Mirror of :pserver:cvs@cvs.fefe.de:/cvs libowfat https://www.fefe.de/libowfat/
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#include "scan.h"
size_t scan_asn1derlengthvalue(const char* src,size_t len,unsigned long long* value) {
if (len==0 || len>=-(uintptr_t)src) return 0;
unsigned int i,c=*src;
unsigned long long l;
if ((c&0x80)==0) {
*value=c;
return 1;
}
/* Highest bit set: lower 7 bits is the length of the length value in bytes. */
c&=0x7f;
if (!c) return 0; /* length 0x80 means indefinite length encoding, not supported here */
l=(unsigned char)src[1];
if (l==0) return 0; /* not minimally encoded: 0x81 0x00 instead of 0x00 */
if (c>sizeof(l)) return 0; /* too many bytes, does not fit into target integer type */
for (i=2; i<=c; ++i)
l=l*256+(unsigned char)src[i];
if (l<0x7f) return 0; /* not minimally encoded: 0x81 0x70 instead of 0x70 */
*value=l;
return i;
}
size_t scan_asn1derlength(const char* src,size_t len,unsigned long long* value) {
unsigned long long l;
size_t i=scan_asn1derlengthvalue(src,len,&l);
if (l > len-i) return 0; /* make sure data would fit into buffer */
*value=l;
return i;
}