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| //===-- SelectHelper.cpp ----------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#if defined(__APPLE__)
// Enable this special support for Apple builds where we can have unlimited
// select bounds. We tried switching to poll() and kqueue and we were panicing
// the kernel, so we have to stick with select for now.
#define _DARWIN_UNLIMITED_SELECT
#endif
#include "lldb/Utility/SelectHelper.h"
#include "lldb/Utility/LLDBAssert.h"
#include "lldb/Utility/Status.h"
#include "lldb/lldb-enumerations.h"
#include "lldb/lldb-types.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Optional.h"
#include <algorithm>
#include <chrono>
#include <errno.h>
#if defined(_WIN32)
// Define NOMINMAX to avoid macros that conflict with std::min and std::max
#define NOMINMAX
#include <winsock2.h>
#else
#include <sys/time.h>
#include <sys/select.h>
#endif
SelectHelper::SelectHelper()
: m_fd_map(), m_end_time() // Infinite timeout unless
// SelectHelper::SetTimeout() gets called
{}
void SelectHelper::SetTimeout(const std::chrono::microseconds &timeout) {
using namespace std::chrono;
m_end_time = steady_clock::time_point(steady_clock::now() + timeout);
}
void SelectHelper::FDSetRead(lldb::socket_t fd) {
m_fd_map[fd].read_set = true;
}
void SelectHelper::FDSetWrite(lldb::socket_t fd) {
m_fd_map[fd].write_set = true;
}
void SelectHelper::FDSetError(lldb::socket_t fd) {
m_fd_map[fd].error_set = true;
}
bool SelectHelper::FDIsSetRead(lldb::socket_t fd) const {
auto pos = m_fd_map.find(fd);
if (pos != m_fd_map.end())
return pos->second.read_is_set;
else
return false;
}
bool SelectHelper::FDIsSetWrite(lldb::socket_t fd) const {
auto pos = m_fd_map.find(fd);
if (pos != m_fd_map.end())
return pos->second.write_is_set;
else
return false;
}
bool SelectHelper::FDIsSetError(lldb::socket_t fd) const {
auto pos = m_fd_map.find(fd);
if (pos != m_fd_map.end())
return pos->second.error_is_set;
else
return false;
}
static void updateMaxFd(llvm::Optional<lldb::socket_t> &vold,
lldb::socket_t vnew) {
if (!vold.hasValue())
vold = vnew;
else
vold = std::max(*vold, vnew);
}
lldb_private::Status SelectHelper::Select() {
lldb_private::Status error;
#ifdef _WIN32
// On windows FD_SETSIZE limits the number of file descriptors, not their
// numeric value.
lldbassert(m_fd_map.size() <= FD_SETSIZE);
if (m_fd_map.size() > FD_SETSIZE)
return lldb_private::Status("Too many file descriptors for select()");
#endif
llvm::Optional<lldb::socket_t> max_read_fd;
llvm::Optional<lldb::socket_t> max_write_fd;
llvm::Optional<lldb::socket_t> max_error_fd;
llvm::Optional<lldb::socket_t> max_fd;
for (auto &pair : m_fd_map) {
pair.second.PrepareForSelect();
const lldb::socket_t fd = pair.first;
#if !defined(__APPLE__) && !defined(_WIN32)
lldbassert(fd < static_cast<int>(FD_SETSIZE));
if (fd >= static_cast<int>(FD_SETSIZE)) {
error.SetErrorStringWithFormat("%i is too large for select()", fd);
return error;
}
#endif
if (pair.second.read_set)
updateMaxFd(max_read_fd, fd);
if (pair.second.write_set)
updateMaxFd(max_write_fd, fd);
if (pair.second.error_set)
updateMaxFd(max_error_fd, fd);
updateMaxFd(max_fd, fd);
}
if (!max_fd.hasValue()) {
