std.utf
Category | Functions |
---|---|
Decode | decode decodeFront |
Lazy decode | byCodeUnit byChar byWchar byDchar byUTF |
Encode | encode toUTF8 toUTF16 toUTF32 toUTFz toUTF16z |
Length | codeLength count stride strideBack |
Index | toUCSindex toUTFindex |
Validation | isValidDchar isValidCodepoint validate |
Miscellaneous | replacementDchar UseReplacementDchar UTFException |
Source std/utf.d
- class
UTFException
: core.exception.UnicodeException; - Exception thrown on errors in std.utf functions.Examples:
import std.exception : assertThrown; char[4] buf; assertThrown!UTFException(encode(buf, cast(dchar) 0xD800)); assertThrown!UTFException(encode(buf, cast(dchar) 0xDBFF)); assertThrown!UTFException(encode(buf, cast(dchar) 0xDC00)); assertThrown!UTFException(encode(buf, cast(dchar) 0xDFFF)); assertThrown!UTFException(encode(buf, cast(dchar) 0x110000));
- pure nothrow @nogc @safe this(string
msg
, stringfile
= __FILE__, size_tline
= __LINE__, Throwablenext
= null);
pure nothrow @safe this(stringmsg
, size_tindex
, stringfile
= __FILE__, size_tline
= __LINE__, Throwablenext
= null); - Standard exception constructors.
- const string
toString
(); - Returns:A string detailing the invalid UTF sequence.
- pure nothrow @nogc @safe bool
isValidDchar
(dcharc
); - Check whether the given Unicode code point is valid.Parameters:
dchar c
code point to check Returns:true if and only ifc
is a valid Unicode code pointNote '\uFFFE' and '\uFFFF' are considered valid by
isValidDchar
, as they are permitted for internal use by an application, but they are not allowed for interchange by the Unicode standard.Examples:assert( isValidDchar(cast(dchar) 0x41)); assert( isValidDchar(cast(dchar) 0x00)); assert(!isValidDchar(cast(dchar) 0xD800)); assert(!isValidDchar(cast(dchar) 0x11FFFF));
- bool
isValidCodepoint
(Char)(Charc
)
if (isSomeChar!Char); - Checks if a single character forms a valid code point.When standing alone, some characters are invalid code points. For example the wchar 0xD800 is a so called high surrogate, which can only be interpreted together with a low surrogate following it. As a standalone character it is considered invalid. See Unicode Standard, D90, D91 and D92 for more details.Parameters:
Char c
character to test Char character type of c
Returns:true, ifc
forms a valid code point.Examples:assert( isValidCodepoint(cast(char) 0x40)); assert(!isValidCodepoint(cast(char) 0x80)); assert( isValidCodepoint(cast(wchar) 0x1234)); assert(!isValidCodepoint(cast(wchar) 0xD800)); assert( isValidCodepoint(cast(dchar) 0x0010FFFF)); assert(!isValidCodepoint(cast(dchar) 0x12345678));
- uint
stride
(S)(auto ref Sstr
, size_tindex
)
if (is(S : const(char[])) || isRandomAccessRange!S && is(immutable(ElementType!S) == immutable(char)));
uintstride
(S)(auto ref Sstr
)
if (is(S : const(char[])) || isInputRange!S && is(immutable(ElementType!S) == immutable(char)));
uintstride
(S)(auto ref Sstr
, size_tindex
)
if (is(S : const(wchar[])) || isRandomAccessRange!S && is(immutable(ElementType!S) == immutable(wchar)));
pure @safe uintstride
(S)(auto ref Sstr
)
if (is(S : const(wchar[])));
uintstride
(S)(auto ref Sstr
)
if (isInputRange!S && is(immutable(ElementType!S) == immutable(wchar)) && !is(S : const(wchar[])));
uintstride
(S)(auto ref Sstr
, size_tindex
= 0)
if (is(S : const(dchar[])) || isInputRange!S && is(immutable(ElementEncodingType!S) == immutable(dchar))); - Calculate the length of the UTF sequence starting at
index
instr
.Parameters:S str
input range of UTF code units. Must be random access if index
is passedsize_t index
