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LazUtf8: Refactor UTF8FindNearestCharStart. Resolves Issue #0029851.

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git-svn-id: trunk@51973 -
This commit is contained in:
bart 2016-03-17 10:42:52 +00:00
parent 34be9ae2d0
commit b192fb9760
1 changed files with 12 additions and 35 deletions
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47
components/lazutils/lazutf8.pas
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@ -643,45 +643,22 @@ begin
end;
{ Find the start of the UTF8 character which contains BytePos,
if BytePos is not part of a valid Utf8Codepoint the function returns BytePos
Len is length in byte, BytePos starts at 0 }
function UTF8FindNearestCharStart(UTF8Str: PChar; Len: SizeInt; BytePos: SizeInt
): SizeInt;
function UTF8FindNearestCharStart(UTF8Str: PChar; Len: SizeInt; BytePos: SizeInt): SizeInt;
var
CurPos: PChar;
CharLen: Integer;
begin
Result:=0;
if (UTF8Str<>nil) and (Len>0) and (BytePos>=0) then begin
Result:=BytePos;
if Result>Len then Result:=Len-1;
if (Result>0) and (ord(UTF8Str[Result]) and %11000000=%10000000) then begin
dec(Result);
if (Result>0) and (ord(UTF8Str[Result]) and %11000000=%10000000) then begin
dec(Result);
if (Result>0) and (ord(UTF8Str[Result]) and %11000000=%10000000) then begin
dec(Result);
// should be four byte character
if (ord(UTF8Str[Result]) and %11111000<>%11110000) then begin
// broken UTF8 character
inc(Result,3);
end else begin
// is four byte character
end;
end else if (ord(UTF8Str[Result]) and %11110000<>%11100000) then begin
// broken UTF8 character, should be three byte
inc(Result,2);
end else
begin
// is three byte character
end;
end else if (ord(UTF8Str[Result]) and %11100000<>%11000000) then begin
// broken UTF8 character, should be two byte
inc(Result);
end else
begin
// is two byte character
end;
end;
end;
if (BytePos > Len-1) then BytePos := Len - 1;
CurPos := Utf8Str + BytePos;
//No need to check the result value, since when it retuns False CurPos will be reset
//to it's original value, and that's what we want to return in that case
Utf8TryFindCodepointStart(Utf8Str, CurPos, CharLen);
Result := CurPos - Utf8Str;
end;
{ Len is the length in bytes of UTF8Str
CharIndex is the position of the desired char (starting at 0), in chars
}