STRING(SDL )

Shore Programmer's Manual - 3 November 94

NAME

SYNOPSIS

// in SDL:
interface obj_containing_string {
public:
    attribute string str_attr;
    attribute text   text_attr;
};

// signature of C++ binding for string/text types
// (The public part of the class declarations for 
// string and text attributes.)
class sdl_string
{
 public:
    char get(int n) const;    // get n'th character
    void get(char *s) const;    // get copy of entire string
    void get(char *s, int from, int len) const; // get a range of bytes

    void set(int n, char c);    // set n'th character
    void set(const char *s); // s is null-terminated
    void set(const char *s, int from, int len); // set a range of bytes

    int strlen(void) const;    //length of currently stored string
    int blen() const;          // available space as binary data.

    // C Library style names for modifying the string
    const char *memcpy(const char *s, int len); 
    void    bcopy(const char *s, int len);
    const char *strcpy(const char *s);
    const char *strcat(const char *s);

    // conversion to C string.
    operator const char *() const;
    // const void * conversion, for use with mem/bcopy routines.
    operator const void *() const;
    const char * operator=(const char *); // conversion from C string
};

DESCRIPTION

The SDL string type provides a variable length string facility for use in the definition of SDL interface object types. The SDL text type is similar too, and allows the same operations as the string type, but there may at most one text attribute per SDL object. If an SDL object containing a text attribute is a named object any data contained in the text attribute is accessible as a Unix file through the Shore Server. Attributes of SDL objects declared as string or text can be accessed within SDL/C++ programs as if they were instances of a C++ class with the method signature shown above. The C++ binding of the SDL string type is designed for easy inter-operation with C-style null terminated strings and char* pointers, and can be used with many of the functions described in string(3) (declared in the header file <string.h>. )

String attributes also can be used to store memory areas (arrays of characters bounded by a count, not terminated by a null character) String attributes can be used to store such an area by using one of the memcpy or bcopy member functions described below. Use of string-style member functions and memory area member functions cannot be intermixed.

The member functions that modify the value of a string attribute will allocate temporary storage as necessary to store string or memory area values; the value of a string attribute may be treated as a const char * pointer value in many contexts, but the attribute may only be modified through member functions of the string class.

The following examples are base on use of an SDL C++ binding based on the SDL object type definition

interface obj_containing_string {
public:
    attribute string str_attr;
    attribute text   text_attr;
};

REF(obj_containing_string) sref_val;
char *s;
char *s1, *s2;
int n;
int i;
int len;
char c;

The get member functions retrieve character values from the string attribute.

    sref->str_attr.get(n);

    sref->str_attr.get(s);

    sref->str_attr.get(s,i,len)

The set member functions set the string value or subranges of the string value in a manner analogous to the get functions;

    sref.update()->str_attr.get(n);

    sref.update()->str_attr.get(s);

    sref.update()->str_attr.get(s,i,len)

A string attribute can be used as a const char * pointer, either via implicit coercion or explicit casting. For example, a string attribute could be printed using printf by explicitly casting the reference to a const char * value.

    printf("str_attr: %s\n",(const char *)(sref->str_attr))

extern "C" long atoi(const char *);
    int nval = atoi(sref->str_attr);

    sref->str_attr.strlen()

    strlen(sref->str.attr);

    sref->str_attr.blen()

    sref.update()->str_attr.strcpy(s2)

    sref.update()->str_attr = s2;

    sref.update()->str_attr.strcat(s2)

    sref.update()->str_attr.memcpy(s2,len)

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