starting index of UTF sequence (default: 0) Returns:The number of code units in the UTF sequence. For UTF-8, this is a value between 1 and 4 (as per RFC 3629, section 3). For UTF-16, it is either 1 or 2. For UTF-32, it is always 1.Throws:May throw a UTFException ifstr
[index
] is not the start of a valid UTF sequence.Note
stride
will only analyze the firststr
[index
] element. It will not fully verify the validity of the UTF sequence, nor even verify the presence of the sequence: it will not actually guarantee that index + stride(str, index) <= str.length.Examples:writeln("a".stride); // 1 writeln("λ".stride); // 2 writeln("aλ".stride); // 1 writeln("aλ".stride(1)); // 2 writeln("𐐷".stride); // 4
- uint
strideBack
(S)(auto ref Sstr
, size_tindex
)
if (is(S : const(char[])) || isRandomAccessRange!S && is(immutable(ElementType!S) == immutable(char)));
uintstrideBack
(S)(auto ref Sstr
)
if (is(S : const(char[])) || isRandomAccessRange!S && hasLength!S && is(immutable(ElementType!S) == immutable(char)));
uintstrideBack
(S)(auto ref Sstr
)
if (isBidirectionalRange!S && is(immutable(ElementType!S) == immutable(char)) && !isRandomAccessRange!S);
uintstrideBack
(S)(auto ref Sstr
, size_tindex
)
if (is(S : const(wchar[])) || isRandomAccessRange!S && is(immutable(ElementType!S) == immutable(wchar)));
uintstrideBack
(S)(auto ref Sstr
)
if (is(S : const(wchar[])) || isBidirectionalRange!S && is(immutable(ElementType!S) == immutable(wchar)));
uintstrideBack
(S)(auto ref Sstr
, size_tindex
)
if (isRandomAccessRange!S && is(immutable(ElementEncodingType!S) == immutable(dchar)));
uintstrideBack
(S)(auto ref Sstr
)
if (isBidirectionalRange!S && is(immutable(ElementEncodingType!S) == immutable(dchar))); - Calculate the length of the UTF sequence ending one code unit before
index
instr
.Parameters:S str
bidirectional range of UTF code units. Must be random access if index
is passedsize_t index
index one past end of UTF sequence (default: str
.length)Returns:The number of code units in the UTF sequence. For UTF-8, this is a value between 1 and 4 (as per RFC 3629, section 3). For UTF-16, it is either 1 or 2. For UTF-32, it is always 1.Throws:May throw a UTFException ifstr
[index
] is not one past the end of a valid UTF sequence.Note
strideBack
will only analyze the element at str[index - 1] element. It will not fully verify the validity of the UTF sequence, nor even verify the presence of the sequence: it will not actually guarantee that strideBack(str, index) <= index.Examples:writeln("a".strideBack); // 1 writeln("λ".strideBack); // 2 writeln("aλ".strideBack); // 2 writeln("aλ".strideBack(1)); // 1 writeln("𐐷".strideBack); // 4
- pure @safe size_t
toUCSindex
(C)(const(C)[]str
, size_tindex
)
if (isSomeChar!C); - Given
index
intostr
and assuming thatindex
is at the start of a UTF sequence,toUCSindex
determines the number of UCS characters up toindex
. So,index
is the index of a code unit at the beginning of a code point, and the return value is how many code points into the string that that code point is.Examples:writeln(toUCSindex(`hello world`, 7)); // 7 writeln(toUCSindex(`hello world`w, 7)); // 7 writeln(toUCSindex(`hello world`d, 7)); // 7 writeln(toUCSindex(`Ma Chérie`, 7)); // 6 writeln(toUCSindex(`Ma Chérie`w, 7)); // 7 writeln(toUCSindex(`Ma Chérie`d, 7)); // 7 writeln(toUCSindex(`さいごの果実 / ミツバチと科学者`, 9)); // 3 writeln(toUCSindex(`さいごの果実 / ミツバチと科学者`w, 9)); // 9 writeln(toUCSindex(`さいごの果実 / ミツバチと科学者`d, 9)); // 9
- pure @safe size_t
toUTFindex
(C)(const(C)[]str
, size_tn
)
if (isSomeChar!C); - Given a UCS index
n
intostr
, returns the UTF index. So,n
is how many code points into the string the code point is, and the array index of the code unit is returned.Examples:writeln(toUTFindex(`hello world`, 7)); // 7 writeln(toUTFindex(`hello world`w, 7)); // 7 writeln(toUTFindex(`hello world`d, 7)); // 7 writeln(toUTFindex(`Ma Chérie`, 6)); // 7 writeln(toUTFindex(`Ma Chérie`w, 7)); // 7 writeln(toUTFindex(`Ma Chérie`d, 7)); // 7 writeln(toUTFindex(`さいごの果実 / ミツバチと科学者`, 3)); // 9 writeln(toUTFindex(`さいごの果実 / ミツバチと科学者`w, 9)); // 9 writeln(toUTFindex(`さいごの果実 / ミツバチと科学者`d, 9)); // 9
- alias
UseReplacementDchar
= std.typecons.Flag!"useReplacementDchar".Flag; - Whether or not to replace invalid UTF with replacementDchar
- dchar
decode
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar, S)(auto ref Sstr
, ref size_tindex
)
if (!isSomeString!S && isRandomAccessRange!S && hasSlicing!S && hasLength!S && isSomeChar!(ElementType!S));
pure @trusted dchardecode
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar, S)(auto ref scope Sstr
, ref size_tindex
)
if (isSomeString!S); - Decodes and returns the code point starting at
str
[index
].index
is advanced to one past the decoded code point. If the code point is not well-formed, then a UTFException is thrown andindex
remains unchanged.decode will only work with strings and random access ranges of code units with length and slicing, whereas decodeFront will work with any input range of code units.Parameters:useReplacementDchar if invalid UTF, return replacementDchar rather than throwing S str
input string or indexable Range size_t index
starting index into s[]; incremented by number of code units processed Returns:decoded characterThrows:UTFException ifstr
[index
] is not the start of a valid UTF sequence and useReplacementDchar is No.useReplacementDcharExamples:size_t i; assert("a".decode(i) == 'a' && i == 1); i = 0; assert("å".decode(i) == 'å' && i == 2); i = 1; assert("aå".decode(i) == 'å' && i == 3); i = 0; assert("å"w.decode(i) == 'å' && i == 1); // ë as a multi-code point grapheme i = 0; assert("e\u0308".decode(i) == 'e' && i == 1); // ë as a single code point grapheme i = 0; assert("ë".decode(i) == 'ë' && i == 2); i = 0; assert("ë"w.decode(i) == 'ë' && i == 1);
- dchar
decodeFront
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar, S)(ref Sstr
, out size_tnumCodeUnits
)
if (!isSomeString!S && isInputRange!S && isSomeChar!(ElementType!S));
pure @trusted dchardecodeFront
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar, S)(ref scope Sstr
, out size_tnumCodeUnits
)
if (isSomeString!S);
dchardecodeFront
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar, S)(ref Sstr
)
if (isInputRange!S && isSomeChar!(ElementType!S)); decodeFront
is a variant of decode which specifically decodes the first code point. Unlike decode,decodeFront
accepts any input range of code units (rather than just a string or random access range). It also takes the range by ref and pops off the elements as it decodes them. IfnumCodeUnits
is passed in, it gets set to the number of code units which were in the code point which was decoded.Parameters:useReplacementDchar if invalid UTF, return replacementDchar rather than throwing S str
input string or indexable Range size_t numCodeUnits
set to number of code units processed Returns:decoded characterThrows:UTFException ifstr
.front is not the start of a valid UTF sequence. If an exception is thrown, then there is no guarantee as to the number of code units which were popped off, as it depends on the type of range being used and how many code units had to be popped off before the code point was determined to be invalid.Examples:import std.range.primitives; string str = "Hello, World!"; assert(str.decodeFront == 'H' && str == "ello, World!"); str = "å"; assert(str.decodeFront == 'å' && str.empty); str = "å"; size_t i; assert(str.decodeFront(i) == 'å' && i == 2 && str.empty);
- dchar
decodeBack
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar, S)(ref Sstr
, out size_tnumCodeUnits
)
if (isSomeString!S);
dchardecodeBack
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar, S)(ref Sstr
, out size_tnumCodeUnits
)
if (!isSomeString!S && isSomeChar!(ElementType!S) && isBidirectionalRange!S && (isRandomAccessRange!S && hasLength!S || !isRandomAccessRange!S));
dchardecodeBack
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar, S)(ref Sstr
)
if (isSomeString!S || isRandomAccessRange!S && hasLength!S && isSomeChar!(ElementType!S) || !isRandomAccessRange!S && isBidirectionalRange!S && isSomeChar!(ElementType!S)); decodeBack
is a variant of decode which specifically decodes the last code point. Unlike decode,decodeBack
accepts any bidirectional range of code units (rather than just a string or random access range). It also takes the range by ref and pops off the elements as it decodes them. IfnumCodeUnits
is passed in, it gets set to the number of code units which were in the code point which was decoded.Parameters:useReplacementDchar if invalid UTF, return replacementDchar rather than throwing S str
input string or bidirectional Range size_t numCodeUnits
gives the number of code units processed Returns:A decoded UTF character.Throws:UTFException ifstr
.back is not the end of a valid UTF sequence. If an exception is thrown, thestr
itself remains unchanged, but there is no guarantee as to the value ofnumCodeUnits
(when passed).Examples:import std.range.primitives; string str = "Hello, World!"; assert(str.decodeBack == '!' && str == "Hello, World"); str = "å"; assert(str.decodeBack == 'å' && str.empty); str = "å"; size_t i; assert(str.decodeBack(i) == 'å' && i == 2 && str.empty);
- pure @safe size_t
encode
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar)(out char[4]buf
, dcharc
);
pure @safe size_tencode
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar)(out wchar[2]buf
, dcharc
);
pure @safe size_tencode
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar)(out dchar[1]buf
, dcharc
); - Encodes
c
into the static array,buf
, and returns the actual length of the encoded character (a number between 1 and 4 for char[4] buffers and a number between 1 and 2 for wchar[2] buffers).Throws:UTFException ifc
is not a valid UTF code point.Examples:import std.exception : assertThrown; import std.typecons : Yes; char[4] buf; assert(encode(buf, '\u0000') == 1 && buf[0 .. 1] == "\u0000"); assert(encode(buf, '\u007F') == 1 && buf[0 .. 1] == "\u007F"); assert(encode(buf, '\u0080') == 2 && buf[0 .. 2] == "\u0080"); assert(encode(buf, '\uE000') == 3 && buf[0 .. 3] == "\uE000"); assert(encode(buf, 0xFFFE) == 3 && buf[0 .. 3] == "\xEF\xBF\xBE"); assertThrown!UTFException(encode(buf, cast(dchar) 0x110000)); encode!(Yes.useReplacementDchar)(buf, cast(dchar) 0x110000); auto slice = buf[]; writeln(slice.decodeFront); // replacementDchar
Examples:import std.exception : assertThrown; import std.typecons : Yes; wchar[2] buf; assert(encode(buf, '\u0000') == 1 && buf[0 .. 1] == "\u0000"); assert(encode(buf, '\uD7FF') == 1 && buf[0 .. 1] == "\uD7FF"); assert(encode(buf, '\uE000') == 1 && buf[0 .. 1] == "\uE000"); assert(encode(buf, '\U00010000') == 2 && buf[0 .. 2] == "\U00010000"); assert(encode(buf, '\U0010FFFF') == 2 && buf[0 .. 2] == "\U0010FFFF"); assertThrown!UTFException(encode(buf, cast(dchar) 0xD800)); encode!(Yes.useReplacementDchar)(buf, cast(dchar) 0x110000); auto slice = buf[]; writeln(slice.decodeFront); // replacementDchar
Examples:import std.exception : assertThrown; import std.typecons : Yes; dchar[1] buf; assert(encode(buf, '\u0000') == 1 && buf[0] == '\u0000'); assert(encode(buf, '\uD7FF') == 1 && buf[0] == '\uD7FF'); assert(encode(buf, '\uE000') == 1 && buf[0] == '\uE000'); assert(encode(buf, '\U0010FFFF') == 1 && buf[0] == '\U0010FFFF'); assertThrown!UTFException(encode(buf, cast(dchar) 0xD800)); encode!(Yes.useReplacementDchar)(buf, cast(dchar) 0x110000); writeln(buf[0]); // replacementDchar
- pure @safe void
encode
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar)(ref scope char[]str
, dcharc
);
pure @safe voidencode
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar)(ref scope wchar[]str
, dcharc
);
pure @safe voidencode
(UseReplacementDchar useReplacementDchar = No.useReplacementDchar)(ref scope dchar[]str
, dcharc
); - Encodes
c
instr
's encoding and appends it tostr
.Throws:UTFException ifc
is not a valid UTF code point.Examples:char[] s = "abcd".dup; dchar d1 = 'a'; dchar d2 = 'ø'; encode(s, d1); writeln(s.length); // 5 writeln(s); // "abcda" encode(s, d2); writeln(s.length); // 7 writeln(s); // "abcdaø"
- pure nothrow @nogc @safe ubyte
codeLength
(C)(dcharc
)
if (isSomeChar!C); - Returns the number of code units that are required to encode the code point
c
when C is the character type used to encode it.Examples:writeln(codeLength!char('a')); // 1 writeln(codeLength!wchar('a')); // 1 writeln(codeLength!dchar('a')); // 1 writeln(codeLength!char('\U0010FFFF')); // 4 writeln(codeLength!wchar('\U0010FFFF')); // 2 writeln(codeLength!dchar('\U0010FFFF')); // 1
- size_t
codeLength
(C, InputRange)(InputRangeinput
)
if (isSomeFiniteCharInputRange!InputRange); - Returns the number of code units that are required to encode str in a string whose character type is C. This is particularly useful when slicing one string with the length of another and the two string types use different character types.Parameters:
C the character type to get the encoding length for InputRange input
the input range to calculate the encoding length from Returns:The number of code units ininput
when encoded to CExamples:assert(codeLength!char("hello world") == "hello world".length); assert(codeLength!wchar("hello world") == "hello world"w.length); assert(codeLength!dchar("hello world") == "hello world"d.length); assert(codeLength!char(`プログラミング`) == `プログラミング`.length); assert(codeLength!wchar(`プログラミング`) == `プログラミング`w.length); assert(codeLength!dchar(`プログラミング`) == `プログラミング`d.length); string haystack = `Être sans la verité, ça, ce ne serait pas bien.`; wstring needle = `Être sans la verité`; assert(haystack[codeLength!char(needle) .. $] == `, ça, ce ne serait pas bien.`);
- pure @safe void
validate
(S)(in Sstr
)
if (isSomeString!S); - Checks to see if
str
is well-formed unicode or not.Throws:UTFException ifstr
is not well-formed.Examples:import std.exception : assertThrown; char[] a = [167, 133, 175]; assertThrown!UTFException(validate(a));
- string
toUTF8
(S)(Ss
)
if (isSomeFiniteCharInputRange!S); - Encodes the elements of
s
to UTF-8 and returns a newly allocated string of the elements.Parameters:S s
the string to encode Returns:A UTF-8 stringSee Also:For a lazy, non-allocating version of these functions, see byUTF.Examples:import std.algorithm.comparison : equal; // The ö is represented by two UTF-8 code units assert("Hellø"w.toUTF8.equal(['H', 'e', 'l', 'l', 0xC3, 0xB8])); // 𐐷 is four code units in UTF-8 assert("𐐷"d.toUTF8.equal([0xF0, 0x90, 0x90, 0xB7]));
- wstring
toUTF16
(S)(Ss
)
if (isSomeFiniteCharInputRange!S); - Encodes the elements of
s
to UTF-16 and returns a newly GC allocated wstring of the elements.Parameters:S s
the range to encode Returns:A UTF-16 stringSee Also:For a lazy, non-allocating version of these functions, see byUTF.Examples:import std.algorithm.comparison : equal; // these graphemes are two code units in UTF-16 and one in UTF-32 writeln("𤭢"d.length); // 1 writeln("𐐷"d.length); // 1 assert("𤭢"d.toUTF16.equal([0xD852, 0xDF62])); assert("𐐷"d.toUTF16.equal([0xD801, 0xDC37]));
