Types PAnsiChar, PWideChar. Functions for working with ASCIIZ strings that change the contents of a string

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Contents

• 1. Function StrCat. Adding one string to the end of another
• 2. Function StrLCat. Add a string to the end of another string with a given limit on the length of the resulting string
• 3. StrLower and StrUpper functions. Converting characters to upper and lower case
• 4. Function StrCopy. Copying one string to another
• 5. Function StrECopy. Copying one string to another, returning a pointer to the end of the string
• 6. Function StrLCopy. Copy a specified number of characters from one string to another
• 7. Function StrMove. Move one string to another
• Related topics

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1. Function StrCat. Adding one string to the end of another

The StrCat function appends one string to the end of another and returns a pointer to the resulting string. The function has two implementations for PAnsiChar and PWideChar types

function StrCat(Dest: PAnsiChar; const Source: PAnsiChar): PAnsiChar;
function StrCat(Dest: PWideChar; const Source: PWideChar): PWideChar;

here

• Dest – destination string. Another string Source is added to this string;
• Source – source string that is added to the end of the Dest string.

Example.

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  ps1 : PAnsiChar; // Declaring variables of type PAnsiChar
  ps2 : PAnsiChar;
  ps3 : PAnsiChar;
  s : string;
begin
  // 1. Initialize variables ps1, ps2
  ps1 := 'bestprog';
  ps2 := '.net';

  // 2. ps3 = ps1 + ps2
  StrCat(ps3, ps1); // ps3 = 'bestprog'
  StrCat(ps3, ps2); // ps3 = 'bestprog.net'

  // 3. Output ps3 to console
  Writeln(StrPas(ps3));
  readln;
end.

  ⇑

2. Function StrLCat. Add a string to the end of another string with a given limit on the length of the resulting string

Using the StrLCat function, you can add one string to another with a constraint on the resulting string. For the PAnsiChar and PWideChar types, the function declarations are as follows

function StrLCat(Dest: PAnsiChar; const Source: PAnsiChar; MaxLen: Cardinal): PAnsiChar;
function StrLCat(Dest: PWideChar; const Source: PWideChar; MaxLen: Cardinal): PWideChar;

here

• Dest – destination string. This is the resulting string to which the Source string is added;
• Source – source string. This string is added to the string Dest;
• MaxLen – maximum length of the resulting string.

The function returns a pointer to the resulting string.

Example.

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  ps1 : PWideChar;
  ps2 : PWideChar;
  ps3 : PWideChar;

begin

  // Function StrLCat

  // 1. Form strings ps1, ps2
  // 1.1. Reserve 10 characters (20 bytes) of memory
  ps1 := WideStrAlloc(10);
  ps2 := WideStrAlloc(10);

  // 1.2. Copy data to strings
  StrCopy(ps1, '12345');
  StrCopy(ps2, '67890');

  // 1.3. Print the strings ps1, ps2 for control
  Writeln('ps1 = ', StrPas(ps1));
  Writeln('ps2 = ', StrPas(ps2));

  // 2. Reserve memory for the resulting string
  ps3 := WideStrAlloc(20);

  // 3. Add the string ps1 to the resulting string,
  // string ps3 - 3 characters
  StrLCat(ps3, ps1, 3); // ps3 = '123'

  // 4. Add string ps2 to string ps3,
  // ps3 string max 5 characters
  StrLCat(ps3, ps2, 5); // ps3 = '12367'

  // 5. Display ps3
  Writeln('ps3 = ', StrPas(ps3));

  // 6. Release memory previously allocated
  // under the lines ps1, ps2, ps3
  StrDispose(ps1);
  StrDispose(ps2);
  StrDispose(ps3);

  Readln;
end.

Результат

ps1 = 12345
ps2 = 67890
ps3 = 12367

  ⇑

3. StrLower and StrUpper functions. Converting characters to upper and lower case

The StrLower function converts the characters of a string to lowercase if they are in uppercase. The StrUpper function does the opposite of StrLower and converts the characters in a string to uppercase. The work of both functions applies only to the characters of the Latin alphabet.

