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<h1>Target Communication Framework Services - Expressions</h1>

<ul>
    <li><a href='#VersionHistory'>Version History</a>
    <li><a href='#Overview'>Overview</a>
    <li><a href='#Cmds'>Commands</a>
    <ul>
        <li><a href='#CmdGetContext'>Get Context</a>
        <li><a href='#CmdGetChildren'>Get Children</a>
        <li><a href='#CmdCreate'>Create</a>
        <li><a href='#CmdCreateInScope'>Create In Scope</a>
        <li><a href='#CmdDispose'>Dispose</a>
        <li><a href='#CmdEvaluate'>Evaluate</a>
        <li><a href='#CmdAssign'>Assign</a>
    </ul>
    <li><a href='#API'>API</a>
</ul>

<h1>Expressions Service</h1>

<h2><a name='VersionHistory'>Version History</a></h2>

<table border=1 cellpadding=8>
    <tr>
        <th>Version
        <th>Date
        <th>Change
    <tr>
        <td>1.0
        <td>2011-11-11
        <td>Initial
</table>

<h2><a name='Overview'>Overview</a></h2>

<p>Expressions service allows TCF client to perform expression evaluation on remote target.
The service can be used to retrieve or modify values of variables or any data structures in remote target memory.</p>

<p>After expression is created using either <a href='#CmdCreate'>Create</a> or <a href='#CmdCreateInScope'>Create In Scope</a> command,
it can be evaluated multiple times, for example, each time the target is suspended. If an expression denotes a storage location, it can be used in
<a href='#CmdAssign'>Assign</a> command to change stored value. When expression is not needed anymore, it should be disposed using
<a href='#CmdDispose'>Dispose</a> command.</p>

<p>Expressions syntax is extended C/C++ syntax. Extensions to regular C/C++ syntax are:</p>
<ol>
  <li>Special characters in identifiers: <b>$"X"</b>, or just <b>"X"</b> if followed by ::, where X is object name that can contain any characters.
  <li>Symbol IDs in expressions: <b>${X}</b>, where X is symbol ID as returned by the <a href='TCF Service - Symbols.html'>Symbols Service</a>.
  <li>CPU registers: <b>$X</b>, where X is a register name, e.g. $ax
  <li>Debug print function: <b>$printf(fmt, ...)</b>, see <a href='TCF Service - Debug Print.html'>Debug Print Service</a>.
  <li>Debug context ID: <b>$thread</b>, current context ID, same as returned by the <a href='TCF Service - Run Control.html'>Run Control Service</a>.
  <li>OS loader breakpoint address: <b>$loader_brk</b>
  <li>OS loader state address: <b>$loader_state</b>
</ol>

<p>The service uses standard format for error reports,
see <a href='TCF Error Report Format.html'>Error Report Format</a>.</p>

<h2><a name='Cmds'>Commands</a></h2>

<h3><a name='CmdGetContext'>Get Context</a></h3>

<pre><b><font face="Courier New" size=2 color=#333399>
C &bull; <i>&lt;token&gt;</i> &bull; Expressions &bull; getContext &bull; <i>&lt;string: context ID&gt;</i> &bull;
</font></b></pre>

<p>The command retrieves expression context info for given context ID</p>

<p>Reply:</p>

<pre><b><font face="Courier New" size=2 color=#333399>
R &bull; <i>&lt;token&gt;</i> &bull; <i>&lt;error report&gt;</i> &bull; <i>&lt;context data&gt;</i> &bull;

<i>&lt;context data&gt;</i>
    &rArr; null
    &rArr; <i>&lt;object&gt;</i>
</font></b></pre>

<p>Context data object should, at least, contain member
<b><font face="Courier New" size=2 color=#333399>"ID" : <i>&lt;string&gt;.</i></font></b>
Context data is expected to be cached by clients.</p>

<p>Predefined expression context properties are:</p>
<ul>
    <li><code><b><font face="Courier New" size=2 color=#333399>"ID" : <i>&lt;string&gt;</i></font></b></code>
    - ID of the context, same as getContext command argument.

