97 lines
2.1 KiB
C
97 lines
2.1 KiB
C
#include "trans.h"
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#define PADDING '='
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unsigned char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
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"abcdefghijklmnopqrstuvwxyz" \
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"0123456789" \
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"+/";
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unsigned char *
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encode(unsigned char *op, int np)
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{
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extern unsigned char s[];
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unsigned char *sp;
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int n;
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sp = s;
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switch (np) {
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case 3:
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*sp++ = b64[(*op & ~3) >> 2];
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n = (*op++ & 3) << 4;
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*sp++ = b64[n + ((*op & ~15) >> 4)];
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n = (*op++ & 15) << 2;
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*sp++ = b64[n + ((*op & 192) >> 6)];
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*sp = b64[*op & ~192];
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break;
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case 2:
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*sp++ = b64[(*op & ~3) >> 2];
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n = (*op++ & 3) << 4;
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*sp++ = b64[n + ((*op & ~15) >> 4)];
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*sp++ = b64[(*op & 15) << 2];
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*sp = PADDING;
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break;
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case 1:
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*sp++ = b64[(*op & ~3) >> 2];
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*sp++ = b64[(*op & 3) << 4];
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*sp++ = PADDING;
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*sp = PADDING;
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break;
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}
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return s;
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}
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unsigned char *
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decode(unsigned char *sp, int *np)
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{
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extern unsigned char o[];
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unsigned char *op;
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int n, b, atob(int c);
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op = o;
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switch (*np) {
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case 4:
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n = atob(*sp++) << 2;
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b = atob(*sp++);
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*op++ = n + ((b & ~15) >> 4);
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n = (b & 15) << 4;
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b = atob(*sp++);
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*op++ = n + ((b & ~3) >> 2);
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*op = ((b & 3) << 6) + atob(*sp);
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break;
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case 3:
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n = atob(*sp++) << 2;
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b = atob(*sp++);
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*op++ = n + ((b & ~15) >> 4);
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n = (b & 15) << 4;
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*op = n + ((atob(*sp) & ~3) >> 2);
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break;
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case 2:
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n = atob(*sp++) << 2;
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*op = n + ((atob(*sp) & ~15) >> 4);
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break;
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}
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*np = op-o+1;
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return o;
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}
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int atob(int c)
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{
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if (c >= 'A' && c <= 'Z')
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c -= 'A';
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else if (c >= 'a' && c <= 'z')
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c = c - 'a' + 26;
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else if (c >= '0' && c <= '9')
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c = c - '0' + 26 * 2;
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else if (c == '+')
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c = 62;
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else
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c = 63;
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return c;
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}
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