SetStringFix - method of the PmBuffer object

Writing the character string with fixed length.
Empty SetStringFix(Long nOffset, String sValue, Long nLength, [Long nPad], [Long 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 being written.
nLength(Long) Fixed size of reserved space in the data block for the string in bytes. The string is not terminated by the NULL character, but if its current length is smaller than the defined fixed length then it is usually filled by defined character nPad (usually NULL or space) up to the defined fixed length.
nPad[optional] (Long) The value of the character that will be used for folling up the string from right to the defined fixed length. The value 0 (default) is the NULL character. The value 32 is the space 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 OS 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).
See also:
JavaScriptSelect and copy to clipboard

var oBuf = Pm.CreatePmBuffer();
var s1 = "Help me!";
oBuf.SetStringFix(-2, s1, 8, 0, 1);

oBuf.AutoOffset = 0;
var nSize = oBuf.GetSize();

var val = oBuf.GetStringFix(-4, nSize, 1);  //val = "Help me!"

Pm9.00.04: Created
PROMOTIC 9.0.13 SCADA system documentation - MICROSYS, spol. s r.o.

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