[fpc-devel] Performance of string handling in trunk
pascaldragon at googlemail.com
Wed Jun 26 14:02:24 CEST 2013
Am 26.06.2013 13:59, schrieb Michael Schnell:
> I think the implementation would be quite easy, straight forward, fast
> and compatible.
> - The compiler knows the static encoding type of each string variable.
> - The dynamic encoding type of a String is preset to the static
> encoding type when the string is allocated
> - only RawByteStrings (EncodingType $FFFF) are allowed to change
> their dynamic encoding type, with other Strings this will lead to
> unpredictable results
> When Strings are assigned:
> - If the static encoding type of source and target is identical (be
> it normal or RAW) (already checked by the compiler) -> the same
> happens as with the pre-Unicode compiler (setting the pointer to the
> StringRecord and managing the RefCount)
> - If the target is statically defined as RawByteString (already
> checked by the compiler) -> the same happens
> - If the source is statically defined as RawByteString (already
> checked by the compiler), code is implemented that checks if the
> dynamic encoding of the source is identical to the (known to the
> compiler) static encoding type of the target -> the same happens
> otherwise the conversion library is called. Same checks the _dynamic_
> encoding type of source and target (thus it only needs to be provided
> with the Strings themselves and no additional information generated by
> the compiler) and does the conversion appropriately.
> When doing operation on two Strings (such as "+" and compare), one of
> the operators is (virtually) copied to a String with the same encoding
> type as the other.
> - if one operand is a RawByteString use the (static or dynamic)
> encoding of the other.
> - if both are RawByteStrings use the dynamic encoding use the dynamic
> encoding of one of them (supposedly this is no alternate case to before)
> If the conversion library sees a dynamic encoding type of $FFFF for
> either source or target it will fail and issue an exception.
See my previously sent answer...
More information about the fpc-devel