rfc:remove_zend_api
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rfc:remove_zend_api [2009/03/30 22:42] – Flesh out the project plan, and finish solution discussion pbiggar | rfc:remove_zend_api [2009/04/05 19:33] – linkify pbiggar | ||
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- | ====== | + | ====== |
* Version: 1.0 | * Version: 1.0 | ||
* Date: 2009-03-27 | * Date: 2009-03-27 | ||
* Author: Paul Biggar < | * Author: Paul Biggar < | ||
- | * Status: | + | * Status: |
+ | ===== Introduction ===== | ||
- | A better way to provide | + | This RFC provides |
- | ===== Introduction ===== | + | See also php_native_interface. |
- | ** Naturally, this seems insane. Please bear with me. ** | ||
- | ===== What' | + | ===== Why remove |
=== Zend API === | === Zend API === | ||
Line 19: | Line 19: | ||
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: | 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 | + | * Used to write PHP's standard libraries, 3rd party extensions, and much of PECL. |
- | * Allows hot (performance-sensitive) code to be rewritten in C for speed | + | * Allows wrapping of C/C++ libraries in order to allow the to be accessed from user-code. |
+ | | ||
* Used to embed PHP into within C/C++ applications using the embed SAPI | * Used to embed PHP into within C/C++ applications using the embed SAPI | ||
=== Problems === | === 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 ZendEngine | + | 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 |
- | 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, | + | 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, |
- | 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. | + | 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. |
+ | * 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. | ||
- | ===== What's the solution? ===== | ||
- | === Design Criteria === | + | A proposed replacement for the Zend API is described in php_native_interace. 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, |
- | * Greatly reduce the coupling between the Zend Engine and its users | ||
- | * Support all major use cases of the Zend API | ||
- | * preferably simplifying each use case | ||
- | |||
- | === Solution === | ||
- | |||
- | Take the use case of wrapping a C library to expose its functionality in user space. The major idea is to " | ||
- | |||
- | Lets take a simple example. Assume we have a C library XXX, with 3 functions, x, y and z. We'd like to expose this in user space as a class called MyXXX, with methods a and b. We create a file with the signatures of x, y and z: | ||
- | |||
- | extensions/ | ||
- | < | ||
- | int x (int, int); | ||
- | void y (char*, int); | ||
- | void z (char*, int); | ||
- | </ | ||
- | |||
- | We then write our user space code: | ||
- | |||
- | extensions/ | ||
- | < | ||
- | class MyXXX | ||
- | { | ||
- | | ||
- | { | ||
- | | ||
- | } | ||
- | |||
- | | ||
- | { | ||
- | $foo = \internals\XXX\x ($w1, $w2); | ||
- | \internals\XXX\y ($this-> | ||
- | } | ||
- | |||
- | | ||
- | { | ||
- | $foo = \internals\XXX\x ($m1, $m2); | ||
- | \internals\XXX\z ($this-> | ||
- | return $foo; | ||
- | } | ||
- | } | ||
- | </ | ||
- | |||
- | 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. | ||
- | |||
- | === Zend engine === | ||
- | |||
- | Since the libraries would no longer use the Zend API, the tight coupling would be broken. It would now be possible to change major parts of the Zend engine without affecting the operation of any other part of PHP. | ||
- | |||
- | === Extensions/ | ||
- | |||
- | It would no longer be necessary to know the Zend API to write extensions. Instead, only the API of the C library is necessary, and the interface can be created in PHP user code. | ||
- | |||
- | === Embed SAPI === | ||
- | |||
- | The same interface used for libraries can be used to handle many of the use cases of the C API. However, it is likely that a means to call PHP user code from C/C++ code, will be required. | ||
- | |||
- | |||
- | === Other PHP implementations === | ||
- | |||
- | Since PHP extensions are no longer written in the Zend API, other PHP implementations, | ||
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This is a simple design. In reality, it would need to be prototyped to determine whether this makes sense for every use case, and that there would be little sacrificed to make it work. The work on it should probably progress in roughly the following order: | This is a simple design. In reality, it would need to be prototyped to determine whether this makes sense for every use case, and that there would be little sacrificed to make it work. The work on it should probably progress in roughly the following order: | ||
- | * Prototype a single library | + | * Follow |
- | * perhaps readline? | + | * Convert |
- | * Manually write interface code between | + | |
- | + | ||
- | * Discuss requirements with other PHP implementations | + | |
- | + | ||
- | * Write a utility to generate the interface code automatically | + | |
- | * Using SWIG? | + | |
- | * Test 5 or 6 libraries | + | |
- | * Test more complicated functionality | + | |
- | + | ||
- | * Convert | + | |
- | 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. | + | Naturally, before the last step it will be necessary to get consensus from other internals developers that this is a good idea. |
rfc/remove_zend_api.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1