1 files changed, 51 insertions, 0 deletions
diff --git a/lib/impure/nre/private/util.nim b/lib/impure/nre/private/util.nim
new file mode 100644
index 000000000..ed8420776
--- /dev/null
+++ b/lib/impure/nre/private/util.nim
@@ -0,0 +1,51 @@
+## INTERNAL FILE FOR USE ONLY BY nre.nim.
+import std/tables
+
+const Ident = {'a'..'z', 'A'..'Z', '0'..'9', '_', '\128'..'\255'}
+const StartIdent = Ident - {'0'..'9'}
+
+template formatStr*(howExpr, namegetter, idgetter): untyped =
+  let how = howExpr
+  var val = newStringOfCap(how.len)
+  var i = 0
+  var lastNum = 1
+
+  while i < how.len:
+    if how[i] != '$':
+      val.add(how[i])
+      i += 1
+    else:
+      if how[i + 1] == '$':
+        val.add('$')
+        i += 2
+      elif how[i + 1] == '#':
+        var id {.inject.} = lastNum
+        val.add(idgetter)
+        lastNum += 1
+        i += 2
+      elif how[i + 1] in {'0'..'9'}:
+        i += 1
+        var id {.inject.} = 0
+        while i < how.len and how[i] in {'0'..'9'}:
+          id += (id * 10) + (ord(how[i]) - ord('0'))
+          i += 1
+        val.add(idgetter)
+        lastNum = id + 1
+      elif how[i + 1] in StartIdent:
+        i += 1
+        var name {.inject.} = ""
+        while i < how.len and how[i] in Ident:
+          name.add(how[i])
+          i += 1
+        val.add(namegetter)
+      elif how[i + 1] == '{':
+        i += 2
+        var name {.inject.} = ""
+        while i < how.len and how[i] != '}':
+          name.add(how[i])
+          i += 1
+        i += 1
+        val.add(namegetter)
+      else:
+        raise newException(ValueError, "Syntax error in format string at " & $i)
+  val