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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
    <title>Target Communication Framework Services - Expressions</title>
</head>

<body lang='EN-US'>

<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 Services.html#ErrorFormat'>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>"" : <i>&lt;&gt;</i></font></b></code>
    - .

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

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

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

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

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

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

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

</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>

<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.
 *
 * @noimplement 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>/**
     * Service name.
     */</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.
         * @return context ID.
         */</font>
        String getID();

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

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

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

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

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

        <font color=#3F5FBF>/**
         * Get complete map of context properties.
         * @return 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.
     * @since 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.
     * @noimplement 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.
         * @return type ID.
         */</font>
        String getTypeID();

        <font color=#3F5FBF>/**
         * Check endianness of the values.
         * Big-endian means decreasing numeric significance with increasing byte number.
         * @return 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.
         * @return true if the value is implicit pointer.
         * @since 1.3
         */</font>
        <font color=#7F0055>boolean</font> isImplicitPointer();

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

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

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

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

        <font color=#3F5FBF>/**
         * Get complete map of value properties.
         * @return 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>/** @since 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>/** @since 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
     *
     * @param id - context ID.
     * @param done - call back interface called when operation is completed.
     * @return - 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.
         * @param token - command handle
         * @param error - error description if operation failed, null if succeeded.
         * @param 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. expression with type of a struct, union, or class - fields;
     * 2. expression with type of an enumeration - enumerators;
     * 3. expression with type of an array - array elements;
     * 4. stack frame - function arguments and local variables;
     * 5. thread - top stack frame function arguments and local variables;
     * 6. process - global variables;
     *
     * Children list does *not* include IDs of expressions that were created by clients
     * using "create" command.
     *
     * @param parent_context_id - parent context ID.
     * @param done - call back interface called when operation is completed.
     * @return - 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.
         * @param token - command handle
         * @param error - error description if operation failed, null if succeeded.
         * @param 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.
     * @param parent_id - a context ID that can be used to resolve symbol names.
     * @param language - language of expression script, null means default language
     * @param expression - expression script
     * @param done - call back interface called when operation is completed.
     * @return - 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.
     * @param scope - see SCOPE_* attribute definitions.
     * @param expression - expression script
     * @param done - call back interface called when operation is completed.
     * @return - pending command handle.
     * @since 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.
         * @param token - command handle
         * @param error - error description if operation failed, null if succeeded.
         * @param 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()
     * @param id - the expression context ID
     * @param done - call back interface called when operation is completed.
     * @return - 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.
         * @param token - command handle
         * @param 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.
     * @param id - the expression context ID
     * @param done - call back interface called when operation is completed.
     * @return - 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.
         * @param token - command handle
         * @param error - error description if operation failed, null if succeeded.
         * @param 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.
     * @param id - expression ID.
     * @param value - value as an array of bytes.
     * @param done - call back interface called when operation is completed.
     * @return - 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.
         * @param token - command handle
         * @param 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.
     * @param listener - event listener implementation.
     */</font>
    <font color=#7F0055>void</font> addListener(ExpressionsListener listener);

    <font color=#3F5FBF>/**
     * Remove expressions service event listener.
     * @param 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.
         * @param id - expression context ID.
         */</font>
        <font color=#7F0055>void</font> valueChanged(String id);
    }
}
</pre>

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