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255 lines
6.4 KiB
C
255 lines
6.4 KiB
C
/* Licensed under BSD-MIT - see LICENSE file for details */
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#include "base64.h"
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#include <errno.h>
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#include <string.h>
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#include <assert.h>
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#include <stdint.h>
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/**
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* sixbit_to_b64 - maps a 6-bit value to the base64 alphabet
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* @param map A base 64 map (see base64_init_map)
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* @param sixbit Six-bit value to map
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* @return a base 64 character
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*/
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static char sixbit_to_b64(const base64_maps_t *maps, const uint8_t sixbit)
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{
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assert(sixbit <= 63);
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return maps->encode_map[(unsigned char)sixbit];
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}
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/**
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* sixbit_from_b64 - maps a base64-alphabet character to its 6-bit value
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* @param maps A base 64 maps structure (see base64_init_maps)
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* @param sixbit Six-bit value to map
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* @return a six-bit value
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*/
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static int8_t sixbit_from_b64(const base64_maps_t *maps,
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const unsigned char b64letter)
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{
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int8_t ret;
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ret = maps->decode_map[(unsigned char)b64letter];
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if (ret == (char)0xff) {
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errno = EDOM;
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return -1;
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}
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return ret;
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}
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bool base64_char_in_alphabet(const base64_maps_t *maps, const char b64char)
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{
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return (maps->decode_map[(const unsigned char)b64char] != (char)0xff);
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}
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void base64_init_maps(base64_maps_t *dest, const char src[64])
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{
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unsigned char i;
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memcpy(dest->encode_map,src,64);
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memset(dest->decode_map,0xff,256);
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for (i=0; i<64; i++) {
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dest->decode_map[(unsigned char)src[i]] = i;
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}
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}
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size_t base64_encoded_length(size_t srclen)
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{
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return ((srclen + 2) / 3) * 4;
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}
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void base64_encode_triplet_using_maps(const base64_maps_t *maps,
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char dest[4], const char src[3])
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{
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char a = src[0];
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char b = src[1];
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char c = src[2];
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dest[0] = sixbit_to_b64(maps, (a & 0xfc) >> 2);
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dest[1] = sixbit_to_b64(maps, ((a & 0x3) << 4) | ((b & 0xf0) >> 4));
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dest[2] = sixbit_to_b64(maps, ((c & 0xc0) >> 6) | ((b & 0xf) << 2));
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dest[3] = sixbit_to_b64(maps, c & 0x3f);
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}
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void base64_encode_tail_using_maps(const base64_maps_t *maps, char dest[4],
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const char *src, const size_t srclen)
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{
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char longsrc[3] = { 0 };
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assert(srclen <= 3);
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memcpy(longsrc, src, srclen);
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base64_encode_triplet_using_maps(maps, dest, longsrc);
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memset(dest+1+srclen, '=', 3-srclen);
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}
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ssize_t base64_encode_using_maps(const base64_maps_t *maps,
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char *dest, const size_t destlen,
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const char *src, const size_t srclen)
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{
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size_t src_offset = 0;
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size_t dest_offset = 0;
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if (destlen < base64_encoded_length(srclen)) {
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errno = EOVERFLOW;
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return -1;
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}
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while (srclen - src_offset >= 3) {
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base64_encode_triplet_using_maps(maps, &dest[dest_offset], &src[src_offset]);
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src_offset += 3;
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dest_offset += 4;
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}
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if (src_offset < srclen) {
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base64_encode_tail_using_maps(maps, &dest[dest_offset], &src[src_offset], srclen-src_offset);
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dest_offset += 4;
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}
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memset(&dest[dest_offset], '\0', destlen-dest_offset);
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return dest_offset;
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}
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size_t base64_decoded_length(size_t srclen)
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{
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return ((srclen+3)/4*3);
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}
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ssize_t base64_decode_quartet_using_maps(const base64_maps_t *maps, char dest[3],
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const char src[4])
