File contents
/*ident "@(#)cls4:lib/stream/streambuf.c 1.5" */
/*******************************************************************************
C++ source for the C++ Language System, Release 3.0. This product
is a new release of the original cfront developed in the computer
science research center of AT&T Bell Laboratories.
Copyright (c) 1993 UNIX System Laboratories, Inc.
Copyright (c) 1991, 1992 AT&T and UNIX System Laboratories, Inc.
Copyright (c) 1984, 1989, 1990 AT&T. All Rights Reserved.
THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE of AT&T and UNIX System
Laboratories, Inc. The copyright notice above does not evidence
any actual or intended publication of such source code.
*******************************************************************************/
#include <iostream.h>
#include "streamdefs.h"
#include <string.h>
#include <memory.h>
/*
Allocate some space for the buffer.
Returns: EOF on error
0 on success
*/
int streambuf::doallocate()
{
char *buf = new char[STREAMBUFSIZE] ;
if ( !buf ) return EOF ;
setb(buf,buf+STREAMBUFSIZE,1) ;
return 0;
}
/*
Come here on a put to a full buffer. Allocate the buffer if
it is uninitialized.
Returns: EOF on error
the argument on success
*/
int streambuf::overflow(int c)
{
if ( c==EOF ) return zapeof(c) ;
if ( allocate() == EOF) return EOF;
if ( x_pptr <= x_epptr ) return sputc(c) ;
else return EOF ;
}
/*
Fill a buffer.
Returns: EOF on error or end of input
next character on success
*/
int streambuf::underflow()
{
if ( x_pptr > x_egptr ) setg(x_eback,x_gptr,x_pptr) ;
if ( x_egptr > x_gptr ) return 0 ;
else return EOF ;
}
int streambuf::pbackfail(int)
{
return EOF;
}
int streambuf::sync()
{
// It's unclear exactly what this should do. Should it reset
// the buffer or what. One theory (that used to be in the code.
// was that it should insert a 0. Which seems to be the
// right thing for "strings".
// if ( x_pptr && x_epptr > x_pptr ) sputc(0) ;
return EOF ;
}
streampos streambuf::seekpos(streampos p, int m)
{
return seekoff(p, ios::beg, m) ;
}
streampos streambuf::seekoff(streampos,ios::seek_dir,int)
{
return EOF ;
}
int streambuf::xsputn(register const char* s, int n)
{
register int req = n ;
if ( unbuffered() ) {
while( req-- > 0 ) {
if ( sputc(*s++) == EOF ) return n-req-1 ;
}
return n ;
}
register int avail = x_epptr-x_pptr ;
while ( avail < req ) {
memcpy(x_pptr,s,avail) ;
s += avail ;
pbump(avail) ;
req -= avail ;
if ( overflow(zapeof(*s++)) == EOF ) return n-req ;
--req ;
avail = x_epptr-x_pptr ;
}
memcpy(x_pptr,s,req ) ;
pbump(req) ;
return n ;
}
int streambuf::xsgetn(register char* s, int n)
{
register char* p = s ;
register int req = n ;
if ( req <= 0 ) return 0 ;
if ( unbuffered() ) {
while (req-- > 0 ) {
register int c ;
if ( (c=sbumpc() ) != EOF ) *p++ = c ;
else return p-s ;
}
return n ;
}
register int avail = x_egptr-x_gptr ;
while ( avail < req ) {
memcpy(p,x_gptr,avail) ;
p += avail ;
req -= avail ;
gbump(avail) ;
if ( underflow()==EOF ) return p-s ;
avail = x_egptr-x_gptr ;
}
memcpy(p,x_gptr,req) ;
gbump(req) ;
return n ;
}
streambuf* streambuf::setbuf(char* p , int len)
{
if ( x_base ) return 0 ;
if ( len <= 0 || p == 0 ) {
// make it unbuffered
setb(0,0,0) ;
setg(0,0,0) ;
setp(0,0);
unbuffered(1) ;
}
else {
setb(p,p+len,0) ;
setg(p,p,p) ;
setp(p,p+len) ;
unbuffered(0) ;
}
return this;
}
streambuf* streambuf::setbuf(unsigned char* p, int len)
{
return setbuf((char*)p,len) ;
}
streambuf::streambuf() :
x_unbuf(0), alloc(0)
{
setb(0,0,0);
setg(0,0,0);
setp(0,0);
}
streambuf::streambuf(char* p, int l) :
x_unbuf(0), alloc(0)
{
setb(0,0,0);
setbuf(p,l) ;
}
streambuf::~streambuf()
{
sync() ;
if (x_base && alloc) delete x_base;
}
int streambuf::x_snextc()
{
// called by snextc to handle underflow
if ( x_egptr==0 || x_gptr != x_egptr ) {
// we stepped beyond x_gptr meaning snextc was called when
// x_gptr == x_egptr rather than when x_gptr+1=x_egptr.
underflow() ;
gbump(1) ;
}
return sgetc() ;
}