3 set: original file name present */
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45 | while (xread_char(src_fd) != 0);
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46 | }
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47 |
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48 | /* Discard file comment if any */
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49 | if (header.formatted.flags & 0x10) {
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50 | /* bit 4 set: file comment present */
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51 | while (xread_char(src_fd) != 0);
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52 | }
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53 |
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54 | /* Read the header checksum */
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55 | if (header.formatted.flags & 0x02) {
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56 | xread_char(src_fd);
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57 | xread_char(src_fd);
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58 | }
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59 | }
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