Merge pull request #10037 from dotty-staging/port-classfile

Port classfile parsing improvements

Author: liufengyun

compiler/src/dotty/tools/dotc/core/Contexts.scala

@@ -14,7 +14,7 @@ import Uniques._
 import ast.Trees._
 import ast.untpd
 import Flags.GivenOrImplicit
-import util.{NoSource, SimpleIdentityMap, SourceFile, HashSet}
+import util.{NoSource, SimpleIdentityMap, SourceFile, HashSet, ReusableInstance}
 import typer.{Implicits, ImportInfo, Inliner, SearchHistory, SearchRoot, TypeAssigner, Typer, Nullables}
 import Nullables.{NotNullInfo, given}
 import Implicits.ContextualImplicits
@@ -26,6 +26,7 @@ import scala.io.Codec
 import collection.mutable
 import printing._
 import config.{JavaPlatform, SJSPlatform, Platform, ScalaSettings}
+import classfile.ReusableDataReader
 
 import scala.annotation.internal.sharable
 
@@ -912,6 +913,8 @@ object Contexts {
 
     private var charArray = new Array[Char](256)
 
+    private[core] val reusableDataReader = ReusableInstance(new ReusableDataReader())
+
     def sharedCharArray(len: Int): Array[Char] =
       while len > charArray.length do
         charArray = new Array[Char](charArray.length * 2)

compiler/src/dotty/tools/dotc/core/classfile/AbstractFileReader.scala

@@ -5,6 +5,7 @@ package classfile
 
 import java.lang.Float.intBitsToFloat
 import java.lang.Double.longBitsToDouble
+import java.io.{ByteArrayInputStream, DataInputStream}
 
 import io.AbstractFile
 
@@ -14,16 +15,22 @@ import io.AbstractFile
  * @author Philippe Altherr
  * @version 1.0, 23/03/2004
  */
-class AbstractFileReader(val file: AbstractFile) {
-
-  /** the buffer containing the file
-   */
-  val buf: Array[Byte] = file.toByteArray
+final class AbstractFileReader(val buf: Array[Byte]) extends DataReader {
+  def this(file: AbstractFile) = this(file.toByteArray)
 
   /** the current input pointer
    */
   var bp: Int = 0
 
+  /** extract a byte at position bp from buf
+   */
+  def getByte(mybp: Int): Byte =
+    buf(mybp)
+
+  def getBytes(mybp: Int, bytes: Array[Byte]): Unit = {
+    System.arraycopy(buf, mybp, bytes, 0, bytes.length)
+  }
+
   /** return byte at offset 'pos'
    */
   @throws(classOf[IndexOutOfBoundsException])
@@ -60,13 +67,13 @@ class AbstractFileReader(val file: AbstractFile) {
   /** extract a character at position bp from buf
    */
   def getChar(mybp: Int): Char =
-    (((buf(mybp) & 0xff) << 8) + (buf(mybp + 1) & 0xff)).toChar
+    (((getByte(mybp) & 0xff) << 8) + (getByte(mybp+1) & 0xff)).toChar
 
   /** extract an integer at position bp from buf
    */
   def getInt(mybp: Int): Int =
-    ((buf(mybp  ) & 0xff) << 24) + ((buf(mybp + 1) & 0xff) << 16) +
-    ((buf(mybp + 2) & 0xff) << 8) + (buf(mybp + 3) & 0xff)
+    ((getByte(mybp) & 0xff) << 24) + ((getByte(mybp + 1) & 0xff) << 16) +
+    ((getByte(mybp + 2) & 0xff) << 8) + (getByte(mybp + 3) & 0xff)
 
   /** extract a long integer at position bp from buf
    */
@@ -81,6 +88,9 @@ class AbstractFileReader(val file: AbstractFile) {
    */
   def getDouble(mybp: Int): Double = longBitsToDouble(getLong(mybp))
 
+  def getUTF(mybp: Int, len: Int): String =
+    new DataInputStream(new ByteArrayInputStream(buf, mybp, len)).readUTF
+
   /** skip next 'n' bytes
    */
   def skip(n: Int): Unit = { bp += n }