1 | /* |
2 | * Copyright 2016-present Facebook, Inc. |
3 | * |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
5 | * you may not use this file except in compliance with the License. |
6 | * You may obtain a copy of the License at |
7 | * |
8 | * http://www.apache.org/licenses/LICENSE-2.0 |
9 | * |
10 | * Unless required by applicable law or agreed to in writing, software |
11 | * distributed under the License is distributed on an "AS IS" BASIS, |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
13 | * See the License for the specific language governing permissions and |
14 | * limitations under the License. |
15 | */ |
16 | |
17 | #include <folly/portability/SysUio.h> |
18 | |
19 | #include <errno.h> |
20 | #include <stdio.h> |
21 | |
22 | #include <folly/ScopeGuard.h> |
23 | #include <folly/portability/Sockets.h> |
24 | #include <folly/portability/SysFile.h> |
25 | #include <folly/portability/Unistd.h> |
26 | |
27 | template <class F, class... Args> |
28 | static int wrapPositional(F f, int fd, off_t offset, Args... args) { |
29 | off_t origLoc = lseek(fd, 0, SEEK_CUR); |
30 | if (origLoc == off_t(-1)) { |
31 | return -1; |
32 | } |
33 | if (lseek(fd, offset, SEEK_SET) == off_t(-1)) { |
34 | return -1; |
35 | } |
36 | |
37 | int res = (int)f(fd, args...); |
38 | |
39 | int curErrNo = errno; |
40 | if (lseek(fd, origLoc, SEEK_SET) == off_t(-1)) { |
41 | if (res == -1) { |
42 | errno = curErrNo; |
43 | } |
44 | return -1; |
45 | } |
46 | errno = curErrNo; |
47 | |
48 | return res; |
49 | } |
50 | |
51 | #if !FOLLY_HAVE_PREADV |
52 | extern "C" ssize_t preadv(int fd, const iovec* iov, int count, off_t offset) { |
53 | return wrapPositional(readv, fd, offset, iov, count); |
54 | } |
55 | #endif |
56 | |
57 | #if !FOLLY_HAVE_PWRITEV |
58 | extern "C" ssize_t pwritev(int fd, const iovec* iov, int count, off_t offset) { |
59 | return wrapPositional(writev, fd, offset, iov, count); |
60 | } |
61 | #endif |
62 | |
63 | #ifdef _WIN32 |
64 | template <bool isRead> |
65 | static ssize_t doVecOperation(int fd, const iovec* iov, int count) { |
66 | if (!count) { |
67 | return 0; |
68 | } |
69 | if (count < 0 || count > folly::kIovMax) { |
70 | errno = EINVAL; |
71 | return -1; |
72 | } |
73 | |
74 | // We only need to worry about locking if the file descriptor is |
75 | // not a socket. We have no way of locking sockets :( |
76 | // The correct way to do this for sockets is via sendmsg/recvmsg, |
77 | // but this is good enough for now. |
78 | bool shouldLock = !folly::portability::sockets::is_fh_socket(fd); |
79 | if (shouldLock && lockf(fd, F_LOCK, 0) == -1) { |
80 | return -1; |
81 | } |
82 | SCOPE_EXIT { |
83 | if (shouldLock) { |
84 | lockf(fd, F_ULOCK, 0); |
85 | } |
86 | }; |
87 | |
88 | ssize_t bytesProcessed = 0; |
89 | int curIov = 0; |
90 | void* curBase = iov[0].iov_base; |
91 | size_t curLen = iov[0].iov_len; |
92 | while (curIov < count) { |
93 | ssize_t res = 0; |
94 | if (isRead) { |
95 | res = read(fd, curBase, (unsigned int)curLen); |
96 | if (res == 0 && curLen != 0) { |
97 | break; // End of File |
98 | } |
99 | } else { |
100 | res = write(fd, curBase, (unsigned int)curLen); |
101 | // Write of zero bytes is fine. |
102 | } |
103 | |
104 | if (res == -1) { |
105 | return -1; |
106 | } |
107 | |
108 | if (size_t(res) == curLen) { |
109 | curIov++; |
110 | if (curIov < count) { |
111 | curBase = iov[curIov].iov_base; |
112 | curLen = iov[curIov].iov_len; |
113 | } |
114 | } else { |
115 | curBase = (void*)((char*)curBase + res); |
116 | curLen -= res; |
117 | } |
118 | |
119 | if (bytesProcessed + res < 0) { |
120 | // Overflow |
121 | errno = EINVAL; |
122 | return -1; |
123 | } |
124 | bytesProcessed += res; |
125 | } |
126 | |
127 | return bytesProcessed; |
128 | } |
129 | |
130 | extern "C" ssize_t readv(int fd, const iovec* iov, int count) { |
131 | return doVecOperation<true>(fd, iov, count); |
132 | } |
133 | |
134 | extern "C" ssize_t writev(int fd, const iovec* iov, int count) { |
135 | return doVecOperation<false>(fd, iov, count); |
136 | } |
137 | #endif |
138 | |