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Commit d07fb882 authored by Jesse Wilson's avatar Jesse Wilson
Browse files

Optimizing skipValue() to avoid allocation. 

I ran a quick benchmark on a desktop VM: this shortened the time
to parse a complete JSON document by ~25%.

Change-Id: Id479734654addfe86f4bf251f0dd6e78843023bf
http://microbenchmarks.appspot.com/run/jessewilson@google.com/twitter.JsonParseBenchmark/366001
parent 1ba41714

core/java/android/util/JsonReader.java

+23 −13
Original line number Diff line number Diff line
@@ -210,6 +210,9 @@ public final class JsonReader implements Closeable { 
    /** The text of the next literal value. */

    private String value;



    /** True if we're currently handling a skipValue() call. */

    private boolean skipping = false;



    /**

     * Creates a new instance that reads a JSON-encoded stream from {@code in}.

     */
@@ -560,8 +563,8 @@ public final class JsonReader implements Closeable { 
     * stream contains unrecognized or unhandled values.

     */

    public void skipValue() throws IOException {

        // TODO: suppress string creation while elements are being skipped!



        skipping = true;

        try {

            int count = 0;

            do {

                JsonToken token = advance();
@@ -571,6 +574,9 @@ public final class JsonReader implements Closeable { 
                    count--;

                }

            } while (count != 0);

        } finally {

            skipping = false;

        }

    }



    private JsonScope peekStack() {
@@ -864,7 +870,9 @@ public final class JsonReader implements Closeable { 
                int c = buffer[pos++];



                if (c == quote) {

                    if (builder == null) {

                    if (skipping) {

                        return "skipped!";

                    } else if (builder == null) {

                        return new String(buffer, start, pos - start - 1);

                    } else {

                        builder.append(buffer, start, pos - start - 1);
@@ -921,7 +929,9 @@ public final class JsonReader implements Closeable { 
                    case '\r':

                    case '\n':

                        pos--;

                        if (builder == null) {

                        if (skipping) {

                            return "skipped!";

                        } else if (builder == null) {

                            return new String(buffer, start, pos - start);

                        } else {

                            builder.append(buffer, start, pos - start);