previous_codepoint_offset()

MAYAFLUX_API size_t MayaFlux::Portal::Text::previous_codepoint_offset	(	std::string_view	text,
		size_t	byte_offset
	)

Byte offset of the codepoint boundary before byte_offset.

Walks backward over continuation-pattern bytes to the start of the preceding codepoint. Returns 0 if byte_offset is already 0.

Parameters

text	UTF-8 encoded string.
byte_offset	Current byte offset, must be a codepoint boundary.

Returns

Byte offset of the previous codepoint boundary.

Definition at line 198 of file TypeSetter.cpp.

{
    if (byte_offset == 0) {
        return 0;
    }
 
    size_t pos = byte_offset - 1;
    constexpr size_t max_continuation_bytes = 3;
    size_t steps = 0;
 
    while (pos > 0 && steps < max_continuation_bytes
        && (static_cast<uint8_t>(text[pos]) & 0xC0) == 0x80) {
        --pos;
        ++steps;
    }
 
    return pos;
}

Referenced by erase(), index_at(), and move().

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