IOEncoding usage in V4REV

Assume there is some “not-latin” text  (it could be russian or umlauts or something similar). And we have to store it to the Valentina database and then read it back.

UTF16 Encoding

Revolution has a property to get an UTF16-encoded content – unicodeText. So we can easily get it doing something like this one:

put unicodeText of field “ValueField” into uniText

Seems to be ready to pass this value to some vField, but Revolution externals (including V4REV) receive the data as a char* in C language. But UTF16 have ZERO bytes, so REV external cannot operate on it so far. It is obviously we should pass the data encoded with some single-byte code-page to avoid it. In most cases it could be UTF8.

UTF8 Encoding

So we do following –

  • Set an appropriate IOEncoding property for the database first (we promise pass  any strings to this db as UTF8 and vice versa – any string received from this database will be in UTF8):

get VDatabase_IOEncoding( mDBRef, “UTF-8” )

  • Prepare UTF16 value:

put unicodeText of field “ValueField” into uniText
  • Decode it to UTF8:
put uniDecode( uniText, “UTF8”) into univalue
  • Write it to the database:
put VTable_Field( inTblRef, 1 ) into fldRef        // or Vcursor_Field(…)
get VField_Value( fldRef,  univalue )
get VTable_AddRecord( inTblRef)                       // or VCursor_AddRecord(…)
  • Reading data back:

get VTable_FirstRecord(inTblRef)
put VTable_Field( inTblRef, 1 ) into fldRef
put uniEncode( VField_Value( fldRef ), “UTF8”) into fldValue

Native Encoding (Recomended)

Also, you can omit UTF16-UTF8 transformation using some “natural” code-page. But you should note it is OS dependent.

// If MacOS Then
 get VDatabase_IOEncoding( mDBRef, “Macintosh” )
// else
 get VDatabase_IOEncoding( mDBRef, “Latin1” )

…

// WRITING data into db:

put text of field “ValueField” into myValue

put VTable_Field( inTblRef, 1 ) into fldRef
get VField_Value( fldRef,  myvalue )
get VTable_AddRecord( inTblRef)

// READING data back from db:

get VTable_FirstRecord(inTblRef)
put VTable_Field( inTblRef, 1 ) into fldRef
put  VField_Value( fldRef ) into fldValue

NOTE: you must set VDatabase_IOEncoding() after each VDatabase_Open() or VDatabase_Create() or after connect to a Valentina Server. This is your “contract” with database about encoding of IO strings.