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#include "charptr-cast.hh"
#include "file-system.hh"
#include "finally.hh"
#include "logging.hh"
#include "serialise.hh"
#include "signals.hh"
#include <fcntl.h>
#include <unistd.h>
namespace nix {
std::string readFile(int fd)
{
struct stat st;
if (fstat(fd, &st) == -1)
throw SysError("statting file");
return drainFD(fd, true, st.st_size);
}
std::string readLine(int fd)
{
std::string s;
while (1) {
checkInterrupt();
char ch;
// FIXME: inefficient
ssize_t rd = read(fd, &ch, 1);
if (rd == -1) {
if (errno != EINTR)
throw SysError("reading a line");
} else if (rd == 0)
throw EndOfFile("unexpected EOF reading a line");
else {
if (ch == '\n') return s;
s += ch;
}
}
}
void writeLine(int fd, std::string s)
{
s += '\n';
writeFull(fd, s);
}
void readFull(int fd, char * buf, size_t count)
{
while (count) {
checkInterrupt();
ssize_t res = read(fd, buf, count);
if (res == -1) {
if (errno == EINTR) continue;
throw SysError("reading from file");
}
if (res == 0) throw EndOfFile("unexpected end-of-file");
count -= res;
buf += res;
}
}
void writeFull(int fd, std::string_view s, bool allowInterrupts)
{
while (!s.empty()) {
if (allowInterrupts) checkInterrupt();
ssize_t res = write(fd, s.data(), s.size());
if (res == -1 && errno != EINTR)
throw SysError("writing to file");
if (res > 0)
s.remove_prefix(res);
}
}
std::string drainFD(int fd, bool block, const size_t reserveSize)
{
// the parser needs two extra bytes to append terminating characters, other users will
// not care very much about the extra memory.
StringSink sink(reserveSize + 2);
sink << drainFDSource(fd, block);
return std::move(sink.s);
}
Generator<Bytes> drainFDSource(int fd, bool block)
{
// silence GCC maybe-uninitialized warning in finally
int saved = 0;
if (!block) {
saved = fcntl(fd, F_GETFL);
if (fcntl(fd, F_SETFL, saved | O_NONBLOCK) == -1)
throw SysError("making file descriptor non-blocking");
}
Finally finally([&]() {
if (!block) {
if (fcntl(fd, F_SETFL, saved) == -1)
throw SysError("making file descriptor blocking");
}
});
std::array<unsigned char, 64 * 1024> buf;
while (1) {
checkInterrupt();
ssize_t rd = read(fd, buf.data(), buf.size());
if (rd == -1) {
if (!block && (errno == EAGAIN || errno == EWOULDBLOCK))
break;
if (errno != EINTR)
throw SysError("reading from file");
}
else if (rd == 0) break;
else co_yield std::span{charptr_cast<char *>(buf.data()), (size_t) rd};
}
}
AutoCloseFD::AutoCloseFD() : fd{-1} {}
AutoCloseFD::AutoCloseFD(int fd) : fd{fd} {}
AutoCloseFD::AutoCloseFD(AutoCloseFD && that) : fd{that.fd}
{
that.fd = -1;
}
AutoCloseFD & AutoCloseFD::operator =(AutoCloseFD && that) noexcept(false)
{
close();
fd = that.fd;
that.fd = -1;
return *this;
}
AutoCloseFD::~AutoCloseFD()
{
try {
close();
} catch (...) {
ignoreException();
}
}
int AutoCloseFD::get() const
{
return fd;
}
void AutoCloseFD::close()
{
if (fd != -1) {
if (::close(fd) == -1)
/* This should never happen. */
throw SysError("closing file descriptor %1%", fd);
fd = -1;
}
}
void AutoCloseFD::fsync()
{
if (fd != -1) {
int result;
#if __APPLE__
result = ::fcntl(fd, F_FULLFSYNC);
#else
result = ::fsync(fd);
#endif
if (result == -1)
throw SysError("fsync file descriptor %1%", fd);
}
}
AutoCloseFD::operator bool() const
{
return fd != -1;
}
int AutoCloseFD::release()
{
int oldFD = fd;
fd = -1;
return oldFD;
}
void Pipe::create()
{
int fds[2];
#if HAVE_PIPE2
if (pipe2(fds, O_CLOEXEC) != 0) throw SysError("creating pipe");
#else
if (pipe(fds) != 0) throw SysError("creating pipe");
closeOnExec(fds[0]);
closeOnExec(fds[1]);
#endif
readSide = AutoCloseFD{fds[0]};
writeSide = AutoCloseFD{fds[1]};
}
void Pipe::close()
{
readSide.close();
writeSide.close();
}
void closeExtraFDs()
{
constexpr int MAX_KEPT_FD = 2;
static_assert(std::max({STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO}) == MAX_KEPT_FD);
// Both Linux and FreeBSD support close_range.
#if __linux__ || __FreeBSD__
auto closeRange = [](unsigned int first, unsigned int last, int flags) -> int {
// musl does not have close_range as of 2024-08-10
// patch: https://www.openwall.com/lists/musl/2024/08/01/9
#if HAVE_CLOSE_RANGE
return close_range(first, last, flags);
#else
return syscall(SYS_close_range, first, last, flags);
#endif
};
// first try to close_range everything we don't care about. if this
// returns an error with these parameters we're running on a kernel
// that does not implement close_range (i.e. pre 5.9) and fall back
// to the old method. we should remove that though, in some future.
if (closeRange(3, ~0U, 0) == 0) {
return;
}
#endif
#if __linux__
try {
for (auto & s : readDirectory("/proc/self/fd")) {
auto fd = std::stoi(s.name);
if (fd > MAX_KEPT_FD) {
debug("closing leaked FD %d", fd);
close(fd);
}
}
return;
} catch (SysError &) {
}
#endif
int maxFD = 0;
maxFD = sysconf(_SC_OPEN_MAX);
for (int fd = MAX_KEPT_FD + 1; fd < maxFD; ++fd)
close(fd); /* ignore result */
}
void closeOnExec(int fd)
{
int prev;
if ((prev = fcntl(fd, F_GETFD, 0)) == -1 ||
fcntl(fd, F_SETFD, prev | FD_CLOEXEC) == -1)
throw SysError("setting close-on-exec flag");
}
}
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