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/////////////////////////////////////////////////////////////////
// FileBuffer.h
//
// Buffered file reading.
/////////////////////////////////////////////////////////////////
#ifndef FILEBUFFER_H
#define FILEBUFFER_H
#include <string>
#include <fstream>
#include <iostream>
using namespace std;
const int BufferSize = 1000;
/////////////////////////////////////////////////////////////////
// FileBuffer
//
// Class for buffering file reading.
/////////////////////////////////////////////////////////////////
class FileBuffer {
ifstream file;
char buffer[BufferSize];
int currPos;
int size;
bool isEOF;
bool isValid;
bool canUnget;
public:
// Some common routines
FileBuffer (const char *filename) : file (filename), currPos (0), size (0), isEOF (false), isValid (!file.fail()), canUnget (false){}
~FileBuffer (){ close(); }
bool fail () const { return !isValid; }
bool eof () const { return (!isValid || isEOF); }
void close(){ file.close(); isValid = false; }
/////////////////////////////////////////////////////////////////
// FileBuffer::Get()
//
// Retrieve a character from the file buffer. Returns true if
// and only if a character is read.
/////////////////////////////////////////////////////////////////
bool Get (char &ch){
// check to make sure that there's more stuff in the file
if (!isValid || isEOF) return false;
// if the buffer is empty, it's time to reload it
if (currPos == size){
file.read (buffer, BufferSize);
size = file.gcount();
isEOF = (size == 0);
currPos = 0;
if (isEOF) return false;
}
// store the read character
ch = buffer[currPos++];
canUnget = true;
return true;
}
/////////////////////////////////////////////////////////////////
// FileBuffer::UnGet()
//
// Unretrieve the most recently read character from the file
// buffer. Note that this allows only a one-level undo.
/////////////////////////////////////////////////////////////////
void UnGet (){
assert (canUnget);
assert (isValid);
assert (currPos > 0);
currPos--;
assert (currPos < size);
isEOF = false;
canUnget = false;
}
/////////////////////////////////////////////////////////////////
// FileBuffer::GetLine()
//
// Retrieve characters of text until a newline character is
// encountered. Terminates properly on end-of-file condition.
/////////////////////////////////////////////////////////////////
void GetLine (string &s){
char ch;
s = "";
while (Get (ch) && ch != '\n')
s += ch;
}
};
#endif
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