From 7558c08e7dfb3d15be1bfa9a627373d20dcf2e51 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Sun, 6 Dec 2020 08:42:01 +1000
Subject: [PATCH] analyse: provide defaults for bits, window, and minimum

---
 tools/analyse.cpp | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/tools/analyse.cpp b/tools/analyse.cpp
index 9eb3cbf..98a3140 100644
--- a/tools/analyse.cpp
+++ b/tools/analyse.cpp
@@ -56,27 +56,44 @@ static bool region_equal (emory::chunk::region const &a, emory::chunk::region co
 ///////////////////////////////////////////////////////////////////////////////
 enum {
     ARG_SELF,
+
+    ARGS_INPUT,
+    ARGS_OUTPUT,
+
     ARG_BITS,
     ARG_WINDOW,
-    ARGS_MINIMUM,
-    ARGS_INPUT,
+    ARG_MINIMUM,
 
     NUM_ARGS,
+    NUM_ARGS_REQUIRED = 3,
 };
 
 
+static constexpr std::size_t DEFAULT_BITS    =  12;
+static constexpr std::size_t DEFAULT_WINDOW  =   4;
+static constexpr std::ptrdiff_t DEFAULT_MINIMUM = 512;
+
+
 //-----------------------------------------------------------------------------
 int main (int argc, char const **argv)
 {
-    if (argc != NUM_ARGS) {
-        std::cerr << "usage: " << argv[ARG_SELF] << " <bits> <window> <minimum> <input>\n";
+    if (argc < NUM_ARGS_REQUIRED) {
+        std::cerr << "usage: " << argv[ARG_SELF] << " <input> <output> [bits] [window] [minimum]\n"
+                  << "default bits = "    << DEFAULT_BITS    << '\n'
+                  << "default window = "  << DEFAULT_WINDOW  << '\n'
+                  << "default minimum = " << DEFAULT_MINIMUM << '\n';
         return EXIT_FAILURE;
     }
 
+    #define PARSE_DEFAULT(NAME, TYPE)                           \
+    argc > ARG_##NAME                                           \
+        ? cruft::parse::from_string<TYPE> (argv[ARG_##NAME])    \
+        : DEFAULT_##NAME
+
     emory::chunk::params const p {
-        .bits    = cruft::parse::from_string<std::size_t> (argv[ARG_BITS  ]),
-        .window  = cruft::parse::from_string<std::size_t> (argv[ARG_WINDOW]),
-        .minimum = cruft::parse::from_string<std::ptrdiff_t> (argv[ARGS_MINIMUM]),
+        .bits    = PARSE_DEFAULT (BITS, std::size_t),
+        .window  = PARSE_DEFAULT (WINDOW, std::size_t),
+        .minimum = PARSE_DEFAULT (MINIMUM, std::ptrdiff_t),
     };
 
     cruft::mapped_file data (argv[ARGS_INPUT]);