Difference between revisions of "String"
m (Added Russian page link)
m (Added Russian page link)
Latest revision as of 09:51, 16 January 2021
A string is always one character larger than it appears. The extra item is the null terminator (binary zero, typed as
\0). This is required because a pointer to a string is generally passed around, rather than the array itself, and a pointer does not contain data on the string's length.
Without the terminator it would be impossible to determine where the string ended and where the next variable, or just unassigned memory, began. This is what a buffer overflow is, and those are bad news!
Creating from string literal
char* MyString = "Hello world"; // must assign to pointer!
This code creates a string from a string literal. The double quote marks are special syntax which generate an array of
char from their contents. The code above therefore:
- Assigns 12 bytes of memory, somewhere arbitrary, to store the string. This is one byte for each character, plus an automatic twelfth for the null terminator.
- Creates a local
charpointer containing the address of the first character (H in this case).
String literals are often handed with
const variables. This is because a string literal will stay in memory for the process's whole lifespan.
MyStringin the Visual Studio debugger, you will see the entire string. This is special behaviour to make examining strings easier; strictly speaking it should just show you the pointee (i.e. the first character, H).
Creating by size
char MyString; // accepts a static size only int StringLen = 12; char* pMyString = new char[StringLen]; // accepts a variable size delete pMyString; // always delete / delete anything created with 'new' after use
This code both allocates two 12-byte strings, but does not write anything to them (so their contents will be either blank or gibberish). They need to be assigned to, ideally with a string function like
The difference between them is that one creates an array in the function's memory space, while the other creates a pointer in the function and uses
new to allocate the string itself somewhere else. The advantage of
new is that you can allocate an array of a size determined at run-time, but the downside is that if you aren't scrupulous about calling
delete for arrays) you will suffer a memory leak.
Unicode strings behave similarly to ASCII strings, but are instead arrays of
wchar_t. They are operated on by their own set of string functions, normally with 'wc' or 'wcs' (wide char string) in their name.
wchar_t* MyWideString = L"Здравей свят";
L marks the string literal as being Unicode. You need to do this even if the characters are all ASCII-compatible.
There are a multitude of functions which process strings, of which the most common ASCII variants have Source-specific
V_* equivalents. See MSDN for a quite comprehensive list, or search VS' Class View for "V_str".