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{
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signed char a;
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signed char b;
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signed char c;
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signed char d;
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a = sixbit_from_b64(maps, src[0]);
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b = sixbit_from_b64(maps, src[1]);
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c = sixbit_from_b64(maps, src[2]);
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d = sixbit_from_b64(maps, src[3]);
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if ((a == -1) || (b == -1) || (c == -1) || (d == -1)) {
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return -1;
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}
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dest[0] = (a << 2) | (b >> 4);
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dest[1] = ((b & 0xf) << 4) | (c >> 2);
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dest[2] = ((c & 0x3) << 6) | d;
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return 0;
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}
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ssize_t base64_decode_tail_using_maps(const base64_maps_t *maps, char dest[3],
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const char * src, const size_t srclen)
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{
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char longsrc[4];
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int quartet_result;
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size_t insize = srclen;
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while (insize != 0 &&
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src[insize-1] == '=') { /* throw away padding symbols */
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insize--;
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}
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if (insize == 0) {
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return 0;
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}
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if (insize == 1) {
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/* the input is malformed.... */
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errno = EINVAL;
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return -1;
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}
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memcpy(longsrc, src, insize);
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memset(longsrc+insize, 'A', 4-insize);
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quartet_result = base64_decode_quartet_using_maps(maps, dest, longsrc);
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if (quartet_result == -1) {
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return -1;
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}
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return insize - 1;
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}
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ssize_t base64_decode_using_maps(const base64_maps_t *maps,
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char *dest, const size_t destlen,
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const char *src, const size_t srclen)
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{
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ssize_t dest_offset = 0;
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ssize_t i;
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ssize_t more;
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if (destlen < base64_decoded_length(srclen)) {
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errno = EOVERFLOW;
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return -1;
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}
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for(i=0; srclen - i > 4; i+=4) {
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if (base64_decode_quartet_using_maps(maps, &dest[dest_offset], &src[i]) == -1) {
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return -1;
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}
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dest_offset += 3;
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}
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more = base64_decode_tail_using_maps(maps, &dest[dest_offset], &src[i], srclen - i);
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if (more == -1) {
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return -1;
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}
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dest_offset += more;
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memset(&dest[dest_offset], '\0', destlen-dest_offset);
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return dest_offset;
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}
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/**
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* base64_maps_rfc4648 - pregenerated maps struct for rfc4648
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*/
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const base64_maps_t base64_maps_rfc4648 = {
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
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"\xff\xff\xff\xff\xff" /* 0 */ \
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"\xff\xff\xff\xff\xff" /* 5 */ \
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"\xff\xff\xff\xff\xff" /* 10 */ \
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"\xff\xff\xff\xff\xff" /* 15 */ \
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"\xff\xff\xff\xff\xff" /* 20 */ \
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"\xff\xff\xff\xff\xff" /* 25 */ \
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"\xff\xff\xff\xff\xff" /* 30 */ \
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"\xff\xff\xff\xff\xff" /* 35 */ \
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"\xff\xff\xff\x3e\xff" /* 40 */ \
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"\xff\xff\x3f\x34\x35" /* 45 */ \
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"\x36\x37\x38\x39\x3a" /* 50 */ \
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"\x3b\x3c\x3d\xff\xff" /* 55 */ \
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"\xff\xff\xff\xff\xff" /* 60 */ \
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"\x00\x01\x02\x03\x04" /* 65 A */ \
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"\x05\x06\x07\x08\x09" /* 70 */ \
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"\x0a\x0b\x0c\x0d\x0e" /* 75 */ \
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"\x0f\x10\x11\x12\x13" /* 80 */ \
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"\x14\x15\x16\x17\x18" /* 85 */ \
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"\x19\xff\xff\xff\xff" /* 90 */ \
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"\xff\xff\x1a\x1b\x1c" /* 95 */ \
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"\x1d\x1e\x1f\x20\x21" /* 100 */ \
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"\x22\x23\x24\x25\x26" /* 105 */ \
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"\x27\x28\x29\x2a\x2b" /* 110 */ \
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"\x2c\x2d\x2e\x2f\x30" /* 115 */ \
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"\x31\x32\x33\xff\xff" /* 120 */ \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 125 */ \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 155 */ \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 185 */ \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 215 */ \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 245 */
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};
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