    <li><code><b><font face="Courier New" size=2 color=#333399>"ParentID" : <i>&lt;string&gt;</i></font></b></code>
    - ID of a parent context.

    <li><code><b><font face="Courier New" size=2 color=#333399>"SymbolID" : <i>&lt;string&gt;</i></font></b></code>
    - symbol ID if expression designates a symbol. The symbol ID can be used with <a href='TCF Service - Symbols.html'>Symbols Service</a> to get symbol data.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Expression" : <i>&lt;string&gt;</i></font></b></code>
    - text of the expression.

    <li><code><b><font face="Courier New" size=2 color=#333399>"CanAssign" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if expression designates a storage location, so new value can be assigned (stored) at the location.

    <li><code><b><font face="Courier New" size=2 color=#333399>"HasFuncCall" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if expression cantains a function call, which needs to be executed in the debug context.
    Evaluation of such expressions resumes and suspends target thread or CPU.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Class" : <i>&lt;number&gt;</i></font></b></code>
    - symbol class of the expression type. See <a href='TCF Service - Symbols.html'>Symbols Service</a> for definition of symbol classes.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Type" : <i>&lt;string&gt;</i></font></b></code>
    - symbol ID of the expression type.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Size" : <i>&lt;number&gt;</i></font></b></code>
    - size (in bytes) of the expression value.
</ul>

<h3><a name='CmdGetChildren'>Get Children</a></h3>

<pre><b><font face="Courier New" size=2 color=#333399>
C &bull; <i>&lt;token&gt;</i> &bull; Expressions &bull; getChildren &bull; <i>&lt;string: parent context ID&gt;</i> &bull;
</font></b></pre>

<p>Retrieve children IDs for given parent ID.
   Meaning of the operation depends on parent kind:</p>
<ol>
    <li>parent is stack frame: children are function arguments and local variables</li>
    <li>parent is thread: children are top stack frame function arguments and local variables</li>
    <li>parent is expression with type of a struct, union, or class: children are symbol IDs of fields</li>
    <li>parent is expression with type of an enumeration: children are symbol IDs of enumerators</li>
</ol>
<p>Children list does not include IDs of expressions that were created by clients using "create" command.</p>

<p>Reply:</p>

<pre><b><font face="Courier New" size=2 color=#333399>
R &bull; <i>&lt;token&gt;</i> &bull; <i>&lt;error report&gt;</i> &bull; <i>&lt;array: children IDs&gt;</i> &bull;
</font></b></pre>

<h3><a name='CmdCreate'>Create</a></h3>

<pre><b><font face="Courier New" size=2 color=#333399>
C &bull; <i>&lt;token&gt;</i> &bull; Expressions &bull; create &bull; <i>&lt;string: parent context ID&gt;</i> &bull; <i>&lt;string: language&gt;</i> &bull; <i>&lt;string: expression&gt;</i> &bull;
</font></b></pre>

<p>Create an expression context. The context should be disposed after use.</p>
<p>"parent context ID" is a context ID that can be used to resolve symbol names. It can be process, thread or stack frame.
<p>"language" - language of expression script, null means default language.</p>
<p>"expression" - the expression script.</p>

<p>Reply:</p>

<pre><b><font face="Courier New" size=2 color=#333399>
R &bull; <i>&lt;token&gt;</i> &bull; <i>&lt;error report&gt;</i> &bull; <i>&lt;string: expression context ID&gt;</i> &bull;
</font></b></pre>

<h3><a name='CmdCreateInScope'>Create In Scope</a></h3>

<pre><b><font face="Courier New" size=2 color=#333399>
C &bull; <i>&lt;token&gt;</i> &bull; Expressions &bull; createInScope &bull; <i>&lt;object: scope&gt;</i> &bull; <i>&lt;string: expression&gt;</i> &bull;
</font></b></pre>

<p>Create an expression context in a scope. The context should be disposed after use.</p>
<p>"scope" controls symbols resolution and and interpretation of the expression script.</p>
<p>Predefined properties of the expression scope are:</p>
<ul>
    <li><code><b><font face="Courier New" size=2 color=#333399>"ContextID" : <i>&lt;string&gt;</i></font></b></code>
    - context ID that can be used to resolve symbol names. It can be process, thread or stack frame.
    <li><code><b><font face="Courier New" size=2 color=#333399>"Address" : <i>&lt;string&gt;</i></font></b></code>
    - code instruction address in the parent context. The address identifies compilation unit, function and/or basic block to be used as expression evaluation environment.
    <li><code><b><font face="Courier New" size=2 color=#333399>"Language" : <i>&lt;string&gt;</i></font></b></code>
    - language of expression script.
</ul>
<p>"expression" - the expression script.</p>

<p>Reply:</p>

<pre><b><font face="Courier New" size=2 color=#333399>
R &bull; <i>&lt;token&gt;</i> &bull; <i>&lt;error report&gt;</i> &bull; <i>&lt;string: expression context ID&gt;</i> &bull;
</font></b></pre>

<h3><a name='CmdDispose'>Dispose</a></h3>

<pre><b><font face="Courier New" size=2 color=#333399>
C &bull; <i>&lt;token&gt;</i> &bull; Expressions &bull; dispose &bull; <i>&lt;string: expression ID&gt;</i> &bull;
</font></b></pre>

<p>Dispose an expression context that was created by "create" or "createInScope" commands.</p>

<p>Reply:</p>

<pre><b><font face="Courier New" size=2 color=#333399>
R &bull; <i>&lt;token&gt;</i> &bull; <i>&lt;error report&gt;</i> &bull;
</font></b></pre>

<h3><a name='CmdEvaluate'>Evaluate</a></h3>

<pre><b><font face="Courier New" size=2 color=#333399>
C &bull; <i>&lt;token&gt;</i> &bull; Expressions &bull; evaluate &bull; <i>&lt;string: expression ID&gt;</i> &bull;
</font></b></pre>

<p>Evaluate value of an expression.</p>

<p>Reply:</p>

<pre><b><font face="Courier New" size=2 color=#333399>
R &bull; <i>&lt;token&gt;</i> &bull; <i>&lt;array of bytes: value&gt;</i> &bull; <i>&lt;error report&gt;</i> &bull; <i>&lt;object: value properties&gt;</i> &bull;
</font></b></pre>

<p>Predefined properties of the expression value are:</p>
<ul>
    <li><code><b><font face="Courier New" size=2 color=#333399>"Class" : <i>&lt;number&gt;</i></font></b></code>
    - symbol class of the expression value type. See <a href='TCF Service - Symbols.html'>Symbols Service</a> for definition of symbol classes.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Type" : <i>&lt;string&gt;</i></font></b></code>
    - symbol ID of the expression value type.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Symbol" : <i>&lt;string&gt;</i></font></b></code>
    - symbol ID if the expression designates a symbol.

    <li><code><b><font face="Courier New" size=2 color=#333399>"BitStride" : <i>&lt;number&gt;</i></font></b></code>
    - if the value is an array, and if the amount of storage allocated to hold each element of the array is different from
      the amount of storage that is normally allocated to hold an individual object of the indicated element type,
      then BitStride is the size (in bits) of each element of the array.

    <li><code><b><font face="Courier New" size=2 color=#333399>"BinaryScale" : <i>&lt;number&gt;</i></font></b></code>
    - if the value is a fixed point binary number, BinaryScale is the exponent of the base two scale factor to be applied to the value.

    <li><code><b><font face="Courier New" size=2 color=#333399>"DecimalScale" : <i>&lt;number&gt;</i></font></b></code>
    - if the value is a fixed point decimal number, DecimalScale is the exponent of the base ten scale factor to be applied to the value.

    <li><code><b><font face="Courier New" size=2 color=#333399>"ImplicitPointer" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if the value is result of implicit pointer dereference.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Register" : <i>&lt;string&gt;</i></font></b></code>
    - register ID if the expression designates a register.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Address" : <i>&lt;number&gt;</i></font></b></code>
    - memory address if the expression designates a location in the parent context memory.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Pieces" : <i>&lt;array&gt;</i></font></b></code>
    - <font color=#FF7000>TBD</font>

    <li><code><b><font face="Courier New" size=2 color=#333399>"BigEndian" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if the value is big endian.

