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Lua API.html
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<div class="document" id="dfhack-lua-api">
<h1 class="title">DFHack Lua API</h1>
<div class="contents topic" id="contents">
<p class="topic-title first">Contents</p>
<ul class="simple">
<li><a class="reference internal" href="#df-structure-wrapper" id="id1">DF structure wrapper</a><ul>
<li><a class="reference internal" href="#typed-object-references" id="id2">Typed object references</a><ul>
<li><a class="reference internal" href="#primitive-references" id="id3">Primitive references</a></li>
<li><a class="reference internal" href="#struct-references" id="id4">Struct references</a></li>
<li><a class="reference internal" href="#container-references" id="id5">Container references</a></li>
<li><a class="reference internal" href="#bitfield-references" id="id6">Bitfield references</a></li>
</ul>
</li>
<li><a class="reference internal" href="#named-types" id="id7">Named types</a></li>
<li><a class="reference internal" href="#global-functions" id="id8">Global functions</a></li>
<li><a class="reference internal" href="#recursive-table-assignment" id="id9">Recursive table assignment</a></li>
</ul>
</li>
<li><a class="reference internal" href="#dfhack-utilities" id="id10">DFHack utilities</a><ul>
<li><a class="reference internal" href="#persistent-configuration-storage" id="id11">Persistent configuration storage</a></li>
</ul>
</li>
</ul>
</div>
<div class="section" id="df-structure-wrapper">
<h1><a class="toc-backref" href="#id1">DF structure wrapper</a></h1>
<p>DF structures described by the xml files in library/xml are exported
to lua code as a tree of objects and functions under the <tt class="docutils literal">df</tt> global,
which broadly maps to the <tt class="docutils literal">df</tt> namespace in C++.</p>
<p><strong>WARNING</strong>: The wrapper provides almost raw access to the memory
of the game, so mistakes in manipulating objects are as likely to
crash the game as equivalent plain C++ code would be. E.g. NULL
pointer access is safely detected, but dangling pointers aren't.</p>
<p>Objects managed by the wrapper can be broadly classified into the following groups:</p>
<ol class="arabic">
<li><p class="first">Typed object pointers (references).</p>
<p>References represent objects in DF memory with a known type.</p>
<p>In addition to fields and methods defined by the wrapped type,
every reference has some built-in properties and methods.</p>
</li>
<li><p class="first">Untyped pointers</p>
<p>Represented as lightuserdata.</p>
<p>In assignment to a pointer NULL can be represented either as
<tt class="docutils literal">nil</tt>, or a NULL lightuserdata; reading a NULL pointer field
returns <tt class="docutils literal">nil</tt>.</p>
</li>
<li><p class="first">Named types</p>
<p>Objects in the <tt class="docutils literal">df</tt> tree that represent identity of struct, class,
enum and bitfield types. They host nested named types, static
methods, builtin properties & methods, and, for enums and bitfields,
the bi-directional mapping between key names and values.</p>
</li>
<li><p class="first">The <tt class="docutils literal">global</tt> object</p>
<p><tt class="docutils literal">df.global</tt> corresponds to the <tt class="docutils literal"><span class="pre">df::global</span></tt> namespace, and
behaves as a mix between a named type and a reference, containing
both nested types and fields corresponding to global symbols.</p>
</li>
</ol>
<p>In addition to the <tt class="docutils literal">global</tt> object and top-level types the <tt class="docutils literal">df</tt>
global also contains a few global builtin utility functions.</p>
<div class="section" id="typed-object-references">
<h2><a class="toc-backref" href="#id2">Typed object references</a></h2>
<p>The underlying primitive lua object is userdata with a metatable.
Every structured field access produces a new userdata instance.</p>
<p>All typed objects have the following built-in features:</p>
<ul>
<li><p class="first"><tt class="docutils literal">ref1 == ref2</tt>, <tt class="docutils literal">tostring(ref)</tt></p>
<p>References implement equality by type & pointer value, and string conversion.</p>
</li>
<li><p class="first"><tt class="docutils literal">pairs(ref)</tt></p>
<p>Returns an iterator for the sequence of actual C++ field names
and values. Fields are enumerated in memory order. Methods and
lua wrapper properties are not included in the iteration.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref._kind</tt></p>
<p>Returns one of: <tt class="docutils literal">primitive</tt>, <tt class="docutils literal">struct</tt>, <tt class="docutils literal">container</tt>,
or <tt class="docutils literal">bitfield</tt>, as appropriate for the referenced object.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref._type</tt></p>
<p>Returns the named type object or a string that represents
the referenced object type.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref:sizeof()</tt></p>
<p>Returns <em>size, address</em></p>
</li>
<li><p class="first"><tt class="docutils literal">ref:new()</tt></p>
<p>Allocates a new instance of the same type, and copies data
from the current object.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref:delete()</tt></p>
<p>Destroys the object with the C++ <tt class="docutils literal">delete</tt> operator.
