| vlm | 337167e | 2005-11-26 11:25:14 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2005 Lev Walkin <vlm@lionet.info>. All rights reserved. |
| 3 | * Redistribution and modifications are permitted subject to BSD license. |
| 4 | */ |
| 5 | #include <asn_system.h> |
| 6 | #include <per_support.h> |
| 7 | |
| 8 | /* |
| 9 | * Extract a small number of bits (<= 24) from the specified PER data pointer. |
| 10 | */ |
| 11 | int32_t |
| 12 | per_get_few_bits(asn_per_data_t *pd, int nbits) { |
| 13 | size_t off; /* Next after last bit offset */ |
| 14 | uint32_t accum; |
| 15 | uint8_t *buf; |
| 16 | |
| 17 | if(nbits < 0 || pd->nboff + nbits > pd->nbits) |
| 18 | return -1; |
| 19 | if(nbits == 0) |
| 20 | return 0; |
| 21 | |
| 22 | /* |
| 23 | * Normalize position indicator. |
| 24 | */ |
| 25 | if(pd->nboff >= 8) { |
| 26 | pd->buffer += (pd->nboff >> 3); |
| 27 | pd->nbits -= (pd->nboff & ~0x07); |
| 28 | pd->nboff &= 0x07; |
| 29 | } |
| 30 | off = (pd->nboff += nbits); |
| 31 | buf = pd->buffer; |
| 32 | |
| 33 | /* |
| 34 | * Extract specified number of bits. |
| 35 | */ |
| 36 | if(off <= 8) |
| 37 | accum = (buf[0]) >> (8 - off); |
| 38 | else if(off <= 16) |
| 39 | accum = ((buf[0] << 8) + buf[1]) >> (16 - off); |
| 40 | else if(off <= 24) |
| 41 | accum = ((buf[0] << 16) + (buf[1] << 8) + buf[2]) >> (24 - off); |
| 42 | else if(off <= 31) |
| 43 | accum = ((buf[0] << 24) + (buf[1] << 16) |
| 44 | + (buf[2] << 8) + (buf[3])) >> (32 - off); |
| 45 | else { |
| 46 | pd->nboff -= nbits; /* Oops, revert back */ |
| 47 | return -1; |
| 48 | } |
| 49 | |
| 50 | return (accum & ((1 << nbits) - 1)); |
| 51 | } |
| 52 | |
| 53 | /* |
| 54 | * Extract a large number of bits from the specified PER data pointer. |
| 55 | */ |
| 56 | int |
| 57 | per_get_many_bits(asn_per_data_t *pd, uint8_t *dst, int alright, int nbits) { |
| 58 | int32_t value; |
| 59 | |
| 60 | if(alright && (nbits & 7)) { |
| 61 | /* Perform right alignment of a first few bits */ |
| 62 | value = per_get_few_bits(pd, nbits & 0x07); |
| 63 | if(value < 0) return -1; |
| 64 | *dst++ = value; /* value is already right-aligned */ |
| 65 | nbits &= ~7; |
| 66 | } |
| 67 | |
| 68 | while(nbits) { |
| 69 | if(nbits >= 24) { |
| 70 | value = per_get_few_bits(pd, 24); |
| 71 | if(value < 0) return -1; |
| 72 | *(dst++) = value >> 16; |
| 73 | *(dst++) = value >> 8; |
| 74 | *(dst++) = value; |
| 75 | nbits -= 24; |
| 76 | } else { |
| 77 | value = per_get_few_bits(pd, nbits); |
| 78 | if(value < 0) return -1; |
| 79 | if(nbits & 7) { /* implies alright */ |
| 80 | value <<= 8 - (nbits & 7), |
| 81 | nbits += 8 - (nbits & 7); |
| 82 | if(nbits > 24) |
| 83 | *dst++ = value >> 24; |
| 84 | } |
| 85 | if(nbits > 16) |
| 86 | *dst++ = value >> 16; |
| 87 | if(nbits > 8) |
| 88 | *dst++ = value >> 8; |
| 89 | *dst++ = value; |
| 90 | break; |
| 91 | } |
| 92 | } |
| 93 | |
| 94 | return 0; |
| 95 | } |
| 96 | |
| 97 | /* |
| 98 | * Get the length "n" from the stream. |
| 99 | */ |
| 100 | ssize_t |
| 101 | uper_get_length(asn_per_data_t *pd, int ebits, int *repeat) { |
| 102 | ssize_t value; |
| 103 | |
| 104 | *repeat = 0; |
| 105 | |
| 106 | if(ebits >= 0) return per_get_few_bits(pd, ebits); |
| 107 | |
| 108 | value = per_get_few_bits(pd, 8); |
| 109 | if(value < 0) return -1; |
| 110 | if((value & 128) == 0) /* #10.9.3.6 */ |
| 111 | return (value & 0x7F); |
| 112 | if((value & 64) == 0) { /* #10.9.3.7 */ |
| 113 | value = ((value & 63) << 8) | per_get_few_bits(pd, 8); |
| 114 | if(value < 0) return -1; |
| 115 | return value; |
| 116 | } |
| 117 | value &= 63; /* this is "m" from X.691, #10.9.3.8 */ |
| 118 | if(value < 1 || value > 4) |
| 119 | return -1; |
| 120 | *repeat = 1; |
| 121 | return (16384 * value); |
| 122 | } |
| 123 | |
| 124 | /* |
| 125 | * Get the normally small non-negative whole number. |
| 126 | * X.691, #10.6 |
| 127 | */ |
| 128 | ssize_t |
| 129 | uper_get_nsnnwn(asn_per_data_t *pd) { |
| 130 | ssize_t value; |
| 131 | |
| 132 | value = per_get_few_bits(pd, 7); |
| 133 | if(value & 64) { /* implicit (value < 0) */ |
| 134 | value &= 63; |
| 135 | value <<= 2; |
| 136 | value |= per_get_few_bits(pd, 2); |
| 137 | if(value & 128) /* implicit (value < 0) */ |
| 138 | return -1; |
| 139 | if(value == 0) |
| 140 | return 0; |
| 141 | if(value >= 3) |
| 142 | return -1; |
| 143 | value = per_get_few_bits(pd, 8 * value); |
| 144 | return value; |
| 145 | } |
| 146 | |
| 147 | return value; |
| 148 | } |