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95 lines
2.9 KiB
C
Executable File
95 lines
2.9 KiB
C
Executable File
/*
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* linux/lib/string.c
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* Modified to take care of kernel versions
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*/
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#include "string_compat.h"
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#include <linux/errno.h> //E2BIG
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#if LINUX_VERSION_CODE <= KERNEL_VERSION(4,3,0)
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#include <asm/byteorder.h>
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#include <asm/word-at-a-time.h>
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#include <asm/page.h> //PAGE_SIZE
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/**
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* strscpy - Copy a C-string into a sized buffer
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* @dest: Where to copy the string to
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* @src: Where to copy the string from
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* @count: Size of destination buffer
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*
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* Copy the string, or as much of it as fits, into the dest buffer.
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* The routine returns the number of characters copied (not including
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* the trailing NUL) or -E2BIG if the destination buffer wasn't big enough.
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* The behavior is undefined if the string buffers overlap.
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* The destination buffer is always NUL terminated, unless it's zero-sized.
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*
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* Preferred to strlcpy() since the API doesn't require reading memory
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* from the src string beyond the specified "count" bytes, and since
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* the return value is easier to error-check than strlcpy()'s.
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* In addition, the implementation is robust to the string changing out
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* from underneath it, unlike the current strlcpy() implementation.
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*
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* Preferred to strncpy() since it always returns a valid string, and
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* doesn't unnecessarily force the tail of the destination buffer to be
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* zeroed. If the zeroing is desired, it's likely cleaner to use strscpy()
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* with an overflow test, then just memset() the tail of the dest buffer.
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*/
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ssize_t strscpy(char *dest, const char *src, size_t count)
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{
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const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
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size_t max = count;
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long res = 0;
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if (count == 0)
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return -E2BIG;
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#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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/*
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* If src is unaligned, don't cross a page boundary,
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* since we don't know if the next page is mapped.
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*/
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if ((long)src & (sizeof(long) - 1)) {
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size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
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if (limit < max)
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max = limit;
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}
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#else
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/* If src or dest is unaligned, don't do word-at-a-time. */
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if (((long) dest | (long) src) & (sizeof(long) - 1))
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max = 0;
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#endif
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while (max >= sizeof(unsigned long)) {
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unsigned long c, data;
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c = *(unsigned long *)(src+res);
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*(unsigned long *)(dest+res) = c;
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if (has_zero(c, &data, &constants)) {
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data = prep_zero_mask(c, data, &constants);
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data = create_zero_mask(data);
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return res + find_zero(data);
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}
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res += sizeof(unsigned long);
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count -= sizeof(unsigned long);
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max -= sizeof(unsigned long);
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}
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while (count) {
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char c;
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c = src[res];
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dest[res] = c;
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if (!c)
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return res;
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res++;
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count--;
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}
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/* Hit buffer length without finding a NUL; force NUL-termination. */
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if (res)
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dest[res-1] = '\0';
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return -E2BIG;
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}
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#endif //kernel 4.3.0
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