Add Printable (#270)

Printable is a new type that changes how printing of Chisel types is represented
It uses an ordered collection rather than a format string and specifiers
Features:
 - Custom String Interpolator for Scala-like printf
 - String-like manipulation of "hardware strings" for custom pretty-printing
 - Default pretty-printing for Chisel data types

1 files changed, 150 insertions, 0 deletions

diff --git a/chiselFrontend/src/main/scala/chisel3/core/Printable.scala b/chiselFrontend/src/main/scala/chisel3/core/Printable.scala
new file mode 100644
index 00000000..13d5d74e
--- /dev/null
+++ b/chiselFrontend/src/main/scala/chisel3/core/Printable.scala
@@ -0,0 +1,150 @@
+// See LICENSE for license details.
+
+package chisel3.core
+
+import chisel3.internal.firrtl.Component
+import chisel3.internal.HasId
+
+import scala.collection.mutable
+
+import java.util.{
+  MissingFormatArgumentException,
+  UnknownFormatConversionException
+}
+
+/** Superclass of things that can be printed in the resulting circuit
+  *
+  * Usually created using the custom string interpolator p"..."
+  * TODO Should we provide more functions like map and mkPrintable?
+  */
+sealed abstract class Printable {
+  /** Unpack into format String and a List of String arguments (identifiers)
+    * @note This must be called after elaboration when Chisel nodes actually
+    *   have names
+    */
+  def unpack: (String, Iterable[String])
+  /** Allow for appending Printables like Strings */
+  final def +(that: Printable) = Printables(List(this, that))
+  /** Allow for appending Strings to Printables */
+  final def +(that: String) = Printables(List(this, PString(that)))
+}
+object Printable {
+  /** Pack standard printf fmt, args* style into Printable
+    */
+  def pack(fmt: String, data: Data*): Printable = {
+    val args = data.toIterator
+
+    // Error handling
+    def carrotAt(index: Int) = (" " * index) + "^"
+    def errorMsg(index: Int) =
+      s"""|    fmt = "$fmt"
+          |           ${carrotAt(index)}
+          |    data = ${data mkString ", "}""".stripMargin
+    def getArg(i: Int): Data = {
+      if (!args.hasNext) {
+        val msg = "has no matching argument!\n" + errorMsg(i)
+          // Exception wraps msg in s"Format Specifier '$msg'"
+        throw new MissingFormatArgumentException(msg)
+      }
+      args.next()
+    }
+
+    val pables = mutable.ListBuffer.empty[Printable]
+    var str = ""
+    var percent = false
+    for ((c, i) <- fmt.zipWithIndex) {
+      if (percent) {
+        val arg = c match {
+          case FirrtlFormat(x) => FirrtlFormat(x.toString, getArg(i))
+          case 'n' => Name(getArg(i))
+          case 'N' => FullName(getArg(i))
+          case '%' => Percent
+          case x =>
+            val msg = s"Illegal format specifier '$x'!\n" + errorMsg(i)
+            throw new UnknownFormatConversionException(msg)
+        }
+        pables += PString(str dropRight 1) // remove format %
+        pables += arg
+        str = ""
+        percent = false
+      } else {
+        str += c
+        percent = c == '%'
+      }
+    }
+    if (percent) {
+      val msg = s"Trailing %\n" + errorMsg(fmt.size - 1)
+      throw new UnknownFormatConversionException(msg)
+    }
+    require(!args.hasNext,
+      s"Too many arguments! More format specifier(s) expected!\n" +
+      errorMsg(fmt.size))
+
+    pables += PString(str)
+    Printables(pables)
+  }
+}
+
+case class Printables(pables: Iterable[Printable]) extends Printable {
+  require(pables.hasDefiniteSize, "Infinite-sized iterables are not supported!")
+  final def unpack: (String, Iterable[String]) = {
+    val (fmts, args) = pables.map(_.unpack).unzip
+    (fmts.mkString, args.flatten)
+  }
+}
+/** Wrapper for printing Scala Strings */
+case class PString(str: String) extends Printable {
+  final def unpack: (String, Iterable[String]) =
+    (str replaceAll ("%", "%%"), List.empty)
+}
+/** Superclass for Firrtl format specifiers for Bits */
+sealed abstract class FirrtlFormat(specifier: Char) extends Printable {
+  def bits: Bits
+  def unpack: (String, Iterable[String]) = {
+    val id = if (bits.isLit) bits.ref.name else bits.instanceName
+    (s"%$specifier", List(id))
+  }
+}
+object FirrtlFormat {
+  final val legalSpecifiers = List('d', 'x', 'b', 'c')
+
+  def unapply(x: Char): Option[Char] =
+    Option(x) filter (x => legalSpecifiers contains x)
+
+  /** Helper for constructing Firrtl Formats
+    * Accepts data to simplify pack
+    */
+  def apply(specifier: String, data: Data): FirrtlFormat = {
+    val bits = data match {
+      case b: Bits => b
+      case d => throw new Exception(s"Trying to construct FirrtlFormat with non-bits $d!")
+    }
+    specifier match {
+      case "d" => Decimal(bits)
+      case "x" => Hexadecimal(bits)
+      case "b" => Binary(bits)
+      case "c" => Character(bits)
+      case c => throw new Exception(s"Illegal format specifier '$c'!")
+    }
+  }
+}
+/** Format bits as Decimal */
+case class Decimal(bits: Bits) extends FirrtlFormat('d')
+/** Format bits as Hexidecimal */
+case class Hexadecimal(bits: Bits) extends FirrtlFormat('x')
+/** Format bits as Binary */
+case class Binary(bits: Bits) extends FirrtlFormat('b')
+/** Format bits as Character */
+case class Character(bits: Bits) extends FirrtlFormat('c')
+/** Put innermost name (eg. field of bundle) */
+case class Name(data: Data) extends Printable {
+  final def unpack: (String, Iterable[String]) = (data.ref.name, List.empty)
+}
+/** Put full name within parent namespace (eg. bundleName.field) */
+case class FullName(hasId: HasId) extends Printable {
+  final def unpack: (String, Iterable[String]) = (hasId.instanceName, List.empty)
+}
+/** Represents escaped percents */
+case object Percent extends Printable {
+  final def unpack: (String, Iterable[String]) = ("%%", List.empty)
+}