Start factoring out Unix assumptions

This splits files and adds new identifiers in preperation for supporting
windows, but no Windows-specific code is actually added yet.

src/libutil/environment-variables.cc

@@ -32,18 +32,4 @@ std::map<std::string, std::string> getEnv()
     return env;
 }
 
-
-void clearEnv()
-{
-    for (auto & name : getEnv())
-        unsetenv(name.first.c_str());
-}
-
-void replaceEnv(const std::map<std::string, std::string> & newEnv)
-{
-    clearEnv();
-    for (auto & newEnvVar : newEnv)
-        setenv(newEnvVar.first.c_str(), newEnvVar.second.c_str(), 1);
-}
-
 }

src/libutil/file-descriptor.cc

@@ -8,74 +8,14 @@
 
 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);
-}
-
-
-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 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)
+void writeLine(Descriptor fd, std::string s)
 {
     s += '\n';
     writeFull(fd, s);
 }
 
 
-std::string drainFD(int fd, bool block, const size_t reserveSize)
+std::string drainFD(Descriptor 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.
@@ -85,58 +25,26 @@ std::string drainFD(int fd, bool block, const size_t reserveSize)
 }
 
 
-void drainFD(int fd, Sink & sink, 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::vector<unsigned char> buf(64 * 1024);
-    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 sink({reinterpret_cast<char *>(buf.data()), size_t(rd)});
-    }
-}
-
 //////////////////////////////////////////////////////////////////////
 
-AutoCloseFD::AutoCloseFD() : fd{-1} {}
 
+AutoCloseFD::AutoCloseFD() : fd{INVALID_DESCRIPTOR} {}
 
-AutoCloseFD::AutoCloseFD(int fd) : fd{fd} {}
+
+AutoCloseFD::AutoCloseFD(Descriptor fd) : fd{fd} {}
 
 
 AutoCloseFD::AutoCloseFD(AutoCloseFD && that) : fd{that.fd}
 {
-    that.fd = -1;
+    that.fd = INVALID_DESCRIPTOR;
 }
 
 
 AutoCloseFD & AutoCloseFD::operator =(AutoCloseFD && that)
 {
     close();
     fd = that.fd;
-    that.fd = -1;
+    that.fd = INVALID_DESCRIPTOR;
     return *this;
 }
 
@@ -151,64 +59,54 @@ AutoCloseFD::~AutoCloseFD()
 }
 
 
-int AutoCloseFD::get() const
+Descriptor AutoCloseFD::get() const
 {
     return fd;
 }
 
 
 void AutoCloseFD::close()
 {
-    if (fd != -1) {
-        if (::close(fd) == -1)
+    if (fd != INVALID_DESCRIPTOR) {
+        if(::close(fd) == -1)
             /* This should never happen. */
             throw SysError("closing file descriptor %1%", fd);
-        fd = -1;
+        fd = INVALID_DESCRIPTOR;
     }
 }
 
 void AutoCloseFD::fsync()
 {
-  if (fd != -1) {
-      int result;
+    if (fd != INVALID_DESCRIPTOR) {
+        int result;
+        result =
 #if __APPLE__
-      result = ::fcntl(fd, F_FULLFSYNC);
+            ::fcntl(fd, F_FULLFSYNC)
 #else
-      result = ::fsync(fd);
+            ::fsync(fd)
 #endif
-      if (result == -1)
-          throw SysError("fsync file descriptor %1%", fd);
-  }
+            ;
+        if (result == -1)
+            throw SysError("fsync file descriptor %1%", fd);
+    }
 }
 
 
 AutoCloseFD::operator bool() const
 {
-    return fd != -1;
+    return fd != INVALID_DESCRIPTOR;
 }
 
 
-int AutoCloseFD::release()
+Descriptor AutoCloseFD::release()
 {
-    int oldFD = fd;
-    fd = -1;
+    Descriptor oldFD = fd;
+    fd = INVALID_DESCRIPTOR;
     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 = fds[0];
-    writeSide = fds[1];
-}
+//////////////////////////////////////////////////////////////////////
 
 
 void Pipe::close()
@@ -217,38 +115,4 @@ void Pipe::close()
     writeSide.close();
 }
 
