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lib/string/zustr2stp.[ch]: Remove zustr2stp(); keep ZUSTR2STP()

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The function should never be used; it's always used via its wrapper
macro.  To simplify, and reduce chances of confusion: remove the
function, and implement the macro directly in terms of
stpcpy(mempcpy(strnlen())).

Update the documentation, and improve the example, which was rather
confusing.

Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
This commit is contained in:
Alejandro Colomar
2023-12-03 21:43:07 +01:00
committed by Serge Hallyn
parent ba43b49a52
commit ffb3992467
3 changed files with 22 additions and 54 deletions
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14
lib/string/zustr2stp.c
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@@ -1,17 +1,7 @@
/*
* SPDX-FileCopyrightText: 2022-2023, Alejandro Colomar <alx@kernel.org>
* SPDX-License-Identifier: BSD-3-Clause
*/
// SPDX-FileCopyrightText: 2022-2024, Alejandro Colomar <alx@kernel.org>
// SPDX-License-Identifier: BSD-3-Clause
#include <config.h>
#include <stddef.h>
#ident "$Id$"
#include "string/zustr2stp.h"
extern inline char *zustr2stp(char *restrict dst, const char *restrict src,
size_t sz);

61
lib/string/zustr2stp.h
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@@ -1,79 +1,58 @@
/*
* SPDX-FileCopyrightText: 2022-2023, Alejandro Colomar <alx@kernel.org>
* SPDX-License-Identifier: BSD-3-Clause
*/
// SPDX-FileCopyrightText: 2022-2024, Alejandro Colomar <alx@kernel.org>
// SPDX-License-Identifier: BSD-3-Clause
#ifndef SHADOW_INCLUDE_LIBMISC_ZUSTR2STP_H_
#define SHADOW_INCLUDE_LIBMISC_ZUSTR2STP_H_
#ifndef SHADOW_INCLUDE_LIB_STRING_ZUSTR2STP_H_
#define SHADOW_INCLUDE_LIB_STRING_ZUSTR2STP_H_
#include <config.h>
#include <assert.h>
#include <stddef.h>
#include <string.h>
#include "must_be.h"
#include "sizeof.h"
#define ZUSTR2STP(dst, src) \
({ \
static_assert(!is_array(dst) || sizeof(dst) > SIZEOF_ARRAY(src), ""); \
\
zustr2stp(dst, src, NITEMS(src)); \
})
inline char *zustr2stp(char *restrict dst, const char *restrict src, size_t sz);
/*
* SYNOPSIS
* char *zustr2stp(char *restrict dst,
* const char src[restrict .sz], size_t sz);
* char *ZUSTR2STP(char *restrict dst, const char src[restrict]);
*
* ARGUMENTS
* dst Destination buffer where to copy a string.
*
* src Source null-padded character sequence to be copied into
* dst.
*
* sz Size of the *source* buffer.
* dst Destination buffer.
* src Source null-padded character sequence.
*
* DESCRIPTION
* This function copies the null-padded character sequence pointed
* to by src, into a string at the buffer pointed to by dst.
* This macro copies at most NITEMS(src) non-null bytes from the
* array pointed to by src, followed by a null character, to the
* buffer pointed to by dst.
*
* RETURN VALUE
* dst + strlen(dst)
* This function returns a pointer to the terminating NUL
* byte.
*
* ERRORS
* This function doesn't set errno.
*
* CAVEATS
* This function doesn't know the size of the destination buffer.
* It assumes it will always be large enough. Since the size of
* the source buffer is known to the caller, it should make sure to
* allocate a destination buffer of at least `sz + 1`.
* allocate a destination buffer of at least `NITEMS(src) + 1`.
*
* EXAMPLES
* char src[13] = "Hello, world!" // No '\0' in this buffer!
* char dst[NITEMS(src) + 1];
* char hostname[NITEMS(utmp->ut_host) + 1];
*
* zustr2stp(dst, src, NITEMS(src));
* puts(dst);
* len = ZUSTR2STP(hostname, utmp->ut_host) - hostname;
* puts(hostname);
*/
inline char *
zustr2stp(char *restrict dst, const char *restrict src, size_t sz)
{
return stpcpy(mempcpy(dst, src, strnlen(src, sz)), "");
}
#define ZUSTR2STP(dst, src) \
({ \
static_assert(!is_array(dst) || sizeof(dst) > SIZEOF_ARRAY(src), ""); \
\
stpcpy(mempcpy(dst, src, strnlen(src, NITEMS(src))), ""); \
})
#endif // include guard