6.6 Mapping for Simple Built-In Types

The Slice built-in types are mapped to C++ types as shown in Table 6.1.

Table 6.1. Mapping of Slice built-in types to C++.

Slice	C++
bool	bool
byte	Ice::Byte
short	Ice::Short
int	Ice::Int
long	Ice::Long
float	Ice::Float
double	Ice::Double
string	std::string

Slice bool and string map to C++ bool and std::string. The remaining built-in Slice types map to C++ type definitions instead of C++ native types. This allows the Ice run time to provide a definition as appropriate for each target archi­tecture. (For example, Ice::Int might be defined as long on one architecture and as int on another.)

Note that Ice::Byte is a typedef for unsigned char. This guarantees that byte values are always in the range 0..255.

All the basic types are guaranteed to be distinct C++ types, that is, you can safely overload functions that differ in only the types in Table 6.1.

6.6.1 Alternate String Mapping

You can use a metadata directive, ["cpp:type:wstring"], to map strings to C++ std::wstring. This is useful for applications that use languages with alpha­bets that cannot be represented in 8‑bit characters. The metadata directive can be applied to any Slice construct. For containers (such as modules, interfaces, or structures), the metadata directive applies to all strings within the container. A corresponding metadata directive, ["cpp:type:string"] can be used to selec­tively override the mapping defined by the enclosing container. For example:

["cpp:type:wstring"]
struct S1 {
    string x;             // Maps to std::wstring
    ["cpp:type:wstring"]
    string y;             // Maps to std::wstring
    ["cpp:type:string"]
    string z;             // Maps to std::string
};

struct S2 {
    string x;             // Maps to std::string
    ["cpp:type:string"]
    string y;             // Maps to std::string
    ["cpp:type:wstring"]
    string z;             // Maps to std::wstring
};

With these metadata directives, the strings are mapped as indicated by the comments. By default, narrow strings are encoded as UTF‑8, and wide strings use Unicode in an encoding that is appropriate for the platform on which the applica­tion executes. You can override the encoding for narrow and wide strings by regis­tering a string converter with the Ice run time. (See Section 32.24 for details.)