format: add trivial printf wrapper

Makefile.am

@@ -51,6 +51,9 @@ UTIL_FILES   =			\
     fixed.hpp			\
     float.cpp			\
     float.hpp			\
+    format.cpp			\
+    format.hpp			\
+    format.ipp			\
     fourcc.cpp			\
     fourcc.hpp			\
     guid.cpp			\
@@ -315,6 +318,7 @@ TEST_BIN = 			\
     test/extent			\
     test/fixed			\
     test/float			\
+    test/format			\
     test/hash/murmur		\
     test/hash/fasthash          \
     test/hmac			\

format.cpp

@@ -0,0 +1,26 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "format.hpp"
+
+#include <utility>
+
+
+//std::string
+//util::format (std::string &&fmt)
+//{
+//    return std::move (fmt);
+//}

format.hpp

@@ -0,0 +1,47 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_FORMAT_HPP
+#define __UTIL_FORMAT_HPP
+
+#include <stdexcept>
+#include <string>
+
+namespace util {
+    namespace format {
+        template <typename ...Args>
+        std::string render (const std::string &fmt, Args&&...);
+
+        class error : public std::runtime_error
+        { using runtime_error::runtime_error; };
+
+        // value-specifier mismatch
+        class value_error : public error
+        { using error::error; };
+
+        // malformed format specifier
+        class format_error : public error
+        { using error::error; };
+
+        // missing format specifier
+        class missing_error : public error
+        { using error::error; };
+    }
+}
+
+#include "format.ipp"
+
+#endif

format.ipp

@@ -0,0 +1,94 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#if defined(__UTIL_FORMAT_IPP)
+#error
+#endif
+#define __UTIL_FORMAT_IPP
+
+#include "debug.hpp"
+
+#include <algorithm>
+#include <sstream>
+#include <stdexcept>
+#include <iterator>
+
+namespace util {
+    namespace detail { namespace format {
+        template <typename InputIt>
+        void
+        render (InputIt first,
+                InputIt last,
+                std::ostringstream &dest)
+        {
+            static const char DELIMITER = '%';
+            if (std::find (first, last, DELIMITER) != last)
+                throw util::format::missing_error ("format specifier without value");
+
+            std::copy (first, last, std::ostream_iterator<char> (dest));
+        }
+
+
+        template <typename InputIt,
+                  typename ValueT,
+                  typename ...Args>
+        void
+        render (InputIt first,
+                InputIt last,
+                std::ostringstream &dest,
+                const ValueT& val,
+                Args&& ...args)
+        {
+            CHECK (first <= last);
+
+            static const char DELIMITER = '%';
+            auto cursor = std::find (first, last, DELIMITER);
+            std::copy (first, cursor, std::ostream_iterator<char> (dest));
+
+            if (cursor == last)
+                return;
+
+            auto spec = cursor + 1;
+            if (spec == last)
+                throw util::format::format_error ("missing format specifier");
+
+            if (*spec != 's')
+                throw util::format::format_error ("unhandled format specifier");
+
+            dest << val;
+
+            render (spec + 1, last, dest, std::forward<Args> (args)...);
+        }
+    } }
+
+    namespace format {
+        template <typename ...Args>
+        std::string
+        render (const std::string &fmt, Args&&... args)
+        {
+            std::ostringstream out;
+
+            util::detail::format::render (
+                fmt.begin (),
+                fmt.end (),
+                out,
+                std::forward<Args> (args)...
+            );
+
+            return out.str ();
+        }
+    }
+}

test/format.cpp

@@ -0,0 +1,20 @@
+#include "format.hpp"
+
+#include "tap.hpp"
+
+int
+main (void)
+{
+    using namespace std::string_literals;
+
+    util::TAP::logger tap;
+
+    tap.expect_eq (util::format::render ("identity"), "identity"s, "identity literal");
+    tap.expect_eq (util::format::render ("%s", "identity"s), "identity"s, "identity substitution");
+
+    tap.expect_throw<util::format::missing_error> ([] (void) { util::format::render ("%s"); });
+    tap.expect_throw<util::format::format_error>  ([] (void) { util::format::render ("%!", 42); });
+    tap.expect_throw<util::format::format_error>  ([] (void) { util::format::render ("%", 42); });
+
+    return tap.status ();
+}