| /// \page interop Interacting with the Generated Code |
| /// |
| /// \section intro Introduction |
| /// |
| /// The main way to interact with the generated code is via action code placed within <code>{</code> and |
| /// <code>}</code> characters in your rules. In general, you are advised to keep the code you embed within |
| /// these actions, and the grammar itself to an absolute minimum. Rather than embed code directly in your |
| /// grammar, you should construct an API, that is called from the actions within your grammar. This way |
| /// you will keep the grammar clean and maintainable and separate the code generators or other code |
| /// from the definition of the grammar itself. |
| /// |
| /// However, when you wish to call your API functions, or insert small pieces of code that do not |
| /// warrant external functions, you will need to access elements of tokens, return elements from |
| /// parser rules and perhaps the internals of the recognizer itself. The C runtime provides a number |
| /// of MACROs that you can use within your action code. It also provides a number of performant |
| /// structures that you may find useful for building symbol tables, lists, tries, stacks, arrays and so on (all |
| /// of which are managed so that your memory allocation problems are minimized.) |
| /// |
| /// \section rules Parameters and Returns from Parser Rules |
| /// |
| /// The C target does not differ from the Java target in any major ways here, and you should consult |
| /// the standard documentation for the use of parameters on rules and the returns clause. You should |
| /// be aware though, that the rules generate C function calls and therefore the input and returns |
| /// clauses are subject to the constraints of C scoping. |
| /// |
| /// You should note that if your parser rule returns more than a single entity, then the return |
| /// type of the generated rule function is a struct, which is returned by value. This is also the case |
| /// if your rule is part of a tree building grammar (uses the <code>output=AST;</code> option. |
| /// |
| /// Other than the notes above, you can use any pre-declared type as an input or output parameter |
| /// for your rule. |
| /// |
| /// \section memory Memory Management |
| /// |
| /// You are responsible for allocating and freeing any memory used by your own |
| /// constructs, ANTLR will track and release any memory allocated internally for tokens, trees, stacks, scopes |
| /// and so on. This memory is returned to the malloc pool when you call the free method of any |
| /// ANTLR3 produced structure. |
| /// |
| /// For performance reasons, and to avoid thrashing the malloc allocation system, memory for amy elements |
| /// of your generated parser is allocated in chunks and parcelled out by factories. For instance memory |
| /// for tokens is created as an array of tokens, and a token factory hands out the next available slot |
| /// to the lexer. When you free the lexer, the allocated memory is returned to the pool. The same applies |
| /// to 'strings' that contain the token text and various other text elements accessed within the lexer. |
| /// |
| /// The only side effect of this is that after your parse and analysis is complete, if you wish to retain |
| /// anything generated automatically, you must copy it before freeing the recognizer structures. In practice |
| /// it is usually practical to retain the recognizer context objects until your processing is complete or |
| /// to use your own allocation scheme for generating output etc. |
| /// |
| /// The advantage of using object factories is of course that memory leaks and accessing de-allocated |
| /// memory are bugs that rarely occur within the ANTLR3 C runtime. Further, allocating memory for |
| /// tokens, trees and so on is very fast. |
| /// |
| /// \section ctx The CTX Macro |
| /// |
| /// The CTX macro is a fundamental parameter that is passed as the first parameter to any generated function |
| /// concerned with your lexer, parser, or tree parser. The is is the context pointer for your generated |
| /// recognizer and is how you invoke the generated functions, and access the data embedded within your generated |
| /// recognizer. While you can use it to directly access stacks, scopes and so on, this is not really recommended |
| /// as you should use the $xxx references that are available generically within ANTLR grammars. |
| /// |
| /// The context pointer is used because this removes the need for any global/static variables at all, either |
| /// within the generated code, or the C runtime. This is of course fundamental to creating free threading |
| /// recognizers. Wherever a function call or rule call required the ctx parameter, you either reference it |
| /// via the CTX macro, or the ctx parameter is in fact the return type from calling the 'constructor' |
| /// function for your parser/lexer/tree parser (see code example in "How to build Generated Code" .) |
| /// |
