Add utility formats for modifying parameter name extraction

2 files changed, 48 insertions, 1 deletions

diff --git a/shared/src/main/scala/DerivedFormats.scala b/shared/src/main/scala/DerivedFormats.scala
index 122e744..03e632f 100644
--- a/shared/src/main/scala/DerivedFormats.scala
+++ b/shared/src/main/scala/DerivedFormats.scala
@@ -11,7 +11,7 @@ trait DerivedFormats { self: BasicFormats =>
 
   /** Convert the name of a parameter to that of a field in a JSON object. This
     * method can be overriden to use alternative naming conventions. */
-  def extractFieldName(paramName: String): String = paramName
+  @inline def extractFieldName(paramName: String): String = paramName
 
   def combine[T](ctx: CaseClass[JsonFormat, T]): JsonFormat[T] =
     new JsonFormat[T] {
diff --git a/shared/src/main/scala/caseFormats.scala b/shared/src/main/scala/caseFormats.scala
new file mode 100644
index 0000000..909e357
--- /dev/null
+++ b/shared/src/main/scala/caseFormats.scala
@@ -0,0 +1,47 @@
+package spray.json
+
+/** Serialize parametersOfCaseClasses as parameters_of_case_classes. */
+trait SnakeCase { self: DerivedFormats =>
+  override def extractFieldName(paramName: String) =
+    FieldNaming.substituteCamel(paramName, '_')
+}
+
+/** Serialize parametersOfCaseClasses as parameters-of-case-classes. */
+trait KebabCase { self: DerivedFormats =>
+  override def extractFieldName(paramName: String) =
+    FieldNaming.substituteCamel(paramName, '-')
+}
+
+object FieldNaming {
+
+  @inline final private def isLower(ch: Char): Boolean =
+    ((ch & 0x20) != 0) || (ch == '_')
+
+  @inline final def substituteCamel(paramName: String, substitute: Char) = {
+    val length = paramName.length
+    val builder = new StringBuilder(length)
+    var i = 0
+    while (i < length) {
+      val cur = paramName(i)
+      val lower = isLower(cur)
+      if (lower) {
+        builder.append(cur)
+      } else {
+        builder.append((cur ^ 0x20).toChar)
+      }
+      if (lower && i + 1 < length) {
+        val next = paramName(i + 1)
+        if (!isLower(next)) {
+          builder.append(substitute)
+          builder.append((next ^ 0x20).toChar)
+        } else {
+          builder.append(next)
+        }
+        i += 1
+      }
+      i += 1
+    }
+    builder.result()
+  }
+
+}