Subprocess: allow non-copyable callbacks

[folly.git] / folly / Subprocess.h

diff --git a/folly/Subprocess.h b/folly/Subprocess.h
index 531d9181dd25f3cb38ad33bc7c236cd3c4b2f5d9..e922ee0d261a8cfdeb348b95cbafb2d215eb1484 100644 (file)
--- a/folly/Subprocess.h
+++ b/folly/Subprocess.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2016 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -90,8 +90,8 @@
  * make sure to serialize your signals (i.e. kill()) with the waits --
  * either wait & signal from the same thread, or use a mutex.
  */
-#ifndef FOLLY_SUBPROCESS_H_
-#define FOLLY_SUBPROCESS_H_
+
+#pragma once
 
 #include <sys/types.h>
 #include <signal.h>
@@ -108,8 +108,10 @@
 #include <boost/container/flat_map.hpp>
 #include <boost/operators.hpp>
 
+#include <folly/Exception.h>
 #include <folly/File.h>
 #include <folly/FileUtil.h>
+#include <folly/Function.h>
 #include <folly/gen/String.h>
 #include <folly/io/IOBufQueue.h>
 #include <folly/MapUtil.h>
@@ -612,7 +614,7 @@ class Subprocess {
    * expensive implementation choice, in order to make closeParentFd()
    * thread-safe.
    */
-  typedef std::function<bool(int, int)> FdCallback;
+  using FdCallback = folly::Function<bool(int, int)>;
   void communicate(FdCallback readCallback, FdCallback writeCallback);
 
   /**
@@ -621,17 +623,13 @@ class Subprocess {
    * descriptors.  Use the readLinesCallback() helper to get template
    * deduction.  For example:
    *
-   *   auto read_cb = Subprocess::readLinesCallback(
-   *     [](int fd, folly::StringPiece s) {
-   *       std::cout << fd << " said: " << s;
-   *       return false;  // Keep reading from the child
-   *     }
-   *   );
    *   subprocess.communicate(
-   *     // ReadLinesCallback contains StreamSplitter contains IOBuf, making
-   *     // it noncopyable, whereas std::function must be copyable.  So, we
-   *     // keep the callback in a local, and instead pass a reference.
-   *     std::ref(read_cb),
+   *     Subprocess::readLinesCallback(
+   *       [](int fd, folly::StringPiece s) {
+   *         std::cout << fd << " said: " << s;
+   *         return false;  // Keep reading from the child
+   *       }
+   *     ),
    *     [](int pdf, int cfd){ return true; }  // Don't write to the child
    *   );
    *
@@ -683,6 +681,7 @@ class Subprocess {
         if (ret == -1 && errno == EAGAIN) {  // No more data for now
           return false;
         }
+        checkUnixError(ret, "read");
         if (ret == 0) {  // Reached end-of-file
           splitter.flush();  // Ignore return since the file is over anyway
           return true;
@@ -704,14 +703,14 @@ class Subprocess {
 
   // Helper to enable template deduction
   template <class Callback>
-  static ReadLinesCallback<Callback> readLinesCallback(
+  static auto readLinesCallback(
       Callback&& fdLineCb,
-      uint64_t maxLineLength = 0,  // No line length limit by default
+      uint64_t maxLineLength = 0, // No line length limit by default
       char delimiter = '\n',
-      uint64_t bufSize = 1024) {
-    return ReadLinesCallback<Callback>(
-      std::move(fdLineCb), maxLineLength, delimiter, bufSize
-    );
+      uint64_t bufSize = 1024)
+      -> ReadLinesCallback<typename std::decay<Callback>::type> {
+    return ReadLinesCallback<typename std::decay<Callback>::type>(
+        std::forward<Callback>(fdLineCb), maxLineLength, delimiter, bufSize);
   }
 
   /**
@@ -869,5 +868,3 @@ inline Subprocess::Options& Subprocess::Options::operator|=(
 }
 
 }  // namespace folly
-
-#endif /* FOLLY_SUBPROCESS_H_ */