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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;
/** Syntax node for a slice expression, e.g. obj[:len(obj):2]. */
public final class SliceExpression extends Expression {
private final Expression object;
private final Expression start;
private final Expression end;
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 Expression getStart() {
return start;
}
public Expression getEnd() {
return end;
}
public Expression getStep() {
return step;
}
@Override
public void prettyPrint(Appendable buffer) throws IOException {
boolean startIsDefault =
(start instanceof Identifier) && ((Identifier) start).getName().equals("None");
boolean endIsDefault =
(end instanceof Identifier) && ((Identifier) end).getName().equals("None");
boolean stepIsDefault =
(step instanceof IntegerLiteral) && ((IntegerLiteral) step).getValue().equals(1);
object.prettyPrint(buffer);
buffer.append('[');
// Start and end are omitted if they are the literal identifier None, which is the default value
// inserted by the parser if no bound is given. Likewise, step is omitted if it is the literal
// integer 1.
//
// The first separator colon is unconditional. The second separator appears only if step is
// printed.
if (!startIsDefault) {
start.prettyPrint(buffer);
}
buffer.append(':');
if (!endIsDefault) {
end.prettyPrint(buffer);
}
if (!stepIsDefault) {
buffer.append(':');
step.prettyPrint(buffer);
}
buffer.append(']');
}
@Override
Object doEval(Environment env) throws EvalException, InterruptedException {
Object objValue = object.eval(env);
Object startValue = start.eval(env);
Object endValue = end.eval(env);
Object stepValue = step.eval(env);
Location loc = getLocation();
if (objValue instanceof SkylarkList) {
SkylarkList<?> list = (SkylarkList<?>) objValue;
Object slice = list.getSlice(startValue, endValue, stepValue, loc);
return SkylarkType.convertToSkylark(slice, env);
} 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
void validate(ValidationEnvironment env) throws EvalException {
object.validate(env);
}
}
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