com.facebook.buck.util.CommandSplitter.java Source code

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Here is the source code for com.facebook.buck.util.CommandSplitter.java

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/*
 * Copyright 2015-present Facebook, Inc.
 *
 * 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.facebook.buck.util;

import com.google.common.collect.ImmutableList;

import java.util.Iterator;
import java.util.List;

/**
 * Splits an argument list into a list of command invocations whose total length will not exceed
 * the specified limit if possible. If that is not possible, all arguments that exceed the limit
 * will be used in their own invocation separate from all other arguments to minimize the maximal
 * command length.
 */
public class CommandSplitter {

    private final int desiredLimit;
    private final ImmutableList<String> commandPrefix;
    private final int commandPrefixLength;

    private static final int DEFAULT_DESIRED_LIMIT = 32 * 1024;

    public CommandSplitter(List<String> commandPrefix, int desiredLimit) {
        this.desiredLimit = desiredLimit;
        this.commandPrefix = ImmutableList.copyOf(commandPrefix);
        int commandPrefixLength = 0;
        for (String argument : commandPrefix) {
            commandPrefixLength += argument.length() + 1; // +1 for separator
        }
        this.commandPrefixLength = commandPrefixLength;
    }

    public CommandSplitter(List<String> commandPrefix) {
        this(commandPrefix, DEFAULT_DESIRED_LIMIT);
    }

    public ImmutableList<ImmutableList<String>> getCommandsForArguments(Iterable<String> arguments) {
        Iterator<String> argumentIterator = arguments.iterator();
        if (!argumentIterator.hasNext()) {
            return ImmutableList.of();
        }

        ImmutableList.Builder<ImmutableList<String>> commands = ImmutableList.builder();
        ImmutableList.Builder<String> commandBuilder = ImmutableList.builder();

        String firstArgument = argumentIterator.next();
        commandBuilder.addAll(commandPrefix).add(firstArgument);
        int commandLength = commandPrefixLength + firstArgument.length() + 1; // +1 for separator

        while (argumentIterator.hasNext()) {
            // Loop invariant: commandBuilder contains at least one argument after the command prefix.
            String argument = argumentIterator.next();
            int updatedCommandLength = commandLength + argument.length() + 1; // +1 for separator
            if (updatedCommandLength > desiredLimit) {
                // Put the current command into the output list and start building a new command
                commands.add(commandBuilder.build());
                commandBuilder = ImmutableList.<String>builder().addAll(commandPrefix);
                commandLength = commandPrefixLength;
            }
            commandBuilder.add(argument);
            commandLength += argument.length() + 1; // +1 for separator
        }

        commands.add(commandBuilder.build());

        return commands.build();
    }

}