8261744: Implement CharsetDecoder ASCII and latin-1 fast-paths

Reviewed-by: naoto, alanb

src/java.base/share/classes/java/lang/String.java

@@ -1008,6 +1008,27 @@ public final class String
 
     //////////////////////////////// utf8 ////////////////////////////////////
 
+    /**
+     * Decodes ASCII from the source byte array into the destination
+     * char array. Used via JavaLangAccess from UTF_8 and other charset
+     * decoders.
+     *
+     * @return the number of bytes successfully decoded, at most len
+     */
+    /* package-private */
+    static int decodeASCII(byte[] sa, int sp, char[] da, int dp, int len) {
+        if (!StringCoding.hasNegatives(sa, sp, len)) {
+            StringLatin1.inflate(sa, sp, da, dp, len);
+            return len;
+        } else {
+            int start = sp;
+            int end = sp + len;
+            while (sp < end && sa[sp] >= 0) {
+                da[dp++] = (char) sa[sp++];
+            }
+            return sp - start;
+        }
+    }
 
     private static boolean isNotContinuation(int b) {
         return (b & 0xc0) != 0x80;

src/java.base/share/classes/java/lang/System.java

@@ -1981,6 +1981,11 @@ public final class System {
      * Initialize the system class.  Called after thread initialization.
      */
     private static void initPhase1() {
+
+        // register the shared secrets - do this first, since SystemProps.initProperties
+        // might initialize CharsetDecoders that rely on it
+        setJavaLangAccess();
+
         // VM might invoke JNU_NewStringPlatform() to set those encoding
         // sensitive properties (user.home, user.name, boot.class.path, etc.)
         // during "props" initialization.
@@ -2026,8 +2031,6 @@ public final class System {
         Thread current = Thread.currentThread();
         current.getThreadGroup().add(current);
 
-        // register shared secrets
-        setJavaLangAccess();
 
         // Subsystems that are invoked during initialization can invoke
         // VM.isBooted() in order to avoid doing things that should
@@ -2277,6 +2280,14 @@ public final class System {
                 return String.getBytesUTF8NoRepl(s);
             }
 
+            public void inflateBytesToChars(byte[] src, int srcOff, char[] dst, int dstOff, int len) {
+                StringLatin1.inflate(src, srcOff, dst, dstOff, len);
+            }
+
+            public int decodeASCII(byte[] src, int srcOff, char[] dst, int dstOff, int len) {
+                return String.decodeASCII(src, srcOff, dst, dstOff, len);
+            }
+
             public void setCause(Throwable t, Throwable cause) {
                 t.setCause(cause);
             }