string: add tests for character_position

string.hpp

@@ -149,6 +149,12 @@ namespace cruft {
 
     ///////////////////////////////////////////////////////////////////////////
     /// Calculate the line and column of an iterator within a view.
+    ///
+    /// Returns an anonymous struct containing the line and column number.
+    ///
+    /// The column number for newline is undefined. However it should never
+    /// return the value {0,-1} and so it should not result in underruns when
+    /// offsetting a pointer using the column index.
     template <typename IteratorT>
     auto
     character_position (

test/string.cpp

@@ -6,6 +6,39 @@
 #include <vector>
 
 
+///////////////////////////////////////////////////////////////////////////////
+void
+test_position (cruft::TAP::logger &tap)
+{
+    char const *string = "a\nb\nc\n";
+
+    struct {
+        int offset;
+
+        int line;
+        int column;
+    } TESTS[] = {
+        { 0, 0,  0 },
+        { 1, 1, -1 },
+        { 2, 1,  0 },
+        { 3, 2, -1 },
+        { 4, 2,  0 },
+        { 5, 3, -1 },
+    };
+
+    for (auto const &t: TESTS) {
+        auto const pos = cruft::character_position ({string, strlen(string) }, string + t.offset);
+
+        tap.expect (
+            pos.line == t.line && pos.column == t.column,
+            "character_position %!:%!",
+            t.line,
+            t.column
+        );
+    }
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 void
 test_tokeniser (cruft::TAP::logger &tap)
@@ -43,6 +76,7 @@ main (int, char**)
     cruft::TAP::logger tap;
 
     test_tokeniser (tap);
+    test_position (tap);
 
     return tap.status ();
 }