- dstring
toUTF32
(S)(scope Ss
)
if (isSomeFiniteCharInputRange!S); - Encodes the elements of
s
to UTF-32 and returns a newly GC allocated dstring of the elements.Parameters:S s
the range to encode Returns:A UTF-32 stringSee Also:For a lazy, non-allocating version of these functions, see byUTF.Examples:import std.algorithm.comparison : equal; // these graphemes are two code units in UTF-16 and one in UTF-32 writeln("𤭢"w.length); // 2 writeln("𐐷"w.length); // 2 assert("𤭢"w.toUTF32.equal([0x00024B62])); assert("𐐷"w.toUTF32.equal([0x00010437]));
- template
toUTFz
(P) if (is(P : C*, C) && isSomeChar!C) - Returns a C-style zero-terminated string equivalent to str. str must not contain embedded '\0''s as any C function will treat the first '\0' that it sees as the end of the string. If str.empty is true, then a string containing only '\0' is returned.
toUTFz
accepts any type of string and is templated on the type of character pointer that you wish to convert to. It will avoid allocating a new string if it can, but there's a decent chance that it will end up having to allocate a new string - particularly when dealing with character types other than char. Warning 1: If the result oftoUTFz
equals str.ptr, then if anything alters the character one past the end of str (which is the '\0' character terminating the string), then the string won't be zero-terminated anymore. The most likely scenarios for that are if you append to str and no reallocation takes place or when str is a slice of a larger array, and you alter the character in the larger array which is one character past the end of str. Another case where it could occur would be if you had a mutable character array immediately after str in memory (for example, if they're member variables in a user-defined type with one declared right after the other) and that character array happened to start with '\0'. Such scenarios will never occur if you immediately use the zero-terminated string after callingtoUTFz
and the C function using it doesn't keep a reference to it. Also, they are unlikely to occur even if you save the zero-terminated string (the cases above would be among the few examples of where it could happen). However, if you save the zero-terminate string and want to be absolutely certain that the string stays zero-terminated, then simply append a '\0' to the string and use its ptr property rather than callingtoUTFz
. Warning 2: When passing a character pointer to a C function, and the C function keeps it around for any reason, make sure that you keep a reference to it in your D code. Otherwise, it may go away during a garbage collection cycle and cause a nasty bug when the C code tries to use it.Examples:auto p1 = toUTFz!(char*)("hello world"); auto p2 = toUTFz!(const(char)*)("hello world"); auto p3 = toUTFz!(immutable(char)*)("hello world"); auto p4 = toUTFz!(char*)("hello world"d); auto p5 = toUTFz!(const(wchar)*)("hello world"); auto p6 = toUTFz!(immutable(dchar)*)("hello world"w);
- pure @safe const(wchar)*
toUTF16z
(C)(const(C)[]str
)
if (isSomeChar!C); toUTF16z
is a convenience function for toUTFz!(const(wchar)*).Encodes string s into UTF-16 and returns the encoded string.toUTF16z
is suitable for calling the 'W' functions in the Win32 API that take an LPCWSTR argument.Examples:string str = "Hello, World!"; const(wchar)* p = str.toUTF16z; writeln(p[str.length]); // '\0'
- pure nothrow @nogc @safe size_t
count
(C)(const(C)[]str
)
if (isSomeChar!C); - Returns the total number of code points encoded in
str
.Supercedes This function supercedes toUCSindex.
