nghttpx: Simplify move ctor and operator

src/allocator.h

@@ -32,6 +32,7 @@
 #endif // !_WIN32
 
 #include <cassert>
+#include <utility>
 
 #include "template.h"
 
@@ -65,25 +66,19 @@ struct BlockAllocator {
   ~BlockAllocator() { reset(); }
 
   BlockAllocator(BlockAllocator &&other) noexcept
-      : retain(other.retain),
-        head(other.head),
+      : retain{std::exchange(other.retain, nullptr)},
+        head{std::exchange(other.head, nullptr)},
         block_size(other.block_size),
-        isolation_threshold(other.isolation_threshold) {
-    other.retain = nullptr;
-    other.head = nullptr;
-  }
+        isolation_threshold(other.isolation_threshold) {}
 
   BlockAllocator &operator=(BlockAllocator &&other) noexcept {
     reset();
 
-    retain = other.retain;
-    head = other.head;
+    retain = std::exchange(other.retain, nullptr);
+    head = std::exchange(other.head, nullptr);
     block_size = other.block_size;
     isolation_threshold = other.isolation_threshold;
 
-    other.retain = nullptr;
-    other.head = nullptr;
-
     return *this;
   }
 

src/memchunk.h

@@ -44,6 +44,7 @@ struct iovec {
 #include <array>
 #include <algorithm>
 #include <string>
+#include <utility>
 
 #include "template.h"
 
@@ -111,11 +112,10 @@ template <typename Memchunk> struct Memchunks {
       : pool(pool), head(nullptr), tail(nullptr), len(0) {}
   Memchunks(const Memchunks &) = delete;
   Memchunks(Memchunks &&other) noexcept
-      : pool(other.pool), head(other.head), tail(other.tail), len(other.len) {
-    // keep other.pool
-    other.head = other.tail = nullptr;
-    other.len = 0;
-  }
+      : pool{other.pool}, // keep other.pool
+        head{std::exchange(other.head, nullptr)},
+        tail{std::exchange(other.tail, nullptr)},
+        len{std::exchange(other.len, 0)} {}
   Memchunks &operator=(const Memchunks &) = delete;
   Memchunks &operator=(Memchunks &&other) noexcept {
     if (this == &other) {
@@ -125,12 +125,9 @@ template <typename Memchunk> struct Memchunks {
     reset();
 
     pool = other.pool;
-    head = other.head;
-    tail = other.tail;
-    len = other.len;
-
-    other.head = other.tail = nullptr;
-    other.len = 0;
+    head = std::exchange(other.head, nullptr);
+    tail = std::exchange(other.tail, nullptr);
+    len = std::exchange(other.len, 0);
 
     return *this;
   }
@@ -335,14 +332,12 @@ template <typename Memchunk> struct PeekMemchunks {
         peeking(true) {}
   PeekMemchunks(const PeekMemchunks &) = delete;
   PeekMemchunks(PeekMemchunks &&other) noexcept
-      : memchunks(std::move(other.memchunks)),
-        cur(other.cur),
-        cur_pos(other.cur_pos),
-        cur_last(other.cur_last),
-        len(other.len),
-        peeking(other.peeking) {
-    other.reset();
-  }
+      : memchunks{std::move(other.memchunks)},
+        cur{std::exchange(other.cur, nullptr)},
+        cur_pos{std::exchange(other.cur_pos, nullptr)},
+        cur_last{std::exchange(other.cur_last, nullptr)},
+        len{std::exchange(other.len, 0)},
+        peeking{std::exchange(other.peeking, true)} {}
   PeekMemchunks &operator=(const PeekMemchunks &) = delete;
   PeekMemchunks &operator=(PeekMemchunks &&other) noexcept {
     if (this == &other) {
@@ -350,13 +345,11 @@ template <typename Memchunk> struct PeekMemchunks {
     }
 
     memchunks = std::move(other.memchunks);
-    cur = other.cur;
-    cur_pos = other.cur_pos;
-    cur_last = other.cur_last;
-    len = other.len;
-    peeking = other.peeking;
-
-    other.reset();
+    cur = std::exchange(other.cur, nullptr);
+    cur_pos = std::exchange(other.cur_pos, nullptr);
+    cur_last = std::exchange(other.cur_last, nullptr);
+    len = std::exchange(other.len, 0);
+    peeking = std::exchange(other.peeking, true);
 
     return *this;
   }

src/template.h

@@ -36,6 +36,7 @@
 #include <typeinfo>
 #include <algorithm>
 #include <ostream>
+#include <utility>
 
 namespace nghttp2 {
 
@@ -89,21 +90,17 @@ template <typename T> struct DList {
   DList &operator=(const DList &) = delete;
 
   DList(DList &&other) noexcept
-      : head(other.head), tail(other.tail), len(other.len) {
-    other.head = other.tail = nullptr;
-    other.len = 0;
-  }
+      : head{std::exchange(other.head, nullptr)},
+        tail{std::exchange(other.tail, nullptr)},
+        len{std::exchange(other.len, 0)} {}
 
   DList &operator=(DList &&other) noexcept {
     if (this == &other) {
       return *this;
     }
-    head = other.head;
-    tail = other.tail;
-    len = other.len;
-
-    other.head = other.tail = nullptr;
-    other.len = 0;
+    head = std::exchange(other.head, nullptr);
+    tail = std::exchange(other.tail, nullptr);
+    len = std::exchange(other.len, 0);
 
     return *this;
   }
@@ -250,10 +247,7 @@ public:
   ImmutableString(const ImmutableString &other)
       : len(other.len), base(copystr(std::begin(other), std::end(other))) {}
   ImmutableString(ImmutableString &&other) noexcept
-      : len(other.len), base(other.base) {
-    other.len = 0;
-    other.base = "";
-  }
+      : len{std::exchange(other.len, 0)}, base{std::exchange(other.base, "")} {}
   ~ImmutableString() {
     if (len) {
       delete[] base;
@@ -278,10 +272,8 @@ public:
     if (len) {
       delete[] base;
     }
-    len = other.len;
-    base = other.base;
-    other.len = 0;
-    other.base = "";
+    len = std::exchange(other.len, 0);
+    base = std::exchange(other.base, "");
     return *this;
   }