1 /*
2 * Copyright (C) 2019 The Android Open Source Project
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 "sys/sendfile.h"
18
19 #include <errno.h>
20 #include <unistd.h>
21
22 namespace {
23 // This value is arbitrarily chosen.
24 constexpr size_t kBufSize = 4096;
25 } // namespace
26
27 // TODO(ZX-429): This is a painfully simple sendfile implementation that does
28 // not attempt to optimize for anything and is only provided as something that "works".
sendfile(int out_fd,int in_fd,off_t * offset,size_t count)29 ssize_t sendfile(int out_fd, int in_fd, off_t *offset, size_t count) {
30 // We don't support seek() for now.
31 if (offset != nullptr) {
32 errno = ESPIPE;
33 return -1;
34 }
35
36 size_t total = 0;
37 unsigned char buffer[kBufSize];
38 while(count > 0) {
39 int bytes = read(in_fd, buffer, sizeof(buffer));
40 if (bytes == 0) {
41 break;
42 }
43
44 if (bytes < 0) {
45 return bytes;
46 }
47
48 count -= bytes;
49
50 unsigned char *data = buffer;
51 while(bytes > 0) {
52 int written = write(out_fd, data, bytes);
53 if (written < 0) {
54 return written;
55 }
56
57
58 bytes -= written;
59 data += written;
60 total += written;
61 }
62 }
63
64 return total;
65 }
66