rfc:php_native_interface

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rfc:php_native_interface [2009/04/05 16:32] – created by direct copy of remove_zend_api. pbiggarrfc:php_native_interface [2009/04/09 11:15] – Remove duplicate text pbiggar
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-====== Removal of the Zend API ======+====== PHP Native Interface ======
   * Version: 1.0.x   * Version: 1.0.x
   * Date: 2009-03-27   * Date: 2009-03-27
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-Provides a rationale for replacing the Zend API with *phpni*, a PHP Native Interface. Includes the design of *phpni*, and emphasizes a means to improve the Zend Engine as a result of the replacement.+Design of the design of //phpni//, a native interface for PHP, designed to replace the Zend API.
  
-===== Introduction ===== +The need for such a native interface is described separately in [[remove_zend_api]].
- +
-This RFC is in two parts, which will probably be split off in the future: +
- +
-  * The need to remove external access to the Zend Engine (aka remove the Zend API) +
-  * The design of a "PHP native interface", dubbed *phpni*, to deal with this problem. +
- +
- +
- +
-===== Why remove the Zend API? ===== +
- +
-=== Zend API === +
- +
-The Zend API is a large set of functions, macros and data-structures which are used to interact with the Zend Engine. It serves 3 major purposes, roughly in order of importance: +
- +
-  * Used to write PHP's standard libraries, 3rd party extensions, and much of PECL. +
-    * Allows wrapping of C/C++ libraries in order to allow the to be accessed from user-code. +
-    * Allows hot (performance-sensitive) code to be rewritten in C for speed +
-  * Used to embed PHP into within C/C++ applications using the embed SAPI +
- +
-=== Problems === +
- +
-The main problem with it is that it constrains the implementation of the Zend Engine. The Zend API creates a tight coupling between the Zend Engine and its clients, restricting greatly our ability to change the Zend Engine. By requiring backwards compatability with the Zend Engine, we are ensuring that the Zend Engine can only be modified in minor ways. This holds the Zend Engine to design decisions made nearly 10 years ago, and prevents PHP from getting much faster in the long term. +
- +
-The Zend API also makes it difficult to write PHP extensions. Although most of the API is not terribly difficult to work with, concepts like copy-on-write, change-on-write sets, and separation appear to be tricky concepts for many people. The only documentation is Sara Golemon's book, and the actual code is not well commented. Although zend_parse_parameters has simplified the parameter parsing somewhat, it seems that a simpler way of writing extensions would be welcome. +
- +
-A number of other PHP implementations exist, such as IBM's Project Zero, Phalanger, Roadsend, Quercus and phc. Many of these projects find it very difficult to re-use PHP's standard libraries. They have chosen different strategies: +
- +
-  * Quercus and Roadsend have reimplemented popular extensions. This means that probably 90% of extensions are unavailable. It also means that future and private extensions cannot be available. +
-  * Phalanger and Project Zero attempt to re-use the existing libraries by marshalling their data into the Zend API. This appears to be slow and error-prone. In particular, Project Zero reports speed problems from marshalling Unicode strings into the Zend API (and those are then passed to C libraries, possably requiring extra marshaling). +
-  * phc is designed around reusing the Zend API for compatibility with the PHP. This constrains many of the optimizations phc would wish to perform. +
- +
- +
-The second half of this RFC describes a solution to this issue: the PHP Native Interface. However, to actually solve this issue, a decision must be made to not only use the PHP Native Interface to provide an interface between extensions and implementations, but also to disallow any external access to the Zend API.+
  
  
 ===== phpni: The PHP Native Interface ===== ===== phpni: The PHP Native Interface =====
  
-This describes the design of *phpni*, the PHP Native Interface. This design is in early stages. The stages required until completion are described later (link?).+This describes the design of //phpni//, the PHP Native Interface. This design is in early stages. The stages required until completion are described later.
  
  
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 </file> </file>
  
-In order to interface between these two, it will be necessary to have a tool to automatically wrap the C functions. SWIG could be used to create this tool.+=== Interface === 
 +In order to interface between the PHP code and the C functions, a tool will be required to generate code. This tool will obviously be implementation specific. SWIG could be used to create this.
  
 === Zend engine === === Zend engine ===
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 Since PHP extensions are no longer written in the Zend API, other PHP implementations, such as Roadsend, Project Zero, Phalanger and Quercus should be reuse the libraries without difficulty. In addition, if the coupling is between the interpreter and its components is simple enough, it may be possible for other implementations to be slotted in directly. However, though this would be a nice side-effect, it should probably not be considered a priority. Since PHP extensions are no longer written in the Zend API, other PHP implementations, such as Roadsend, Project Zero, Phalanger and Quercus should be reuse the libraries without difficulty. In addition, if the coupling is between the interpreter and its components is simple enough, it may be possible for other implementations to be slotted in directly. However, though this would be a nice side-effect, it should probably not be considered a priority.
  
 +===== Problems with current design =====
 +
 +As the design progresses, problems will be identified, which must be solved. This section will keep track of them:
 +
 +=== Problems to be dealt with ===
 +
 +  * Strings:
 +    * How can we identify that an int field is the length of char* field?
 +    * Who will be responsible for freeing passed memory?
 +    * How do we decide whether to make a copy of the string?
 +    * How do we know if we can modify the string in place?
 +      * TODO: look at how JNI does it
 +
 +=== Problems solved ===
 +
 +  * Performance of say, pointer arithmetic, will suffer
 +    * With the basic design (v1.0), it should be simple to put a C layer above the C library, and wrap that instead.
  
 ===== Similar projects ===== ===== Similar projects =====
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 === Non-PHP === === Non-PHP ===
  
-phpni differs from many of these in that it is designed not to add new features, but instead to replace an existing facility - the ability to call C libraries. As such, dynamic linking is not part of the spec.+//phpni// differs from many of these in that it is designed not to add new features, but instead to replace an existing facility - the ability to call C libraries. As such, dynamic linking is not part of the spec.
  
   * ctypes (Python) http://docs.python.org/library/ctypes.html   * ctypes (Python) http://docs.python.org/library/ctypes.html
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   * Haskell 98 Foreign Function Interface http://www.cse.unsw.edu.au/~chak/haskell/ffi/   * Haskell 98 Foreign Function Interface http://www.cse.unsw.edu.au/~chak/haskell/ffi/
   * CFFI (Common Lisp): Common-Lisp FFI: http://common-lisp.net/project/cffi/   * CFFI (Common Lisp): Common-Lisp FFI: http://common-lisp.net/project/cffi/
 +  * SICStus Prolog FLI: http://www.sics.se/sicstus/docs/latest/html/sicstus.html/Mixing-C-and-Prolog.html --- //nlopes 2009/04/06 18:17//
  
 === For PHP === === For PHP ===
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     * perhaps readline?     * perhaps readline?
     * Manually write interface code between the header and the PHP code.     * Manually write interface code between the header and the PHP code.
 +    * Solve problems raised in email discussion
 +      * Look at other implementations, in particular JNI
  
   * Discuss requirements with other PHP implementations   * Discuss requirements with other PHP implementations
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   * Convert entire set of PHP extensions   * Convert entire set of PHP extensions
- 
- 
-Naturally, before the last step it will be necessary to get consensus from other internals developers that this is a good idea. It would be worthwhile to produce a document discussing the experience so far. 
  
  
  
rfc/php_native_interface.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1

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