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[The Fifth Horseman]

Okay, I have a program that moves across a bunch of records stored into memory and reports information about each (number, adress, some initial values).

#include <iostream>
#include <conio.h>
#include <fstream>
#include <math.h>
#include <iomanip>

using namespace std;

ifstream::pos_type size;
char *cache;

unsigned char unsign(char in)
     { 
      if (in>=0) return in;
      else return in+256;
     }

int readshint(unsigned __int64 o=0)
     {
      unsigned int out=0;
     for (int i=0; i<=1; i++)
        { out+=int(unsign(cache[i+o])*pow(256, i));}
      return out;
     }

void report (unsigned long int record, unsigned long int offset)
     {
      cout << "\nRecord " << setfill('0') << setw(2) << dec << record 
           << " at " << setw(4) << hex << offset << "h : "
           << dec << readshint(offset) << " x " << readshint(offset+2) 
           << " pixels.\n";
     }

unsigned char countrecords (unsigned short int offset=0)
     {
      if (readshint(offset+4)==0)
      { return 1; }
      else
      { return countrecords(offset+readshint(offset+4))+1; }
     }
     
unsigned short int taketarget (unsigned short int records)
     {  
        int target=0;
        cout << "\nEnter target record number:\n";
       while (target<1 || target>records)
         { cin >> target;
         /*if (target<1 || target>records)
           { cout << "Enter a number between 1 and " << records << ".\n"; }*/
         }
        return target;
     }

void save (unsigned short int offset)
     {
      cout << "\nNOT IMPLEMENTED YET!!!\n";
      return;
     }
     
main () {
  ifstream infile ("in.chp", ios::in|ios::binary|ios::ate);
  if (infile.is_open())
  {
    size = infile.tellg();
    cache = new unsigned (unsign(char [size]));
    infile.seekg (0, ios::beg);
    infile.read (cache, size);
    infile.close();
    cout << "CHP read to memory.\n";
    unsigned short int records=countrecords(), offset=0, target=1;
    cout << dec << records << " records found in file.\n";
    char trigger;
    do {
    /*cout << "Enter target record number...\n";
     do {
        cin >> target;
        if (target>records || target==0)
        cout << "Enter a value between 1 and " << records << ".\n";
        } while (target>records || target<1);*/
    for (int recind=1; recind<target; recind++)
    { offset+=readshint(offset+4); }
    report(target, offset);
    cout << "[N]ext, [P]revious, [i]ndex, [s]ave, [E]xit?\n";
    do {
        trigger=tolower(getch());
       } while (trigger!='n' && trigger!='p' && trigger!='i' && trigger!='s' && trigger!='e');
    switch (tolower(trigger))
      {
       case 'n': if (target<records-1) target++; else target=records; goto end;
       case 'p': if (target>1) target--; goto end;
       case 'i': target=taketarget(records); goto end;
       case 's': save(offset); goto end;     
       end:;
      }   
    } while (tolower(trigger)!='e');
    delete[] cache;
  }
  else cout << "Unable to open input file\n";
  cout << "\n";
  system("PAUSE");
}

Full sourcecode

It (mostly) works, but the following function doesn't work as intended.

unsigned short int taketarget (unsigned short int records)
     {  
        int target=0;
        cout << "\nEnter target record number:\n";
       while (target<1 || target>records)
         { cin >> target;
         if (target<1 || target>records)
           { cout << "Enter a number between 1 and " << records << ".\n"; }
         }
        return target;
     }

It's supposed to keep prompting the user until valid input is entered.
It does just fine if the user enters numeric values - but if a character is entered, the function loops infinitely without giving the user any way to enter new input.

What may be the cause of this behavior?