For PAnsiChar and PWideChar types, the function declaration is as follows

function StrLower(Str: PAnsiChar): PAnsiChar;
function StrLower(Str: PWideChar): PWideChar;
function StrUpper(Str: PAnsiChar): PAnsiChar;
function StrUpper(Str: PWideChar): PWideChar;

here

• Str is a string whose characters are converted to the appropriate case.

Example.

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  ps1 : PWideChar;

begin

  // Functions StrLower, StrUpper

  // 1. Form string ps1
  ps1 := StrNew('ABCdefgh');
  Writeln('ps1 = ', StrPas(ps1));

  // 2. Convert characters of string ps1 to lowercase
  StrLower(ps1);
  Writeln('StrLower(ps1) = ', StrPas(ps1));

  // 3. Convert characters to uppercase
  StrUpper(ps1);
  Writeln('StrUpper(ps1) = ', StrPas(ps1));

  // 4. Free memory allocated for string ps1
  StrDispose(ps1);

  Readln;
end.

Result

ps1 = ABCdefgh
StrLower(ps1) = abcdefgh
StrUpper(ps1) = ABCDEFGH

  ⇑

4. Function StrCopy. Copying one string to another

The StrCopy function copies the value of one string to another. According to the function declaration documentation for the PAnsiChar and PWideChar types, the following

function StrCopy(Dest: PAnsiChar; const Source: PAnsiChar): PAnsiChar;
function StrCopy(Dest: PWideChar; const Source: PWideChar): PWideChar;

here

• Dest – destination string;
• Source – source string. Both strings are located in different areas of memory.

The function returns a pointer to the beginning of the resulting string.
When the function is called, the memory for the source string must be pre-allocated.

Example.

The example demonstrates various operations on strings of the PWideChar type, namely:

• console input and conversion from String type to PWideChar type;
• getting a memory fragment for a String type string (function WideStrAlloc());
• creation of a string of type PWideChar;
• displaying a string of type PWideChar;
• copying strings of type PWideChar using the StrCopy function;
• release of memory allocated for string of PWideChar type.

 

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  ps1 : PWideChar;
  ps2 : PWideChar;
  s : string;

begin
  // Function StrCopy

  // 1. Create original string,
  // a string is entered from the keyboard in a console application
  Write('s = ');
  Readln(s);

  // 2. Convert s => ps1
  // 2.1. Allocate memory for string ps1,
  // the memory size is equal to the length of the string s
  ps1 := StrNew(WideStrAlloc(Length(s)));

  // 2.2. Copy string s => ps1
  StrPCopy(ps1, s);

  // 3. Allocate memory for string ps2,
  // the memory size is equal to the length of the string ps1
  ps2 := StrNew(ps1); // this is also a copy

  // 4. Display string ps2
  Writeln('ps2 = ', StrPas(ps2));

  // 5. Change string ps1
  ps1[0] := '+';
  ps1[1] := '=';

  // 6. Print the string ps1 again
  Writeln('ps1 = ', StrPas(ps1));

  // 7. Copy string ps1 to string ps2 - StrCopy function
  StrCopy(ps2, ps1); // ps2 <= ps1

  // 8. Print ps2 string again
  Writeln('ps2 = ', StrPas(ps2));

  // 9. Free memory allocated for strings ps1, ps2
  StrDispose(ps1);
  StrDispose(ps2);

  Readln;
end.

Result

s = 12345
ps2 = 12345
ps1 = +=345
ps2 = +=345

  ⇑

5. Function StrECopy. Copying one string to another, returning a pointer to the end of the string

The StrECopy function, like the StrCopy function, copies one string to another. The peculiarity of this function is that the pointer is set to the end of the resulting string, and not to the beginning. The function declaration for the PAnsiChar and PWideChar types is as follows

function StrECopy(Dest: PAnsiChar; const Source: PAnsiChar): PAnsiChar;
function StrECopy(Dest: PWideChar; const Source: PWideChar): PWideChar;

here

• Dest – destination string;
• Source – source string.

Example.

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  ps1 : PAnsiChar;
  ps2 : PAnsiChar;
  ps3 : PAnsiChar;

begin
  // Function StrECopy

  // 1. Set string of type PAnsiChar
  ps1 := AnsiStrAlloc(20);
  StrCopy(ps1, 'ABCD'); // ps1 = 'ABCD'
  Writeln('ps1 = ', ps1);

  // 2. Set the ps2 pointer to the beginning of the string ps1
  ps2 := ps1;
  Writeln('ps2 = ', ps2);

  // 3. Append to string ps1 the string 'DEF'
  StrECopy(ps1, 'DEF');
  Writeln('StrECopy(ps1, ''DEF'')');
  Writeln('ps1 = ', ps1); // ps1 = DEF
  Writeln('ps2 = ', ps2); // ps2 = DEF - the ps2 pointer has also shifted

  Readln;
end.

Result

ps1 = ABCD
ps2 = ABCD
StrECopy(ps1, 'DEF')
ps1 = DEF
ps2 = DEF

  ⇑

6. Function StrLCopy. Copy a specified number of characters from one string to another

The StrLCopy function is designed to copy a given number of characters from a source string to the resulting string. The function specification for the PAnsiChar and PWideChar types is

function StrLCopy(Dest: PAnsiChar; const Source: PAnsiChar; MaxLen: Cardinal): PAnsiChar;
function StrLCopy(Dest: PWideChar; const Source: PWideChar; MaxLen: Cardinal): PWideChar;

here

• Dest – destination string;
• Source – source string;
• MaxLen – the number of characters from the string Source to be copied into the string Dest.

Example.

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  ps1 : PWideChar;
  ps2 : PWideChar;

begin
  // Function StrLCopy

  // Source string
  ps1 := StrNew('Hello, world!');

  // Create a new string
  ps2 := StrNew(ps1);

  // Copy first 5 characters of string ps1 => ps2
  StrLCopy(ps2, ps1, 5); // ps2 = 'Hello'

  Writeln('ps1 = ', StrPas(ps1));
  Writeln('ps2 = ', StrPas(ps2));

  Readln;
end.

Result

ps1 = Hello, world!
ps2 = Hello

  ⇑

7. Function StrMove. Move one string to another

The StrMove function moves a sequence of characters from a source string to a destination string. The function declaration for the PAnsiChar and PWideChar types is

function StrMove(Dest: PAnsiChar; const Source: PAnsiChar; Count: Cardinal): PAnsiChar;
function StrMove(Dest: PWideChar; const Source: PWideChar; Count: Cardinal): PWideChar;

here

• Dest – destination string;
• Source – source string;
• Count – the number of characters to be copied.

The function returns a pointer to the target string. The function does not destroy the original string Source.

Example.

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  ps1 : PWideChar;
  ps2 : PWideChar;

begin
  // Function StrMove

  // 1. Form string ps1
  ps1 := StrNew('ABCDEFGH');
  Writeln('ps1 = ', StrPas(ps1));

  // 2. Allocate a piece of memory for a string ps2
  // The fragment size is equal to the length of the string ps1
  ps2 := WideStrAlloc(StrLen(ps1));

  // 3. Transfer data from string ps1, transfer 5 characters.
  StrMove(ps2, ps1, 5);

  // 4. Add character '\0' to end of string ps2
  ps2[5] := #0;

  // 4. Display strings
  Writeln('ps2 = ', StrPas(ps2));
  Writeln('ps1 = ', StrPas(ps1));

  // 5. Free memory allocated for strings ps1, ps2
  StrDispose(ps1);
  StrDispose(ps2);

  Readln;
end.

Example.

ps1 = ABCDEFGH
ps2 = ABCDE
ps1 = ABCDEFGH

  ⇑

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Related topics

• Implementation of strings of PChar type in computer memory. Types PAnsiChar, PWideChar. Memory allocation for strings. Access by index
• String compare functions. Functions StrComp, StrIComp, StrLComp, StrLIComp
• Functions for searching and getting information about strings. Functions StrEnd, StrLen, StrPos, StrScan, StrRScan

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