path: root/doc/unistr.texi

@node unistr.h
@chapter Elementary Unicode string functions @code{<unistr.h>}

This include file declares elementary functions for Unicode strings.  It is
essentially the equivalent of what @code{<string.h>} is for C strings.

@menu
* Elementary string checks::
* Elementary string conversions::
* Elementary string functions::
* Elementary string functions with memory allocation::
* Elementary string functions on NUL terminated strings::
@end menu

@node Elementary string checks
@section Elementary string checks

@cindex validity
@cindex verification
@cindex well-formed
The following function is available to verify the integrity of a Unicode string.

@deftypefun {const uint8_t *} u8_check (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx {const uint16_t *} u16_check (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx {const uint32_t *} u32_check (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n})
This function checks whether a Unicode string is well-formed.
It returns NULL if valid, or a pointer to the first invalid unit otherwise.
@end deftypefun

@node Elementary string conversions
@section Elementary string conversions

@cindex converting
The following functions perform conversions between the different forms of Unicode strings.

@deftypefun {uint16_t *} u8_to_u16 (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n}, uint16_t@tie{}*@var{resultbuf}, size_t@tie{}*@var{lengthp})
Converts an UTF-8 string to an UTF-16 string.

The @var{resultbuf} and @var{lengthp} arguments are as described in
chapter @ref{Conventions}.
@end deftypefun

@deftypefun {uint32_t *} u8_to_u32 (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n}, uint32_t@tie{}*@var{resultbuf}, size_t@tie{}*@var{lengthp})
Converts an UTF-8 string to an UTF-32 string.

The @var{resultbuf} and @var{lengthp} arguments are as described in
chapter @ref{Conventions}.
@end deftypefun

@deftypefun {uint8_t *} u16_to_u8 (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n}, uint8_t@tie{}*@var{resultbuf}, size_t@tie{}*@var{lengthp})
Converts an UTF-16 string to an UTF-8 string.

The @var{resultbuf} and @var{lengthp} arguments are as described in
chapter @ref{Conventions}.
@end deftypefun

@deftypefun {uint32_t *} u16_to_u32 (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n}, uint32_t@tie{}*@var{resultbuf}, size_t@tie{}*@var{lengthp})
Converts an UTF-16 string to an UTF-32 string.

The @var{resultbuf} and @var{lengthp} arguments are as described in
chapter @ref{Conventions}.
@end deftypefun

@deftypefun {uint8_t *} u32_to_u8 (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n}, uint8_t@tie{}*@var{resultbuf}, size_t@tie{}*@var{lengthp})
Converts an UTF-32 string to an UTF-8 string.

The @var{resultbuf} and @var{lengthp} arguments are as described in
chapter @ref{Conventions}.
@end deftypefun

@deftypefun {uint16_t *} u32_to_u16 (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n}, uint16_t@tie{}*@var{resultbuf}, size_t@tie{}*@var{lengthp})
Converts an UTF-32 string to an UTF-16 string.

The @var{resultbuf} and @var{lengthp} arguments are as described in
chapter @ref{Conventions}.
@end deftypefun

@node Elementary string functions
@section Elementary string functions

@menu
* Iterating::
* Creating Unicode strings::
* Copying Unicode strings::
* Comparing Unicode strings::
* Searching for a character::
* Counting characters::
@end menu

@node Iterating
@subsection Iterating over a Unicode string

@cindex iterating
The following functions inspect and return details about the first character
in a Unicode string.

@deftypefun int u8_mblen (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx int u16_mblen (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx int u32_mblen (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n})
Returns the length (number of units) of the first character in @var{s}, which
is no longer than @var{n}.  Returns 0 if it is the NUL character.  Returns -1
upon failure.

This function is similar to @posixfunc{mblen}, except that it operates on a
Unicode string and that @var{s} must not be NULL.
@end deftypefun

@deftypefun int u8_mbtouc (ucs4_t@tie{}*@var{puc}, const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx int u16_mbtouc (ucs4_t@tie{}*@var{puc}, const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx int u32_mbtouc (ucs4_t@tie{}*@var{puc}, const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n})
Returns the length (number of units) of the first character in @var{s},
putting its @code{ucs4_t} representation in @code{*@var{puc}}.  Upon failure,
@code{*@var{puc}} is set to @code{0xfffd}, and an appropriate number of units
is returned.