error.SetErrorString("no valid file descriptors");
return error;
}
const unsigned nfds = static_cast<unsigned>(*max_fd) + 1;
fd_set *read_fdset_ptr = nullptr;
fd_set *write_fdset_ptr = nullptr;
fd_set *error_fdset_ptr = nullptr;
// Initialize and zero out the fdsets
#if defined(__APPLE__)
llvm::SmallVector<fd_set, 1> read_fdset;
llvm::SmallVector<fd_set, 1> write_fdset;
llvm::SmallVector<fd_set, 1> error_fdset;
if (max_read_fd.hasValue()) {
read_fdset.resize((nfds / FD_SETSIZE) + 1);
read_fdset_ptr = read_fdset.data();
}
if (max_write_fd.hasValue()) {
write_fdset.resize((nfds / FD_SETSIZE) + 1);
write_fdset_ptr = write_fdset.data();
}
if (max_error_fd.hasValue()) {
error_fdset.resize((nfds / FD_SETSIZE) + 1);
error_fdset_ptr = error_fdset.data();
}
for (auto &fd_set : read_fdset)
FD_ZERO(&fd_set);
for (auto &fd_set : write_fdset)
FD_ZERO(&fd_set);
for (auto &fd_set : error_fdset)
FD_ZERO(&fd_set);
#else
fd_set read_fdset;
fd_set write_fdset;
fd_set error_fdset;
if (max_read_fd.hasValue()) {
FD_ZERO(&read_fdset);
read_fdset_ptr = &read_fdset;
}
if (max_write_fd.hasValue()) {
FD_ZERO(&write_fdset);
write_fdset_ptr = &write_fdset;
}
if (max_error_fd.hasValue()) {
FD_ZERO(&error_fdset);
error_fdset_ptr = &error_fdset;
}
#endif
// Set the FD bits in the fdsets for read/write/error
for (auto &pair : m_fd_map) {
const lldb::socket_t fd = pair.first;
if (pair.second.read_set)
FD_SET(fd, read_fdset_ptr);
if (pair.second.write_set)
FD_SET(fd, write_fdset_ptr);
if (pair.second.error_set)
FD_SET(fd, error_fdset_ptr);
}
// Setup our timeout time value if needed
struct timeval *tv_ptr = nullptr;
struct timeval tv = {0, 0};
while (true) {
using namespace std::chrono;
// Setup out relative timeout based on the end time if we have one
if (m_end_time.hasValue()) {
tv_ptr = &tv;
const auto remaining_dur = duration_cast<microseconds>(
m_end_time.getValue() - steady_clock::now());
if (remaining_dur.count() > 0) {
// Wait for a specific amount of time
const auto dur_secs = duration_cast<seconds>(remaining_dur);
const auto dur_usecs = remaining_dur % seconds(1);
tv.tv_sec = dur_secs.count();
tv.tv_usec = dur_usecs.count();
} else {
// Just poll once with no timeout
tv.tv_sec = 0;
tv.tv_usec = 0;
}
}
const int num_set_fds = ::select(nfds, read_fdset_ptr, write_fdset_ptr,
error_fdset_ptr, tv_ptr);
if (num_set_fds < 0) {
// We got an error
error.SetErrorToErrno();
if (error.GetError() == EINTR) {
error.Clear();
continue; // Keep calling select if we get EINTR
} else
return error;
} else if (num_set_fds == 0) {
// Timeout
error.SetError(ETIMEDOUT, lldb::eErrorTypePOSIX);
error.SetErrorString("timed out");
return error;
} else {
// One or more descriptors were set, update the FDInfo::select_is_set
// mask so users can ask the SelectHelper class so clients can call one
// of:
for (auto &pair : m_fd_map) {
const int fd = pair.first;
if (pair.second.read_set) {
if (FD_ISSET(fd, read_fdset_ptr))
pair.second.read_is_set = true;
}
if (pair.second.write_set) {
if (FD_ISSET(fd, write_fdset_ptr))
pair.second.write_is_set = true;
}
if (pair.second.error_set) {
if (FD_ISSET(fd, error_fdset_ptr))
pair.second.error_is_set = true;
}
}
break;
}
}
return error;
}
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