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