9124f303f7
This patch implements the 'pread()' and 'pwrite()' functions in the libc. A lock guard prevents the parallel execution of either or both functions. Fixes #278.
76 lines
1.4 KiB
C++
76 lines
1.4 KiB
C++
/*
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* \brief 'pread()' and 'pwrite()' implementations
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* \author Christian Prochaska
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* \date 2012-07-11
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*/
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/*
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* Copyright (C) 2012 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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/* Genode includes */
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#include <base/lock.h>
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/* libc includes */
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#include <sys/types.h>
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#include <sys/uio.h>
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#include <unistd.h>
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static Genode::Lock rw_lock;
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struct Read
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{
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ssize_t operator()(int fd, void *buf, size_t count)
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{
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return read(fd, buf, count);
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}
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};
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struct Write
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{
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ssize_t operator()(int fd, const void *buf, size_t count)
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{
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return write(fd, buf, count);
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}
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};
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template <typename Rw_func, typename Buf_type>
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static ssize_t pread_pwrite_impl(Rw_func rw_func, int fd, Buf_type buf, ::size_t count, ::off_t offset)
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{
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Genode::Lock_guard<Genode::Lock> rw_lock_guard(rw_lock);
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off_t old_offset = lseek(fd, 0, SEEK_CUR);
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if (old_offset == -1)
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return -1;
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if (lseek(fd, offset, SEEK_SET) == -1)
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return -1;
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ssize_t result = rw_func(fd, buf, count);
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if (lseek(fd, old_offset, SEEK_SET) == -1)
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return -1;
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return result;
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}
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extern "C" ssize_t pread(int fd, void *buf, ::size_t count, ::off_t offset)
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{
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return pread_pwrite_impl(Read(), fd, buf, count, offset);
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}
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extern "C" ssize_t pwrite(int fd, const void *buf, ::size_t count, ::off_t offset)
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{
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return pread_pwrite_impl(Write(), fd, buf, count, offset);
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}
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