Changeset View
Changeset View
Standalone View
Standalone View
head/contrib/bearssl/src/int/i31_decred.c
| Property | Old Value | New Value |
|---|---|---|
| svn:eol-style | null | native \ No newline at end of property |
| svn:keywords | null | FreeBSD=%H \ No newline at end of property |
| svn:mime-type | null | text/plain \ No newline at end of property |
| /* | |||||
| * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org> | |||||
| * | |||||
| * Permission is hereby granted, free of charge, to any person obtaining | |||||
| * a copy of this software and associated documentation files (the | |||||
| * "Software"), to deal in the Software without restriction, including | |||||
| * without limitation the rights to use, copy, modify, merge, publish, | |||||
| * distribute, sublicense, and/or sell copies of the Software, and to | |||||
| * permit persons to whom the Software is furnished to do so, subject to | |||||
| * the following conditions: | |||||
| * | |||||
| * The above copyright notice and this permission notice shall be | |||||
| * included in all copies or substantial portions of the Software. | |||||
| * | |||||
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | |||||
| * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF | |||||
| * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND | |||||
| * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS | |||||
| * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN | |||||
| * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | |||||
| * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | |||||
| * SOFTWARE. | |||||
| */ | |||||
| #include "inner.h" | |||||
| /* see inner.h */ | |||||
| void | |||||
| br_i31_decode_reduce(uint32_t *x, | |||||
| const void *src, size_t len, const uint32_t *m) | |||||
| { | |||||
| uint32_t m_ebitlen, m_rbitlen; | |||||
| size_t mblen, k; | |||||
| const unsigned char *buf; | |||||
| uint32_t acc; | |||||
| int acc_len; | |||||
| /* | |||||
| * Get the encoded bit length. | |||||
| */ | |||||
| m_ebitlen = m[0]; | |||||
| /* | |||||
| * Special case for an invalid (null) modulus. | |||||
| */ | |||||
| if (m_ebitlen == 0) { | |||||
| x[0] = 0; | |||||
| return; | |||||
| } | |||||
| /* | |||||
| * Clear the destination. | |||||
| */ | |||||
| br_i31_zero(x, m_ebitlen); | |||||
| /* | |||||
| * First decode directly as many bytes as possible. This requires | |||||
| * computing the actual bit length. | |||||
| */ | |||||
| m_rbitlen = m_ebitlen >> 5; | |||||
| m_rbitlen = (m_ebitlen & 31) + (m_rbitlen << 5) - m_rbitlen; | |||||
| mblen = (m_rbitlen + 7) >> 3; | |||||
| k = mblen - 1; | |||||
| if (k >= len) { | |||||
| br_i31_decode(x, src, len); | |||||
| x[0] = m_ebitlen; | |||||
| return; | |||||
| } | |||||
| buf = src; | |||||
| br_i31_decode(x, buf, k); | |||||
| x[0] = m_ebitlen; | |||||
| /* | |||||
| * Input remaining bytes, using 31-bit words. | |||||
| */ | |||||
| acc = 0; | |||||
| acc_len = 0; | |||||
| while (k < len) { | |||||
| uint32_t v; | |||||
| v = buf[k ++]; | |||||
| if (acc_len >= 23) { | |||||
| acc_len -= 23; | |||||
| acc <<= (8 - acc_len); | |||||
| acc |= v >> acc_len; | |||||
| br_i31_muladd_small(x, acc, m); | |||||
| acc = v & (0xFF >> (8 - acc_len)); | |||||
| } else { | |||||
| acc = (acc << 8) | v; | |||||
| acc_len += 8; | |||||
| } | |||||
| } | |||||
| /* | |||||
| * We may have some bits accumulated. We then perform a shift to | |||||
| * be able to inject these bits as a full 31-bit word. | |||||
| */ | |||||
| if (acc_len != 0) { | |||||
| acc = (acc | (x[1] << acc_len)) & 0x7FFFFFFF; | |||||
| br_i31_rshift(x, 31 - acc_len); | |||||
| br_i31_muladd_small(x, acc, m); | |||||
| } | |||||
| } | |||||