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/*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <folly/portability/SysUio.h>
#include <cerrno>
#include <cstdio>
#include <folly/ScopeGuard.h>
#include <folly/portability/Sockets.h>
#include <folly/portability/SysFile.h>
#include <folly/portability/Unistd.h>
template <class F, class... Args>
static int wrapPositional(F f, int fd, off_t offset, Args... args) {
off_t origLoc = lseek(fd, 0, SEEK_CUR);
if (origLoc == off_t(-1)) {
return -1;
}
if (lseek(fd, offset, SEEK_SET) == off_t(-1)) {
return -1;
}
int res = (int)f(fd, args...);
int curErrNo = errno;
if (lseek(fd, origLoc, SEEK_SET) == off_t(-1)) {
if (res == -1) {
errno = curErrNo;
}
return -1;
}
errno = curErrNo;
return res;
}
#if !FOLLY_HAVE_PREADV
extern "C" ssize_t preadv(int fd, const iovec* iov, int count, off_t offset) {
return wrapPositional(readv, fd, offset, iov, count);
}
#endif
#if !FOLLY_HAVE_PWRITEV
extern "C" ssize_t pwritev(int fd, const iovec* iov, int count, off_t offset) {
return wrapPositional(writev, fd, offset, iov, count);
}
#endif
#ifdef _WIN32
template <bool isRead>
static ssize_t doVecOperation(int fd, const iovec* iov, int count) {
if (!count) {
return 0;
}
if (count < 0 || count > folly::kIovMax) {
errno = EINVAL;
return -1;
}
// We only need to worry about locking if the file descriptor is
// not a socket. We have no way of locking sockets :(
// The correct way to do this for sockets is via sendmsg/recvmsg,
// but this is good enough for now.
bool shouldLock = !folly::portability::sockets::is_fh_socket(fd);
if (shouldLock && lockf(fd, F_LOCK, 0) == -1) {
return -1;
}
SCOPE_EXIT {
if (shouldLock) {
lockf(fd, F_ULOCK, 0);
}
};
ssize_t bytesProcessed = 0;
int curIov = 0;
void* curBase = iov[0].iov_base;
size_t curLen = iov[0].iov_len;
while (curIov < count) {
ssize_t res = 0;
if (isRead) {
res = read(fd, curBase, (unsigned int)curLen);
if (res == 0 && curLen != 0) {
break; // End of File
}
} else {
res = write(fd, curBase, (unsigned int)curLen);
// Write of zero bytes is fine.
}
if (res == -1) {
return -1;
}
if (size_t(res) == curLen) {
curIov++;
if (curIov < count) {
curBase = iov[curIov].iov_base;
curLen = iov[curIov].iov_len;
}
} else {
curBase = (void*)((char*)curBase + res);
curLen -= res;
}
if (bytesProcessed + res < 0) {
// Overflow
errno = EINVAL;
return -1;
}
bytesProcessed += res;
}
return bytesProcessed;
}
extern "C" ssize_t readv(int fd, const iovec* iov, int count) {
return doVecOperation<true>(fd, iov, count);
}
extern "C" ssize_t writev(int fd, const iovec* iov, int count) {
return doVecOperation<false>(fd, iov, count);
}
#endif
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