Mercurial > libjeffpc
view rand.c @ 742:337fad78b8ae
base64: use a less complicated validity check in the decode loop
Checking each of the four input chars for validity generates horrible
machine code with many comparisons and conditional jumps. We can reduce
this to just one comparison and one conditional jump by making assumptions
about what invalid inputs look like (i.e., 0xff).
Suggested by Timo Sirainen.
Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
author | Josef 'Jeff' Sipek <jeffpc@josefsipek.net> |
---|---|
date | Wed, 29 May 2019 10:58:19 -0400 |
parents | 6f8be69c0d8e |
children |
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/* * Copyright (c) 2015-2018 Josef 'Jeff' Sipek <jeffpc@josefsipek.net> * Copyright (c) 2015 Holly Sipek * * 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 <inttypes.h> #include <jeffpc/rand.h> #include <jeffpc/config.h> #include <jeffpc/error.h> #include <jeffpc/io.h> uint32_t rand32(void) { #ifdef JEFFPC_HAVE_ARC4RANDOM return arc4random(); #else uint32_t val; int ret; int fd; fd = xopen("/dev/urandom", O_RDONLY, 0); if (fd < 0) panic("Failed to get random number: %s", xstrerror(fd)); ret = xread(fd, &val, sizeof(val)); if (ret) panic("Failed to get random number: %s", xstrerror(ret)); xclose(fd); return val; #endif } uint64_t rand64(void) { uint64_t tmp; tmp = rand32(); tmp <<= 32; tmp |= rand32(); return tmp; } void rand_buf(void *buf, size_t len) { #ifdef JEFFPC_HAVE_ARC4RANDOM_BUF arc4random_buf(buf, len); #else int ret; int fd; fd = xopen("/dev/urandom", O_RDONLY, 0); if (fd < 0) panic("Failed to get random buffer: %s", xstrerror(fd)); ret = xread(fd, buf, len); if (ret) panic("Failed to get random buffer: %s", xstrerror(ret)); xclose(fd); #endif }