1
0
Fork 0
mirror of https://gitlab.com/sortix/sortix.git synced 2023-02-13 20:55:38 -05:00
sortix--sortix/libc/ioleast/preadleast.cpp

48 lines
1.6 KiB
C++
Raw Normal View History

/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2012, 2013.
This file is part of the Sortix C Library.
The Sortix C Library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
The Sortix C Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
ioleast/preadleast.cpp
Reads at least as much data as requested or more from the given offset.
*******************************************************************************/
#include <errno.h>
#include <ioleast.h>
#include <stdint.h>
#include <unistd.h>
extern "C"
size_t preadleast(int fd, void* buf, size_t least, size_t max, off_t off)
{
ssize_t amount = pread(fd, buf, max, off);
if ( amount < 0 )
return 0;
if ( least && !amount )
return errno = EEOF, 0;
if ( (size_t) amount < least )
{
void* nextbuf = (uint8_t*) buf + amount;
size_t nextleast = least - amount;
size_t nextmax = max - amount;
off_t nextoff = off + amount;
amount += preadleast(fd, nextbuf, nextleast, nextmax, nextoff);
}
return amount;
}