The number of available units, @var{n}, must be > 0.

This function fails if an invalid sequence of units is encountered at the
beginning of @var{s}, or if additional units (after the @var{n} provided units)
would be needed to form a character.

This function is similar to @posixfunc{mbtowc}, except that it operates on a
Unicode string, @var{puc} and @var{s} must not be NULL, @var{n} must be > 0,
and the NUL character is not treated specially.
@end deftypefun

@deftypefun int u8_mbtouc_unsafe (ucs4_t@tie{}*@var{puc}, const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx int u16_mbtouc_unsafe (ucs4_t@tie{}*@var{puc}, const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx int u32_mbtouc_unsafe (ucs4_t@tie{}*@var{puc}, const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n})
This function is identical to @code{u8_mbtouc}/@code{u16_mbtouc}/@code{u32_mbtouc}.
Earlier versions of this function performed fewer range-checks on the sequence
of units.
@end deftypefun

@deftypefun int u8_mbtoucr (ucs4_t@tie{}*@var{puc}, const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx int u16_mbtoucr (ucs4_t@tie{}*@var{puc}, const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx int u32_mbtoucr (ucs4_t@tie{}*@var{puc}, const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n})
Returns the length (number of units) of the first character in @var{s},
putting its @code{ucs4_t} representation in @code{*@var{puc}}.  Upon failure,
@code{*@var{puc}} is set to @code{0xfffd}, and -1 is returned for an invalid
sequence of units, -2 is returned for an incomplete sequence of units.

The number of available units, @var{n}, must be > 0.

This function is similar to @code{u8_mbtouc}, except that the return value
gives more details about the failure, similar to @posixfunc{mbrtowc}.
@end deftypefun

@node Creating Unicode strings
@subsection Creating Unicode strings one character at a time

The following function stores a Unicode character as a Unicode string in
memory.

@deftypefun int u8_uctomb (uint8_t@tie{}*@var{s}, ucs4_t@tie{}@var{uc}, int@tie{}@var{n})
@deftypefunx int u16_uctomb (uint16_t@tie{}*@var{s}, ucs4_t@tie{}@var{uc}, int@tie{}@var{n})
@deftypefunx int u32_uctomb (uint32_t@tie{}*@var{s}, ucs4_t@tie{}@var{uc}, int@tie{}@var{n})
Puts the multibyte character represented by @var{uc} in @var{s}, returning its
length.  Returns -1 upon failure, -2 if the number of available units, @var{n},
is too small.  The latter case cannot occur if @var{n} >= 6/2/1, respectively.

This function is similar to @posixfunc{wctomb}, except that it operates on a
Unicode strings, @var{s} must not be NULL, and the argument @var{n} must be
specified.
@end deftypefun

@node Copying Unicode strings
@subsection Copying Unicode strings

@cindex copying
The following functions copy Unicode strings in memory.

@deftypefun {uint8_t *} u8_cpy (uint8_t@tie{}*@var{dest}, const@tie{}uint8_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint16_t *} u16_cpy (uint16_t@tie{}*@var{dest}, const@tie{}uint16_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint32_t *} u32_cpy (uint32_t@tie{}*@var{dest}, const@tie{}uint32_t@tie{}*@var{src}, size_t@tie{}@var{n})
Copies @var{n} units from @var{src} to @var{dest}.

This function is similar to @posixfunc{memcpy}, except that it operates on
Unicode strings.
@end deftypefun

@deftypefun {uint8_t *} u8_move (uint8_t@tie{}*@var{dest}, const@tie{}uint8_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint16_t *} u16_move (uint16_t@tie{}*@var{dest}, const@tie{}uint16_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint32_t *} u32_move (uint32_t@tie{}*@var{dest}, const@tie{}uint32_t@tie{}*@var{src}, size_t@tie{}@var{n})
Copies @var{n} units from @var{src} to @var{dest}, guaranteeing correct
behavior for overlapping memory areas.

