$ZCONVERT

$ZCONVERT Returns a Converted String

$ZCONVERT(string, mode) returns string with the characters converted as specified by mode. The conversions are of two types:

• Case conversion

• Encoding translation

Case conversion changes the case of each letter character in the string. You can change all letter characters in a string to their lowercase, uppercase, or titlecase form. You can change the initial letter of words or sentences in a string to their uppercase form. Characters that are already in the specified case, and characters with no case (usually any non-alphabetic character) in the string are passed through unchanged. To output a literal quote character (“) within a string, input two quote characters (““). For further case conversion options, including non-ASCII and customized case conversion, refer to the section on “System Classes for National Language Support” in Caché Specialized System Tools and Utilities.

Encoding translation translates string between the internal encoding style used on your system and another encoding style. You can perform input translation; that is, translate string from an external encoding style to the encoding style of your system. You can also perform output translation; that is, translate string from the encoding style of your system to an external encoding style. For further I/O translation options, including non-ASCII and customized translation, refer to the section on “System Classes for National Language Support” in Caché Specialized System Tools and Utilities.

The values you can use for mode are as follows:

If mode is a null string or any value other than the valid characters, you receive a <FUNCTION> error.

Letter Case Translation

You can convert letters in strings to all uppercase letters or all lowercase letters. Conversion works on Unicode letters as well as ASCII letters. The following example converts the Greek alphabet from lowercase to uppercase:

   FOR i=945:1:969 {WRITE $ZCONVERT($CHAR(i),"U")}

However, a small number of letters only have a lowercase letter form. For example, the German eszett ($CHAR(223)) is only defined as a lowercase letter. Attempting to convert it to an uppercase letter results in the same lowercase letter:

  IF $ZCONVERT($CHAR(223),"U")=$ZCONVERT($CHAR(223),"L") {
      WRITE "uppercase and lowercase letter are the same" }
  ELSE {WRITE "uppercase and lowercase are different" }

For this reason, when converting alphanumeric strings to a single letter case it is always preferable to convert to lowercase.

You can perform similar letter case translations using the $TRANSLATE function, as shown in the following example:

  WRITE $TRANSLATE(text,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")

Word and Sentence Translation

“W” and “S” modes determine whether a non-blank character is the first character of a word or the first character of a sentence, and if that character is a letter, translate it to uppercase. All other letters are translated to lowercase. Case translation works on letters in any alphabet, as shown in the following example which converts Greek letters ($CHAR(945) is lowercase alpha; $CHAR(913) is uppercase alpha):

   SET greek=$CHAR(945,946,947,913,914,915)
   WRITE $ZCONVERT(greek,"W")

However the rules determining what constitutes a word or sentence are locale dependent. For example, the following example uses the Spanish inverted exclamation point $CHAR(161). The default (English) locale does not recognize this character as beginning a sentence or word. In this example, all letters in spanish are translated to lowercase:

   SET spanish=$CHAR(161)_"ola MuNdO! "_$CHAR(161)_"olA!"
   SET english="hElLo wOrLd! heLLo!"
   WRITE !,$ZCONVERT(english,"S")
   WRITE !,$ZCONVERT(spanish,"S")

Titlecase Translation

Titlecase (“T”) mode converts every letter in the string to its titlecase form. Titlecase does not selectively uppercase letters based on their position in a word or string. Titlecase is the case that a letter is represented in when it is the first character of a word in a title. For standard Latin letters, the titlecase form is the same as the uppercase form.

Some languages (for example, Croatian) represent particular letters by two letter glyphs. For example, “lj” is a single letter in the Croatian alphabet. This letter has three forms: lowercase “lj”, uppercase “LJ”, and titlecase “Lj”. $ZCONVERT titlecase translation is used for this type of letter conversion.

Three-Parameter Form: Encoding Translation

$ZCONVERT(string, mode, trantable) performs either an input encoding translation or an output encoding translation on string. In the three-argument form, the mode values you can use are either "I" or "O". You must define the mode value. For “I” translations, the string may be a hexadecimal string, such as %4B (the letter “K”); hexadecimal strings are not case-sensitive.

You can use ZZDUMP to display the hexadecimal encoding for a string of characters. You can use $CHAR to specify a character (or string of characters) by its decimal (base 10) encoding; you can use $ZHEX to convert a hexadecimal number to a decimal number, or a decimal number to a hexadecimal number. If the translated value is a non-printing character, Caché displays it as a null string. If the target device cannot represent a translated character, Caché substitutes a question mark (?) character for the non-displayable character.

The trantable value can be a numeric character or a string that specifies the translation table or translation handle to use. The trantable value can be:

• “RAW” which performs no translation for 8-bit characters or 16-bit Latin-1 characters (Unicode characters in which the high-order byte has the value 00). RAW translation should not be used for InterSystems IRIS systems using non-Latin-1 locales, such as rusw.

• “SAME” which translates 8-bit characters to the corresponding Unicode characters.

• “HTML” which adds (output mode) or removes (input mode) HTML escape characters to a string.

• “JS” (or “JSML”) which uses a supplied JavaScript translation table to escape characters in the string for use within JavaScript. For output translations see the table below. For comparison of JS and JSML, see JS and JSML, JSON and JSONML Conversions. For input translations, “\0”, “\000”, “\x00”, and “\u0000” are all valid escape sequences for NULL.

• “JSON” (or “JSONML”) which uses a supplied translation table to convert to JSON format. For output translations see the table below. For comparison of JSON and JSONML, see JS and JSML, JSON and JSONML Conversions. For input translations, “\0”, “\000”, “\x00”, and “\u0000” are all valid escape sequences for NULL.

