Ported new methods to StringReader from nbt parsing

src/main/java/com/mojang/brigadier/StringReader.java

@@ -16,6 +16,7 @@ public class StringReader {
     public static final SimpleCommandExceptionType ERROR_EXPECTED_INT = new SimpleCommandExceptionType("parsing.int.expected", "Expected integer");
     public static final ParameterizedCommandExceptionType ERROR_INVALID_DOUBLE = new ParameterizedCommandExceptionType("parsing.double.invalid", "Invalid double '${value}'", "value");
     public static final SimpleCommandExceptionType ERROR_EXPECTED_DOUBLE = new SimpleCommandExceptionType("parsing.double.expected", "Expected double");
+    public static final ParameterizedCommandExceptionType ERROR_EXPECTED_SYMBOL = new ParameterizedCommandExceptionType("parsing.expected", "Expected '${symbol}'", "symbol");
 
     private final String string;
     private int cursor;
@@ -64,6 +65,10 @@ public class StringReader {
         return string.charAt(cursor);
     }
 
+    public char peek(final int offset) {
+        return string.charAt(cursor + offset);
+    }
+
     public char read() {
         return string.charAt(cursor++);
     }
@@ -76,6 +81,12 @@ public class StringReader {
         return c >= '0' && c <= '9' || c == '.' || c == '-';
     }
 
+    public void skipWhitespace() {
+        while (canRead() && Character.isWhitespace(peek())) {
+            skip();
+        }
+    }
+
     public int readInt() throws CommandException {
         final int start = cursor;
         while (canRead() && isAllowedNumber(peek())) {
@@ -172,4 +183,11 @@ public class StringReader {
             throw ERROR_INVALID_BOOL.create(value);
         }
     }
+
+    public void expect(final char c) throws CommandException {
+        if (!canRead() || peek() != c) {
+            throw ERROR_EXPECTED_SYMBOL.create(String.valueOf(c));
+        }
+        skip();
+    }
 }

src/test/java/com/mojang/brigadier/StringReaderTest.java

@@ -9,6 +9,7 @@ import java.util.Collections;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.fail;
 
 public class StringReaderTest {
     @Test
@@ -55,6 +56,17 @@ public class StringReaderTest {
         assertThat(reader.getCursor(), is(2));
     }
 
+    @Test
+    public void peek_length() throws Exception {
+        final StringReader reader = new StringReader("abc");
+        assertThat(reader.peek(0), is('a'));
+        assertThat(reader.peek(2), is('c'));
+        assertThat(reader.getCursor(), is(0));
+        reader.setCursor(1);
+        assertThat(reader.peek(1), is('c'));
+        assertThat(reader.getCursor(), is(1));
+    }
+
     @Test
     public void read() throws Exception {
         final StringReader reader = new StringReader("abc");
@@ -91,6 +103,27 @@ public class StringReaderTest {
         assertThat(reader.getRead(), equalTo("Hello!"));
     }
 
+    @Test
+    public void skipWhitespace_none() throws Exception {
+        final StringReader reader = new StringReader("Hello!");
+        reader.skipWhitespace();
+        assertThat(reader.getCursor(), is(0));
+    }
+
+    @Test
+    public void skipWhitespace_mixed() throws Exception {
+        final StringReader reader = new StringReader(" \t \t\nHello!");
+        reader.skipWhitespace();
+        assertThat(reader.getCursor(), is(5));
+    }
+
+    @Test
+    public void skipWhitespace_empty() throws Exception {
+        final StringReader reader = new StringReader("");
+        reader.skipWhitespace();
+        assertThat(reader.getCursor(), is(0));
+    }
+
     @Test
     public void readUnquotedString() throws Exception {
         final StringReader reader = new StringReader("hello world");
@@ -320,4 +353,35 @@ public class StringReaderTest {
         assertThat(reader.getRead(), equalTo("12.34"));
         assertThat(reader.getRemaining(), equalTo("foo bar"));
     }
+
+    @Test
+    public void expect_correct() throws Exception {
+        final StringReader reader = new StringReader("abc");
+        reader.expect('a');
+        assertThat(reader.getCursor(), is(1));
+    }
+
+    @Test
+    public void expect_incorrect() throws Exception {
+        final StringReader reader = new StringReader("bcd");
+        try {
+            reader.expect('a');
+            fail();
+        } catch (final CommandException ex) {
+            assertThat(ex.getType(), is(StringReader.ERROR_EXPECTED_SYMBOL));
+            assertThat(ex.getData(), equalTo(ImmutableMap.of("symbol", "a")));
+        }
+    }
+
+    @Test
+    public void expect_none() throws Exception {
+        final StringReader reader = new StringReader("");
+        try {
+            reader.expect('a');
+            fail();
+        } catch (final CommandException ex) {
+            assertThat(ex.getType(), is(StringReader.ERROR_EXPECTED_SYMBOL));
+            assertThat(ex.getData(), equalTo(ImmutableMap.of("symbol", "a")));
+        }
+    }
 }