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The Ice::Identity Type

Each Ice object has an object identity defined as follows:

Slice
module Ice 
{
    struct Identity 
    {
        string name;
        string category;
    }
}

As you can see, an object identity consists of a pair of strings, a name and a category. The complete object identity is the combination of name and category, that is, for two identities to be equal, both name and category must be the same. The category member is usually the empty string, unless you are using servant locatorsdefault servants or callbacks with Glacier2.

If name is an empty string, category must be the empty string as well. (An identity with an empty name and a non-empty category is illegal.) If a proxy contains an identity in which name is empty, Ice interprets that proxy as a null proxy.

Object identities can be represented as strings; the category part appears first and is followed by the name; the two components are separated by a / character, for example:

Factory/File

In this example, Factory is the category, and File is the name. If the name or category member themselves contain a / character, the stringified representation escapes the / character with a \, for example:

Factories\/Factory/Node\/File

In this example, the category is Factories/Factory and the name is Node/File.

Syntax for Stringified Identities

You rarely need to write identities as strings because, typically, your code will be using the identity helper functions identityToString and stringToIdentity, or simply deal with proxies instead of identities. However, on occasion, you will need to use stringified identities in configuration files. If the identities happen to contain meta-characters (such as a slash or backslash), or characters outside the printable ASCII range, these characters may need to be escaped in the stringified representation.

Here are rules that the Ice run time applies when parsing a stringified identity:

  1. The parser scans the stringified identity for an unescaped slash character (/). If such a slash character can be found, the substrings to the left and right of the slash are parsed as the category and name members of the identity, respectively; if no such slash character can be found, the entire string is parsed as the name member of the identity, and the category member is the empty string.
  2. Each of the category (if present) and name substrings are parsed like Slice String Literals, except that an escaped slash character (\/) is converted into a simple slash (/).


Identity Helper Functions

To make conversion of identities to and from strings easier, Ice provides functions to convert an Identity to and from a native string, using the string format described in the preceding paragraph. These helper functions are called identityToString (to stringify an identity into a string) and stringToIdentity (to parse a stringified identity and create the corresponding identity).

ToStringMode Enumeration

When stringifying an identity with identityToString, you can choose the algorithm, or mode, used in this "to string" implementation. These modes correspond to the enumerators of the Ice::ToStringMode enumeration:

Slice
module Ice 
{
    local enum ToStringMode { Unicode, ASCII, Compat }
}

These modes are used only when you create a stringified identity or proxy. The resulting strings are all in the same format.

The selected mode affects only the handling of non-ASCII characters and non-printable ASCII characters, such as the ASCII character with ordinal value 127 (delete).

The table below shows how these characters are encoded depending of the selected ToStringMode:

ToStringModeNon-Printable ASCII Character
other than \a, \b, \f, \n, \r, \t and \v 
Non-ASCII CharacterNotes
Unicode Replaced by its short universal character name.
For example \u007F (delete).
Not escaped - kept as is. The resulting string contains printable ASCII characters
plus possibly non-ASCII characters.
ASCII Replaced by its short universal character name, just like Unicode.

If the character's code point is in the BMP, it's escaped with its short
universal character name (\unnnn); if the character is outside the
BMP, it's escaped with its long universal character name (\Unnnnnnnn).

For example \u20ac (euro sign) and \U0001F34C (banana symbol).

The resulting string contains only printable ASCII characters.
Compat

Replaced by an octal escape sequence with 3 digits, \ooo.

For example \177 (delete).

Replaced by a sequence of 3-digit octal escape sequences, that
represent the UTF-8 encoding of this character.

For example \342\202\254 (euro sign) and 
\360\237\215\214 (banana symbol) 

The resulting string contains only printable ASCII characters.

The default mode is Unicode.

The Compat mode is provided for backwards-compatibility with Ice 3.6 and earlier. These older versions do not recognize universal character names and reject non-printable ASCII characters in stringified identities.

identityToString and stringToIdentity

These helper functions are defined as follows:

namespace Ice 
{
    std::string identityToString(const Identity&, ToStringMode = ToStringMode::Unicode);
    Identity stringToIdentity(const std::string&);
}
namespace Ice 
{
    std::string identityToString(const Identity&, ToStringMode = Unicode);
    Identity stringToIdentity(const std::string&);
}
namespace Ice 
{
    public sealed class Util
    {
        public static string identityToString(Identity id, ToStringMode toStringMode = ToStringMode.Unicode);
        public static Identity stringToIdentity(string s);
    }
}
package com.zeroc.Ice;

public final class Util
{
    public static String identityToString(Identity id, ToStringMode toStringMode);
    public static String identityToString(Identity id); // calls identityToString with ToStringMode.Unicode
    public static Identity stringToIdentity(String s);
}
package Ice;

public final class Util 
{
    public static String identityToString(Identity id, ToStringMode toStringMode);
    public static String identityToString(Identity id); // calls identityToString with ToStringMode.Unicode
    public static Identity stringToIdentity(String s);
}
Ice.stringToIdentity = function(s)
Ice.identityToString = function(ident, toStringMode = Ice.ToStringMode.Unicode)
@interface ICEUtil : NSObject
+(NSMutableString*) identityToString:(ICEIdentity*)ident toStringMode:(ICEToStringMode)toStringMode;
+(NSMutableString*) identityToString:(ICEIdentity*)ident; // calls identityToString with ICEUnicode
+(NSMutableString*) identityToString:(ICEIdentity*)ident;
@end
namespace Ice
{
    function identityToString($ident, $toStringMode=null) // null corresponds to the Unicode mode
    function stringToIdentity($str)
}
# in Ice module
 
def identityToString(ident, toStringMode=None) # None corresponds to the Unicode mode
def stringToIdentity(str)
module Ice
    def Ice.identityToString(str, toStringMode=nil) # nil corresponds to the Unicode mode
    def Ice.stringToIdentity(str)


See Also

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