This function is similar to @posixfunc{memmove}, except that it operates on
Unicode strings.
@end deftypefun

The following function fills a Unicode string.

@deftypefun {uint8_t *} u8_set (uint8_t@tie{}*@var{s}, ucs4_t@tie{}@var{uc}, size_t@tie{}@var{n})
@deftypefunx {uint16_t *} u16_set (uint16_t@tie{}*@var{s}, ucs4_t@tie{}@var{uc}, size_t@tie{}@var{n})
@deftypefunx {uint32_t *} u32_set (uint32_t@tie{}*@var{s}, ucs4_t@tie{}@var{uc}, size_t@tie{}@var{n})
Sets the first @var{n} characters of @var{s} to @var{uc}.  @var{uc} should be
a character that occupies only 1 unit.

This function is similar to @posixfunc{memset}, except that it operates on
Unicode strings.
@end deftypefun

@node Comparing Unicode strings
@subsection Comparing Unicode strings

@cindex comparing
The following function compares two Unicode strings of the same length.

@deftypefun int u8_cmp (const@tie{}uint8_t@tie{}*@var{s1}, const@tie{}uint8_t@tie{}*@var{s2}, size_t@tie{}@var{n})
@deftypefunx int u16_cmp (const@tie{}uint16_t@tie{}*@var{s1}, const@tie{}uint16_t@tie{}*@var{s2}, size_t@tie{}@var{n})
@deftypefunx int u32_cmp (const@tie{}uint32_t@tie{}*@var{s1}, const@tie{}uint32_t@tie{}*@var{s2}, size_t@tie{}@var{n})
Compares @var{s1} and @var{s2}, each of length @var{n}, lexicographically.
Returns a negative value if @var{s1} compares smaller than @var{s2},
a positive value if @var{s1} compares larger than @var{s2}, or 0 if
they compare equal.

This function is similar to @posixfunc{memcmp}, except that it operates on
Unicode strings.
@end deftypefun

The following function compares two Unicode strings of possibly different
lengths.

@deftypefun int u8_cmp2 (const@tie{}uint8_t@tie{}*@var{s1}, size_t@tie{}@var{n1}, const@tie{}uint8_t@tie{}*@var{s2}, size_t@tie{}@var{n2})
@deftypefunx int u16_cmp2 (const@tie{}uint16_t@tie{}*@var{s1}, size_t@tie{}@var{n1}, const@tie{}uint16_t@tie{}*@var{s2}, size_t@tie{}@var{n2})
@deftypefunx int u32_cmp2 (const@tie{}uint32_t@tie{}*@var{s1}, size_t@tie{}@var{n1}, const@tie{}uint32_t@tie{}*@var{s2}, size_t@tie{}@var{n2})
Compares @var{s1} and @var{s2}, lexicographically.
Returns a negative value if @var{s1} compares smaller than @var{s2},
a positive value if @var{s1} compares larger than @var{s2}, or 0 if
they compare equal.

This function is similar to the gnulib function @func{memcmp2}, except that it
operates on Unicode strings.
@end deftypefun

@node Searching for a character
@subsection Searching for a character in a Unicode string

@cindex searching, for a character
The following function searches for a given Unicode character.

@deftypefun {uint8_t *} u8_chr (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n}, ucs4_t@tie{}@var{uc})
@deftypefunx {uint16_t *} u16_chr (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n}, ucs4_t@tie{}@var{uc})
@deftypefunx {uint32_t *} u32_chr (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n}, ucs4_t@tie{}@var{uc})
Searches the string at @var{s} for @var{uc}.  Returns a pointer to the first
occurrence of @var{uc} in @var{s}, or NULL if @var{uc} does not occur in
@var{s}.

This function is similar to @posixfunc{memchr}, except that it operates on
Unicode strings.
@end deftypefun

@node Counting characters
@subsection Counting the characters in a Unicode string

@cindex counting
The following function counts the number of Unicode characters.