If destructor is not available, returns <em>false</em>.</p>
<p><strong>WARNING</strong>: the lua reference object remains as a dangling
pointer, like a raw C++ pointer would.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref:assign(object)</tt></p>
<p>Assigns data from object to ref. Object must either be another
ref of a compatible type, or a lua table; in the latter case
special recursive assignment rules are applied.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">ref:_displace(index[,step])</span></tt></p>
<p>Returns a new reference with the pointer adjusted by index*step.
Step defaults to the natural object size.</p>
</li>
</ul>
<div class="section" id="primitive-references">
<h3><a class="toc-backref" href="#id3">Primitive references</a></h3>
<p>References of the <em>_kind</em> <tt class="docutils literal">'primitive'</tt> are used for objects
that don't fit any of the other reference types. Such
references can only appear as a value of a pointer field,
or as a result of calling the <tt class="docutils literal">_field()</tt> method.</p>
<p>They behave as structs with one field <tt class="docutils literal">value</tt> of the right type.</p>
</div>
<div class="section" id="struct-references">
<h3><a class="toc-backref" href="#id4">Struct references</a></h3>
<p>Struct references are used for class and struct objects.</p>
<p>They implement the following features:</p>
<ul>
<li><p class="first"><tt class="docutils literal">ref.field</tt>, <tt class="docutils literal">ref.field = value</tt></p>
<p>Valid fields of the structure may be accessed by subscript.</p>
<p>Primitive typed fields, i.e. numbers & strings, are converted
to/from matching lua values. The value of a pointer is a reference
to the target, or nil/NULL. Complex types are represented by
a reference to the field within the structure; unless recursive
lua table assignment is used, such fields can only be read.</p>
<p><strong>NOTE:</strong> In case of inheritance, <em>superclass</em> fields have precedence
over the subclass, but fields shadowed in this way can still
be accessed as <tt class="docutils literal"><span class="pre">ref['subclasstype.field']</span></tt>.
This shadowing order is necessary because vtable-based classes
are automatically exposed in their exact type, and the reverse
rule would make access to superclass fields unreliable.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref._field(field)</tt></p>
<p>Returns a reference to a valid field. That is, unlike regular
subscript, it returns a reference to the field within the structure
even for primitive typed fields and pointers.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">ref:vmethod(args...)</span></tt></p>
<p>Named virtual methods are also exposed, subject to the same
shadowing rules.</p>
</li>
<li><p class="first"><tt class="docutils literal">pairs(ref)</tt></p>
<p>Enumerates all real fields (but not methods) in memory
(= declaration) order.</p>
</li>
</ul>
</div>
<div class="section" id="container-references">
<h3><a class="toc-backref" href="#id5">Container references</a></h3>
<p>Containers represent vectors and arrays, possibly resizable.</p>
<p>A container field can associate an enum to the container
reference, which allows accessing elements using string keys
instead of numerical indices.</p>
<p>Implemented features:</p>
<ul>
<li><p class="first"><tt class="docutils literal">ref._enum</tt></p>
<p>If the container has an associated enum, returns the matching
named type object.</p>
</li>
<li><p class="first"><tt class="docutils literal">#ref</tt></p>
<p>Returns the <em>length</em> of the container.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref[index]</tt></p>
<p>Accesses the container element, using either a <em>0-based</em> numerical
index, or, if an enum is associated, a valid enum key string.</p>
<p>Accessing an invalid index is an error, but some container types
may return a default value, or auto-resize instead for convenience.
Currently this relaxed mode is implemented by df-flagarray aka BitArray.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref._field(index)</tt></p>
<p>Like with structs, returns a pointer to the array element, if possible.