• “URL” which adds (output mode) or removes (input mode) URL parameter escape characters to a string. URL encodes the characters "#%&+,:;<=>?@[]^`{|}~ as follows: %20%22%23%25%26%2B%2C%3A%3B%3C%3D%3E%3F%40%5B%5D%5E%60%7B%7C%7D%7E. The space character is encoded as %20. The double quote character (which must be escaped by doubling when included in a quoted string such as "My ""perfect"" code") is encoded as %22. Refer to the table below. Characters higher than $CHAR(255) are represented in Unicode hexadecimal notation: $CHAR(256) = %u0100.

• “UTF8” (UTF-8 encoding) which converts (output mode) 16-bit Unicode characters to a series of 8-bit characters. An ASCII 16–bit Unicode character translates to a single 8–bit character; for example, hex 0041 (the letter “A”) translates to the 8-bit character hex 41. A non-ASCII Unicode character is converted to two or three 8–bit characters. Unicode hex 0080 through 07FF convert to two 8–bit characters; these include the Latin-1 Supplement and Latin Extended characters and the Greek, Cyrillic, Hebrew, and Arabic alphabets. Unicode hex 0800 through FFFF convert to three 8–bit characters; these comprise the rest of the Unicode Basic Multilingual Plane. Thus, the ASCII characters $CHAR(0) through $CHAR(127) are the same in RAW and UTF8 mode; characters $CHAR(128) and above are converted. Input mode reverse this conversion. Refer to Unicode in Using ObjectScript for further details.

• “XML” which adds (output mode) or removes (input mode) XML escape characters to a string.

The following is a table of Output mode escape characters:

URL Conversions

A URL can only contain certain 8-bit ASCII characters. All other characters must be represented by an escape sequence beginning with %. If you wish to convert a string containing Unicode characters to a URL, you must first convert your local representation to an 8-bit intermediate representation, using UTF8 encoding. You then convert the UTF8 results to URL encoding. To convert a URL back to its original Unicode string, you perform the reverse operation. This is shown in the following example:

  IF $SYSTEM.Version.IsUnicode() {
  SET ustring="US$ to "_$CHAR(8364)_" échange"
  WRITE "initial string is: ",ustring,!
ConvertUnicodeToURL
  SET utfo = $ZCONVERT(ustring,"O","UTF8")
  SET urlo = $ZCONVERT(utfo,"O","URL")
  WRITE "Unicode to URL conversion: ",urlo,!
ConvertURLtoUnicode
  SET urli = $ZCONVERT(urlo,"I","URL")
  SET utfi = $ZCONVERT(urli,"I","UTF8")
  WRITE "URL to Unicode conversion: ",utfi
   }
   ELSE {WRITE "This example requires a Unicode installation of Caché"}

JS and JSML, JSON and JSONML Conversions

The JS and JSON translations use UTF-8 encoding for Unicode characters. The JSML and JSONML translations render Unicode characters without encoding. For ASCII characters ($CHAR(0) through $CHAR(127)), JS and JSML encodings are identical. For ASCII characters ($CHAR(0) through $CHAR(127)), JSON and JSONML encodings are identical.

The following example compares the translation of JS and JSML characters:

  FOR i=1:1:256 {SET x=$ZCVT($C(i),"O","JS") SET y=$ZCVT($C(i),"O","JSML") 
               IF x=y {WRITE "."} 
               ELSE {WRITE !!,$ZHEX(i),!,"JS: " ZZDUMP x WRITE !,"JSML: " ZZDUMP y }
              }

Four-Parameter Form: Input/Output String

The handle parameter is a local variable that $ZCONVERT reads at the beginning of execution and writes when it completes execution. It is used to hold information between consecutive invocations of the $ZCONVERT function. It can be used for two purposes: concatenating a string to the beginning of string, and converting extremely long strings.

To concatenate a string to the beginning of string, set handle before invoking $ZCONVERT:

   SET handle="the "
   WRITE $ZCVT("quick brown fox","O","URL",handle),!
   /*  the%20quick%20brown%20fox  */
   WRITE $ZCVT("quick brown fox","O","URL",handle),!
   /*  quick%20brown%20fox  */

Note that $ZCONVERT resets handle when it completes execution. In the previous example, it resets handle to the empty string.

This handle parameter may be used for input conversions. Specifying a handle is useful when dealing with multibyte character sequences when working with partial sets of characters, such as a stream read. In these cases, $ZCONVERT uses the handle parameter to hold a partial character sequence that may be the leading bytes of a multibyte sequence. If there are input characters left in the buffer at the end of a $ZCONVERT which do not make a complete translation unit, these leftover characters are returned in the handle. At the beginning of next $ZCONVERT, if the handle contains data, these leftover characters are prepended to the normal input data. This is particularly valuable for use in UTF8 conversions, as shown in the following example:

  SET handle=""
  WHILE 'stream.AtEnd() {
     WRITE $ZCONVERT(stream.Read(20000),"I","UTF8",handle)
  } 

To convert an extremely long string, it may be necessary to perform more than one string conversions by invoking $ZCONVERT multiple times. $ZCONVERT provides the optional handle parameter to hold the remaining unconverted portion of string. If you specify a handle parameter, it is updated by each invocation of $ZCONVERT. When the string conversion completes, $ZCONVERT sets handle to the empty string.

   SET handle=""
   SET out = $ZCVT(hugestring,"O","HTML",handle)
   IF handle '= "" {
     SET out2 = $ZCVT(handle,"O","HTML",handle)
     WRITE "Converted string is: ",out,out2  }
   ELSE {
     WRITE "Converted string is: ",out }