Home >Backend Development >PHP Tutorial >[Translation] [php extension development and embedded] Chapter 16 - Interesting Flow
[Translation] [php extension development and embedded] Chapter 16 - Interesting Flow
- 黄舟Original
- 2017-02-10 10:27:441447browse
Interesting Streams
One feature that is often mentioned in PHP is the stream context. This is optional The parameters are even available in most stream creation related functions in user space, and it serves as a generalized framework for passing additional information to/from a given wrapper or stream implementation.
Context
The context of each stream contains two internal message types. The first and most commonly used are the context options. These values are arranged in the context In a two-dimensional array, it is usually used to change the initialization behavior of the flow wrapper. There is also a context parameter, which is unknown to the wrapper. Currently, it provides a way for event notification inside the flow wrapper layer. .
php_stream_context *php_stream_context_alloc(void);
A context can be created through this API call, which will allocate some storage space and initialize a HashTable for saving context options and parameters. It will also automatically register as a request termination Resources that will be cleaned up later.
Set options
Internal API and user space API for setting context options are equivalent:
int php_stream_context_set_option(php_stream_context *context,
const char *wrappername, const char *optionname,
zval *optionvalue);The following is the user space prototype:
bool stream_context_set_option(resource $context,
string $wrapper, string $optionname,
mixed $value);
The only difference between them is the data type required in user space and internally. The following example uses these two API calls to initiate an HTTP request through the built-in wrapper and overrides user_agent through a context option. Settings.
php_stream *php_varstream_get_homepage(const char *alt_user_agent TSRMLS_DC)
{
php_stream_context *context;
zval tmpval;
context = php_stream_context_alloc(TSRMLS_C);
ZVAL_STRING(&tmpval, alt_user_agent, 0);
php_stream_context_set_option(context, "http", "user_agent", &tmpval);
return php_stream_open_wrapper_ex("http://www.php.net", "rb", REPORT_ERRORS | ENFORCE_SAFE_MODE, NULL, context);
}
##In php-5.4.10 used by the translator, php_stream_context_alloc() was added Thread safety control has been implemented, so the example has been modified accordingly. Please pay attention when testing.
It should be noted here that tmpval does not allocate any persistence. The storage space, its string value is set by copying. php_stream_context_set_option() will automatically copy the incoming zval content.
Get Return options
#The API call used to retrieve context options is exactly the mirror image of the corresponding settings API:
int php_stream_context_get_option(php_stream_context *context,
const char *wrappername, const char *optionname,
zval ***optionvalue);
Review the previous , the context options are stored in a nested HashTable. When retrieving a value from a HashTable, the general method is to pass a pointer to zval ** to zend_hash_find(). Of course, since php_stream_context_get_option() is zend_hash_find() A special agent, their semantics are the same.
The following is a simplified example of using the built-in http wrapper to set user_agent using php_stream_context_get_option():
zval **ua_zval;
char *user_agent = "PHP/5.1.0";
if (context &&
php_stream_context_get_option(context, "http",
"user_agent", &ua_zval) == SUCCESS &&
Z_TYPE_PP(ua_zval) == IS_STRING) {
user_agent = Z_STRVAL_PP(ua_zval);
}
In this case, non-string values will be discarded, because numeric values are meaningless for user-agent strings. Other context options, such as max_redirects, require numeric values, because in character Storing numeric values in string zvals is not universal, so a type conversion needs to be performed to make the setting legal.
不幸的是这些变量是上下文拥有的, 因此它们不能直接转换; 而需要首先进行隔离再进行转换, 最终如果需要还要进行销毁:
long max_redirects = 20;
zval **tmpzval;
if (context &&
php_stream_context_get_option(context, "http",
"max_redirects", &tmpzval) == SUCCESS) {
if (Z_TYPE_PP(tmpzval) == IS_LONG) {
max_redirects = Z_LVAL_PP(tmpzval);
} else {
zval copyval = **tmpzval;
zval_copy_ctor(©val);
convert_to_long(©val);
max_redirects = Z_LVAL(copyval);
zval_dtor(©val);
}
}实际上, 在这个例子中, zval_dtor()并不是必须的. IS_LONG的变量并不需要zval容器之外的存储空间, 因此zval_dtor()实际上不会有真正的操作. 在这个例子中包含它是为了完整性考虑, 对于字符串, 数组, 对象, 资源以及未来可能的其他类型, 就需要这个调用了.
参数
虽然用户空间API中看起来参数和上下文选项是类似的, 但实际上在语言内部的php_stream_context结构体中它们被定义为不同的成员.
目前只支持一个上下文参数: 通知器. php_stream_context结构体中的这个元素可以指向下面的php_stream_notifier结构体:
typedef struct {
php_stream_notification_func func;
void (*dtor)(php_stream_notifier *notifier);
void *ptr;
int mask;
size_t progress, progress_max;
} php_stream_notifier;当将一个php_stream_notifier结构体赋值给context->notifier时, 它将提供一个回调函数func, 在特定的流上发生下表中的PHP_STREAM_NOTIFY_*代码表示的事件时被触发. 每个事件将会对应下面第二张表中的PHP_STREAM_NOTIFY_SEVERITY_*的级别:
事件代码 |
含义 |
RESOLVE |
主机地址解析完成.多数基于套接字的包装器将在连接之前执行这个查询. |
CONNECT |
套接字流连接到远程资源完成. |
AUTH_REQUIRED |
The requested resource is not available,The reason is access control and missing authorization |
MIME_TYPE_IS |
#mime-type of the remote resource is not available |
FILE_SIZE_IS |
Current available size of remote resources |
##REDIRECTED |
##Original URL Request results in redirect to other location |
| PROGRESS
|
Due to the transmission of additional data, the php_stream_notifier structure's progress and (Possible)progress_max element is updated(Progress information,Please refer to phpmanualcurl_setopt#CURLOPT_PROGRESSFUNCTION and CURLOPT_NOPROGRESSOptions) |
COMPLETED |
No more data available on the stream |
FAILURE |
##RequestedURL The resource was unsuccessful or incomplete |
AUTH_RESULT |
The remote system has processed the authorization authentication |
security code |
|
#INFO |
Information update.Equivalent to a E_NOTICEError |
WARN |
Minor error condition.Equivalent to an E_WARNINGError |
| ##ERR
|
Interrupt Error Condition .Equivalent to an E_ERRORError. |