Flag and bit arrays cannot return such pointer, so it fails with an error.</p>
</li>
<li><p class="first"><tt class="docutils literal">pairs(ref)</tt>, <tt class="docutils literal">ipairs(ref)</tt></p>
<p>If the container has no associated enum, both behave identically,
iterating over numerical indices in order. Otherwise, ipairs still
uses numbers, while pairs tries to substitute enum keys whenever
possible.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref:resize(new_size)</tt></p>
<p>Resizes the container if supported, or fails with an error.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref:insert(index,item)</tt></p>
<p>Inserts a new item at the specified index. To add at the end,
use <tt class="docutils literal">#ref</tt> as index.</p>
</li>
<li><p class="first"><tt class="docutils literal">ref:erase(index)</tt></p>
<p>Removes the element at the given valid index.</p>
</li>
</ul>
</div>
<div class="section" id="bitfield-references">
<h3><a class="toc-backref" href="#id6">Bitfield references</a></h3>
<p>Bitfields behave like special fixed-size containers.
The <tt class="docutils literal">_enum</tt> property points to the bitfield type.</p>
<p>Numerical indices correspond to the shift value,
and if a subfield occupies multiple bits, the
<tt class="docutils literal">ipairs</tt> order would have a gap.</p>
</div>
</div>
<div class="section" id="named-types">
<h2><a class="toc-backref" href="#id7">Named types</a></h2>
<p>Named types are exposed in the <tt class="docutils literal">df</tt> tree with names identical
to the C++ version, except for the <tt class="docutils literal">::</tt> vs <tt class="docutils literal">.</tt> difference.</p>
<p>All types and the global object have the following features:</p>
<ul>
<li><p class="first"><tt class="docutils literal">type._kind</tt></p>
<p>Evaluates to one of <tt class="docutils literal"><span class="pre">struct-type</span></tt>, <tt class="docutils literal"><span class="pre">class-type</span></tt>, <tt class="docutils literal"><span class="pre">enum-type</span></tt>,
<tt class="docutils literal"><span class="pre">bitfield-type</span></tt> or <tt class="docutils literal">global</tt>.</p>
</li>
<li><p class="first"><tt class="docutils literal">type._identity</tt></p>
<p>Contains a lightuserdata pointing to the underlying
DFHack::type_instance object.</p>
</li>
</ul>
<p>Types excluding the global object also support:</p>
<ul>
<li><p class="first"><tt class="docutils literal">type:sizeof()</tt></p>
<p>Returns the size of an object of the type.</p>
</li>
<li><p class="first"><tt class="docutils literal">type:new()</tt></p>
<p>Creates a new instance of an object of the type.</p>
</li>
<li><p class="first"><tt class="docutils literal">type:is_instance(object)</tt></p>
<p>Returns true if object is same or subclass type, or a reference
to an object of same or subclass type. It is permissible to pass
nil, NULL or non-wrapper value as object; in this case the
method returns nil.</p>
</li>
</ul>
<p>In addition to this, enum and bitfield types contain a
bi-directional mapping between key strings and values, and
also map <tt class="docutils literal">_first_item</tt> and <tt class="docutils literal">_last_item</tt> to the min and
max values.</p>
<p>Struct and class types with instance-vector attribute in the
xml have a <tt class="docutils literal">type.find(key)</tt> function that wraps the find
method provided in C++.</p>
</div>
<div class="section" id="global-functions">
<h2><a class="toc-backref" href="#id8">Global functions</a></h2>
<p>The <tt class="docutils literal">df</tt> table itself contains the following functions and values:</p>
<ul>
<li><p class="first"><tt class="docutils literal">NULL</tt>, <tt class="docutils literal">df.NULL</tt></p>
<p>Contains the NULL lightuserdata.</p>
</li>
<li><p class="first"><tt class="docutils literal">df.isnull(obj)</tt></p>
<p>Evaluates to true if obj is nil or NULL; false otherwise.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">df.isvalid(obj[,allow_null])</span></tt></p>
<p>For supported objects returns one of <tt class="docutils literal">type</tt>, <tt class="docutils literal">voidptr</tt>, <tt class="docutils literal">ref</tt>.</p>
<p>If <em>allow_null</em> is true, and obj is nil or NULL, returns <tt class="docutils literal">null</tt>.</p>
<p>Otherwise returns <em>nil</em>.</p>
</li>
<li><p class="first"><tt class="docutils literal">df.sizeof(obj)</tt></p>
<p>For types and refs identical to <tt class="docutils literal">obj:sizeof()</tt>.
