xref: /aosp_15_r20/external/antlr/runtime/C/doxygen/mainpage.dox (revision 16467b971bd3e2009fad32dd79016f2c7e421deb)

// Main page documentation for ANTLR3C runtime. Contains
// doxygen things only.
//

/// \mainpage ANTLR3 C Runtime API and Usage Guide.
///
/// \section version Version 3.3.1
///
/// This documentation is specifically for the C rutime version 3.1.x.x, which is
/// specifically for use with version 3.1.x.x of the ANTLR recognizer generation
/// tool. While some of the documentation may well apply to prior or future versions
/// you should consult the manuals for the correct version whenever possible.
///
/// \section chchchchangeesss Changes from 3.2 to 3.3.1
///
/// Some changes in 3.3.1 may require small changes in your invoking programs or
/// in the grammar itself. Please read about them here before emailing the user group,
/// where you will be told to come and read about them here, unless they were missed
/// from this list.
///
/// - \subpage changes331 Check here for API changes
///
/// \section intro Introduction
///
/// The ANTLR3 recognizer generation tool is written in Java, but allows the generation
/// of code targeted for a number of other languages. Each target language provides a code
/// generation template for the tool and a runtime library for use by generated recognizers.
/// The C runtime tracks the Java runtime releases and in general when a new version of the
/// tool is released, a new version of the C runtime will be released at the same time.
///
/// The documentation here is in three parts:
///
/// - \subpage build Building the runtime itself from source code;
/// - \subpage generate How to tell ANTLR to generate code for the C target;
/// - \subpage buildrec How to build the generated code
/// - \subpage using Using the runtime and the libraries and so on;
/// - \subpage runtime The documentation of the runtime code and functions;
///
/// \section background Background Information
///
/// The ANTLR 3 C runtime and code generation templates were written by <a href="http://www.linkedin.com/in/jimidle"> Jim Idle</a>
/// (jimi|at|temporal-wave|dott/com) of <a href="http://www.temporal-wave.com">Temporal Wave LLC</a>.
///
/// The C runtime and therefore the code generated to utilize the runtime reflects the object model of the
/// Java version of the runtime as closely as a language without class structures and inheritance can.
/// Compromises have only been made where performance would be adversely affected such as minimizing the
/// number of pointer to pointer to pointer to function type structures that could ensue through trying to
/// model inheritance too exactly. Other differences include the use of token and string factories to minimize
/// the number of calls to system functions such as calloc().This model was adopted so that overriding any
/// default implementation of a function is relatively simple for the grammar programmer.
///
/// The generated code is free threading (subject to the systems calls used on any particular platform
/// being likewise free threading.)
///
/// \subsection model Runtime Model
///
/// As there is no such thing as an object reference in C, the runtime defines a number of typedef structs that reflect
/// the calling interface chosen by Terence Parr for the Java version of the same. The initialization of a parser,
/// lexer, input stream or other internal structure therefore consists of allocating the memory required for
/// an instance of the typedef struct that represents the interface, initializing any counters, and buffers etc,
/// then populating a number of pointers to functions that implement the equivalent of the methods in the Java class.
///
/// The use and initialization of the C versions of a parser is therefore similar to the examples given for Java,
/// but with a bent towards C of course. You may need to be aware of memory allocation and freeing operations
/// in certain environments such as Windows, where you cannot allocate memory in one DLL and free it in another.
///
/// The runtime provides a number of structures and interfaces that the author has found useful when writing action and
/// processing code within java parsers, and furthermore were required by the C runtime code if it was not to
/// depart too far from the logical layout of the Java model. These include the C equivalents of String, List,
/// Hashtable, Vector and Trie, implemented by pointers to structures. These are freely available for your own programming needs.
///
/// A goal of the generated code was to minimize the tracking, allocation and freeing of memory for reasons of both
/// performance and reliability. In essence any memory used by a lexer, parser or tree parser is automatically tracked and
/// freed when the instance of it is released. There are therefore factory functions for tokens and so on such that they
/// can be allocated in blocks and parceled out as they are required. They are all then freed in one go, minimizing the
/// risk of memory leaks and alloc/free thrashing. This has only one side effect, being that if you wish to preserve some structure generated by
/// the lexer, parser or tree parser, then you must make a copy of it before freeing those structures, and track it yourself
/// after that. In practice, it is easy enough just not to release the antlr generated components until you are
/// finished with their results.
///
/// \section targets Target Platforms
///
/// The C project is constructed such that it will compile on any reasonable ANSI C compiler in either 64 or 32 bit mode,
/// with all warnings turned on. This is true of both the runtime code and the generated code and has been summarily tested
/// with Visual Studio .Net (2003, 2005 and 2008) and later versions of gcc on Redhat Linux, as well as on AIX 5.2/5.3, Solaris 9/10,
/// HPUX 11.xx, OSX (PowerPC and Intel) and Cygwin.
///
/// \b Notes
///   - The C runtime is constructed such that the library can be integrated as an archive library, or a shared library/DLL.
///   - The C language target code generation templates are distributed with the source code for the ANTLR tool itself.
///
/// \section performance Performance
///
/// It is C :-). Basic testing of performance against the Java runtime,
/// using the JDK1.6 java source code, and the Java parser provided in the examples (which is a tough test as it includes
/// backtracking and memoization) show that the C runtime uses about half the memory and is between 2 and 3 times the speed.
/// Tests of non-backtracking, non-memoizing parsers, indicate results significantly better than this.
///
/// \section examples Downloading Examples
///
/// The <a href="http://www.antlr.org/download.html">downloads page</a> of the ANTLR web site contains a downloadable
/// zip/tar of examples projects for use with the C runtime model. It contains .sln files and source code for a
/// number of example grammars and helps to see how to invoke and call the generated recognizers.
///