@deftypefun size_t u8_mbsnlen (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx size_t u16_mbsnlen (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx size_t u32_mbsnlen (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n})
Counts and returns the number of Unicode characters in the @var{n} units
from @var{s}.

This function is similar to the gnulib function @func{mbsnlen}, except that
it operates on Unicode strings.
@end deftypefun

@node Elementary string functions with memory allocation
@section Elementary string functions with memory allocation

@cindex duplicating
The following function copies a Unicode string.

@deftypefun {uint8_t *} u8_cpy_alloc (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx {uint16_t *} u16_cpy_alloc (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{n})
@deftypefunx {uint32_t *} u32_cpy_alloc (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{n})
Makes a freshly allocated copy of @var{s}, of length @var{n}.
@end deftypefun

@node Elementary string functions on NUL terminated strings
@section Elementary string functions on NUL terminated strings

@menu
* Iterating over a NUL terminated Unicode string::
* Length::
* Copying a NUL terminated Unicode string::
* Comparing NUL terminated Unicode strings::
* Duplicating a NUL terminated Unicode string::
* Searching for a character in a NUL terminated Unicode string::
* Searching for a substring::
* Tokenizing::
@end menu

@node Iterating over a NUL terminated Unicode string
@subsection Iterating over a NUL terminated Unicode string

The following functions inspect and return details about the first character
in a Unicode string.

@deftypefun int u8_strmblen (const@tie{}uint8_t@tie{}*@var{s})
@deftypefunx int u16_strmblen (const@tie{}uint16_t@tie{}*@var{s})
@deftypefunx int u32_strmblen (const@tie{}uint32_t@tie{}*@var{s})
Returns the length (number of units) of the first character in @var{s}.
Returns 0 if it is the NUL character.  Returns -1 upon failure.
@end deftypefun

@cindex iterating
@deftypefun int u8_strmbtouc (ucs4_t@tie{}*@var{puc}, const@tie{}uint8_t@tie{}*@var{s})
@deftypefunx int u16_strmbtouc (ucs4_t@tie{}*@var{puc}, const@tie{}uint16_t@tie{}*@var{s})
@deftypefunx int u32_strmbtouc (ucs4_t@tie{}*@var{puc}, const@tie{}uint32_t@tie{}*@var{s})
Returns the length (number of units) of the first character in @var{s},
putting its @code{ucs4_t} representation in @code{*@var{puc}}.  Returns 0
if it is the NUL character.  Returns -1 upon failure.
@end deftypefun

@deftypefun {const uint8_t *} u8_next (ucs4_t@tie{}*@var{puc}, const@tie{}uint8_t@tie{}*@var{s})
@deftypefunx {const uint16_t *} u16_next (ucs4_t@tie{}*@var{puc}, const@tie{}uint16_t@tie{}*@var{s})
@deftypefunx {const uint32_t *} u32_next (ucs4_t@tie{}*@var{puc}, const@tie{}uint32_t@tie{}*@var{s})
Forward iteration step.  Advances the pointer past the next character,
or returns NULL if the end of the string has been reached.  Puts the
character's @code{ucs4_t} representation in @code{*@var{puc}}.
@end deftypefun

The following function inspects and returns details about the previous
character in a Unicode string.

@deftypefun {const uint8_t *} u8_prev (ucs4_t@tie{}*@var{puc}, const@tie{}uint8_t@tie{}*@var{s}, const@tie{}uint8_t@tie{}*@var{start})
@deftypefunx {const uint16_t *} u16_prev (ucs4_t@tie{}*@var{puc}, const@tie{}uint16_t@tie{}*@var{s}, const@tie{}uint16_t@tie{}*@var{start})
@deftypefunx {const uint32_t *} u32_prev (ucs4_t@tie{}*@var{puc}, const@tie{}uint32_t@tie{}*@var{s}, const@tie{}uint32_t@tie{}*@var{start})
Backward iteration step.  Advances the pointer to point to the previous
character (the one that ends at @code{@var{s}}), or returns NULL if the
beginning of the string (specified by @code{@var{start}}) had been reached.
Puts the character's @code{ucs4_t} representation in @code{*@var{puc}}.
Note that this function works only on well-formed Unicode strings.
@end deftypefun

@node Length
@subsection Length of a NUL terminated Unicode string

The following functions determine the length of a Unicode string.

@deftypefun size_t u8_strlen (const@tie{}uint8_t@tie{}*@var{s})
@deftypefunx size_t u16_strlen (const@tie{}uint16_t@tie{}*@var{s})
@deftypefunx size_t u32_strlen (const@tie{}uint32_t@tie{}*@var{s})
Returns the number of units in @var{s}.

This function is similar to @posixfunc{strlen} and @posixfunc{wcslen}, except
that it operates on Unicode strings.
@end deftypefun

@deftypefun size_t u8_strnlen (const@tie{}uint8_t@tie{}*@var{s}, size_t@tie{}@var{maxlen})
@deftypefunx size_t u16_strnlen (const@tie{}uint16_t@tie{}*@var{s}, size_t@tie{}@var{maxlen})
@deftypefunx size_t u32_strnlen (const@tie{}uint32_t@tie{}*@var{s}, size_t@tie{}@var{maxlen})
Returns the number of units in @var{s}, but at most @var{maxlen}.

This function is similar to @posixfunc{strnlen} and @posixfunc{wcsnlen}, except
that it operates on Unicode strings.
@end deftypefun

@node Copying a NUL terminated Unicode string
@subsection Copying a NUL terminated Unicode string

@cindex copying
The following functions copy portions of Unicode strings in memory.

@deftypefun {uint8_t *} u8_strcpy (uint8_t@tie{}*@var{dest}, const@tie{}uint8_t@tie{}*@var{src})
@deftypefunx {uint16_t *} u16_strcpy (uint16_t@tie{}*@var{dest}, const@tie{}uint16_t@tie{}*@var{src})
@deftypefunx {uint32_t *} u32_strcpy (uint32_t@tie{}*@var{dest}, const@tie{}uint32_t@tie{}*@var{src})
Copies @var{src} to @var{dest}.

This function is similar to @posixfunc{strcpy} and @posixfunc{wcscpy}, except
that it operates on Unicode strings.
@end deftypefun

@deftypefun {uint8_t *} u8_stpcpy (uint8_t@tie{}*@var{dest}, const@tie{}uint8_t@tie{}*@var{src})
@deftypefunx {uint16_t *} u16_stpcpy (uint16_t@tie{}*@var{dest}, const@tie{}uint16_t@tie{}*@var{src})
@deftypefunx {uint32_t *} u32_stpcpy (uint32_t@tie{}*@var{dest}, const@tie{}uint32_t@tie{}*@var{src})
Copies @var{src} to @var{dest}, returning the address of the terminating NUL
in @var{dest}.

This function is similar to @posixfunc{stpcpy}, except that it operates on
Unicode strings.
@end deftypefun

@deftypefun {uint8_t *} u8_strncpy (uint8_t@tie{}*@var{dest}, const@tie{}uint8_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint16_t *} u16_strncpy (uint16_t@tie{}*@var{dest}, const@tie{}uint16_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint32_t *} u32_strncpy (uint32_t@tie{}*@var{dest}, const@tie{}uint32_t@tie{}*@var{src}, size_t@tie{}@var{n})
Copies no more than @var{n} units of @var{src} to @var{dest}.

This function is similar to @posixfunc{strncpy} and @posixfunc{wcsncpy}, except
that it operates on Unicode strings.
@end deftypefun

@deftypefun {uint8_t *} u8_stpncpy (uint8_t@tie{}*@var{dest}, const@tie{}uint8_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint16_t *} u16_stpncpy (uint16_t@tie{}*@var{dest}, const@tie{}uint16_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint32_t *} u32_stpncpy (uint32_t@tie{}*@var{dest}, const@tie{}uint32_t@tie{}*@var{src}, size_t@tie{}@var{n})
Copies no more than @var{n} units of @var{src} to @var{dest}.  Returns a
pointer past the last non-NUL unit written into @var{dest}.  In other words,
if the units written into @var{dest} include a NUL, the return value is the
address of the first such NUL unit, otherwise it is
@code{@var{dest} + @var{n}}.

