cmUVStreambuf: Add std::streambuf implementation for uv_stream_t

This will allow std::istream/std::ostream-based interaction with
processes spawned by libuv.

1 files changed, 219 insertions, 0 deletions

diff --git a/Source/cmUVStreambuf.h b/Source/cmUVStreambuf.h
new file mode 100644
index 0000000..29e4fde
--- /dev/null
+++ b/Source/cmUVStreambuf.h
@@ -0,0 +1,219 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#ifndef cmUVStreambuf_h
+#define cmUVStreambuf_h
+
+#include "cmUVHandlePtr.h"
+
+#include "cm_uv.h"
+
+#include <algorithm>
+#include <cstring>
+#include <streambuf>
+#include <vector>
+
+/*
+ * This file is based on example code from:
+ *
+ * http://www.voidcn.com/article/p-vjnlygmc-gy.html
+ *
+ * The example code was distributed under the following license:
+ *
+ * Copyright 2007 Edd Dawson.
+ * Distributed under the Boost Software License, Version 1.0.
+ *
+ * Boost Software License - Version 1.0 - August 17th, 2003
+ *
+ * Permission is hereby granted, free of charge, to any person or organization
+ * obtaining a copy of the software and accompanying documentation covered by
+ * this license (the "Software") to use, reproduce, display, distribute,
+ * execute, and transmit the Software, and to prepare derivative works of the
+ * Software, and to permit third-parties to whom the Software is furnished to
+ * do so, all subject to the following:
+ *
+ * The copyright notices in the Software and this entire statement, including
+ * the above license grant, this restriction and the following disclaimer,
+ * must be included in all copies of the Software, in whole or in part, and
+ * all derivative works of the Software, unless such copies or derivative
+ * works are solely in the form of machine-executable object code generated by
+ * a source language processor.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+ * SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+ * FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+template <typename CharT, typename Traits = std::char_traits<CharT>>
+class cmBasicUVStreambuf : public std::basic_streambuf<CharT, Traits>
+{
+public:
+  cmBasicUVStreambuf(std::size_t bufSize = 256, std::size_t putBack = 8);
+  ~cmBasicUVStreambuf() override;
+
+  bool is_open() const;
+
+  cmBasicUVStreambuf* open(uv_stream_t* stream);
+
+  cmBasicUVStreambuf* close();
+
+protected:
+  typename cmBasicUVStreambuf::int_type underflow() override;
+  std::streamsize showmanyc() override;
+
+  // FIXME: Add write support
+
+private:
+  uv_stream_t* Stream = nullptr;
+  void* OldStreamData;
+  const std::size_t PutBack;
+  std::vector<CharT> InputBuffer;
+  bool EndOfFile;
+
+  void StreamReadStartStop();
+
+  void StreamRead(ssize_t nread);
+  void HandleAlloc(uv_buf_t* buf);
+};
+
+template <typename CharT, typename Traits>
+cmBasicUVStreambuf<CharT, Traits>::cmBasicUVStreambuf(std::size_t bufSize,
+                                                      std::size_t putBack)
+  : PutBack(std::max<std::size_t>(putBack, 1))
+  , InputBuffer(std::max<std::size_t>(this->PutBack, bufSize) + this->PutBack)
+{
+  this->close();
+}
+
+template <typename CharT, typename Traits>
+cmBasicUVStreambuf<CharT, Traits>::~cmBasicUVStreambuf()
+{
+  this->close();
+}
+
+template <typename CharT, typename Traits>
+bool cmBasicUVStreambuf<CharT, Traits>::is_open() const
+{
