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diff --git a/butl/curl b/butl/curl
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+// file      : butl/curl -*- C++ -*-
+// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUTL_CURL
+#define BUTL_CURL
+
+#include <string>
+#include <type_traits>
+
+#include <butl/export>
+
+#include <butl/process>
+#include <butl/fdstream>
+#include <butl/small-vector>
+
+namespace butl
+{
+  // Perform a method (GET, POST, PUT) on a URL using the curl(1) program.
+  // Throw process_error and io_error (both derive from system_error) in case
+  // of errors.
+  //
+  // The I (in) and O (out) can be of the following types/values:
+  //
+  // nullfd   Signal that no input/output is expected.
+  //
+  // path     Read input/write output from/to a file. If the special "-"
+  //          value is used, then instead input is connected to the curl::out
+  //          ofdstream member and output -- to the curl::in ifdstream member.
+  //          Note that the argument type should be path, not string (i.e.,
+  //          pass path("-")).
+  //
+  // other    Forwarded as is to process_start(). Normally either int or
+  //          auto_fd.
+  //
+  // For example:
+  //
+  //   curl (nullfd,     // No input expected for GET.
+  //         path ("-"), // Write response to curl::in.
+  //         2,
+  //         curl::get,
+  //         "http://example.org");
+  //
+  //   curl (path ("-"),         // Read request from curl::out.
+  //         path::temp_path (), // Write result to a file.
+  //         2,
+  //         curl::post,
+  //         "http://example.org");
+  //
+  //   curl (nullfd,
+  //         fdnull (), // Write result to /dev/null.
+  //         2,
+  //         curl::get,
+  //         "tftp://localhost/foo");
+  //
+  // Typical usage:
+  //
+  // try
+  // {
+  //   curl c (nullfd,                 // No input expected.
+  //           path ("-"),             // Output to curl::in.
+  //           2,                      // Diagnostics to stderr.
+  //           curl::get,              // GET method.
+  //           "https://example.org",
+  //           "-A", "foobot/1.2.3");  // Additional curl(1) options.
+  //
+  //   for (string s; getline (c.in, s); )
+  //     cout << s << endl;
+  //
+  //   c.in.close ();
+  //
+  //   if (!c.wait ())
+  //     ... // curl returned non-zero status.
+  // }
+  // catch (const std::system_error& e)
+  // {
+  //   cerr << "curl error: " << e << endl;
+  // }
+  //
+  // Notes:
+  //
+  // 1. If opened, in/out streams are in the binary mode.
+  //
+  // 2. If opened, in/out must be explicitly closed before calling wait().
+  //
+  // 3. Only binary data HTTP POST is currently supported (the --data-binary
+  //    curl option).
+  //
+  class LIBBUTL_EXPORT curl: public process
+  {
+  public:
+    enum method_type {get, put, post};
+
+    ifdstream in;
+    ofdstream out;
+
+    template <typename I,
+              typename O,
+              typename E,
+              typename... A>
+    curl (I&& in,
+          O&& out,
+          E&& err,
+          method_type,
+          const std::string& url,
+          A&&... options);
+
+    // Version with the command line callback (see process_run() for details).
+    //
+    template <typename C,
+              typename I,
+              typename O,
+              typename E,
+              typename... A>
+    curl (const C&,
+          I&& in,
+          O&& out,
+          E&& err,
+          method_type,
+          const std::string& url,
+          A&&... options);
+
+  private:
+    enum method_proto {ftp_get, ftp_put, http_get, http_post};
+    using method_proto_options = small_vector<const char*, 2>;
+
+    method_proto
+    translate (method_type, const std::string& url, method_proto_options&);
+
+  private:
+    template <typename T>
+    struct is_other
+    {
+      using type = typename std::remove_reference<
+        typename std::remove_cv<T>::type>::type;
+
+      static const bool value = !(std::is_same<type, nullfd_t>::value ||
+                                  std::is_same<type, path>::value);
+    };
+
+    struct io_data
+    {
+      fdpipe pipe;
+      method_proto_options options;
+      std::string storage;
+    };
+
+    int
+    map_in (nullfd_t, method_proto, io_data&);
+
+    int
+    map_in (const path&, method_proto, io_data&);
+
+    template <typename I>
+    typename std::enable_if<is_other<I>::value, I>::type
+    map_in (I&&, method_proto, io_data&);
+
+    int
+    map_out (nullfd_t, method_proto, io_data&);
+
+    int
+    map_out (const path&, method_proto, io_data&);
+
+    template <typename O>
+    typename std::enable_if<is_other<O>::value, O>::type
+    map_out (O&&, method_proto, io_data&);
+  };
+}
+
+#include <butl/curl.ixx>
+#include <butl/curl.txx>
+
+#endif // BUTL_CURL