Standards:Unicode 5.0, ASCII, ISO-8859-1, WINDOWS-1252Throws:UTFException ifstr
is not well-formed.Examples:writeln(count("")); // 0 writeln(count("a")); // 1 writeln(count("abc")); // 3 writeln(count("\u20AC100")); // 4
- enum dchar
replacementDchar
; - Inserted in place of invalid UTF sequences.
- auto
byCodeUnit
(R)(Rr
)
if (isConvertibleToString!R && !isStaticArray!R || isInputRange!R && isSomeChar!(ElementEncodingType!R)); - Iterate a range of char, wchar, or dchars by code unit.The purpose is to bypass the special case decoding that std.range.primitives.front does to character arrays. As a result, using ranges with
byCodeUnit
can be nothrow while std.range.primitives.front throws when it encounters invalid Unicode sequences. A code unit is a building block of the UTF encodings. Generally, an individual code unit does not represent what's perceived as a full character (a.k.a. a grapheme cluster in Unicode terminology). Many characters are encoded with multiple code units. For example, the UTF-8 code units for ø are 0xC3 0xB8. That means, an individual element ofbyCodeUnit
often does not form a character on its own. Attempting to treat it as one while iterating over the resulting range will give nonsensical results.Parameters:R r
an input range of characters (including strings) or a type that implicitly converts to a string type. Returns:Ifr
is not an auto-decodable string (i.e. a narrow string or a user-defined type that implicitly converts to a string type), thenr
is returned. Otherwise,r
is converted to its corresponding string type (if it's not already a string) and wrapped in a random-access range where the element encoding type of the string (its code unit) is the element type of the range, and that range returned. The range has slicing. Ifr
is quirky enough to be a struct or class which is an input range of characters on its own (i.e. it has the input range API as member functions), and it's implicitly convertible to a string type, thenr
is returned, and no implicit conversion takes place. Ifr
is wrapped in a new range, then that range has a source property for returning the string that's currently contained within that range.See Also:Refer to the std.uni docs for a reference on Unicode terminology. For a range that iterates by grapheme cluster (written character) see std.uni.byGrapheme.Examples:import std.range.primitives; import std.traits : isAutodecodableString; auto r = "Hello, World!".byCodeUnit(); static assert(hasLength!(typeof(r))); static assert(hasSlicing!(typeof(r))); static assert(isRandomAccessRange!(typeof(r))); static assert(is(ElementType!(typeof(r)) == immutable char)); // contrast with the range capabilities of standard strings (with or // without autodecoding enabled). auto s = "Hello, World!"; static assert(isBidirectionalRange!(typeof(r))); static if (isAutodecodableString!(typeof(s))) { // with autodecoding enabled, strings are non-random-access ranges of // dchar. static assert(is(ElementType!(typeof(s)) == dchar)); static assert(!isRandomAccessRange!(typeof(s))); static assert(!hasSlicing!(typeof(s))); static assert(!hasLength!(typeof(s))); } else { // without autodecoding, strings are normal arrays. static assert(is(ElementType!(typeof(s)) == immutable char)); static assert(isRandomAccessRange!(typeof(s))); static assert(hasSlicing!(typeof(s))); static assert(hasLength!(typeof(s))); }
Examples:byCodeUnit
does no Unicode decodingstring noel1 = "noe\u0308l"; // noël using e + combining diaeresis assert(noel1.byCodeUnit[2] != 'ë'); writeln(noel1.byCodeUnit[2]); // 'e' string noel2 = "no\u00EBl"; // noël using a precomposed ë character // Because string is UTF-8, the code unit at index 2 is just // the first of a sequence that encodes 'ë' assert(noel2.byCodeUnit[2] != 'ë');
Examples:byCodeUnit
