1/*
2 * Copyright 2013-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#pragma once
18
19#include <algorithm>
20#include <cerrno>
21
22#include <folly/portability/SysUio.h>
23#include <folly/portability/Unistd.h>
24
25/**
26 * Helper functions and templates for FileUtil.cpp. Declared here so
27 * they can be unittested.
28 */
29namespace folly {
30namespace fileutil_detail {
31
32// Wrap call to f(args) in loop to retry on EINTR
33template <class F, class... Args>
34ssize_t wrapNoInt(F f, Args... args) {
35 ssize_t r;
36 do {
37 r = f(args...);
38 } while (r == -1 && errno == EINTR);
39 return r;
40}
41
42inline void incr(ssize_t /* n */) {}
43inline void incr(ssize_t n, off_t& offset) {
44 offset += off_t(n);
45}
46
47// Wrap call to read/pread/write/pwrite(fd, buf, count, offset?) to retry on
48// incomplete reads / writes. The variadic argument magic is there to support
49// an additional argument (offset) for pread / pwrite; see the incr() functions
50// above which do nothing if the offset is not present and increment it if it
51// is.
52template <class F, class... Offset>
53ssize_t wrapFull(F f, int fd, void* buf, size_t count, Offset... offset) {
54 char* b = static_cast<char*>(buf);
55 ssize_t totalBytes = 0;
56 ssize_t r;
57 do {
58 r = f(fd, b, count, offset...);
59 if (r == -1) {
60 if (errno == EINTR) {
61 continue;
62 }
63 return r;
64 }
65
66 totalBytes += r;
67 b += r;
68 count -= r;
69 incr(r, offset...);
70 } while (r != 0 && count); // 0 means EOF
71
72 return totalBytes;
73}
74
75// Wrap call to readv/preadv/writev/pwritev(fd, iov, count, offset?) to
76// retry on incomplete reads / writes.
77template <class F, class... Offset>
78ssize_t wrapvFull(F f, int fd, iovec* iov, int count, Offset... offset) {
79 ssize_t totalBytes = 0;
80 ssize_t r;
81 do {
82 r = f(fd, iov, std::min<int>(count, kIovMax), offset...);
83 if (r == -1) {
84 if (errno == EINTR) {
85 continue;
86 }
87 return r;
88 }
89
90 if (r == 0) {
91 break; // EOF
92 }
93
94 totalBytes += r;
95 incr(r, offset...);
96 while (r != 0 && count != 0) {
97 if (r >= ssize_t(iov->iov_len)) {
98 r -= ssize_t(iov->iov_len);
99 ++iov;
100 --count;
101 } else {
102 iov->iov_base = static_cast<char*>(iov->iov_base) + r;
103 iov->iov_len -= r;
104 r = 0;
105 }
106 }
107 } while (count);
108
109 return totalBytes;
110}
111
112} // namespace fileutil_detail
113} // namespace folly
114