Various noexcept specifiers in IOBuf

Summary: [Folly] Various `noexcept` specifiers in `IOBuf`.

Reviewed By: Orvid

Differential Revision: D10081705

fbshipit-source-id: 5516e7deca4edd50ea99e61e10cd413f3c0f17ae

folly/io/IOBuf.cpp

@@ -335,7 +335,7 @@ unique_ptr<IOBuf> IOBuf::takeOwnership(
   }
 }
 
-IOBuf::IOBuf(WrapBufferOp, const void* buf, std::size_t capacity)
+IOBuf::IOBuf(WrapBufferOp, const void* buf, std::size_t capacity) noexcept
     : IOBuf(
           InternalConstructor(),
           0,
@@ -347,13 +347,14 @@ IOBuf::IOBuf(WrapBufferOp, const void* buf, std::size_t capacity)
           static_cast<uint8_t*>(const_cast<void*>(buf)),
           capacity) {}
 
-IOBuf::IOBuf(WrapBufferOp op, ByteRange br) : IOBuf(op, br.data(), br.size()) {}
+IOBuf::IOBuf(WrapBufferOp op, ByteRange br) noexcept
+    : IOBuf(op, br.data(), br.size()) {}
 
 unique_ptr<IOBuf> IOBuf::wrapBuffer(const void* buf, std::size_t capacity) {
   return std::make_unique<IOBuf>(WRAP_BUFFER, buf, capacity);
 }
 
-IOBuf IOBuf::wrapBufferAsValue(const void* buf, std::size_t capacity) {
+IOBuf IOBuf::wrapBufferAsValue(const void* buf, std::size_t capacity) noexcept {
   return IOBuf(WrapBufferOp::WRAP_BUFFER, buf, capacity);
 }
 
@@ -399,7 +400,7 @@ IOBuf::IOBuf(
     uint8_t* buf,
     std::size_t capacity,
     uint8_t* data,
-    std::size_t length)
+    std::size_t length) noexcept
     : next_(this),
       prev_(this),
       data_(data),
@@ -1048,7 +1049,7 @@ size_t IOBuf::fillIov(struct iovec* iov, size_t len) const {
   return 0;
 }
 
-size_t IOBufHash::operator()(const IOBuf& buf) const {
+size_t IOBufHash::operator()(const IOBuf& buf) const noexcept {
   folly::hash::SpookyHashV2 hasher;
   hasher.Init(0, 0);
   io::Cursor cursor(&buf);
@@ -1066,7 +1067,7 @@ size_t IOBufHash::operator()(const IOBuf& buf) const {
   return static_cast<std::size_t>(h1);
 }
 
-ordering IOBufCompare::impl(const IOBuf& a, const IOBuf& b) const {
+ordering IOBufCompare::impl(const IOBuf& a, const IOBuf& b) const noexcept {
   io::Cursor ca(&a);
   io::Cursor cb(&b);
   for (;;) {
@@ -1081,6 +1082,7 @@ ordering IOBufCompare::impl(const IOBuf& a, const IOBuf& b) const {
     if (r != ordering::eq) {
       return r;
     }
+    // Cursor::skip() may throw if n is too large, but n is not too large here
     ca.skip(n);
     cb.skip(n);
   }

folly/io/IOBuf.h

@@ -392,13 +392,15 @@ class IOBuf {
    * Similar to wrapBuffer(), but returns IOBuf by value rather than
    * heap-allocating it.
    */
-  static IOBuf wrapBufferAsValue(const void* buf, std::size_t capacity);
-  static IOBuf wrapBufferAsValue(ByteRange br) {
+  static IOBuf wrapBufferAsValue(
+      const void* buf,
+      std::size_t capacity) noexcept;
+  static IOBuf wrapBufferAsValue(ByteRange br) noexcept {
     return wrapBufferAsValue(br.data(), br.size());
   }
 
-  IOBuf(WrapBufferOp op, const void* buf, std::size_t capacity);
-  IOBuf(WrapBufferOp op, ByteRange br);
+  IOBuf(WrapBufferOp op, const void* buf, std::size_t capacity) noexcept;
+  IOBuf(WrapBufferOp op, ByteRange br) noexcept;
 
   /**
    * Convenience function to create a new IOBuf object that copies data from a
@@ -1329,7 +1331,7 @@ class IOBuf {
       uint8_t* buf,
       std::size_t capacity,
       uint8_t* data,
-      std::size_t length);
+      std::size_t length) noexcept;
 
   void unshareOneSlow();
   void unshareChained();
@@ -1463,8 +1465,8 @@ class IOBuf {
  * Hasher for IOBuf objects. Hashes the entire chain using SpookyHashV2.
  */
 struct IOBufHash {
-  size_t operator()(const IOBuf& buf) const;
-  size_t operator()(const std::unique_ptr<IOBuf>& buf) const {
+  size_t operator()(const IOBuf& buf) const noexcept;
+  size_t operator()(const std::unique_ptr<IOBuf>& buf) const noexcept {
     return buf ? (*this)(*buf) : 0;
   }
 };
@@ -1489,7 +1491,7 @@ struct IOBufCompare {
   }
 
  private:
-  ordering impl(IOBuf const& a, IOBuf const& b) const;
+  ordering impl(IOBuf const& a, IOBuf const& b) const noexcept;
 };
 
 /**