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Docs: LazUtils/lazutf8. Updates topic content in UTF8Length, UTF8LengthFast.

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(cherry picked from commit c87b73cadc)
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dsiders 2021-12-29 17:41:25 +00:00 committed by Maxim Ganetsky
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commit 19cd1d185f
1 changed files with 24 additions and 5 deletions
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29
docs/xml/lazutils/lazutf8.xml
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@ -423,10 +423,16 @@ end;
<var>UTF8Length</var> is a function used to get the character length for the specified UTF-8-encoded string. The return value contains the number of UTF-8-encoded characters (or codepoints) found in the byte values for the string.
</p>
<p>
An overloaded variant of the function is provided which uses the <var>PChar</var> type to access the byte values in the string.
An overloaded variant of the function is provided which uses the <var>PChar</var> type to specify the byte values in the string. Internally, the String variant casts its value a PChar type and calls the overloaded variant.
</p>
<p>
UTF8Length iterates over the bytes in the UTF-8-encoded string data, and calls UTF8CodepointSize to determine the number of bytes needed for each codepoint. Use UTF8LengthFast for a version of the routine optimized for speed.
</p>
</descr>
<seealso/>
<seealso>
<link id="UTF8CodepointSize"/>
<link id="UTF8LengthFast"/>
</seealso>
</element>
<element name="UTF8Length.Result">
<short>Number of codepoints in the byte values for the string.</short>
@ -447,10 +453,23 @@ end;
</short>
<descr>
<p>
<var>UTF8LengthFast</var> gets the length of a UTF-8-encoded string in codepoints (or characters). UTF8LengthFast is the fast version of <var>UTF8Length</var>. It does not call the UTF8CodepointSize function. The UTF-8-encoded data is assumed to be valid. The native data size for the CPU is used to process blocks of UTF-8-encoded data. For a 64-bit CPU, this means that 8 bytes are read and processed at once.
<var>UTF8LengthFast</var> is an overloaded <var>PtrInt</var> function used to get the length of a UTF-8-encoded string in codepoints. UTF8LengthFast is the fast version of <var>UTF8Length</var>. It does not call the UTF8CodepointSize function. The UTF-8-encoded string data is assumed to be valid. The native data size for the CPU is used to process blocks of UTF-8-encoded data. For a 64-bit CPU, this means that 8 bytes are read and processed at once.
</p>
<p>
The overloaded variants allow the UTF-8-encoded data to be specified as either a String type, or a null-terminated PChar type. Internally, the String-based variant casts its data to a PChar type and calls the overloaded variant.
</p>
<p>
UTF8LengthFast is a Free Pascal implementation of the C routine provided by Colin Percival:
</p>
<p>
<url href="http://www.daemonology.net/blog/2008-06-05-faster-utf8-strlen.html">
Even faster UTF-8 character counting
</url>
</p>
</descr>
<seealso/>
<seealso>
<link id="UTF8Length"/>
</seealso>
</element>
<element name="UTF8LengthFast.Result">
<short>Number of codepoints in the string.</short>
@ -2388,7 +2407,7 @@ end;
<var>stdcp</var> contains the <var>TStandardCodePageEnum</var> enumeration value that identifies the default code page for the platform.
</p>
<p>
The return value is set from the <var>CP_UTF8</var> constant.
The return value is set to the <var>CP_UTF8</var> constant.
</p>
</descr>
<seealso/>