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

Change-Id: I0dd0f9a9c2003fb887e076127e7f825fd3289c76

11 files changed, 348 insertions, 320 deletions

diff --git a/src/libstore/lock.cc b/src/libstore/lock.cc
index b52e87ae0..05296757d 100644
--- a/src/libstore/lock.cc
+++ b/src/libstore/lock.cc
@@ -1,4 +1,5 @@
 #include "lock.hh"
+#include "logging.hh"
 #include "file-system.hh"
 #include "globals.hh"
 #include "pathlocks.hh"
diff --git a/src/libstore/pathlocks.hh b/src/libstore/pathlocks.hh
index 4921df352..7fcfa2e40 100644
--- a/src/libstore/pathlocks.hh
+++ b/src/libstore/pathlocks.hh
@@ -1,7 +1,7 @@
 #pragma once
 ///@file
 
-#include "util.hh"
+#include "file-descriptor.hh"
 
 namespace nix {
 
diff --git a/src/libutil/file-descriptor.cc b/src/libutil/file-descriptor.cc
new file mode 100644
index 000000000..ec22f17ab
--- /dev/null
+++ b/src/libutil/file-descriptor.cc
@@ -0,0 +1,251 @@
+#include "file-system.hh"
+#include "finally.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);
+    drainFD(fd, sink, block);
+    return std::move(sink.s);
+}
+
+
+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::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 sink({(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)
+{
+    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 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 (SysError &) {
+    }
+#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");
+}
+
+}
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);
+}
diff --git a/src/libutil/file-system.cc b/src/libutil/file-system.cc
index e5ba42eb6..9804c449c 100644
--- a/src/libutil/file-system.cc
+++ b/src/libutil/file-system.cc
@@ -3,10 +3,10 @@
 #include <atomic>
 
 #include "environment-variables.hh"
+#include "file-descriptor.hh"
 #include "file-system.hh"
 #include "finally.hh"
 #include "serialise.hh"
-#include "util.hh"
 #include "signals.hh"
 #include "types.hh"
 
@@ -278,16 +278,6 @@ unsigned char getFileType(const Path & path)
 }
 
 
-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 readFile(const Path & path)
 {
     AutoCloseFD fd{open(path.c_str(), O_RDONLY | O_CLOEXEC)};
diff --git a/src/libutil/file-system.hh b/src/libutil/file-system.hh
index 1d91ef334..b9b753980 100644
--- a/src/libutil/file-system.hh
+++ b/src/libutil/file-system.hh
@@ -6,7 +6,7 @@
  */
 
 #include "types.hh"
-#include "util.hh"
+#include "file-descriptor.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -143,7 +143,6 @@ unsigned char getFileType(const Path & path);
 /**
  * Read the contents of a file into a string.
  */
-std::string readFile(int fd);
 std::string readFile(const Path & path);
 void readFile(const Path & path, Sink & sink);
 
diff --git a/src/libutil/logging.cc b/src/libutil/logging.cc
index 731d1034d..8d9e18d09 100644
--- a/src/libutil/logging.cc
+++ b/src/libutil/logging.cc
@@ -1,4 +1,5 @@
 #include "environment-variables.hh"
+#include "file-descriptor.hh"
 #include "logging.hh"
 #include "util.hh"
 #include "config.hh"
diff --git a/src/libutil/meson.build b/src/libutil/meson.build
index 8af251d1b..a4813d9a3 100644
--- a/src/libutil/meson.build
+++ b/src/libutil/meson.build
@@ -13,6 +13,7 @@ libutil_sources = files(
   'escape-string.cc',
   'exit.cc',
   'experimental-features.cc',
+  'file-descriptor.cc',
   'file-system.cc',
   'git.cc',
   'hash.cc',
@@ -62,6 +63,7 @@ libutil_headers = files(
   'exit.hh',
   'experimental-features.hh',
   'experimental-features-json.hh',
+  'file-descriptor.hh',
   'file-system.hh',
   'finally.hh',
   'fmt.hh',
diff --git a/src/libutil/serialise.hh b/src/libutil/serialise.hh
index d1c791823..d4a14bbf0 100644
--- a/src/libutil/serialise.hh
+++ b/src/libutil/serialise.hh
@@ -5,6 +5,7 @@
 
 #include "types.hh"
 #include "util.hh"
+#include "file-descriptor.hh"
 
 namespace boost::context { struct stack_context; }
 
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index ac3071ba8..55f3154c9 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -52,34 +52,6 @@
 namespace nix {
 
 
-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);
-}
-
-
 std::string getUserName()
 {
     auto pw = getpwuid(geteuid());
@@ -196,78 +168,6 @@ std::optional<Path> getSelfExe()
 
 
 
-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);
-    drainFD(fd, sink, block);
-    return std::move(sink.s);
-}
-
-
-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::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 sink({(char *) buf.data(), (size_t) rd});
-    }
-}
-
 //////////////////////////////////////////////////////////////////////
 
 unsigned int getMaxCPU()
@@ -303,102 +203,6 @@ unsigned int getMaxCPU()
 //////////////////////////////////////////////////////////////////////
 
 
-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)
-{
-    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();
-}
 
 
 //////////////////////////////////////////////////////////////////////
@@ -762,39 +566,6 @@ void runProgram2(const RunOptions & options)
 }
 
 
-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 (SysError &) {
-    }
-#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");
-}
-
-
 //////////////////////////////////////////////////////////////////////
 
 
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 63a4fcb6a..d0e207146 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -39,17 +39,6 @@ struct Source;
 extern const std::string nativeSystem;
 
 
-/**
- * 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);
-
-
 std::string getUserName();
 
 /**
@@ -103,56 +92,11 @@ Path createNixStateDir();
 
 
 /**
- * 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);
-
-MakeError(EndOfFile, Error);
-
-
-/**
- * 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);
-
-/**
  * If cgroups are active, attempt to calculate the number of CPUs available.
  * If cgroups are unavailable or if cpu.max is set to "max", return 0.
  */
 unsigned int getMaxCPU();
 
-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();
-};
-
-
 class Pid
 {
     pid_t pid = -1;
@@ -172,7 +116,6 @@ public:
     pid_t release();
 };
 
-
 /**
  * Kill all processes running under the specified uid by sending them
  * a SIGKILL.
@@ -279,17 +222,6 @@ public:
  */
 std::vector<char *> stringsToCharPtrs(const Strings & ss);
 
-/**
- * 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(FormatError, Error);
 
@@ -596,15 +528,6 @@ struct MaintainCount
  */
 void commonChildInit();
 
-/**
- * Create a Unix domain socket.
- */
-AutoCloseFD createUnixDomainSocket();
-
-/**
- * Create a Unix domain socket in listen mode.
- */
-AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
 
 /**
  * Bind a Unix domain socket to a path.