Utf8TryFindCodepointStart function

In unit LazUTF8

Tries to find the start of a valid UTF-8 codepoint in a string.

Declaration

pascal

function Utf8TryFindCodepointStart(AString: PChar; var CurPos: PChar; 
 out CodepointLen: Integer): Boolean

Arguments

`AString`	Pointer to the string to examine in the function.
`CurPos`	Pointer to the first position in the string examined in the function.
`CodepointLen`	Number of bytes in the codepoint, or 0 when invalid.

Function result

True when the bytes at the specified position are a valid UTF-8 codepoint.

Description

Utf8TryFindCodepointStart is a Boolean function which tries to find the start of a valid UTF-8 codepoint at the specified position in AString.

The return value contains True if the bytes at the specified position are a valid UTF-8 codepoint (1 - 4 bytes). When the return value is True, the value in CurPos is updated to contain the position in AString where the UTF-8 codepoint begins. Otherwise, the value in CurPos is unchanged. Please note, when CurPos points beyond the end of AString you will get a crash!

UTF8CodepointStrictSize will NOT "look" beyond the terminating #0 in a PChar, so this is safe with AnsiString values.

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.