| /// \section macros Pre-Defined convenience MACROs |
| /// |
| /// While the author is not fond of using C MACROs to hide code or structure access, in the case of generated |
| /// code, they serve two useful purposes. The first is to simplify the references to internal constructs, |
| /// the second is to facilitate the change of any internal interface without requiring you to port grammars |
| /// from earlier versions (just regenerate and recompile). As of release 3.1, these macros are stable and |
| /// will only change their usage interface in the event of bugs being discovered. You are encouraged to |
| /// use these macros in your code, rather than access the raw interface. |
| /// |
| /// \bNB: Macros that act like statements must be terminated with a ';'. The macro body does not |
| /// supply this, nor should it. Macros that call functions are declared with () even if they |
| /// have no parameters, macros that reference fields do not have a () declaration. |
| /// |
| /// \section lexermacros Lexer Macros |
| /// |
| /// There are a number of macros that are useful exclusively within lexer rules. There are additional |
| /// macros, common to all recognizer, and these are documented in the section Common Macros. |
| /// |
| /// \subsection lexer LEXER |
| /// |
| /// The <code>LEXER</code> macro returns a pointer to the base lexer object, which is of type #pANTLR3_LEXER. This is |
| /// not the pointer to your generated lexer, which is supplied by the CTX macro, |
| /// but to the common implementation of a lexer interface, |
| /// which is supplied to all generated lexers. |
| /// |
| /// \subsection lexstate LEXSTATE |
| /// |
| /// Provides a pointer to the lexer shared state structure, which is where the tokens for a |
| /// rule are constructed and the status elements of the lexer are kept. This pointer is of type |
| /// #pANTLR3_RECOGNIZER_SHARED_STATE.In general you should only access elements of this structure |
| /// if there is not already another MACRO or standard $xxxx antlr reference that refers to it. |
| /// |
| /// \subsection la LA(n) |
| /// |
| /// The <code>LA</code> macro returns the character at index n from the current input stream index. The return |
| /// type is #ANTLR3_UINT32. Hence <code>LA(1)</code> returns the character at the current input position (the |
| /// character that will be consumed next), <code>LA(-1)</code> returns the character that has just been consumed |
| /// and so on. The <code>LA(n)</code> macro is useful for constructing semantic predicates in lexer rules. The |
| /// reference <code>LA(0)</code> is undefined and will cause an error in your lexer. |
| /// |
| /// \subsection getcharindex GETCHARINDEX() |
| /// |
| /// The <code>GETCHARINDEX</code> macro returns the index of the current character position as a 0 based |
| /// offset from the start of the input stream. It returns a value type of #ANTLR3_UINT32. |
| /// |
| /// \subsection getline GETLINE() |
| /// |
| /// The <code>GETLINE</code> macro returns the line number of current character (<code>LA(1)</code> in the input |
| /// stream. It returns a value type of #ANTLR3_UINT32. Note that the line number is incremented |
| /// automatically by an input stream when it sees the input character '\n'. The character that causes |
| /// the line number to increment can be changed by calling the SetNewLineChar() method on the input |
| /// stream before invoking the lexer and after creating the input stream. |
| /// |
| /// \subsection gettext GETTEXT() |
| /// |
| /// The <code>GETTEXT</code> macro returns the text currently matched by the lexer rule. In general you should use the |
| /// generic $text reference in ANTLR to retrieve this. The return type is a reference type of #pANTLR3_STRING |
| /// which allows you to manipulate the text you have retrieved (\b NB this does not change the input stream |
| /// only the text you copy from the input stream when you use this MACRO or $text). |
| /// |
| /// The reference $text->chars or GETTEXT()->chars will reference a pointer to the '\\0' terminated character |
| /// string that the ANTLR3 #pANTLR3_STRING represents. String space is allocated automatically as well as |
| /// the structure that holds the string. The #pANTLR3_STRING_FACTORY associated with the lexer handles this |
| /// and when you close the lexer, it will automatically free any space allocated for strings and their structures. |
| /// |
| /// \subsection getcharpositioninline GETCHARPOSITIONINLINE() |
| /// |
| /// The <code>GETCHARPOSITIONINLINE</code> returns the zero based offset of character <code>LA(1)</code> |
| /// from the start of the current input line. See the macro <code>GETLINE</code> for details on what the |
| /// line number means. |
| /// |
| /// \subsection emit EMIT() |
| /// |
| /// The macro <code>EMIT</code> causes the text range currently matched to the lexer rule to be emitted |
| /// immediately as the token for the rule. Subsequent text is matched but ignored. The type used for the |