+  return this->Stream != nullptr;
+}
+
+template <typename CharT, typename Traits>
+cmBasicUVStreambuf<CharT, Traits>* cmBasicUVStreambuf<CharT, Traits>::open(
+  uv_stream_t* stream)
+{
+  this->close();
+  this->Stream = stream;
+  this->EndOfFile = false;
+  if (this->Stream) {
+    this->OldStreamData = this->Stream->data;
+    this->Stream->data = this;
+  }
+  this->StreamReadStartStop();
+  return this;
+}
+
+template <typename CharT, typename Traits>
+cmBasicUVStreambuf<CharT, Traits>* cmBasicUVStreambuf<CharT, Traits>::close()
+{
+  if (this->Stream) {
+    uv_read_stop(this->Stream);
+    this->Stream->data = this->OldStreamData;
+  }
+  this->Stream = nullptr;
+  CharT* readEnd = this->InputBuffer.data() + this->InputBuffer.size();
+  this->setg(readEnd, readEnd, readEnd);
+  return this;
+}
+
+template <typename CharT, typename Traits>
+typename cmBasicUVStreambuf<CharT, Traits>::int_type
+cmBasicUVStreambuf<CharT, Traits>::underflow()
+{
+  if (!this->is_open()) {
+    return Traits::eof();
+  }
+
+  if (this->gptr() < this->egptr()) {
+    return Traits::to_int_type(*this->gptr());
+  }
+
+  this->StreamReadStartStop();
+  while (this->in_avail() == 0) {
+    uv_run(this->Stream->loop, UV_RUN_ONCE);
+  }
+  if (this->in_avail() == -1) {
+    return Traits::eof();
+  }
+  return Traits::to_int_type(*this->gptr());
+}
+
+template <typename CharT, typename Traits>
+std::streamsize cmBasicUVStreambuf<CharT, Traits>::showmanyc()
+{
+  if (!this->is_open() || this->EndOfFile) {
+    return -1;
+  }
+  return 0;
+}
+
+template <typename CharT, typename Traits>
+void cmBasicUVStreambuf<CharT, Traits>::StreamReadStartStop()
+{
+  if (this->Stream) {
+    uv_read_stop(this->Stream);
+    if (this->gptr() >= this->egptr()) {
+      uv_read_start(
+        this->Stream,
+        [](uv_handle_t* handle, size_t /* unused */, uv_buf_t* buf) {
+          auto streambuf =
+            static_cast<cmBasicUVStreambuf<CharT, Traits>*>(handle->data);
+          streambuf->HandleAlloc(buf);
+        },
+        [](uv_stream_t* stream2, ssize_t nread, const uv_buf_t* /* unused */) {
+          auto streambuf =
+            static_cast<cmBasicUVStreambuf<CharT, Traits>*>(stream2->data);
+          streambuf->StreamRead(nread);
+        });
+    }
+  }
+}
+
+template <typename CharT, typename Traits>
+void cmBasicUVStreambuf<CharT, Traits>::HandleAlloc(uv_buf_t* buf)
+{
+  auto size = this->egptr() - this->gptr();
+  std::memmove(this->InputBuffer.data(), this->gptr(),
+               this->egptr() - this->gptr());
+  this->setg(this->InputBuffer.data(), this->InputBuffer.data(),
+             this->InputBuffer.data() + size);
+  buf->base = this->egptr();
+#ifdef _WIN32
+#  define BUF_LEN_TYPE ULONG
+#else
+#  define BUF_LEN_TYPE size_t
+#endif
+  buf->len = BUF_LEN_TYPE(
+    (this->InputBuffer.data() + this->InputBuffer.size() - this->egptr()) *
+    sizeof(CharT));
+#undef BUF_LEN_TYPE
+}
+
+template <typename CharT, typename Traits>
+void cmBasicUVStreambuf<CharT, Traits>::StreamRead(ssize_t nread)
+{
+  if (nread > 0) {
+    this->setg(this->eback(), this->gptr(),
+               this->egptr() + nread / sizeof(CharT));
+    uv_read_stop(this->Stream);
+  } else if (nread < 0 || nread == UV_EOF) {
+    this->EndOfFile = true;
+    uv_read_stop(this->Stream);
+  }
+}
+
+using cmUVStreambuf = cmBasicUVStreambuf<char>;
+
+#endif