For lightuserdata returns <em>nil, address</em></p>
</li>
<li><p class="first"><tt class="docutils literal">df.new(obj)</tt>, <tt class="docutils literal">df.delete(obj)</tt>, <tt class="docutils literal">df.assign(obj, obj2)</tt></p>
<p>Equivalent to using the matching methods of obj.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">df._displace(obj,index[,step])</span></tt></p>
<p>For refs equivalent to the method, but also works with
lightuserdata (step is mandatory then).</p>
</li>
<li><p class="first"><tt class="docutils literal">df.is_instance(type,obj)</tt></p>
<p>Equivalent to the method, but also allows a reference as proxy for its type.</p>
</li>
</ul>
</div>
<div class="section" id="recursive-table-assignment">
<h2><a class="toc-backref" href="#id9">Recursive table assignment</a></h2>
<p>Recursive assignment is invoked when a lua table is assigned
to a C++ object or field, i.e. one of:</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">ref:assign{...}</span></tt></li>
<li><tt class="docutils literal">ref.field = <span class="pre">{...}</span></tt></li>
</ul>
<p>The general mode of operation is that all fields of the table
are assigned to the fields of the target structure, roughly
emulating the following code:</p>
<pre class="literal-block">
function rec_assign(ref,table)
for key,value in pairs(table) do
ref[key] = value
end
end
</pre>
<p>Since assigning a table to a field using = invokes the same
process, it is recursive.</p>
<p>There are however some variations to this process depending
on the type of the field being assigned to:</p>
<ol class="arabic">
<li><p class="first">If the table contains an <tt class="docutils literal">assign</tt> field, it is
applied first, using the <tt class="docutils literal">ref:assign(value)</tt> method.
It is never assigned as a usual field.</p>
</li>
<li><p class="first">When a table is assigned to a non-NULL pointer field
using the <tt class="docutils literal">ref.field = <span class="pre">{...}</span></tt> syntax, it is applied
to the target of the pointer instead.</p>
<p>If the pointer is NULL, the table is checked for a <tt class="docutils literal">new</tt> field:</p>
<ol class="loweralpha simple">
<li>If it is <em>nil</em> or <em>false</em>, assignment fails with an error.</li>
<li>If it is <em>true</em>, the pointer is initialized with a newly
allocated object of the declared target type of the pointer.</li>
<li>Otherwise, <tt class="docutils literal">table.new</tt> must be a named type, or an
object of a type compatible with the pointer. The pointer
is initialized with the result of calling <tt class="docutils literal">table.new:new()</tt>.</li>
</ol>
<p>After this auto-vivification process, assignment proceeds
as if the pointer wasn't NULL.</p>
<p>Obviously, the <tt class="docutils literal">new</tt> field inside the table is always skipped
during the actual per-field assignment processing.</p>
</li>
<li><p class="first">If the target of the assignment is a container, a separate
rule set is used:</p>
<ol class="loweralpha">
<li><p class="first">If the table contains neither <tt class="docutils literal">assign</tt> nor <tt class="docutils literal">resize</tt>
fields, it is interpreted as an ordinary <em>1-based</em> lua
array. The container is resized to the #-size of the
table, and elements are assigned in numeric order:</p>
<pre class="literal-block">
ref:resize(#table);
for i=1,#table do ref[i-1] = table[i] end
</pre>
</li>
<li><p class="first">Otherwise, <tt class="docutils literal">resize</tt> must be <em>true</em>, <em>false</em>, or
an explicit number. If it is not false, the container
is resized. After that the usual struct-like 'pairs'
assignment is performed.</p>
<p>In case <tt class="docutils literal">resize</tt> is <em>true</em>, the size is computed
by scanning the table for the largest numeric key.</p>
</li>
</ol>
<p>This means that in order to reassign only one element of
a container using this system, it is necessary to use:</p>
<pre class="literal-block">
{ resize=false, [idx]=value }
</pre>
</li>
</ol>
<p>Since nil inside a table is indistinguishable from missing key,
it is necessary to use <tt class="docutils literal">df.NULL</tt> as a null pointer value.</p>
<p>This system is intended as a way to define a nested object
tree using pure lua data structures, and then materialize it in
C++ memory in one go. Note that if pointer auto-vivification
is used, an error in the middle of the recursive walk would
not destroy any objects allocated in this way, so the user
should be prepared to catch the error and do the necessary
cleanup.</p>
</div>
</div>
<div class="section" id="dfhack-utilities">
<h1><a class="toc-backref" href="#id10">DFHack utilities</a></h1>
<p>DFHack utility functions are placed in the <tt class="docutils literal">dfhack</tt> global tree.</p>
<p>Currently it defines the following features:</p>
<ul>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.print(args...)</span></tt></p>
<p>Output tab-separated args as standard lua print would do,