</ul>

<h3><a name='CmdAssign'>Assign</a></h3>

<pre><b><font face="Courier New" size=2 color=#333399>
C &bull; <i>&lt;token&gt;</i> &bull; Expressions &bull; assign &bull; <i>&lt;string: expression ID&gt;</i> &bull; <i>&lt;array of bytes: value&gt;</i> &bull;
</font></b></pre>

<p>Assign a value to memory location determined by an expression.</p>

<p>Reply:</p>

<pre><b><font face="Courier New" size=2 color=#333399>
R &bull; <i>&lt;token&gt;</i> &bull; <i>&lt;error report&gt;</i> &bull;
</font></b></pre>

<h2><a name='API'>API</a></h2>

<pre>
<font color=#3F5FBF>/**
 * Expressions service allows TCF client to perform expression evaluation on remote target.
 * The service can be used to retrieve or modify values of variables or any data structures in remote target memory.
 *
 * <font color=#7F9FBF>@noimplement</font> This interface is not intended to be implemented by clients.
 */</font>
<font color=#7F0055>public interface</font> IExpressions <font color=#7F0055>extends</font> IService {

    <font color=#3F5FBF>/**
     * This service name, as it appears on the wire - a TCF name of the service.
     */</font>
    <font color=#7F0055>static final</font> String NAME = "Expressions";

    <font color=#3F5FBF>/**
     * Expression object represent an expression that can be evaluated by remote target.
     * It has a unique ID and contains all information necessary to compute a value.
     * The object data usually includes:
     *   1. process, thread or stack frame ID that should be used to resolve symbol names;
     *   2. a script that can compute a value, like "x.y + z"
     */</font>
    <font color=#7F0055>interface</font> Expression {
        <font color=#3F5FBF>/**
         * Get context ID.
         * <font color=#7F9FBF>@return</font> context ID.
         */</font>
        String getID();

        <font color=#3F5FBF>/**
         * Get parent context ID.
         * <font color=#7F9FBF>@return</font> parent context ID.
         */</font>
        String getParentID();

        <font color=#3F5FBF>/**
         * Get expression script language ID.
         * <font color=#7F9FBF>@return</font> language ID.
         */</font>
        String getLanguage();

        <font color=#3F5FBF>/**
         * Return expression string - the script part of the context.
         * <font color=#7F9FBF>@return</font> expression script string
         */</font>
        String getExpression();

        <font color=#3F5FBF>/**
         * Return symbol ID if the expression represents a symbol (e.g. local variable).
         * <font color=#7F9FBF>@return</font> symbol ID
         */</font>
        String getSymbolID();

        <font color=#3F5FBF>/**
         * Get size of expression value in bits.
         * Can be 0 if value size is even number of bytes, use getSize() in such case.
         * <font color=#7F9FBF>@return</font> size in bits.
         */</font>
        <font color=#7F0055>int</font> getBits();

        <font color=#3F5FBF>/**
         * Get size in bytes. The size can include extra (unused) bits.
         * This is "static" or "declared" size - as determined by expression type.
         * <font color=#7F9FBF>@return</font> size in bytes.
         */</font>
        <font color=#7F0055>int</font> getSize();

        <font color=#3F5FBF>/**
         * Get expression type ID. Symbols service can be used to get type properties.
         * This is "static" or "declared" type ID, actual type of a value can be different -
         * if expression language supports dynamic typing.
         * <font color=#7F9FBF>@return</font> type ID.
         */</font>
        String getTypeID();

        <font color=#3F5FBF>/**
         * Check if the expression can be assigned a new value.
         * <font color=#7F9FBF>@return</font> true if can assign.
         */</font>
        <font color=#7F0055>boolean</font> canAssign();

