Added argagg::fmt_string()

4 files changed, 125 insertions, 2 deletions

diff --git a/CHANGELOG b/CHANGELOG
index bde08f8..a7ab035 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,8 @@
+0.4.3
+-----
+
+- Added argagg::fmt_string() to format a string using the fmt program
+
 0.4.2
 -----
 
diff --git a/examples/joinargs.cpp b/examples/joinargs.cpp
index c45a693..4e74575 100644
--- a/examples/joinargs.cpp
+++ b/examples/joinargs.cpp
@@ -46,6 +46,15 @@ int main(
         "verbose", {"-v", "--verbose"},
         "increases verbosity", 0},
       {
+        "lorem-ipsum", {"--lorem-ipsum"},
+        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do "
+        "eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim "
+        "ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut "
+        "aliquip ex ea commodo consequat. Duis aute irure dolor in "
+        "reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla "
+        "pariatur. Excepteur sint occaecat cupidatat non proident, sunt in "
+        "culpa qui officia deserunt mollit anim id est laborum.", 0},
+      {
         "sep", {"-s", "--sep"},
         "separator (default ',')", 1},
       {
@@ -67,16 +76,20 @@ int main(
   try {
     args = argparser.parse(argc, argv);
   } catch (const std::exception& e) {
-    cerr << usage.str() << argparser << endl
+    ostringstream help;
+    help << usage.str() << argparser << endl
          << "Encountered exception while parsing arguments: " << e.what()
          << endl;
+    cerr << argagg::fmt_string(help.str()) << endl;;
     return EXIT_FAILURE;
   }
 
   // If the help flag was specified then spit out the usage and help text and
   // exit.
   if (args["help"]) {
-    cerr << usage.str() << argparser;
+    ostringstream help;
+    help << usage.str() << argparser;
+    cerr << argagg::fmt_string(help.str()) << endl;;
     return EXIT_SUCCESS;
   }
 
diff --git a/include/argagg/argagg.hpp b/include/argagg/argagg.hpp
index 083730a..18b0b33 100644
--- a/include/argagg/argagg.hpp
+++ b/include/argagg/argagg.hpp
@@ -31,6 +31,11 @@
 #ifndef ARGAGG_ARGAGG_ARGAGG_HPP
 #define ARGAGG_ARGAGG_ARGAGG_HPP
 
+#ifdef __unix__
+#include <stdio.h>
+#include <unistd.h>
+#endif
+
 #include <algorithm>
 #include <array>
 #include <cstdlib>
@@ -587,6 +592,26 @@ struct parser {
 };
 
 
+#ifdef __unix__
+
+
+/**
+ * @brief
+ * Processes the provided string using the fmt util and returns the resulting
+ * output as a string. Not the most efficient (in time or space) but gets the
+ * job done.
+ *
+ * @note
+ * This is only defined if the <tt>__unix__</tt> preprocessor definition
+ * exists since it relies on the POSIX API for forking, executing a process,
+ * and reading/writing to/from file descriptors.
+ */
+std::string fmt_string(const std::string& s);
+
+
+#endif
+
+
 } // namespace argagg
 
 
@@ -1392,6 +1417,61 @@ namespace convert {
 }
 
 
+#ifdef __unix__
+
+inline
+std::string fmt_string(const std::string& s)
+{
+  constexpr int read_end = 0;
+  constexpr int write_end = 1;
+
+  // TODO (vnguyen): This function overall needs to handle possible error
+  // returns from the various syscalls.
+
+  int read_pipe[2];
+  int write_pipe[2];
+  pipe(read_pipe);
+  pipe(write_pipe);
+
+  auto parent_pid = fork();
+  bool is_fmt_proc = (parent_pid == 0);
+  if (is_fmt_proc) {
+    dup2(write_pipe[read_end], STDIN_FILENO);
+    dup2(read_pipe[write_end], STDOUT_FILENO);
+    close(write_pipe[read_end]);
+    close(write_pipe[write_end]);
+    close(read_pipe[read_end]);
+    close(read_pipe[write_end]);
+    const char* argv[] = {"fmt", NULL};
+    execvp(const_cast<char*>(argv[0]), const_cast<char**>(argv));
+  }
+
+  close(write_pipe[read_end]);
+  close(read_pipe[write_end]);
+  auto fmt_write_fd = write_pipe[write_end];
+  write(fmt_write_fd, s.c_str(), s.length());
+  close(fmt_write_fd);
+
+  auto fmt_read_fd = read_pipe[read_end];
+  std::ostringstream os;
+  char buf[64];
+  while (true) {
+    auto read_count = read(
+      fmt_read_fd, reinterpret_cast<void*>(buf), sizeof(buf));
+    if (read_count <= 0) {
+      break;
+    }
+    os.write(buf, static_cast<std::streamsize>(read_count));
+  }
+  close(fmt_read_fd);
+
+  return os.str();
+}
+
+
+#endif
+
+
 } // namespace argagg
 
 
diff --git a/test/test.cpp b/test/test.cpp
index cff7ba9..c9bfd4e 100644
--- a/test/test.cpp
+++ b/test/test.cpp
@@ -927,3 +927,28 @@ TEST_CASE("write options help")
   // Just checking for no exceptions for now.
   std::cout << parser;
 }
+
+
+#ifdef __unix__
+TEST_CASE("fmt_string")
+{
+  std::string test(
+    "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod "
+    "tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim "
+    "veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
+    "commodo consequat. Duis aute irure dolor in reprehenderit in voluptate "
+    "velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint "
+    "occaecat cupidatat non proident, sunt in culpa qui officia deserunt "
+    "mollit anim id est laborum.");
+  std::string test_formatted = argagg::fmt_string(test);
+  std::string expected_output(
+    "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod\n"
+    "tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim\n"
+    "veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea\n"
+    "commodo consequat. Duis aute irure dolor in reprehenderit in voluptate\n"
+    "velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat\n"
+    "cupidatat non proident, sunt in culpa qui officia deserunt mollit anim\n"
+    "id est laborum.\n");
+  CHECK(test_formatted == expected_output);
+}
+#endif