I have a function that takes in a pointer to a series of char. I wish to copy 256 chars from that point, and place them in a string.
msg is not null-terminated.
The below code seems to give me some problem. Is there a correct way to do this?
Init( msg: PCHAR)
var
myStr: String;
begin
for i:= 1 to 256 do
begin
myStr[i] := msg[i-1];
end;
end;
SetString(myStr, msg, 256);
Your code misses SetLength, the corrected version is:
Init( msg: PCHAR)
var
myStr: String;
begin
SetLength(myStr, 256);
for i:= 1 to 256 do
begin
myStr[i] := msg[i-1];
end;
end;
The assignment can be done more efficiently as already answered.
Updated
SetLength allocates 256 characters + terminating 0 for myStr; without SetLength your code is an error: it writes to wild address and will finally result in access violation.
myStr := 'test'. Then, of course, you cannot access myStr[7]. You have to set the length of the string - then you can set its characters.If msg is null-terminated, as it should be, and the 256 characters you want to obtain are followed by the null character, simply do
myStr := msg;
If msg is longer than that, you could just do
myStr := Copy(msg, 1, 256);
In this case, a better method is
myStr := WideCharLenToString(msg, 256);
assuming you are using Delphi 2009 or later, in which the strings are Unicode.
myStr := Copy(msg, 1, 256);
