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Intro

The string class implements dynamically allocated reference-counted 8-bit character strings. The string class is a mixture of L-type and null-terminated strings: it has both the length indicator and the terminating null-symbol. The length of a string is theoretically limited to INT_MAX, and practically is limited to the amount of virtual memory space available to the application.

A string object itself contains only a reference to the first character of the string buffer. A string object can be implicitly converted to a null-terminated string, either a variable or passed as an actual parameter, thus allowing to combine both PTypes strings and traditional C strings in your application. A string object converted to char* or const char* never returns NULL pointers: it guarantees to always point to some data, even if the string is zero-sized.

The reference counting mechanism works transparently (known also as copy-on-write) and safely with regard to multithreading. You can manipulate string objects as if each object had its own copy of string data. Whenever you modify a string object the library safely detaches the buffer from all other string objects that may be using the same buffer and creates a unique copy so that changes won't affect the other "holders" of this string.

NOTE on multithreading: the dynamic string objects themselves are NOT thread-safe. In other words, each thread can manipulate objects (variables) of type string only within their scope. However, it is safe to pass strings as (copy) parameters when, for example, sending a message to a concurrent thread through a message queue. Whenever the recipient thread tries to modify the string, the shared data buffer is safely detached.

The string class is declared in <ptypes.h>.

Constructor/destructors

Operators

A string object can be constructed in 5 different ways:

• default constructor string() creates an empty string.
• copy constructor string(const string& s) creates a copy of the given string s. Actually this constructor only increments the reference count by 1 and no memory allocation takes place.
• string(char c) constructs a new string consisting of one character c.
• string(const char* s) constructs a new string object from a null-terminated string. If s is either NULL or is a pointer to a null character, an empty string object is created. This constructor can be used to assign a string literal to a string object (see examples below).
• string(const char* s, int len) copies len bytes of data from buffer s to the newly allocated string buffer.

Destructor ~string() decrements the reference count for the given string buffer and removes it from the dynamic memory if necessary.

Examples:

Typecasts

Manipulation

Conversion