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https://github.com/jart/cosmopolitan.git
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f4f4caab0e
I wanted a tiny scriptable meltdown proof way to run userspace programs and visualize how program execution impacts memory. It helps to explain how things like Actually Portable Executable works. It can show you how the GCC generated code is going about manipulating matrices and more. I didn't feel fully comfortable with Qemu and Bochs because I'm not smart enough to understand them. I wanted something like gVisor but with much stronger levels of assurances. I wanted a single binary that'll run, on all major operating systems with an embedded GPL barrier ZIP filesystem that is tiny enough to transpile to JavaScript and run in browsers too. https://justine.storage.googleapis.com/emulator625.mp4
79 lines
4.8 KiB
C
79 lines
4.8 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/nexgen32e/crc32.h"
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/**
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* Computes Castagnoli CRC-32 on old computers.
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*/
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uint32_t crc32c$pure(uint32_t init, const void *data, size_t size) {
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extern const uint32_t kCrc32cTab[256];
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const unsigned char *p = data;
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uint32_t h = init ^ 0xffffffff;
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unsigned i;
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for (i = 0; i < size; i++) {
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h = h >> 8 ^ kCrc32cTab[(h & 0xff) ^ p[i]];
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}
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return h ^ 0xffffffff;
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}
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/*
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bench_crc32c$pure for #c per n where c ≈ 0.293ns
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N x1 x8 x64 mBps
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------------------------------------------------------------
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1 4305.000 91.375 44.203 74
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1 75.000 55.875 44.703 73
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2 46.500 35.188 24.617 132
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3 40.333 26.625 19.193 169
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4 32.250 19.969 16.215 200
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7 18.429 15.089 12.033 270
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8 20.625 13.547 11.607 280
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15 15.667 10.775 9.589 339
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16 17.562 10.695 9.419 345
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31 12.226 8.891 8.317 391
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32 13.219 8.480 8.078 402
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63 9.571 8.065 7.731 420
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64 9.672 7.955 7.633 426
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127 8.433 7.548 7.329 443
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128 8.492 7.528 7.352 442
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255 7.557 7.366 7.239 449
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256 7.699 7.342 7.305 445
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511 7.376 7.243 7.223 450
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512 7.408 7.233 7.225 450
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1023 7.188 7.192 7.098 458
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1024 7.171 7.194 7.097 458
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2047 7.130 7.172 7.085 459
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2048 7.117 7.170 7.169 453
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4095 7.063 7.076 7.085 459
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4096 7.078 7.161 7.081 459
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8191 7.041 7.095 7.055 461
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8192 7.051 7.098 7.087 459
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16383 7.039 7.114 7.067 460
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16384 6.876 6.931 7.133 456
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32767 7.055 7.108 7.290 446
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32768 6.868 6.887 6.974 466
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65535 6.984 6.885 6.967 467
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65536 6.877 6.924 10.994 296
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131071 7.166 7.141 7.011 464
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131072 6.853 6.971 7.694 422
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262143 6.853 7.213 7.406 439
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262144 6.852 6.968 7.290 446
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524287 7.398 7.389 7.166 454
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524288 6.851 7.094 7.159 454
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*/
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