istrgdbl.cpp

C标准库源代码

/***
* istrgdbl.cpp - definitions for istream class core double routine
*
*       Copyright (c) 1991-1997, Microsoft Corporation.  All rights reserved.
*
*Purpose:
*       Definitions of member function for istream getdouble().
*       [AT&T C++]
*
*******************************************************************************/

#include <cruntime.h>
#include <internal.h>
#include <ctype.h>
#include <iostream.h>
#pragma hdrstop

/***
*int istream::getdouble(char * buffer, int buflen) - get a double
*
*Purpose:
*       Get a double from stream.
*
*Entry:
*       char * buffer   = area for number to be copied.
*       int buflen      = max. length of buffer
*
*Exit:
*       Returns 0 if fatal error
*       Otherwise, returns length of buffer filled.
*       Sets ios::failbit on error forming number.
*       If successful, buffer[] contains the number, followed by \0.
*
*Exceptions:
*
*******************************************************************************/
int     istream::getdouble(char * buffer, int buflen)   // returns length
{
    int c;
    int i = 0;
    int fDigit = 0;     // true if legal digit encountered
    int fDecimal=0;     // true if '.' encountered or no longer valid
    int fExp=0;         // true if 'E' or 'e' encounted

    if (ipfx(0))
        {
        c=bp->sgetc();
        for (; i<buflen; buffer[i] = (char)c,c=bp->snextc(),i++)
            {
            if (c==EOF)
                {
                state |= ios::eofbit;
                break;
                }
            if ((!i) || (fExp==1))
                {
                if ((c=='-') || (c=='+'))
                    {
                    continue;
                    }
                }
            if ((c=='.') && (!fExp) && (!fDecimal))
                {
                fDecimal++;
                continue;
                }
            if (((c=='E') || (c=='e')) && (!fExp))
                {
                fDecimal++;     // can't allow decimal now
                fExp++;
                continue;
                }
            if (!isdigit(c))
                break;
            if (fExp)
                fExp++;
            else
                fDigit++;
            }
        if (fExp==1)            // E or e with no number after it
            {
            if (bp->sputbackc(buffer[i])!=EOF)
                {
                i--;
                state &= ~(ios::eofbit);
                }
            else
                {
                state |= ios::failbit;
                }
            }
        if ((!fDigit) || (i==buflen))
            state |= ios::failbit;

        // buffer contains a valid number or '\0'
        buffer[i] = '\0';
        isfx();
        }
    return i;
}