Add support for hex notation for uint64 type

Specifically, now we can do:

x = [uint64] 0x0000ffff

cxx.poptions += "-DOFFSET=$x"                 # -DOFFSET=65535
cxx.poptions += "-DOFFSET=$string($x, 16)"    # -DOFFSET=0xffff
cxx.poptions += "-DOFFSET=$string($x, 16, 8)" # -DOFFSET=0x0000ffff

Note that there is no hex notation support for the int64 (signed) type.

4 files changed, 93 insertions, 13 deletions

diff --git a/libbuild2/functions-builtin.cxx b/libbuild2/functions-builtin.cxx
index 93f2d0f..5129a05 100644
--- a/libbuild2/functions-builtin.cxx
+++ b/libbuild2/functions-builtin.cxx
@@ -32,6 +32,56 @@ namespace build2
     return r;
   };
 
+  static const char hex_digits[] = "0123456789abcdef";
+
+  static string
+  to_string (uint64_t i, optional<value> base, optional<value> width)
+  {
+    uint64_t b (base ? convert<uint64_t> (move (*base)) : 10);
+    size_t w (width
+              ? static_cast<size_t> (convert<uint64_t> (move (*width)))
+              : 0);
+
+    // One day we can switch to C++17 std::to_chars().
+    //
+    string r;
+    switch (b)
+    {
+    case 10:
+      {
+        r = to_string (i);
+        if (w > r.size ())
+          r.insert (0, w - r.size (), '0');
+        break;
+      }
+    case 16:
+      {
+        r.reserve (18);
+        r += "0x";
+
+        for (size_t j (64); j != 0; )
+        {
+          j -= 4;
+          size_t d ((i >> j) & 0x0f);
+
+          // Omit leading zeros but watch out for the i==0 corner case.
+          //
+          if (d != 0 || r.size () != 2 || j == 0)
+            r += hex_digits[d];
+        }
+
+        if (w > r.size () - 2)
+          r.insert (2, w - (r.size () - 2), '0');
+
+        break;
+      }
+    default:
+      throw invalid_argument ("unsupported base");
+    }
+
+    return r;
+  }
+
   void
   builtin_functions (function_map& m)
   {
@@ -77,7 +127,10 @@ namespace build2
     //
     f["string"] += [](bool b) {return b ? "true" : "false";};
     f["string"] += [](int64_t i) {return to_string (i);};
-    f["string"] += [](uint64_t i) {return to_string (i);};
+    f["string"] += [](uint64_t i, optional<value> base, optional<value> width)
+    {
+      return to_string (i, move (base), move (width));
+    };
 
     // Quote a value returning its string representation. If escape is true,
     // then also escape (with a backslash) the quote characters being added
diff --git a/libbuild2/utility.hxx b/libbuild2/utility.hxx
index c82dcc2..a285b03 100644
--- a/libbuild2/utility.hxx
+++ b/libbuild2/utility.hxx
@@ -69,6 +69,7 @@ namespace build2
   using butl::alpha;
   using butl::alnum;
   using butl::digit;
+  using butl::wspace;
 
   using butl::trim;
   using butl::next_word;
diff --git a/libbuild2/variable.cxx b/libbuild2/variable.cxx
index 4bd01dc..9cdad0b 100644
--- a/libbuild2/variable.cxx
+++ b/libbuild2/variable.cxx
@@ -515,13 +515,22 @@ namespace build2
     {
       try
       {
-        // May throw invalid_argument or out_of_range.
-        //
-        size_t i;
-        int64_t r (stoll (n.value, &i));
+        const string& v (n.value);
+
+        if (!wspace (v[0]))
+        {
+          // Note that unlike uint64, we don't support hex notation for int64.
+
+          // May throw invalid_argument or out_of_range.
+          //
+          size_t i;
+          int64_t r (stoll (v, &i));
+
+          if (i == v.size ())
+            return r;
 
-        if (i == n.value.size ())
-          return r;
+          // Fall through.
+        }
 
         // Fall through.
       }
@@ -563,13 +572,22 @@ namespace build2
     {
       try
       {
-        // May throw invalid_argument or out_of_range.
-        //
-        size_t i;
-        uint64_t r (stoull (n.value, &i));
+        const string& v (n.value);
+
+        if (!wspace (v[0]))
+        {
+          int b (v[0] == '0' && (v[1] == 'x' || v[1] == 'X') ? 16 : 10);
+
+          // May throw invalid_argument or out_of_range.
+          //
+          size_t i;
+          uint64_t r (stoull (v, &i, b));
+
+          if (i == v.size ())
+            return r;
 
-        if (i == n.value.size ())
-          return r;
+          // Fall through.
+        }
 
         // Fall through.
       }
diff --git a/tests/function/builtin/testscript b/tests/function/builtin/testscript
index 00d594b..02c73ee 100644
--- a/tests/function/builtin/testscript
+++ b/tests/function/builtin/testscript
@@ -77,6 +77,14 @@
   $* <'print $type($identity(abc))'            >''         : untyped
 }
 
+: string
+:
+{
+  $* <'print $string([uint64] 0xffff)'        >'65535'      : uint
+  $* <'print $string([uint64] 0xffff, 16)'    >'0xffff'     : uint-hex
+  $* <'print $string([uint64] 0xffff, 16, 8)' >'0x0000ffff' : uint-hex-width
+}
+
 : sort
 :
 {