This function is similar to @posixfunc{stpncpy}, except that it operates on
Unicode strings.
@end deftypefun

@deftypefun {uint8_t *} u8_strcat (uint8_t@tie{}*@var{dest}, const@tie{}uint8_t@tie{}*@var{src})
@deftypefunx {uint16_t *} u16_strcat (uint16_t@tie{}*@var{dest}, const@tie{}uint16_t@tie{}*@var{src})
@deftypefunx {uint32_t *} u32_strcat (uint32_t@tie{}*@var{dest}, const@tie{}uint32_t@tie{}*@var{src})
Appends @var{src} onto @var{dest}.

This function is similar to @posixfunc{strcat} and @posixfunc{wcscat}, except
that it operates on Unicode strings.
@end deftypefun

@deftypefun {uint8_t *} u8_strncat (uint8_t@tie{}*@var{dest}, const@tie{}uint8_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint16_t *} u16_strncat (uint16_t@tie{}*@var{dest}, const@tie{}uint16_t@tie{}*@var{src}, size_t@tie{}@var{n})
@deftypefunx {uint32_t *} u32_strncat (uint32_t@tie{}*@var{dest}, const@tie{}uint32_t@tie{}*@var{src}, size_t@tie{}@var{n})
Appends no more than @var{n} units of @var{src} onto @var{dest}.

This function is similar to @posixfunc{strncat} and @posixfunc{wcsncat}, except
that it operates on Unicode strings.
@end deftypefun

@node Comparing NUL terminated Unicode strings
@subsection Comparing NUL terminated Unicode strings

@cindex comparing
The following functions compare two Unicode strings.

@deftypefun int u8_strcmp (const@tie{}uint8_t@tie{}*@var{s1}, const@tie{}uint8_t@tie{}*@var{s2})
@deftypefunx int u16_strcmp (const@tie{}uint16_t@tie{}*@var{s1}, const@tie{}uint16_t@tie{}*@var{s2})
@deftypefunx int u32_strcmp (const@tie{}uint32_t@tie{}*@var{s1}, const@tie{}uint32_t@tie{}*@var{s2})
Compares @var{s1} and @var{s2}, lexicographically.
Returns a negative value if @var{s1} compares smaller than @var{s2},
a positive value if @var{s1} compares larger than @var{s2}, or 0 if
they compare equal.

This function is similar to @posixfunc{strcmp} and @posixfunc{wcscmp}, except
that it operates on Unicode strings.
@end deftypefun

@cindex comparing, with collation rules
@deftypefun int u8_strcoll (const@tie{}uint8_t@tie{}*@var{s1}, const@tie{}uint8_t@tie{}*@var{s2})
@deftypefunx int u16_strcoll (const@tie{}uint16_t@tie{}*@var{s1}, const@tie{}uint16_t@tie{}*@var{s2})
@deftypefunx int u32_strcoll (const@tie{}uint32_t@tie{}*@var{s1}, const@tie{}uint32_t@tie{}*@var{s2})
Compares @var{s1} and @var{s2} using the collation rules of the current
locale.
Returns -1 if @var{s1} < @var{s2}, 0 if @var{s1} = @var{s2}, 1 if
@var{s1} > @var{s2}.  Upon failure, sets @code{errno} and returns any value.

This function is similar to @posixfunc{strcoll} and @posixfunc{wcscoll}, except
that it operates on Unicode strings.

Note that this function may consider different canonical normalizations
of the same string as having a large distance.  It is therefore better to
use the function @code{u8_normcoll} instead of this one; see @ref{uninorm.h}.
@end deftypefun

@deftypefun int u8_strncmp (const@tie{}uint8_t@tie{}*@var{s1}, const@tie{}uint8_t@tie{}*@var{s2}, size_t@tie{}@var{n})
@deftypefunx int u16_strncmp (const@tie{}uint16_t@tie{}*@var{s1}, const@tie{}uint16_t@tie{}*@var{s2}, size_t@tie{}@var{n})
@deftypefunx int u32_strncmp (const@tie{}uint32_t@tie{}*@var{s1}, const@tie{}uint32_t@tie{}*@var{s2}, size_t@tie{}@var{n})
Compares no more than @var{n} units of @var{s1} and @var{s2}.

