mfbt/double-conversion/diy-fp.cc@97036ab72558 (annotated)
mfbt/double-conversion/diy-fp.cc
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
| michael@0 | 1 | // Copyright 2010 the V8 project authors. All rights reserved. |
| michael@0 | 2 | // Redistribution and use in source and binary forms, with or without |
| michael@0 | 3 | // modification, are permitted provided that the following conditions are |
| michael@0 | 4 | // met: |
| michael@0 | 5 | // |
| michael@0 | 6 | // * Redistributions of source code must retain the above copyright |
| michael@0 | 7 | // notice, this list of conditions and the following disclaimer. |
| michael@0 | 8 | // * Redistributions in binary form must reproduce the above |
| michael@0 | 9 | // copyright notice, this list of conditions and the following |
| michael@0 | 10 | // disclaimer in the documentation and/or other materials provided |
| michael@0 | 11 | // with the distribution. |
| michael@0 | 12 | // * Neither the name of Google Inc. nor the names of its |
| michael@0 | 13 | // contributors may be used to endorse or promote products derived |
| michael@0 | 14 | // from this software without specific prior written permission. |
| michael@0 | 15 | // |
| michael@0 | 16 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| michael@0 | 17 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| michael@0 | 18 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| michael@0 | 19 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| michael@0 | 20 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| michael@0 | 21 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| michael@0 | 22 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| michael@0 | 23 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| michael@0 | 24 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| michael@0 | 25 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| michael@0 | 26 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| michael@0 | 27 | |
| michael@0 | 28 | |
| michael@0 | 29 | #include "diy-fp.h" |
| michael@0 | 30 | #include "utils.h" |
| michael@0 | 31 | |
| michael@0 | 32 | namespace double_conversion { |
| michael@0 | 33 | |
| michael@0 | 34 | void DiyFp::Multiply(const DiyFp& other) { |
| michael@0 | 35 | // Simply "emulates" a 128 bit multiplication. |
| michael@0 | 36 | // However: the resulting number only contains 64 bits. The least |
| michael@0 | 37 | // significant 64 bits are only used for rounding the most significant 64 |
| michael@0 | 38 | // bits. |
| michael@0 | 39 | const uint64_t kM32 = 0xFFFFFFFFU; |
| michael@0 | 40 | uint64_t a = f_ >> 32; |
| michael@0 | 41 | uint64_t b = f_ & kM32; |
| michael@0 | 42 | uint64_t c = other.f_ >> 32; |
| michael@0 | 43 | uint64_t d = other.f_ & kM32; |
| michael@0 | 44 | uint64_t ac = a * c; |
| michael@0 | 45 | uint64_t bc = b * c; |
| michael@0 | 46 | uint64_t ad = a * d; |
| michael@0 | 47 | uint64_t bd = b * d; |
| michael@0 | 48 | uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32); |
| michael@0 | 49 | // By adding 1U << 31 to tmp we round the final result. |
| michael@0 | 50 | // Halfway cases will be round up. |
| michael@0 | 51 | tmp += 1U << 31; |
| michael@0 | 52 | uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); |
| michael@0 | 53 | e_ += other.e_ + 64; |
| michael@0 | 54 | f_ = result_f; |
| michael@0 | 55 | } |
| michael@0 | 56 | |
| michael@0 | 57 | } // namespace double_conversion |
