100 lines
2.7 KiB
C++
100 lines
2.7 KiB
C++
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/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#include "JSBigString.h"
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#include <glog/logging.h>
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#include <folly/Memory.h>
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#include <folly/ScopeGuard.h>
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#include <folly/portability/Fcntl.h>
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#include <folly/portability/SysMman.h>
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#include <folly/portability/SysStat.h>
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#include <folly/portability/Unistd.h>
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#include <memory>
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namespace facebook {
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namespace react {
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JSBigFileString::JSBigFileString(int fd, size_t size, off_t offset /*= 0*/)
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: m_fd{-1}, m_data{nullptr} {
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folly::checkUnixError(m_fd = dup(fd), "Could not duplicate file descriptor");
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// Offsets given to mmap must be page aligned. We abstract away that
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// restriction by sending a page aligned offset to mmap, and keeping track
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// of the offset within the page that we must alter the mmap pointer by to
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// get the final desired offset.
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if (offset != 0) {
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const static auto ps = sysconf(_SC_PAGESIZE);
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auto d = lldiv(offset, ps);
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m_mapOff = d.quot;
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m_pageOff = d.rem;
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m_size = size + m_pageOff;
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} else {
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m_mapOff = 0;
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m_pageOff = 0;
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m_size = size;
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}
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}
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JSBigFileString::~JSBigFileString() {
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if (m_data) {
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munmap((void *)m_data, m_size);
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}
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close(m_fd);
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}
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const char *JSBigFileString::c_str() const {
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if (m_size == 0) {
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return "";
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}
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if (!m_data) {
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m_data =
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(const char *)mmap(0, m_size, PROT_READ, MAP_PRIVATE, m_fd, m_mapOff);
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CHECK(m_data != MAP_FAILED)
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<< " fd: " << m_fd << " size: " << m_size << " offset: " << m_mapOff
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<< " error: " << std::strerror(errno);
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}
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static const size_t kMinPageSize = 4096;
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CHECK(!(reinterpret_cast<uintptr_t>(m_data) & (kMinPageSize - 1)))
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<< "mmap address misaligned, likely corrupted"
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<< " m_data: " << (const void *)m_data;
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CHECK(m_pageOff <= m_size)
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<< "offset impossibly large, likely corrupted"
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<< " m_pageOff: " << m_pageOff << " m_size: " << m_size;
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return m_data + m_pageOff;
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}
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size_t JSBigFileString::size() const {
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// Ensure mapping has been initialized.
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c_str();
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return m_size - m_pageOff;
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}
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int JSBigFileString::fd() const {
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return m_fd;
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}
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std::unique_ptr<const JSBigFileString> JSBigFileString::fromPath(
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const std::string &sourceURL) {
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int fd = ::open(sourceURL.c_str(), O_RDONLY);
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folly::checkUnixError(fd, "Could not open file", sourceURL);
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SCOPE_EXIT {
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CHECK(::close(fd) == 0);
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};
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struct stat fileInfo;
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folly::checkUnixError(::fstat(fd, &fileInfo), "fstat on bundle failed.");
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return std::make_unique<const JSBigFileString>(fd, fileInfo.st_size);
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}
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} // namespace react
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} // namespace facebook
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