This function is similar to @posixfunc{strncmp} and @posixfunc{wcsncmp}, except
that it operates on Unicode strings.
@end deftypefun

@node Duplicating a NUL terminated Unicode string
@subsection Duplicating a NUL terminated Unicode string

@cindex duplicating
The following function allocates a duplicate of a Unicode string.

@deftypefun {uint8_t *} u8_strdup (const@tie{}uint8_t@tie{}*@var{s})
@deftypefunx {uint16_t *} u16_strdup (const@tie{}uint16_t@tie{}*@var{s})
@deftypefunx {uint32_t *} u32_strdup (const@tie{}uint32_t@tie{}*@var{s})
Duplicates @var{s}, returning an identical malloc'd string.

This function is similar to @posixfunc{strdup} and @posixfunc{wcsdup}, except
that it operates on Unicode strings.
@end deftypefun

@node Searching for a character in a NUL terminated Unicode string
@subsection Searching for a character in a NUL terminated Unicode string

@cindex searching, for a character
The following functions search for a given Unicode character.

@deftypefun {uint8_t *} u8_strchr (const@tie{}uint8_t@tie{}*@var{str}, ucs4_t@tie{}@var{uc})
@deftypefunx {uint16_t *} u16_strchr (const@tie{}uint16_t@tie{}*@var{str}, ucs4_t@tie{}@var{uc})
@deftypefunx {uint32_t *} u32_strchr (const@tie{}uint32_t@tie{}*@var{str}, ucs4_t@tie{}@var{uc})
Finds the first occurrence of @var{uc} in @var{str}.

This function is similar to @posixfunc{strchr} and @posixfunc{wcschr}, except
that it operates on Unicode strings.
@end deftypefun

@deftypefun {uint8_t *} u8_strrchr (const@tie{}uint8_t@tie{}*@var{str}, ucs4_t@tie{}@var{uc})
@deftypefunx {uint16_t *} u16_strrchr (const@tie{}uint16_t@tie{}*@var{str}, ucs4_t@tie{}@var{uc})
@deftypefunx {uint32_t *} u32_strrchr (const@tie{}uint32_t@tie{}*@var{str}, ucs4_t@tie{}@var{uc})
Finds the last occurrence of @var{uc} in @var{str}.

This function is similar to @posixfunc{strrchr} and @posixfunc{wcsrchr}, except
that it operates on Unicode strings.
@end deftypefun

The following functions search for the first occurrence of some Unicode
character in or outside a given set of Unicode characters.

@deftypefun size_t u8_strcspn (const@tie{}uint8_t@tie{}*@var{str}, const@tie{}uint8_t@tie{}*@var{reject})
@deftypefunx size_t u16_strcspn (const@tie{}uint16_t@tie{}*@var{str}, const@tie{}uint16_t@tie{}*@var{reject})
@deftypefunx size_t u32_strcspn (const@tie{}uint32_t@tie{}*@var{str}, const@tie{}uint32_t@tie{}*@var{reject})
Returns the length of the initial segment of @var{str} which consists entirely
of Unicode characters not in @var{reject}.

This function is similar to @posixfunc{strcspn} and @posixfunc{wcscspn}, except
that it operates on Unicode strings.
@end deftypefun

@deftypefun size_t u8_strspn (const@tie{}uint8_t@tie{}*@var{str}, const@tie{}uint8_t@tie{}*@var{accept})
@deftypefunx size_t u16_strspn (const@tie{}uint16_t@tie{}*@var{str}, const@tie{}uint16_t@tie{}*@var{accept})
@deftypefunx size_t u32_strspn (const@tie{}uint32_t@tie{}*@var{str}, const@tie{}uint32_t@tie{}*@var{accept})
Returns the length of the initial segment of @var{str} which consists entirely
of Unicode characters in @var{accept}.

