rfc:remove_zend_api
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rfc:remove_zend_api [2009/03/29 01:58] – Fill out solution and example pbiggar | rfc:remove_zend_api [2009/04/05 16:00] – Restate statement of purpose and version numbers pbiggar | ||
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- | ====== | + | ====== |
- | * Version: 1.0 | + | * Version: 1.0.x |
* Date: 2009-03-27 | * Date: 2009-03-27 | ||
* Author: Paul Biggar < | * Author: Paul Biggar < | ||
- | * Status: | + | * Status: |
- | A better way to provide | + | Provides |
===== Introduction ===== | ===== Introduction ===== | ||
- | ** Naturally, this seems insane. Please bear with me. ** | + | 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", | ||
- | ===== What' | + | |
+ | |||
+ | ===== Why remove | ||
=== Zend API === | === Zend API === | ||
Line 19: | Line 23: | ||
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. | ||
+ | |||
+ | |||
+ | 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, | ||
+ | |||
+ | |||
+ | ===== 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?). | ||
- | ===== What's the solution? ===== | ||
=== Design Criteria === | === Design Criteria === | ||
- | * Greatly reduce the coupling | + | * Remove any couping |
* Support all major use cases of the Zend API | * Support all major use cases of the Zend API | ||
- | * preferably simplifying each use case | + | * embedding within SAPIs |
+ | * proving access to C libraries | ||
+ | * providing the ability to rewrite performance sensitive code in C | ||
Line 45: | Line 62: | ||
Take the use case of wrapping a C library to expose its functionality in user space. The major idea is to " | 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 | + | 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: |
- | xxx/sigs.h | + | extensions/xxx/sigs.h |
+ | < | ||
int x (int, int); | int x (int, int); | ||
void y (char*, int); | void y (char*, int); | ||
void z (char*, int); | void z (char*, int); | ||
+ | </ | ||
We then write our user space code: | We then write our user space code: | ||
- | xxx/ | + | extensions/xxx/ |
+ | < | ||
class MyXXX | class MyXXX | ||
{ | { | ||
Line 75: | Line 95: | ||
} | } | ||
} | } | ||
+ | </ | ||
+ | |||
+ | 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, | ||
+ | |||
+ | |||
+ | ===== Similar projects ===== | ||
+ | |||
+ | === 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. | ||
+ | |||
+ | * ctypes (Python) http:// | ||
+ | * JNI (Java) http:// | ||
+ | * CNI (Java) http:// | ||
+ | * JNA (Java) https:// | ||
+ | * Pyrex (Python) http:// | ||
+ | * Cython (Python) http:// | ||
+ | * FFI (ruby) http:// | ||
+ | * Haskell 98 Foreign Function Interface http:// | ||
+ | * CFFI (Common Lisp): Common-Lisp FFI: http:// | ||
+ | === For PHP === | ||
+ | There is no reason we shouldn' | ||
+ | * FFI http:// | ||
+ | * CodeGen_PECL http:// | ||
+ | * Inline_C http:// | ||
+ | | ||
===== Project Plan ===== | ===== Project Plan ===== | ||
- | This is a simple design. In reality, it would need to be prototyped to determine | + | This is a simple design. In reality, it would need to be prototyped to determine |
+ | * Prototype a single library | ||
+ | * perhaps readline? | ||
+ | * Manually write interface code between the header and the PHP code. | ||
- | ==== Links ==== | + | * 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 entire set of PHP extensions | ||
- | ===== Changelog ===== | + | 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/remove_zend_api.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1