        <font color=#3F5FBF>/**
         * Check if the expression contains target function call.
         * Such expression can resume the target when evaluated.
         * <font color=#7F9FBF>@return</font> true if has a function call.
         */</font>
        <font color=#7F0055>boolean</font> hasFuncCall();

        <font color=#3F5FBF>/**
         * Get complete map of context properties.
         * <font color=#7F9FBF>@return</font> map of context properties.
         */</font>
        Map&lt;String,Object&gt; getProperties();
    }

    <font color=#3F5FBF>/**
     * Expression context property names.
     */</font>
    <font color=#7F0055>static final</font> String
        PROP_ID = "ID",
        PROP_PARENT_ID = "ParentID",
        PROP_SYMBOL_ID = "SymbolID",
        PROP_LANGUAGE = "Language",
        PROP_EXPRESSION = "Expression",
        PROP_BITS = "Bits",
        PROP_SIZE = "Size",
        PROP_TYPE = "Type",
        PROP_CAN_ASSIGN = "CanAssign",
        PROP_HAS_FUNC_CALL = "HasFuncCall";

    <font color=#3F5FBF>/**
     * Expression scope attributes.
     * <font color=#7F9FBF>@since</font> 1.2
     */</font>
    <font color=#7F0055>static final</font> String
        SCOPE_CONTEXT_ID = "ContextID",
        SCOPE_ADDRESS = "Address",
        SCOPE_LANGUAGE = "Language";

    <font color=#3F5FBF>/**
     * Value represents result of expression evaluation.
     * Note that same expression can be evaluated multiple times with different results.
     * <font color=#7F9FBF>@noimplement</font> This interface is not intended to be implemented by clients.
     */</font>
    <font color=#7F0055>interface</font> Value {

        <font color=#3F5FBF>/**
         * Get value type class.
         * @see ISymbols.TypeClass
         * @return
         */</font>
        ISymbols.TypeClass getTypeClass();

        <font color=#3F5FBF>/**
         * Get value type ID. Symbols service can be used to get type properties.
         * <font color=#7F9FBF>@return</font> type ID.
         */</font>
        String getTypeID();

        <font color=#3F5FBF>/**
         * Check endianness of the values.
         * Big-endian means decreasing numeric significance with increasing byte number.
         * <font color=#7F9FBF>@return</font> true if big-endian.
         */</font>
        <font color=#7F0055>boolean</font> isBigEndian();

        <font color=#3F5FBF>/**
         * Implicit pointer means that the value represents a pointer,
         * which value is unknown or optimized away,
         * even though the value it would point to is known.
         * <font color=#7F9FBF>@return</font> true if the value is implicit pointer.
         * <font color=#7F9FBF>@since</font> 1.3
         */</font>
        <font color=#7F0055>boolean</font> isImplicitPointer();

        <font color=#3F5FBF>/**
         * Return register ID if the value represents register variable.
         * <font color=#7F9FBF>@return</font> register ID or null.
         */</font>
        String getRegisterID();

        <font color=#3F5FBF>/**
         * Return symbol ID if the value represents a symbol.
         * <font color=#7F9FBF>@return</font> symbol ID or null.
         */</font>
        String getSymbolID();

        <font color=#3F5FBF>/**
         * Return value memory address, if applicable.
         * <font color=#7F9FBF>@return</font> address or null.
         */</font>
        Number getAddress();

        <font color=#3F5FBF>/**
         * Get value as array of bytes.
         * <font color=#7F9FBF>@return</font> value as array of bytes.
         */</font>
        <font color=#7F0055>byte</font>[] getValue();

        <font color=#3F5FBF>/**
         * Get complete map of value properties.
         * <font color=#7F9FBF>@return</font> map of value properties.
         */</font>
        Map&lt;String,Object&gt; getProperties();
    }