exposes a source property when wrapping narrow strings.import std.algorithm.comparison : equal; import std.range : popFrontN; import std.traits : isAutodecodableString; { auto range = byCodeUnit("hello world"); range.popFrontN(3); assert(equal(range.save, "lo world")); static if (isAutodecodableString!string) // only enabled with autodecoding { string str = range.source; writeln(str); // "lo world" } } // source only exists if the range was wrapped { auto range = byCodeUnit("hello world"d); static assert(!__traits(compiles, range.source)); }
- alias
byChar
= byUTF!(char, Flag.yes).byUTF(R)(R r) if (isAutodecodableString!R && isInputRange!R && isSomeChar!(ElementEncodingType!R));
aliasbyWchar
= byUTF!(wchar, Flag.yes).byUTF(R)(R r) if (isAutodecodableString!R && isInputRange!R && isSomeChar!(ElementEncodingType!R));
aliasbyDchar
= byUTF!(dchar, Flag.yes).byUTF(R)(R r) if (isAutodecodableString!R && isInputRange!R && isSomeChar!(ElementEncodingType!R)); - Iterate an input range of characters by char, wchar, or dchar. These aliases simply forward to byUTF with the corresponding C argument.Parameters:
R r input range of characters, or array of characters - template
byUTF
(C, UseReplacementDchar useReplacementDchar = Yes.useReplacementDchar) if (isSomeChar!C) - Iterate an input range of characters by char type C by encoding the elements of the range.UTF sequences that cannot be converted to the specified encoding are either replaced by U+FFFD per "5.22 Best Practice for U+FFFD Substitution" of the Unicode Standard 6.2 or result in a thrown UTFException. Hence byUTF is not symmetric. This algorithm is lazy, and does not allocate memory. @nogc, pure-ity, nothrow, and @safe-ty are inferred from the r parameter.Parameters:
C char, wchar, or dchar useReplacementDchar UseReplacementDchar.yes means replace invalid UTF with replacementDchar, UseReplacementDchar.no means throw UTFException for invalid UTF Throws:UTFException if invalid UTF sequence and useReplacementDchar is set to UseReplacementDchar.noGC Does not use GC if useReplacementDchar is set to UseReplacementDchar.yes
Returns:A bidirectional range if R is a bidirectional range and not auto-decodable, as defined by std.traits.isAutodecodableString. A forward range if R is a forward range and not auto-decodable. Or, if R is a range and it is auto-decodable and is(ElementEncodingType!typeof(r) == C), then the range is passed to byCodeUnit. Otherwise, an input range of characters.Examples:import std.algorithm.comparison : equal; // hellö as a range of `char`s, which are UTF-8 assert("hell\u00F6".byUTF!char().equal(['h', 'e', 'l', 'l', 0xC3, 0xB6])); // `wchar`s are able to hold the ö in a single element (UTF-16 code unit) assert("hell\u00F6".byUTF!wchar().equal(['h', 'e', 'l', 'l', 'ö'])); // 𐐷 is four code units in UTF-8, two in UTF-16, and one in UTF-32 assert("𐐷".byUTF!char().equal([0xF0, 0x90, 0x90, 0xB7])); assert("𐐷".byUTF!wchar().equal([0xD801, 0xDC37])); assert("𐐷".byUTF!dchar().equal([0x00010437]));
Examples:import std.algorithm.comparison : equal; import std.exception : assertThrown; assert("hello\xF0betty".byChar.byUTF!(dchar, UseReplacementDchar.yes).equal("hello\uFFFDetty")); assertThrown!UTFException("hello\xF0betty".byChar.byUTF!(dchar, UseReplacementDchar.no).equal("hello betty"));
Examples:import std.range.primitives; wchar[] s = ['ă', 'î']; auto rc = s.byUTF!char; static assert(isBidirectionalRange!(typeof(rc))); writeln(rc.back); // 0xae rc.popBack; writeln(rc.back); // 0xc3 rc.popBack; writeln(rc.back); // 0x83 rc.popBack; writeln(rc.back); // 0xc4 auto rw = s.byUTF!wchar; static assert(isBidirectionalRange!(typeof(rw))); writeln(rw.back); // 'î' rw.popBack; writeln(rw.back); // 'ă' auto rd = s.byUTF!dchar; static assert(isBidirectionalRange!(typeof(rd))); writeln(rd.back); // 'î' rd.popBack; writeln(rd.back); // 'ă'