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LazUtils: better implementation of Utf8StringOfChar. The previously uses conversion to Utf16

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only worked if the codepoint was UCS2.

git-svn-id: trunk@42855 -
This commit is contained in:
bart 2013-09-18 10:26:09 +00:00
parent f4e5628407
commit 7e9930404c
1 changed files with 38 additions and 12 deletions
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50
components/lazutils/lazutf8.pas
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@ -2495,20 +2495,46 @@ end;
function Utf8StringOfChar(AUtf8Char: Utf8String; N: Integer): Utf8String;
var
US: UniCodeString;
WC: System.WideChar;
UCharLen, i: Integer;
C1, C2, C3: Char;
PC: PChar;
begin
Result := '';
if Utf8Length(AUtf8Char) <> 1 then Exit;
if Length(AUtf8Char) = 1 then
Result := StringOfChar(AUtf8Char[1], N)
else
begin
//for i := 1 to N do Result := Result + AUtf8Char; //ultimate lame version
WC := Utf8ToUtf16(AUtf8Char)[1]; //we know Utf8Length(AUtf8Char) = 1
SetLength(US, N);
System.FillWord(US[1], N, Word(WC));
Result := Utf16ToUtf8(US);
if (N <= 0) or (Utf8Length(AUtf8Char) <> 1) then Exit;
UCharLen := Length(AUtf8Char);
Case UCharLen of
1: Result := StringOfChar(AUtf8Char[1], N);
2:
begin
SetLength(Result, 2 * N);
System.FillWord(Result[1], N, PWord(Pointer(AUtf8Char))^); ;
end;
3:
begin
SetLength(Result, 3 * N);
C1 := AUtf8Char[1];
C2 := AUtf8Char[2];
C3 := AUtf8Char[3];
PC := PChar(Result);
for i:=1 to N do
begin
PC^ := C1; inc(PC);
PC^ := C2; inc(PC);
PC^ := C3; inc(PC);
end;
end;
4:
begin
SetLength(Result, 4 * N);
System.FillDWord(Result[1], N, PDWord(Pointer(AUtf8Char))^);
end;
else
begin
//In November 2003 UTF-8 was restricted by RFC 3629 to four bytes to match
//the constraints of the UTF-16 character encoding.
//http://en.wikipedia.org/wiki/UTF-8
Result := StringOfChar('?', N);
end;
end;
end;