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/*
* Copyright (c) 2005 Lev Walkin <vlm@lionet.info>. All rights reserved.
* Redistribution and modifications are permitted subject to BSD license.
*/
#include <asn_system.h>
#include <per_support.h>
/*
* Extract a small number of bits (<= 24) from the specified PER data pointer.
*/
int32_t
per_get_few_bits(asn_per_data_t *pd, int nbits) {
size_t off; /* Next after last bit offset */
uint32_t accum;
uint8_t *buf;
if(nbits < 0 || pd->nboff + nbits > pd->nbits)
return -1;
if(nbits == 0)
return 0;
/*
* Normalize position indicator.
*/
if(pd->nboff >= 8) {
pd->buffer += (pd->nboff >> 3);
pd->nbits -= (pd->nboff & ~0x07);
pd->nboff &= 0x07;
}
off = (pd->nboff += nbits);
buf = pd->buffer;
/*
* Extract specified number of bits.
*/
if(off <= 8)
accum = (buf[0]) >> (8 - off);
else if(off <= 16)
accum = ((buf[0] << 8) + buf[1]) >> (16 - off);
else if(off <= 24)
accum = ((buf[0] << 16) + (buf[1] << 8) + buf[2]) >> (24 - off);
else if(off <= 31)
accum = ((buf[0] << 24) + (buf[1] << 16)
+ (buf[2] << 8) + (buf[3])) >> (32 - off);
else {
pd->nboff -= nbits; /* Oops, revert back */
return -1;
}
return (accum & ((1 << nbits) - 1));
}
/*
* Extract a large number of bits from the specified PER data pointer.
*/
int
per_get_many_bits(asn_per_data_t *pd, uint8_t *dst, int alright, int nbits) {
int32_t value;
if(alright && (nbits & 7)) {
/* Perform right alignment of a first few bits */
value = per_get_few_bits(pd, nbits & 0x07);
if(value < 0) return -1;
*dst++ = value; /* value is already right-aligned */
nbits &= ~7;
}
while(nbits) {
if(nbits >= 24) {
value = per_get_few_bits(pd, 24);
if(value < 0) return -1;
*(dst++) = value >> 16;
*(dst++) = value >> 8;
*(dst++) = value;
nbits -= 24;
} else {
value = per_get_few_bits(pd, nbits);
if(value < 0) return -1;
if(nbits & 7) { /* implies alright */
value <<= 8 - (nbits & 7),
nbits += 8 - (nbits & 7);
if(nbits > 24)
*dst++ = value >> 24;
}
if(nbits > 16)
*dst++ = value >> 16;
if(nbits > 8)
*dst++ = value >> 8;
*dst++ = value;
break;
}
}
return 0;
}
/*
* Get the length "n" from the stream.
*/
ssize_t
uper_get_length(asn_per_data_t *pd, int ebits, int *repeat) {
ssize_t value;
*repeat = 0;
if(ebits >= 0) return per_get_few_bits(pd, ebits);
value = per_get_few_bits(pd, 8);
if(value < 0) return -1;
if((value & 128) == 0) /* #10.9.3.6 */
return (value & 0x7F);
if((value & 64) == 0) { /* #10.9.3.7 */
value = ((value & 63) << 8) | per_get_few_bits(pd, 8);
if(value < 0) return -1;
return value;
}
value &= 63; /* this is "m" from X.691, #10.9.3.8 */
if(value < 1 || value > 4)
return -1;
*repeat = 1;
return (16384 * value);
}
/*
* Get the normally small non-negative whole number.
* X.691, #10.6
*/
ssize_t
uper_get_nsnnwn(asn_per_data_t *pd) {
ssize_t value;
value = per_get_few_bits(pd, 7);
if(value & 64) { /* implicit (value < 0) */
value &= 63;
value <<= 2;
value |= per_get_few_bits(pd, 2);
if(value & 128) /* implicit (value < 0) */
return -1;
if(value == 0)
return 0;
if(value >= 3)
return -1;
value = per_get_few_bits(pd, 8 * value);
return value;
}
return value;
}
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