util.{hh,cc}: Split out file-descriptor.{hh,cc}

Change-Id: I0dd0f9a9c2003fb887e076127e7f825fd3289c76

1 files changed, 89 insertions, 0 deletions

diff --git a/src/libutil/file-descriptor.hh b/src/libutil/file-descriptor.hh
new file mode 100644
index 000000000..68324b9d9
--- /dev/null
+++ b/src/libutil/file-descriptor.hh
@@ -0,0 +1,89 @@
+#pragma once
+///@file
+
+#include "error.hh"
+
+namespace nix {
+
+struct Sink;
+struct Source;
+
+/**
+ * Read a line from a file descriptor.
+ */
+std::string readLine(int fd);
+
+/**
+ * Write a line to a file descriptor.
+ */
+void writeLine(int fd, std::string s);
+
+/**
+ * Read the contents of a file into a string.
+ */
+std::string readFile(int fd);
+
+/**
+ * Wrappers arount read()/write() that read/write exactly the
+ * requested number of bytes.
+ */
+void readFull(int fd, char * buf, size_t count);
+void writeFull(int fd, std::string_view s, bool allowInterrupts = true);
+
+/**
+ * Read a file descriptor until EOF occurs.
+ */
+std::string drainFD(int fd, bool block = true, const size_t reserveSize=0);
+
+void drainFD(int fd, Sink & sink, bool block = true);
+
+class AutoCloseFD
+{
+    int fd;
+public:
+    AutoCloseFD();
+    explicit AutoCloseFD(int fd);
+    AutoCloseFD(const AutoCloseFD & fd) = delete;
+    AutoCloseFD(AutoCloseFD&& fd);
+    ~AutoCloseFD();
+    AutoCloseFD& operator =(const AutoCloseFD & fd) = delete;
+    AutoCloseFD& operator =(AutoCloseFD&& fd) noexcept(false);
+    int get() const;
+    explicit operator bool() const;
+    int release();
+    void close();
+    void fsync();
+    void reset() { *this = {}; }
+};
+
+class Pipe
+{
+public:
+    AutoCloseFD readSide, writeSide;
+    void create();
+    void close();
+};
+
+/**
+ * Close all file descriptors except those listed in the given set.
+ * Good practice in child processes.
+ */
+void closeMostFDs(const std::set<int> & exceptions);
+
+/**
+ * Set the close-on-exec flag for the given file descriptor.
+ */
+void closeOnExec(int fd);
+
+MakeError(EndOfFile, Error);
+
+/**
+ * Create a Unix domain socket.
+ */
+AutoCloseFD createUnixDomainSocket();
+
+/**
+ * Create a Unix domain socket in listen mode.
+ */
+AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
+}