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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.build.lib.syntax;
import com.google.devtools.build.lib.events.Location;
import java.io.IOException;
import java.util.List;
import javax.annotation.Nullable;
/** Syntax node for a slice expression, e.g. obj[:len(obj):2]. */
public final class SliceExpression extends Expression {
private final Expression object;
@Nullable private final Expression start;
@Nullable private final Expression end;
@Nullable private final Expression step;
public SliceExpression(Expression object, Expression start, Expression end, Expression step) {
this.object = object;
this.start = start;
this.end = end;
this.step = step;
}
public Expression getObject() {
return object;
}
public @Nullable Expression getStart() {
return start;
}
public @Nullable Expression getEnd() {
return end;
}
public @Nullable Expression getStep() {
return step;
}
@Override
public void prettyPrint(Appendable buffer) throws IOException {
object.prettyPrint(buffer);
buffer.append('[');
// The first separator colon is unconditional. The second separator appears only if step is
// printed.
if (start != null) {
start.prettyPrint(buffer);
}
buffer.append(':');
if (end != null) {
end.prettyPrint(buffer);
}
if (step != null) {
buffer.append(':');
step.prettyPrint(buffer);
}
buffer.append(']');
}
@Override
Object doEval(Environment env) throws EvalException, InterruptedException {
Object objValue = object.eval(env);
Object startValue = start == null ? Runtime.NONE : start.eval(env);
Object endValue = end == null ? Runtime.NONE : end.eval(env);
Object stepValue = step == null ? Runtime.NONE : step.eval(env);
Location loc = getLocation();
if (objValue instanceof SkylarkList) {
return ((SkylarkList<?>) objValue).getSlice(
startValue, endValue, stepValue, loc, env.mutability());
} else if (objValue instanceof String) {
String string = (String) objValue;
List<Integer> indices = EvalUtils.getSliceIndices(startValue, endValue, stepValue,
string.length(), loc);
char[] result = new char[indices.size()];
char[] original = ((String) objValue).toCharArray();
int resultIndex = 0;
for (int originalIndex : indices) {
result[resultIndex] = original[originalIndex];
++resultIndex;
}
return new String(result);
}
throw new EvalException(
loc,
String.format(
"type '%s' has no operator [:](%s, %s, %s)",
EvalUtils.getDataTypeName(objValue),
EvalUtils.getDataTypeName(startValue),
EvalUtils.getDataTypeName(endValue),
EvalUtils.getDataTypeName(stepValue)));
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
public Kind kind() {
return Kind.SLICE;
}
}
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