    <font color=#3F5FBF>/**
     * Expression value property names.
     */</font>
    <font color=#7F0055>static final</font> String
        VAL_CLASS = "Class",
        VAL_TYPE = "Type",
        VAL_BIG_ENDIAN = "BigEndian",
        VAL_REGISTER = "Register",
        VAL_SYMBOL = "Symbol",
        VAL_ADDRESS = "Address";
    <font color=#3F5FBF>/** <font color=#7F9FBF>@since</font> 1.3 */</font>
    <font color=#7F0055>static final</font> String
        VAL_BINARY_SCALE = "BinaryScale",
        VAL_DECIMAL_SCALE = "DecimalScale",
        VAL_IMPLICIT_POINTER = "ImplicitPointer",
        VAL_PIECES = "Pieces";
    <font color=#3F5FBF>/** <font color=#7F9FBF>@since</font> 1.4 */</font>
    <font color=#7F0055>static final</font> String
        VAL_BIT_STRIDE = "BitStride";

    <font color=#3F5FBF>/**
     * Retrieve expression context info for given context ID.
     * @see Expression
     *
     * <font color=#7F9FBF>@param</font> id - context ID.
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     * <font color=#7F9FBF>@return</font> - pending command handle.
     */</font>
    IToken getContext(String id, DoneGetContext done);

    <font color=#3F5FBF>/**
     * Client call back interface for getContext().
     */</font>
    <font color=#7F0055>interface</font> DoneGetContext {
        <font color=#3F5FBF>/**
         * Called when context data retrieval is done.
         * <font color=#7F9FBF>@param</font> token - command handle
         * <font color=#7F9FBF>@param</font> error - error description if operation failed, null if succeeded.
         * <font color=#7F9FBF>@param</font> context - context properties.
         */</font>
        <font color=#7F0055>void</font> doneGetContext(IToken token, Exception error, Expression context);
    }

    <font color=#3F5FBF>/**
     * Retrieve children IDs for given parent ID.
     * Meaning of the operation depends on parent kind:
     * 1. stack frame - function arguments and local variables;
     * 2. thread - top stack frame function arguments and local variables;
     * 3. expression with type of a struct, union, or class - fields;
     * 4. expression with type of an enumeration - enumerators;
     *
     * <font color=#7F9FBF>@param</font> parent_context_id - parent context ID.
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     * <font color=#7F9FBF>@return</font> - pending command handle.
     */</font>
    IToken getChildren(String parent_context_id, DoneGetChildren done);

    <font color=#3F5FBF>/**
     * Client call back interface for getChildren().
     */</font>
    <font color=#7F0055>interface</font> DoneGetChildren {
        <font color=#3F5FBF>/**
         * Called when context list retrieval is done.
         * <font color=#7F9FBF>@param</font> token - command handle
         * <font color=#7F9FBF>@param</font> error - error description if operation failed, null if succeeded.
         * <font color=#7F9FBF>@param</font> context_ids - array of available context IDs.
         */</font>
        <font color=#7F0055>void</font> doneGetChildren(IToken token, Exception error, String[] context_ids);
    }

    <font color=#3F5FBF>/**
     * Create an expression context.
     * The context should be disposed after use.
     * <font color=#7F9FBF>@param</font> parent_id - a context ID that can be used to resolve symbol names.
     * <font color=#7F9FBF>@param</font> language - language of expression script, null means default language
     * <font color=#7F9FBF>@param</font> expression - expression script
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     * <font color=#7F9FBF>@return</font> - pending command handle.
     */</font>
    IToken create(String parent_id, String language, String expression, DoneCreate done);

    <font color=#3F5FBF>/**
     * Create an expression context using given scope to resolve symbols.
     * The context should be disposed after use.
     * <font color=#7F9FBF>@param</font> scope - see SCOPE_* attribute definitions.
     * <font color=#7F9FBF>@param</font> expression - expression script
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     * <font color=#7F9FBF>@return</font> - pending command handle.
     * <font color=#7F9FBF>@since</font> 1.2
     */</font>
    IToken createInScope(Map&lt;String,Object&gt; scope, String expression, DoneCreate done);

