| /* |
| * 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 (<= 31) 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; |
| const uint8_t *buf; |
| |
| if(nbits < 0 || pd->nboff + nbits > pd->nbits) |
| return -1; |
| |
| /* |
| * 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 = nbits ? (buf[0]) >> (8 - off) : 0; |
| 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 if(nbits <= 31) { |
| asn_per_data_t tpd = *pd; |
| /* Here are we with our 31-bits limit plus 1..7 bits offset. */ |
| tpd.nboff -= nbits; |
| accum = per_get_few_bits(&tpd, nbits - 24) << 24; |
| accum |= per_get_few_bits(&tpd, 24); |
| } else { |
| pd->nboff -= nbits; /* Oops, revert back */ |
| return -1; |
| } |
| |
| return (accum & (((uint32_t)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; |
| } |