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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.lib;
import java.util.Set;
/**
* This interface defines a Saxon plug-in used to resolve calls on the XPath 3.0
* functions available-environment-variables() and environment-variable(). The standard
* implementation reads environment variables using the Java method {@link System#getenv()};
* this can be overridden by a user-provided implementation that resolves environment variables
* any way it likes.
*/
public interface EnvironmentVariableResolver {
/**
* Get the list of available environment variables.
*
* @return a set of strings; each such string should be an acceptable argument to the
* method {@link #getEnvironmentVariable(String)}
*/
Set getAvailableEnvironmentVariables();
/**
* Get the value of a specific environment variable
*
* @param name the name of the required environment variable
* @return the value of the named environment variable, or null if the variable is
* not defined. The method must not return null if the name is in the list of variables
* returned by the method {@link #getAvailableEnvironmentVariables()}
*/
String getEnvironmentVariable(String name);
}