Searching Text in Memory without Visual Component in C++ Builder - delphi

Question

I am using C++Builder 10.3 with the VCL 32bit platform. I need to know the best way to search a text file in memory. I wrote the code below which opens a text file into the RichEdit component and searches for and selects some text. The RichEdit is intended to be used as a Visual Component. The TMemoryStream and TStringStream are used in memory but do not offer the methods FindText, SelStart, SelLength and SelText. Can you show how to do this in memory?
UnicodeString MyCrumb;
int StartPos=0, ToEnd=0, FoundAt=0, StartCrumb=0;
TSearchTypes mySearchTypes = TSearchTypes();
RichEdit1->Lines->LoadFromFile( "CrumbFile.txt" );
ToEnd = RichEdit1->Text.Length();
FoundAt = RichEdit1->FindText(L"CrumbStore", StartPos, ToEnd, mySearchTypes);
StartPos = FoundAt+10;
FoundAt = RichEdit1->FindText("crumb", StartPos, ToEnd, mySearchTypes);
StartPos = FoundAt+8;
StartCrumb = FoundAt+8;
FoundAt = RichEdit1->FindText("}", StartPos, ToEnd, mySearchTypes);
EndPos = FoundAt-1;
RichEdit1->SelStart = StartPos;
RichEdit1->SelLength = ( EndPos-StartPos );
MyCrumb = RichEdit1->SelText;

Answer 1

The VCL way is to use TStringList class instead of visual components. However, entire file will be loaded in the memory.
#include <iostream>
#include <memory>
using namespace std;
void FindTextVcl()
{
unique_ptr<TStringList> txt(new TStringList());
txt->LoadFromFile(L"Example.txt"); // Use appropriate TEncoding if need
for (int line_num = 0; line_num != txt->Count; line_num++)
{
int pos = txt->Strings[line_num].Pos("there");
if (pos > 0)
{
cout << "Found at line " << line_num + 1 << ", position " << pos << endl;
break;
}
}
}
The standard library way is like the following example (use wstring and wifstream for UTF-16).
This works for big files because only current string is loaded in the memory.
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
void FindTextStd()
{
ifstream txt("Example.txt");
if (txt.is_open())
{
size_t pos = 0;
size_t line_num = 0;
string line;
while (getline(txt, line))
{
line_num++;
pos = line.find("there");
if (pos != string::npos)
{
cout << "Found at line " << line_num << ", position " << pos + 1 << endl;
break;
}
}
}
}