| /// the token is the name of the lexer rule or, if you have change this by using $type = XXX;, the type |
| /// XXX is used. |
| /// |
| /// \subsection emitnew EMITNEW(t) |
| /// |
| /// The macro <code>EMITNEW</code> causes the supplied token reference <code>t</code> to be used as the |
| /// token emitted by the rule. The parameter <code>t </code> must be of type #pANTLR3_COMMON_TOKEN. |
| /// |
| /// \subsection index INDEX() |
| /// |
| /// The <code>INDEX</code> macro returns the current input position according to the input stream. It is not |
| /// guaranteed to be the character offset in the input stream but is instead used as a value |
| /// for marking and rewinding to specific points in the input stream. Use the macro <code>GETCHARINDEX()</code> |
| /// to find out the position of the <code>LA(1)</code> in the input stream. |
| /// |
| /// \subsection pushstream PUSHSTREAM(str) |
| /// |
| /// The <code>PUSHSTREAM</code> macro, in conjunction with the <code>POPSTREAM</code> macro (called internally in the runtime usually) |
| /// can be used to stack many input streams to the lexer, and implement constructs such as the C pre-processor |
| /// \#include directive. |
| /// |
| /// An input stream that is pushed on to the stack becomes the current input stream for the lexer and |
| /// the state of the previous stream is automatically saved. The input stream will be automatically |
| /// popped from the stack when it is exhausted by the lexer. You may use the macro <code>POPSTREAM</code> |
| /// to return to the previous input stream prior to exhausting the currently stacked input stream. |
| /// |
| /// Here is an example of using the macro in a lexer to implement the C \#include pre-processor directive: |
| /// |
| /// \code |
| /// fragment |
| /// STRING_GUTS : (~('\\'|'"') )* ; |
| /// |
| /// LINE_COMMAND |
| /// : '#' (' ' | '\t')* |
| /// ( |
| /// 'include' (' ' | '\t')+ '"' file = STRING_GUTS '"' (' ' | '\t')* '\r'? '\n' |
| /// { |
| /// pANTLR3_STRING fName; |
| /// pANTLR3_INPUT_STREAM in; |
| /// |
| /// // Create an initial string, then take a substring |
| /// // We can do this by messing with the start and end |
| /// // pointers of tokens and so on. This shows a reasonable way to |
| /// // manipulate strings. |
| /// // |
| /// fName = $file.text; |
| /// printf("Including file '\%s'\n", fName->chars); |
| /// |
| /// // Create a new input stream and take advantage of built in stream stacking |
| /// // in C target runtime. |
| /// // |
| /// in = antlr38BitFileStreamNew(fName->chars); |
| /// PUSHSTREAM(in); |
| /// |
| /// // Note that the input stream is not closed when it EOFs, I don't bother |
| /// // to do it here, but it is up to you to track streams created like this |
| /// // and destroy them when the whole parse session is complete. Remember that you |
| /// // don't want to do this until all tokens have been manipulated all the way through |
| /// // your tree parsers etc as the token does not store the text it just refers |
| /// // back to the input stream and trying to get the text for it will abort if you |
| /// // close the input stream too early. |
| /// // |
| /// |
| /// } |
| /// | (('0'..'9')=>('0'..'9'))+ ~('\n'|'\r')* '\r'? '\n' |
| /// ) |
| /// {$channel=HIDDEN;} |
| /// ; |
| /// \endcode |
| /// |
| /// \subsection popstream POPSTREAM() |
| /// |
| /// Assuming that you have stacked an input stream using the PUSHSTREAM macro, you can |
| /// remove it from the stream stack and revert to the previous input stream. You should be careful |
| /// to pop the stream at an appropriate point in your lexer action, so you do not match characters |
| /// from one stream with those from another in the same rule (unless this is what you want to do) |
| /// |
| /// \subsection settext SETTEXT(str) |
| /// |
| /// A token manufactured by the lexer does not actually physically store the text from the |
| /// input stream to which it matches. The token string is instead created only if you ask for |
| /// the text. However if you wish to change the text that the token represents you can use |
| /// this macro to set it explicitly. Note that this does not change the input stream text |
| /// but associates the supplied #pANTLR3_STRING with the token. This string is then returned |
| /// when parser and tree parser reference the tokens via the $xxx.text reference. |
| /// |
| /// \subsection user1 USER1 USER2 USER3 and CUSTOM |
| /// |
| /// While you can create your own custom token class and have the lexer deal with this, this |
| /// is a lot of work compared to the trivial inheritance that can be achieved in the Java target. |
| /// In many cases though, all that is needed is the addition of a few data items such as an |
| /// integer or a pointer. Rather than require C programmers to create complicated structures |
| /// just to add a few data items, the C target provides a few custom fields in the standard |
| /// token, which will fulfil the needs of most lexers and parsers. |
| /// |