-//////////////////////////////////////////////////////////////////////
-
-void closeMostFDs(const std::set<int> & exceptions)
-{
-#if __linux__
-    try {
-        for (auto & s : readDirectory("/proc/self/fd")) {
-            auto fd = std::stoi(s.name);
-            if (!exceptions.count(fd)) {
-                debug("closing leaked FD %d", fd);
-                close(fd);
-            }
-        }
-        return;
-    } catch (SystemError &) {
-    }
-#endif
-
-    int maxFD = 0;
-    maxFD = sysconf(_SC_OPEN_MAX);
-    for (int fd = 0; fd < maxFD; ++fd)
-        if (!exceptions.count(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");
-}
-
 }

src/libutil/file-descriptor.hh

@@ -9,53 +9,89 @@ namespace nix {
 struct Sink;
 struct Source;
 
+/**
+ * Operating System capability
+ */
+typedef int Descriptor;
+
+const Descriptor INVALID_DESCRIPTOR = -1;
+
+/**
+ * Convert a native `Descriptor` to a POSIX file descriptor
+ *
+ * This is a no-op except on Windows.
+ */
+static inline Descriptor toDesc(int fd)
+{
+    return fd;
+}
+
+/**
+ * Convert a POSIX file descriptor to a native `Descriptor`
+ *
+ * This is a no-op except on Windows.
+ */
+static inline int fromDesc(Descriptor fd, int flags)
+{
+    return fd;
+}
+
 /**
  * Read the contents of a resource into a string.
  */
-std::string readFile(int fd);
+std::string readFile(Descriptor fd);
 
 /**
  * Wrappers arount read()/write() that read/write exactly the
  * requested number of bytes.
  */
-void readFull(int fd, char * buf, size_t count);
+void readFull(Descriptor fd, char * buf, size_t count);
 
-void writeFull(int fd, std::string_view s, bool allowInterrupts = true);
+void writeFull(Descriptor fd, std::string_view s, bool allowInterrupts = true);
 
 /**
  * Read a line from a file descriptor.
  */
-std::string readLine(int fd);
+std::string readLine(Descriptor fd);
 
 /**
  * Write a line to a file descriptor.
  */
-void writeLine(int fd, std::string s);
+void writeLine(Descriptor fd, std::string s);
 
 /**
  * Read a file descriptor until EOF occurs.
  */
-std::string drainFD(int fd, bool block = true, const size_t reserveSize=0);
+std::string drainFD(Descriptor fd, bool block = true, const size_t reserveSize=0);
 
-void drainFD(int fd, Sink & sink, bool block = true);
+void drainFD(
+      Descriptor fd
+    , Sink & sink
+    , bool block = true
+    );
+
+[[gnu::always_inline]]
+inline Descriptor getStandardOut() {
+    return STDOUT_FILENO;
+}
 
 /**
  * Automatic cleanup of resources.
  */
 class AutoCloseFD
 {
-    int fd;
+    Descriptor fd;
 public:
     AutoCloseFD();
-    AutoCloseFD(int fd);
+    AutoCloseFD(Descriptor fd);
     AutoCloseFD(const AutoCloseFD & fd) = delete;
     AutoCloseFD(AutoCloseFD&& fd);
     ~AutoCloseFD();
     AutoCloseFD& operator =(const AutoCloseFD & fd) = delete;
     AutoCloseFD& operator =(AutoCloseFD&& fd);
-    int get() const;
+    Descriptor get() const;
     explicit operator bool() const;
-    int release();
+    Descriptor release();
     void close();
     void fsync();
 };
@@ -72,12 +108,12 @@ public:
  * Close all file descriptors except those listed in the given set.
  * Good practice in child processes.
  */
-void closeMostFDs(const std::set<int> & exceptions);
+void closeMostFDs(const std::set<Descriptor> & exceptions);
 
 /**
  * Set the close-on-exec flag for the given file descriptor.
  */
-void closeOnExec(int fd);
+void closeOnExec(Descriptor fd);
 
 MakeError(EndOfFile, Error);