but without a newline.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">print(args...)</span></tt>, <tt class="docutils literal"><span class="pre">dfhack.println(args...)</span></tt></p>
<p>A replacement of the standard library print function that
works with DFHack output infrastructure.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.printerr(args...)</span></tt></p>
<p>Same as println; intended for errors. Uses red color and logs to stderr.log.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.color([color])</span></tt></p>
<p>Sets the current output color. If color is <em>nil</em> or <em>-1</em>, resets to default.</p>
</li>
<li><p class="first"><tt class="docutils literal">dfhack.is_interactive()</tt></p>
<p>Checks if the thread can access the interactive console and returns <em>true</em> or <em>false</em>.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.lineedit([prompt[,history_filename]])</span></tt></p>
<p>If the thread owns the interactive console, shows a prompt
and returns the entered string. Otherwise returns <em>nil, error</em>.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.interpreter([prompt[,env[,history_filename]]])</span></tt></p>
<p>Starts an interactive lua interpreter, using the specified prompt
string, global environment and command-line history file.</p>
<p>If the interactive console is not accessible, returns <em>nil, error</em>.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.pcall(f[,args...])</span></tt></p>
<p>Invokes f via xpcall, using an error function that attaches
a stack trace to the error. The same function is used by SafeCall
in C++, and dfhack.safecall.</p>
<p>The returned error is a table with separate <tt class="docutils literal">message</tt> and
<tt class="docutils literal">stacktrace</tt> string fields; it implements <tt class="docutils literal">__tostring</tt>.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">safecall(f[,args...])</span></tt>, <tt class="docutils literal"><span class="pre">dfhack.safecall(f[,args...])</span></tt></p>
<p>Just like pcall, but also prints the error using printerr before
returning. Intended as a convenience function.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.with_suspend(f[,args...])</span></tt></p>
<p>Calls <tt class="docutils literal">f</tt> with arguments after grabbing the DF core suspend lock.
Suspending is necessary for accessing a consistent state of DF memory.</p>
<p>Returned values and errors are propagated through after releasing
the lock. It is safe to nest suspends.</p>
<p>Every thread is allowed only one suspend per DF frame, so it is best
to group operations together in one big critical section. A plugin
can choose to run all lua code inside a C++-side suspend lock.</p>
</li>
</ul>
<div class="section" id="persistent-configuration-storage">
<h2><a class="toc-backref" href="#id11">Persistent configuration storage</a></h2>
<p>This api is intended for storing configuration options in the world itself.
It probably should be restricted to data that is world-dependent.</p>
<p>Entries are identified by a string <tt class="docutils literal">key</tt>, but it is also possible to manage
multiple entries with the same key; their identity is determined by <tt class="docutils literal">entry_id</tt>.
Every entry has a mutable string <tt class="docutils literal">value</tt>, and an array of 7 mutable <tt class="docutils literal">ints</tt>.</p>
<ul>
<li><p class="first"><tt class="docutils literal">dfhack.persistent.get(key)</tt>, <tt class="docutils literal">entry:get()</tt></p>
<p>Retrieves a persistent config record with the given string key,
or refreshes an already retrieved entry. If there are multiple
entries with the same key, it is undefined which one is retrieved
by the first version of the call.</p>
<p>Returns entry, or <em>nil</em> if not found.</p>
</li>
<li><p class="first"><tt class="docutils literal">dfhack.persistent.delete(key)</tt>, <tt class="docutils literal">entry:delete()</tt></p>
<p>Removes an existing entry. Returns <em>true</em> if succeeded.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.persistent.get_all(key[,match_prefix])</span></tt></p>
<p>Retrieves all entries with the same key, or starting with key..'/'.
Calling <tt class="docutils literal"><span class="pre">get_all('',true)</span></tt> will match all entries.</p>
<p>If none found, returns nil; otherwise returns an array of entries.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">dfhack.persistent.save({key=str1,</span> <span class="pre">...}[,new])</span></tt>, <tt class="docutils literal"><span class="pre">entry:save([new])</span></tt></p>
<p>Saves changes in an entry, or creates a new one. Passing true as
new forces creation of a new entry even if one already exists;
otherwise the existing one is simply updated.
Returns <em>entry, did_create_new</em></p>
</li>
</ul>
<p>Since the data is hidden in data structures owned by the DF world,
and automatically stored in the save game, these save and retrieval
functions can just copy values in memory without doing any actual I/O.
However, currently every entry has a 180+-byte dead-weight overhead.</p>
</div>
</div>
</div>
</body>
</html>