| /// The token fields user1, user2, and user3 are all value types of #ANTLR_UINT32. In the |
| /// parser you can reference these fields directly from the token: <code>x=TOKNAME { $x->user1 ...</code> |
| /// but when you are building the token in the lexer, you must assign to the fields using the |
| /// macros <code>USER1</code>, <code>USER2</code>, or <code>USER3</code>. As in: |
| /// |
| /// \code |
| /// LEXTOK: 'AAAAA' { USER1 = 99; } ; |
| /// \endcode |
| /// |
| /// |
| /// \section parsermacros Parser and Tree Parser Macros |
| /// |
| /// \subsection parser PARSER |
| /// |
| /// The <code>PARSER</code> macro returns a pointer to the base parser or tree parser object, which is of type #pANTLR3_PARSER |
| /// or #pANTLR3_TREE_PARSER . This is not the pointer to your generated parser, which is supplied by the <code>CTX</code> macro, |
| /// but to the common implementation of a parser or tree parser interface, which is supplied to all generated parsers. |
| /// |
| /// \subsection index INDEX() |
| /// |
| /// When used in the parser, the <code>INDEX</code> macro returns the position of the current |
| /// token ( LT(1) ) in the input token stream. It can be used for <code>MARK</code> and <code>REWIND</code> |
| /// operations. |
| /// |
| /// \subsection lt LT(n) and LA(n) |
| /// |
| /// In the parser, the macro <code>LT(n)</code> returns the #pANTLR3_COMMON_TOKEN at offset <code>n</code> from |
| /// the current token stream input position. The macro <code>LA(n)</code> returns the token type of the token |
| /// at position <code>n</code>. The value <code>n</code> cannot be zero, and such a reference will return |
| /// <code>NULL</code> and possibly cause an error. <code>LA(1)</code> is the token that is about to be |
| /// recognized and <code>LA(-1)</code> is the token that has just been recognized. Values of n that exceed the |
| /// limits of the token stream boundaries will return <code>NULL</code>. |
| /// |
| /// \subsection psrstate PSRSTATE |
| /// |
| /// Returns the shared state pointer of type #pANTLR3_RECOGNIZER_SHARED_STATE. This is not generally |
| /// useful to the grammar programmer as the useful elements have generic $xxx references built in to |
| /// ANTLR. |
| /// |
| /// \subsection adaptor ADAPTOR |
| /// |
| /// When building an AST via a parser, the work of constructing and manipulating trees is done |
| /// by a supplied adaptor class. The default class is usually fine for most tree operations but |
| /// if you wish to build your own specialized linked/tree structure, then you may need to reference |
| /// the adaptor you supply directly. The <code>ADAPTOR</code> macro returns the reference to the tree adaptor |
| /// which is always of type #pANTLR3_BASE_TREE_ADAPTOR, even if it is your custom adapter. |
| /// |
| /// \section commonmacros Macros Common to All Recognizers |
| /// |
| /// \subsection recognizer RECOGNIZER |
| /// |
| /// Returns a reference type of #pANTRL3_BASE_RECOGNIZER, which is the base functionality supplied |
| /// to all recognizers, whether lexers, parsers or tree parsers. You can override methods in this |
| /// interface by installing your own function pointers (once you know what you are doing). |
| /// |
| /// \subsection input INPUT |
| /// |
| /// Returns a reference to the input stream of the appropriate type for the recognizer. In a lexer |
| /// this macro returns a reference type of #pANTLR3_INPUT_STREAM, in a parser this is type |
| /// #pANTLR3_TOKEN_STREAM and in a tree parser this is type #pANTLR3_COMMON_TREE_NODE_STREAM. |
| /// You can of course provide your own implementations of any of these interfaces. |
| /// |
| /// \subsection mark MARK() |
| /// |
| /// This macro will cause the input stream for the current recognizer to be marked with a |
| /// checkpoint. It will return a value type of #ANTLR3_MARKER which you can use as the |
| /// parameter to a <code>REWIND</code> macro to return to the marked point in the input. |
| /// |
| /// If you know you will only ever rewind to the last <code>MARK</code>, then you can ignore the return |
| /// value of this macro and just use the <code>REWINDLAST</code> macro to return to the last <code>MARK</code> that |
| /// was set in the input stream. |
| /// |
| /// \subsection rewind REWIND(m) |
| /// |
| /// Rewinds the appropriate input stream back to the marked checkpoint returned from a prior |
| /// MARK macro call and supplied as the parameter <code>m</code> to the <code>REWIND(m)</code> |
| /// macro. |
| /// |
| /// \subsection rewindlast REWINDLAST() |
| /// |
| /// Rewinds the current input stream (character, tokens, tree nodes) back to the last checkpoint |
| /// marker created by a <code>MARK</code> macro call. Fails silently if there was no prior |
| /// <code>MARK</code> call. |
| /// |
| /// \subsection seek SEEK(n) |
| /// |
| /// Causes the input stream to position itself directly at offset <code>n</code> in the stream. Works for all |
| /// input stream types, both lexer, parser and tree parser. |
| /// |