From c5e4811efcdb7f8b40b62acc60676b1187177565 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Fri, 18 Mar 2022 12:18:22 +1000
Subject: [PATCH] cmdopt2/parser: add `usage` overload for FILE*

---
 cmdopt2/parser.cpp | 44 +++++++++++++++++++++++++++++++++-----------
 cmdopt2/parser.hpp |  1 +
 2 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/cmdopt2/parser.cpp b/cmdopt2/parser.cpp
index b1ac372c..39aedf39 100644
--- a/cmdopt2/parser.cpp
+++ b/cmdopt2/parser.cpp
@@ -184,29 +184,51 @@ parser::parse (int const argc, const char *const *argv)
 
 
 ///////////////////////////////////////////////////////////////////////////////
-void
-parser::usage (int argc, char const * const* argv, std::ostream &os) const
-{
-    os << "Usage:";
+template <typename OutputT>
+static void
+usage (
+    int argc,
+    char const * const* argv,
+    std::vector<cruft::cmdopt2::positional> const &positional,
+    std::vector<cruft::cmdopt2::keyword> const &keyword,
+    OutputT &output
+) {
+    fmt::print (output, "Usage:");
     if (argc > 0)
-        os << ' ' << argv[0];
+        fmt::print (output, " {}", argv[0]);
 
     static char constexpr OPTIONAL[2] { '[', ']' };
     static char constexpr REQUIRED[2] { '<', '>' };
 
-    for (auto const &arg: m_keyword) {
+    for (auto const &arg: keyword) {
         auto const &delimiters = arg.required ? REQUIRED : OPTIONAL;
 
         if (arg.short_)
-            os << ' ' << delimiters[0] << '-'  << *arg.short_ << delimiters[1];
+            fmt::print (output, " {}-{}{}", delimiters[0], '-', *arg.short_, delimiters[1]);
         if (arg.long_)
-            os << ' ' << delimiters[0] << "--" << *arg.long_  << delimiters[1];
+            fmt::print (output, " {}--{}{}", delimiters[0], "--", *arg.long_, delimiters[1]);
     }
 
-    for (auto const &arg: m_positional) {
+    for (auto const &arg: positional) {
         auto const &delimiters = arg.required ? REQUIRED : OPTIONAL;
-        os << ' ' << delimiters[0] << arg.name << delimiters[1];
+        fmt::print (output, " {}{}{}", delimiters[0], arg.name, delimiters[1]);
     }
 
-    os << '\n';
+    fmt::print (output, "\n");
+}
+
+
+//-----------------------------------------------------------------------------
+void
+parser::usage (int argc, char const * const* argv, std::ostream &os) const
+{
+    ::usage (argc, argv, m_positional, m_keyword, os);
+}
+
+
+//-----------------------------------------------------------------------------
+void
+parser::usage (int argc, char const * const* argv, FILE *fp) const
+{
+    ::usage (argc, argv, m_positional, m_keyword, fp);
 }
diff --git a/cmdopt2/parser.hpp b/cmdopt2/parser.hpp
index 87ac2090..333b1d10 100644
--- a/cmdopt2/parser.hpp
+++ b/cmdopt2/parser.hpp
@@ -22,6 +22,7 @@ namespace cruft::cmdopt2 {
         positional& add (positional const&) &;
         keyword& add (keyword const&) &;
 
+        void usage (int argc, char const * const* argv, FILE*) const;
         void usage (int argc, char const * const* argv, std::ostream&) const;
 
     private: