php扩展与嵌入-资源数据类型二
php扩展与嵌入--资源数据类型2
在资源变量中存储的复杂的数据类型通常在初始化时需要一些内存分配，CPU时间或网络通信。但是在请求之间保留类似于数据库连接这种资源，必须要做到持久。资源是否持久是一个必须要考虑到的因素。
首先看内存分配的问题：
在使用php的时候，偏向使用emalloc因为它是malloc的带回收的版本。但是持久化的资源必须在请求间都存在。对于一个文件句柄类的资源来说，如果要加入一个存储文件名的需求，那么必须在头文件中加入如下的代码：
typedef struct _php_sample_descriptor_data { char *filename; FILE *fp;} php_sample_descriptor_data;对应的，要在源文件中进行相应的更改：
static void php_sample_descriptor_dtor( //这个是进行资源回收的回调函数，定义在资源的初始化处。 zend_rsrc_list_entry *rsrc TSRMLS_DC){ php_sample_descriptor_data *fdata = (php_sample_descriptor_data*)rsrc->ptr; fclose(fdata->fp); efree(fdata->filename); efree(fdata);}进行修改后的文件打开函数，需要增加给资源分配空间的操作：
PHP_FUNCTION(sample_fopen) //修改后的fopen{ php_sample_descriptor_data *fdata; FILE *fp; char *filename, *mode; int filename_len, mode_len; if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ss", &filename, &filename_len, &mode, &mode_len) == FAILURE) {// 获取文件名和文件长度 RETURN_NULL(); } if (!filename_len || !mode_len) { php_error_docref(NULL TSRMLS_CC, E_WARNING, "Invalid filename or mode length"); RETURN_FALSE; } fp = fopen(filename, mode); if (!fp) { php_error_docref(NULL TSRMLS_CC, E_WARNING, "Unable to open %s using mode %s", filename, mode); RETURN_FALSE; } <strong>fdata = emalloc(sizeof(php_sample_descriptor_data)); //给包含了文件资源和文件名的结构分配空间 fdata->fp = fp; fdata->filename = estrndup(filename, filename_len);</strong> ZEND_REGISTER_RESOURCE(return_value, fdata, le_sample_descriptor); // 注册资源}对于文件写入函数fwrite同样需要修改：
PHP_FUNCTION(sample_fwrite){ php_sample_descriptor_data *fdata; zval *file_resource; char *data; int data_len; if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "rs", &file_resource, &data, &data_len) == FAILURE ) { RETURN_NULL(); } <strong>ZEND_FETCH_RESOURCE(fdata, php_sample_descriptor_data*, &file_resource, -1, PHP_SAMPLE_DESCRIPTOR_RES_NAME, le_sample_descriptor);</strong> RETURN_LONG(fwrite(data, 1, data_len, fdata->fp));} 对于sample_fclose函数并不需要改变什么，因为它没有操作实际的资源。下面这个函数可以从资源中拿到原本的文件名：
PHP_FUNCTION(sample_fname){ php_sample_descriptor_data *fdata; zval *file_resource; if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "r", &file_resource) == FAILURE ) { RETURN_NULL(); } <strong>ZEND_FETCH_RESOURCE(fdata, php_sample_descriptor_data*, &file_resource, -1, PHP_SAMPLE_DESCRIPTOR_RES_NAME, le_sample_descriptor);</strong> RETURN_STRING(fdata->filename, 1);} 在完成了内存分配之后，由于必须保持持久化，所以必须延迟析构：
对于非持久的资源来说，一旦存放着资源id的变量被unset或fallen out of scope了，那么它们就被从EG(regular_list)中去除掉了。而EG(persistent_list)中使用的索引是键值类的，元素在请求的最后不会不会被自动的去除掉。只有在zend_hash_del()调用或线程/进程完全关闭的情况下才会消除。
EG(persistent_list)也有dtor方法，但是是zend_register_list_descructors_ex()的第二个参数。一般来说，非持久和持久的资源会被注册成两种类型，有的时候也可以合二为一。现在在sample.c中添加一个持久的资源类型。
static int le_sample_descriptor_persist; static void php_sample_descriptor_dtor_persistent( zend_rsrc_list_entry *rsrc TSRMLS_DC){<strong>//这是一个持久化的资源析构函数</strong> php_sample_descriptor_data *fdata = (php_sample_descriptor_data*)rsrc->ptr; <strong>fclose(fdata->fp); pefree(fdata->filename, 1); pefree(fdata, 1);</strong>}PHP_MINIT_FUNCTION(sample){ le_sample_descriptor = zend_register_list_destructors_ex( php_sample_descriptor_dtor, NULL, PHP_SAMPLE_DESCRIPTOR_RES_NAME, module_number); <strong>le_sample_descriptor_persist = zend_register_list_destructors_ex( NULL, php_sample_descriptor_dtor_persistent, PHP_SAMPLE_DESCRIPTOR_RES_NAME, module_number);//注册一个持久化的资源</strong> return SUCCESS;} 下面的这个fopen函数就兼容了持久与非持久的两个资源类型：
PHP_FUNCTION(sample_fopen){ php_sample_descriptor_data *fdata; FILE *fp; char *filename, *mode; int filename_len, mode_len; zend_bool persist = 0; if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC,"ss|b", &filename, &filename_len, &mode, &mode_len, &persist) == FAILURE) { RETURN_NULL(); } if (!filename_len || !mode_len) { php_error_docref(NULL TSRMLS_CC, E_WARNING, "Invalid filename or mode length"); RETURN_FALSE; } fp = fopen(filename, mode); if (!fp) { php_error_docref(NULL TSRMLS_CC, E_WARNING, "Unable to open %s using mode %s", filename, mode); RETURN_FALSE; } if (!persist) {//非持久化的资源 fdata = emalloc(sizeof(php_sample_descriptor_data)); fdata->filename = estrndup(filename, filename_len);//这个做了申请内存和赋值两步操作 fdata->fp = fp; ZEND_REGISTER_RESOURCE(return_value, fdata, le_sample_descriptor); } else {//持久化的资源 list_entry le; char *hash_key; int hash_key_len; fdata =pemalloc(sizeof(php_sample_descriptor_data),1); fdata->filename = pemalloc(filename_len + 1, 1); memcpy(fdata->filename, filename, filename_len + 1); fdata->fp = fp; ZEND_REGISTER_RESOURCE(return_value, fdata, le_sample_descriptor_persist); /* Store a copy in the persistent_list 在persistent_list存储一份副本 */ le.type = le_sample_descriptor_persist; le.ptr = fdata; hash_key_len = spprintf(&hash_key, 0, "sample_descriptor:%s:%s", filename, mode); zend_hash_update(&EG(persistent_list), hash_key, hash_key_len + 1, (void*)&le, sizeof(list_entry), NULL); efree(hash_key); }} 对于非持久化的资源，给定了一个数字的索引，并存放在了跟请求依存的list中。
对于持久化的资源，给定了一个键值类型，这个hashkey可以在接下来的请求中被重新得到。然后把资源放进了persistentlist中。当一个持久的资源out of scope的时候，EG(regular_list)的析构函数会为le_sample_descriptro_persist检查registerlist析构。发现是NULL的话不会有任何的操作。从而也就保证了持久的资源不会被释放掉。当资源被从EG(persistent_list)中去除的时候，要么是线程进程结束了，要么是故意删除掉了。这时候就会去找持久化的析构函数。
资源被申请为持久化的原因就是为了在其他的请求中可以复用：
如果想要复用持久化的资源，那就一定要用到hash_key,当sample_fopen被调用的时候，函数会利用请求的文件名和模式重新创建hash_key，然后尝试在persistent_list中找到它。
PHP_FUNCTION(sample_fopen){ php_sample_descriptor_data *fdata; FILE *fp; char *filename, *mode, *hash_key; int filename_len, mode_len, hash_key_len; zend_bool persist = 0; //判断是否持久 list_entry *existing_file; if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC,"ss|b", &filename, &filename_len, &mode, &mode_len, &persist) == FAILURE) { RETURN_NULL(); } if (!filename_len || !mode_len) { php_error_docref(NULL TSRMLS_CC, E_WARNING, "Invalid filename or mode length"); RETURN_FALSE; } <strong>/* 通过获得一个hash_key尝试寻找一个已经打开的文件 */ hash_key_len = spprintf(&hash_key, 0, "sample_descriptor:%s:%s", filename, mode); if (zend_hash_find(&EG(persistent_list), hash_key, hash_key_len + 1, (void **)&existing_file) == SUCCESS) { /* 成功的找到了这个已经打开的文件句柄资源 */ ZEND_REGISTER_RESOURCE(return_value, existing_file->ptr, le_sample_descriptor_persist); efree(hash_key); return; }</strong> fp = fopen(filename, mode); if (!fp) { php_error_docref(NULL TSRMLS_CC, E_WARNING, "Unable to open %s using mode %s", filename, mode); RETURN_FALSE; } if (!persist) { fdata = emalloc(sizeof(php_sample_descriptor_data)); fdata->filename = estrndup(filename, filename_len); fdata->fp = fp; ZEND_REGISTER_RESOURCE(return_value, fdata, le_sample_descriptor); } else { list_entry le; fdata =pemalloc(sizeof(php_sample_descriptor_data),1); fdata->filename = pemalloc(filename_len + 1, 1); memcpy(data->filename, filename, filename_len + 1); fdata->fp = fp; ZEND_REGISTER_RESOURCE(return_value, fdata, le_sample_descriptor_persist); /* Store a copy in the persistent_list */ le.type = le_sample_descriptor_persist; le.ptr = fdata; /* hash_key has already been created by now */ zend_hash_update(&EG(persistent_list), hash_key, hash_key_len + 1, (void*)&le, sizeof(list_entry), NULL); } efree(hash_key);}注意由于所有的扩展都使用相同的哈希表单去存储资源，所以命名很重要。一般都是用扩展和资源类型名作为前缀。
检查资源可用性：
尽管像文件这种资源可以长期打开，但是类似远程网络资源这种如果在请求之间长期不用的话就有问题。所以在使用一个persistent资源之前，要先确定可用性。
if (zend_hash_find(&EG(persistent_list), hash_key, hash_key_len + 1, (void**)&socket) == SUCCESS) { if (php_sample_socket_is_alive(socket->ptr)) { ZEND_REGISTER_RESOURCE(return_value, socket->ptr, le_sample_socket); return; } zend_hash_del(&EG(persistent_list), hash_key, hash_key_len + 1); //这里会去调用之前注册好的析构函数}
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