Difference between revisions of "Character and string types"
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==== Reference ==== | ==== Reference ==== | ||
* [http://www.freepascal.org/docs-html/ref/refsu13.html FPC UnicodeString documentation] | * [http://www.freepascal.org/docs-html/ref/refsu13.html FPC UnicodeString documentation] | ||
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| + | == WideString == | ||
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| + | Variables of type '''WideString''' (used to represent unicode character strings in COM applications) resemble those of type '''UnicodeString''', but unlike them they are not reference-counted. On Windows they are allocated with a special windows function which allows them to be used for OLE automation. | ||
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| + | {| class="wikitable" style="text-align:center; width:300px" | ||
| + | |- | ||
| + | | style="width: 8%;" | || style="width: 8%;" | || style="width: 8%;" | || style="width: 8%;" | || style="width: 8%;" | a || style="width: 8%;" | || style="width: 8%;" | b || style="width: 8%;" | || style="width: 8%;" | c || style="width: 8%;" | #0 || style="width: 8%;" | #0 | ||
| + | |- | ||
| + | | colspan="4" style="width: 16%;" | Length | ||
| + | |} | ||
| + | |||
| + | ==== Reference ==== | ||
| + | * [http://www.freepascal.org/docs-html/ref/refsu14.html#x37-400003.2.8 FPC WideString documentation] | ||
[[Category: FPC]] | [[Category: FPC]] | ||
[[Category: RTL]] | [[Category: RTL]] | ||
[[Category: Data types]] | [[Category: Data types]] | ||
Revision as of 17:01, 28 December 2013
Free Pascal supports several types of characters and strings.
AnsiChar
A variable of type AnsiChar is exactly 1 byte in size, and contains one ASCII character.
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Reference
WideChar
A variable of type WideChar, also referred to as UnicodeChar. is exactly 2 bytes in size, and contains one (part of) Unicode character in UTF-16 encoding. Note: it is impossible to encode all Unicode code points in 2 bytes. Therefore, 2 WideChars may be needed to encode a single code point.
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References
PChar
A variable of type PChar is basically a pointer to a Char type, but allows additional operations. PChars can be used to access C-style null-terminated strings, e.g. in interaction with certain OS libraries or third-party software.
| a | b | c | #0 |
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Reference
PWideChar
A variable of type PWideChar is a pointer to a WideChar variable.
| a | b | c | #0 | #0 | |||
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Reference
String
The type string may refer to ShortString or AnsiString, depending from the {$H} switch. If the switch is off ({$H-}) then any string declaration will define a ShortString. It size will be 255 chars, if not otherwise specified. If it is on ({$H+}) string without length specifier will define an AnsiString, otherwise a ShortString with specified length.
ShortString
Short strings have a maximum length of 255 characters. The length is stored in the character at index 0.
| #3 | a | b | c |
Reference
AnsiString
Ansistrings are strings that have no length limit. They are reference counted and are guaranteed to be null terminated. Internally, a variable of type AnsiString is treated as a pointer: the actual content of the string is stored on the heap, as much memory as needed to store the string content is allocated.
| a | b | c | #0 | ||||||||
| RefCount | Length | ||||||||||
Reference
UnicodeString
Like AnsiStrings UniCodeStrings are reference counted, null-terminated arrays, but they are implemented as arrays of WideChars instead of regular Chars.
| a | b | c | #0 | #0 | |||||||||||
| RefCount | Length | ||||||||||||||
Reference
WideString
Variables of type WideString (used to represent unicode character strings in COM applications) resemble those of type UnicodeString, but unlike them they are not reference-counted. On Windows they are allocated with a special windows function which allows them to be used for OLE automation.
| a | b | c | #0 | #0 | ||||||
| Length | ||||||||||
