1 /*
2 * Copyright (c) Meta Platforms, Inc. and affiliates.
3 *
4 * This source code is licensed under the MIT license found in the
5 * LICENSE file in the root directory of this source tree.
6 */
7
8 #include "ABI47_0_0JSBigString.h"
9
10 #include <glog/logging.h>
11
12 #include <folly/Memory.h>
13 #include <folly/ScopeGuard.h>
14 #include <folly/portability/Fcntl.h>
15 #include <folly/portability/SysMman.h>
16 #include <folly/portability/SysStat.h>
17 #include <folly/portability/Unistd.h>
18
19 #include <memory>
20
21 namespace ABI47_0_0facebook {
22 namespace ABI47_0_0React {
23
JSBigFileString(int fd,size_t size,off_t offset)24 JSBigFileString::JSBigFileString(int fd, size_t size, off_t offset /*= 0*/)
25 : m_fd{-1}, m_data{nullptr} {
26 folly::checkUnixError(m_fd = dup(fd), "Could not duplicate file descriptor");
27
28 // Offsets given to mmap must be page aligned. We abstract away that
29 // restriction by sending a page aligned offset to mmap, and keeping track
30 // of the offset within the page that we must alter the mmap pointer by to
31 // get the final desired offset.
32 if (offset != 0) {
33 const static auto ps = sysconf(_SC_PAGESIZE);
34 auto d = lldiv(offset, ps);
35
36 m_mapOff = d.quot;
37 m_pageOff = d.rem;
38 m_size = size + m_pageOff;
39 } else {
40 m_mapOff = 0;
41 m_pageOff = 0;
42 m_size = size;
43 }
44 }
45
~JSBigFileString()46 JSBigFileString::~JSBigFileString() {
47 if (m_data) {
48 munmap((void *)m_data, m_size);
49 }
50 close(m_fd);
51 }
52
c_str() const53 const char *JSBigFileString::c_str() const {
54 if (m_size == 0) {
55 return "";
56 }
57 if (!m_data) {
58 m_data =
59 (const char *)mmap(0, m_size, PROT_READ, MAP_PRIVATE, m_fd, m_mapOff);
60 CHECK(m_data != MAP_FAILED)
61 << " fd: " << m_fd << " size: " << m_size << " offset: " << m_mapOff
62 << " error: " << std::strerror(errno);
63 }
64 static const size_t kMinPageSize = 4096;
65 CHECK(!(reinterpret_cast<uintptr_t>(m_data) & (kMinPageSize - 1)))
66 << "mmap address misaligned, likely corrupted"
67 << " m_data: " << (const void *)m_data;
68 CHECK(m_pageOff <= m_size)
69 << "offset impossibly large, likely corrupted"
70 << " m_pageOff: " << m_pageOff << " m_size: " << m_size;
71 return m_data + m_pageOff;
72 }
73
size() const74 size_t JSBigFileString::size() const {
75 // Ensure mapping has been initialized.
76 c_str();
77 return m_size - m_pageOff;
78 }
79
fd() const80 int JSBigFileString::fd() const {
81 return m_fd;
82 }
83
fromPath(const std::string & sourceURL)84 std::unique_ptr<const JSBigFileString> JSBigFileString::fromPath(
85 const std::string &sourceURL) {
86 int fd = ::open(sourceURL.c_str(), O_RDONLY);
87 folly::checkUnixError(fd, "Could not open file", sourceURL);
88 SCOPE_EXIT {
89 CHECK(::close(fd) == 0);
90 };
91
92 struct stat fileInfo;
93 folly::checkUnixError(::fstat(fd, &fileInfo), "fstat on bundle failed.");
94
95 return std::make_unique<const JSBigFileString>(fd, fileInfo.st_size);
96 }
97
98 } // namespace ABI47_0_0React
99 } // namespace ABI47_0_0facebook
100