SetStringVar - method of object PmBuffer

Writing the character string with variable length (terminated by the NULL character).
Empty SetStringVar(Long nOffset, String sValue, [Long nAttr], [Long nEncoding])
PmBuffer.SetStringVar(nOffset, sValue, nAttr, nEncoding)
nOffset(Long) Defines the position of written value in the data block.

The whole written item muyst be inside the data block, or the whole item is added to the end of the data block. The item is written either whole or not read at all.

>= 0 - Index (in bytes, zero-based index) in data block.
-2 - The whole item is added to the end of the data block. The size of the data bloc is then increased by the written item.
-4 - The internal automatic position is used (see AutoOffset). It points behind the last read or written value and increases continually.

If the items are read/written one by one then it is not necessary to define the position, but it is better to use this automated positioning.

sValue(String) String that is being written.
nAttr[optional] (Long)
0 (default) - The text string is saved with the NULL character at the end.
1 - The text string is saved without the NULL ending character.
nEncoding[optional] (Long) Encoding of character string in the data block.
0 (default) - (ANSI) Each character is stored in a single byte. The values from 0 to 127 represent an ASCII character table that is not changing in meaning. The values from 128 to 255 have different meaning in various localizations (code pages, e.g. Windows CP-1250).
1 - (UTF-8) Each character is stored in 1, 2 or 4 bytes, it means has variable length. The advantage is that the latin characters (ASCII) are stored in a single byte. Only special characters and characters with diacritics are stored in multiple bytes. This storage is therefore very efficient.

This encoding is commonly used for data exchange, data persistence and on the web.

2 - (UTF-16) Each character is stored in 2 bytes (or exceptionally in 4 bytes), i.e. it has a fixed length. The advantage is that most characters are stored in 2 bytes so these strings are easy to work with (because of the fixed length).

This encoding is used internally in Windows, but also in JavaScript or .NET, because the mannipulation with these fixed strings is easier.

This method is also functional in Web panels. For nEcoding=0 the characters with higher value than 127 cannot be encoded and for InternetExplorer, the UTF-8 encoding does not work (nEcoding=1).

Pm9.00.04: Created
PROMOTIC 9.0.9 SCADA system documentation - MICROSYS, spol. s r.o.

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