27 lines
765 B
C
27 lines
765 B
C
#include "asn1.h"
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unsigned int scan_asn1tag(const char* src,const char* max,enum asn1_tagclass* tc,enum asn1_tagtype* tt,unsigned long* tag) {
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const char* orig=src;
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*tc=(*src&0xC0);
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*tt=(*src&0x20);
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if (max<src) return 0;
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/* The lower 5 bits are the tag, unless it's 0x1f, in which case the
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* next bytes are the tag: always take the lower 7 bits; the last byte
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* in the sequence is marked by a cleared high bit */
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if ((*src & 0x1f) == 0x1f) {
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unsigned long l=0;
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for (;;) {
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++src;
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if (src>max) return 0;
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if (l>(((unsigned long)-1)>>7)) return 0; /* catch integer overflow */
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l=l*128+(*src&0x7F);
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if (!(*src&0x80)) break;
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}
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*tag=l;
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return (src-orig+1);
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} else {
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*tag=*src&0x1f;
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return 1;
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}
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}
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