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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.common.collect.Interner;
import com.google.devtools.build.lib.concurrent.BlazeInterners;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.events.Location.LineAndColumn;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import com.google.devtools.build.lib.util.Pair;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Objects;
/**
* A table to keep track of line numbers in source files. The client creates a LineNumberTable for
* their buffer using {@link #create}. The client can then ask for the line and column given a
* position using ({@link #getLineAndColumn(int)}).
*/
@AutoCodec
@Immutable
public class LineNumberTable implements Serializable {
private static final Interner<LineNumberTable> LINE_NUMBER_TABLE_INTERNER =
BlazeInterners.newWeakInterner();
/** A mapping from line number (line >= 1) to character offset into the file. */
private final int[] linestart;
private final PathFragment path;
private final int bufferLength;
public LineNumberTable(char[] buffer, PathFragment path) {
this(computeLinestart(buffer), path, buffer.length);
}
@AutoCodec.Instantiator
static LineNumberTable createForSerialization(
int[] linestart, PathFragment path, int bufferLength) {
return LINE_NUMBER_TABLE_INTERNER.intern(new LineNumberTable(linestart, path, bufferLength));
}
LineNumberTable(int[] linestart, PathFragment path, int bufferLength) {
this.linestart = linestart;
this.path = path;
this.bufferLength = bufferLength;
}
static LineNumberTable create(char[] buffer, PathFragment path) {
return new LineNumberTable(buffer, path);
}
private int getLineAt(int offset) {
if (offset < 0) {
throw new IllegalStateException("Illegal position: " + offset);
}
int lowBoundary = 1;
int highBoundary = linestart.length - 1;
while (true) {
if ((highBoundary - lowBoundary) <= 1) {
if (linestart[highBoundary] > offset) {
return lowBoundary;
} else {
return highBoundary;
}
}
int medium = lowBoundary + ((highBoundary - lowBoundary) >> 1);
if (linestart[medium] > offset) {
highBoundary = medium;
} else {
lowBoundary = medium;
}
}
}
LineAndColumn getLineAndColumn(int offset) {
int line = getLineAt(offset);
int column = offset - linestart[line] + 1;
return new LineAndColumn(line, column);
}
PathFragment getPath(int offset) {
return path;
}
Pair<Integer, Integer> getOffsetsForLine(int line) {
if (line <= 0 || line >= linestart.length) {
throw new IllegalArgumentException("Illegal line: " + line);
}
return Pair.of(
linestart[line], line < linestart.length - 1 ? linestart[line + 1] : bufferLength);
}
@Override
public int hashCode() {
return Objects.hash(Arrays.hashCode(linestart), path, bufferLength);
}
@Override
public boolean equals(Object other) {
if (other == null || !other.getClass().equals(getClass())) {
return false;
}
LineNumberTable that = (LineNumberTable) other;
return this.bufferLength == that.bufferLength
&& Arrays.equals(this.linestart, that.linestart)
&& Objects.equals(this.path, that.path);
}
private static int[] computeLinestart(char[] buffer) {
// Compute the size.
int size = 2;
for (int i = 0; i < buffer.length; i++) {
if (buffer[i] == '\n') {
size++;
}
}
int[] linestart = new int[size];
int index = 0;
linestart[index++] = 0; // The 0th line does not exist - so we fill something in
// to make sure the start pos for the 1st line ends up at
// linestart[1]. Using 0 is useful for tables that are
// completely empty.
linestart[index++] = 0; // The first line ("line 1") starts at offset 0.
// Scan the buffer and record the offset of each line start. Doing this
// once upfront is faster than checking each char as it is pulled from
// the buffer.
for (int i = 0; i < buffer.length; i++) {
if (buffer[i] == '\n') {
linestart[index++] = i + 1;
}
}
return linestart;
}
}
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