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https://github.com/justinian/jsix.git
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346c172b32
This new libc is mostly from scratch, with *printf() functions provided by Marco Paland and Eyal Rozenberg's tiny printf library, and malloc and friends provided by dlmalloc.
58 lines
1.4 KiB
C++
58 lines
1.4 KiB
C++
/** \file memset.cpp
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*
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* This file is part of the C standard library for the jsix operating
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* system.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/.
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*/
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#include <string.h>
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#include <__j6libc/bits.h>
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#include <__j6libc/casts.h>
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using namespace __j6libc;
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#if __UINTPTR_WIDTH__ != 64 && __UINTPTR_WIDTH__ != 32
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#error "memset: uintptr_t isn't 4 or 8 bytes"
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#endif
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static inline uintptr_t repval(uint8_t c) {
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uintptr_t r = c;
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r |= r << 8;
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r |= r << 16;
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#if __UINTPTR_WIDTH__ == 64
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r |= r << 32;
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#endif
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return r;
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}
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void *memset(void *s, int c, size_t n) {
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if (!s) return nullptr;
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// First, any unalined initial bytes
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uint8_t *b = cast_to<uint8_t*>(s);
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uint8_t bval = c & 0xff;
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while (n && !is_aligned<uintptr_t>(b)) {
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*b++ = bval;
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--n;
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}
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// As many word-sized writes as possible
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size_t words = n >> word_shift;
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uintptr_t pval = repval(c);
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uintptr_t *p = cast_to<uintptr_t*>(b);
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for (size_t i = 0; i < words; ++i)
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*p++ = pval;
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// Remaining unaligned bytes
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b = reinterpret_cast<uint8_t*>(p);
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size_t remainder = n & word_align_mask;
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for (size_t i = 0; i < remainder; ++i)
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*b++ = bval;
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return s;
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}
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