    <font color=#3F5FBF>/**
     * Client call back interface for create() and createInScope().
     */</font>
    <font color=#7F0055>interface</font> DoneCreate {
        <font color=#3F5FBF>/**
         * Called when context create context command is done.
         * <font color=#7F9FBF>@param</font> token - command handle
         * <font color=#7F9FBF>@param</font> error - error description if operation failed, null if succeeded.
         * <font color=#7F9FBF>@param</font> context - context properties.
         */</font>
        <font color=#7F0055>void</font> doneCreate(IToken token, Exception error, Expression context);
    }

    <font color=#3F5FBF>/**
     * Dispose an expression context that was created by create()
     * <font color=#7F9FBF>@param</font> id - the expression context ID
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     * <font color=#7F9FBF>@return</font> - pending command handle.
     */</font>
    IToken dispose(String id, DoneDispose done);

    <font color=#3F5FBF>/**
     * Client call back interface for dispose().
     */</font>
    <font color=#7F0055>interface</font> DoneDispose {
        <font color=#3F5FBF>/**
         * Called when context dispose command is done.
         * <font color=#7F9FBF>@param</font> token - command handle
         * <font color=#7F9FBF>@param</font> error - error description if operation failed, null if succeeded.
         */</font>
        <font color=#7F0055>void</font> doneDispose(IToken token, Exception error);
    }

    <font color=#3F5FBF>/**
     * Evaluate value of an expression context.
     * <font color=#7F9FBF>@param</font> id - the expression context ID
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     * <font color=#7F9FBF>@return</font> - pending command handle.
     */</font>
    IToken evaluate(String id, DoneEvaluate done);

    <font color=#3F5FBF>/**
     * Client call back interface for evaluate().
     */</font>
    <font color=#7F0055>interface</font> DoneEvaluate {
        <font color=#3F5FBF>/**
         * Called when context dispose command is done.
         * <font color=#7F9FBF>@param</font> token - command handle
         * <font color=#7F9FBF>@param</font> error - error description if operation failed, null if succeeded.
         * <font color=#7F9FBF>@param</font> value - expression evaluation result
         */</font>
        <font color=#7F0055>void</font> doneEvaluate(IToken token, Exception error, Value value);
    }

    <font color=#3F5FBF>/**
     * Assign a value to memory location determined by an expression.
     * <font color=#7F9FBF>@param</font> id - expression ID.
     * <font color=#7F9FBF>@param</font> value - value as an array of bytes.
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     * <font color=#7F9FBF>@return</font> - pending command handle.
     */</font>
    IToken assign(String id, <font color=#7F0055>byte</font>[] value, DoneAssign done);

    <font color=#3F5FBF>/**
     * Client call back interface for assign().
     */</font>
    <font color=#7F0055>interface</font> DoneAssign {
        <font color=#3F5FBF>/**
         * Called when assign command is done.
         * <font color=#7F9FBF>@param</font> token - command handle
         * <font color=#7F9FBF>@param</font> error - error description if operation failed, null if succeeded.
         */</font>
        <font color=#7F0055>void</font> doneAssign(IToken token, Exception error);
    }

    <font color=#3F5FBF>/**
     * Add expressions service event listener.
     * <font color=#7F9FBF>@param</font> listener - event listener implementation.
     */</font>
    <font color=#7F0055>void</font> addListener(ExpressionsListener listener);

    <font color=#3F5FBF>/**
     * Remove expressions service event listener.
     * <font color=#7F9FBF>@param</font> listener - event listener implementation.
     */</font>
    <font color=#7F0055>void</font> removeListener(ExpressionsListener listener);

    <font color=#3F5FBF>/**
     * Registers event listener is notified when registers context hierarchy
     * changes, and when a register is modified by the service commands.
     */</font>
    <font color=#7F0055>interface</font> ExpressionsListener {

        <font color=#3F5FBF>/**
         * Called when expression value was changed and clients
         * need to update themselves. Clients, at least, should invalidate
         * corresponding cached expression data.
         * Not every change is notified - it is not possible,
         * only those, which are not caused by normal execution of the debuggee.
         * At least, changes caused by "assign" command should be notified.
         * <font color=#7F9FBF>@param</font> id - expression context ID.
         */</font>
        <font color=#7F0055>void</font> valueChanged(String id);
    }
}
</pre>

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