This function is similar to @posixfunc{strspn} and @posixfunc{wcsspn}, except
that it operates on Unicode strings.
@end deftypefun

@deftypefun {uint8_t *} u8_strpbrk (const@tie{}uint8_t@tie{}*@var{str}, const@tie{}uint8_t@tie{}*@var{accept})
@deftypefunx {uint16_t *} u16_strpbrk (const@tie{}uint16_t@tie{}*@var{str}, const@tie{}uint16_t@tie{}*@var{accept})
@deftypefunx {uint32_t *} u32_strpbrk (const@tie{}uint32_t@tie{}*@var{str}, const@tie{}uint32_t@tie{}*@var{accept})
Finds the first occurrence in @var{str} of any character in @var{accept}.

This function is similar to @posixfunc{strpbrk} and @posixfunc{wcspbrk}, except
that it operates on Unicode strings.
@end deftypefun

@node Searching for a substring
@subsection Searching for a substring in a NUL terminated Unicode string

@cindex searching, for a substring
The following functions search whether a given Unicode string is a substring
of another Unicode string.

@deftypefun {uint8_t *} u8_strstr (const@tie{}uint8_t@tie{}*@var{haystack}, const@tie{}uint8_t@tie{}*@var{needle})
@deftypefunx {uint16_t *} u16_strstr (const@tie{}uint16_t@tie{}*@var{haystack}, const@tie{}uint16_t@tie{}*@var{needle})
@deftypefunx {uint32_t *} u32_strstr (const@tie{}uint32_t@tie{}*@var{haystack}, const@tie{}uint32_t@tie{}*@var{needle})
Finds the first occurrence of @var{needle} in @var{haystack}.

This function is similar to @posixfunc{strstr} and @posixfunc{wcsstr}, except
that it operates on Unicode strings.
@end deftypefun

@deftypefun bool u8_startswith (const@tie{}uint8_t@tie{}*@var{str}, const@tie{}uint8_t@tie{}*@var{prefix})
@deftypefunx bool u16_startswith (const@tie{}uint16_t@tie{}*@var{str}, const@tie{}uint16_t@tie{}*@var{prefix})
@deftypefunx bool u32_startswith (const@tie{}uint32_t@tie{}*@var{str}, const@tie{}uint32_t@tie{}*@var{prefix})
Tests whether @var{str} starts with @var{prefix}.
@end deftypefun

@deftypefun bool u8_endswith (const@tie{}uint8_t@tie{}*@var{str}, const@tie{}uint8_t@tie{}*@var{suffix})
@deftypefunx bool u16_endswith (const@tie{}uint16_t@tie{}*@var{str}, const@tie{}uint16_t@tie{}*@var{suffix})
@deftypefunx bool u32_endswith (const@tie{}uint32_t@tie{}*@var{str}, const@tie{}uint32_t@tie{}*@var{suffix})
Tests whether @var{str} ends with @var{suffix}.
@end deftypefun

@node Tokenizing
@subsection Tokenizing a NUL terminated Unicode string

The following function does one step in tokenizing a Unicode string.

@deftypefun {uint8_t *} u8_strtok (uint8_t@tie{}*@var{str}, const@tie{}uint8_t@tie{}*@var{delim}, uint8_t@tie{}**@var{ptr})
@deftypefunx {uint16_t *} u16_strtok (uint16_t@tie{}*@var{str}, const@tie{}uint16_t@tie{}*@var{delim}, uint16_t@tie{}**@var{ptr})
@deftypefunx {uint32_t *} u32_strtok (uint32_t@tie{}*@var{str}, const@tie{}uint32_t@tie{}*@var{delim}, uint32_t@tie{}**@var{ptr})
Divides @var{str} into tokens separated by characters in @var{delim}.

This function is similar to @posixfunc{strtok_r} and @posixfunc{wcstok}, except
that it operates on Unicode strings.  Its interface is actually more similar to
@code{wcstok} than to @code{strtok}.
@end deftypefun