SNMP编程

开发平台：
Unix_Linux

stash_cache.c：源码内容
							#include <net-snmp/net-snmp-config.h>
#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif
#include <net-snmp/net-snmp-includes.h>
#include <net-snmp/agent/net-snmp-agent-includes.h>
#include <net-snmp/agent/stash_cache.h>
#if HAVE_DMALLOC_H
#include <dmalloc.h>
#endif
/** @defgroup stash_cache stash_cache: automatically caches data for certain handlers.
 *  This handler caches data in an optimized way which may aleviate
 *  the need for the lower level handlers to perform as much
 *  optimization.  Specifically, somewhere in the lower level handlers
 *  must be a handler that supports the MODE_GET_STASH operation.
 *  Note that the table_iterator helper supports this.
 *  @ingroup handler
 *  @{
 */
netsnmp_stash_cache_info *
netsnmp_get_new_stash_cache(void)
{
    netsnmp_stash_cache_info *cinfo;
    cinfo = SNMP_MALLOC_TYPEDEF(netsnmp_stash_cache_info);
    cinfo->cache_length = 30;
    return cinfo;
}
/** returns a stash_cache handler that can be injected into a given
 *  handler chain.
 */
netsnmp_mib_handler *
netsnmp_get_stash_cache_handler(void)
{
    netsnmp_mib_handler *handler;
    netsnmp_stash_cache_info *cinfo;
    cinfo = netsnmp_get_new_stash_cache();
    if (!cinfo)
        return NULL;
    handler = netsnmp_create_handler("stash_cache", netsnmp_stash_cache_helper);
    if (!handler) {
        free(cinfo);
        return NULL;
    }
    handler->myvoid = cinfo;
    return handler;
}
/** extracts a pointer to the stash_cache info from the reqinfo structure. */
netsnmp_oid_stash_node  **
netsnmp_extract_stash_cache(netsnmp_agent_request_info *reqinfo)
{
    return netsnmp_agent_get_list_data(reqinfo, STASH_CACHE_NAME);
}
/** @internal Implements the stash_cache handler */
int
netsnmp_stash_cache_helper(netsnmp_mib_handler *handler,
                           netsnmp_handler_registration *reginfo,
                           netsnmp_agent_request_info *reqinfo,
                           netsnmp_request_info *requests)
{
    netsnmp_stash_cache_info *cinfo;
    netsnmp_oid_stash_node *cnode;
    netsnmp_variable_list *cdata;
    netsnmp_request_info *request;
    int ret;
    DEBUGMSGTL(("helper:stash_cache", "Got requestn"));
    cinfo = (netsnmp_stash_cache_info *) handler->myvoid;
    if (!cinfo) {
        cinfo = netsnmp_get_new_stash_cache();
        handler->myvoid = cinfo;
    }
    switch (reqinfo->mode) {
    case MODE_GET:
        if ((ret = netsnmp_stash_cache_update(handler, reginfo,
                                              reqinfo, requests, cinfo)))
            return ret;
        for(request = requests; request; request = request->next) {
            cdata =
                netsnmp_oid_stash_get_data(cinfo->cache,
                                           requests->requestvb->name,
                                           requests->requestvb->name_length);
            if (cdata && cdata->val.string && cdata->val_len) {
                snmp_set_var_typed_value(request->requestvb, cdata->type,
                                         cdata->val.string, cdata->val_len);
            }
        }
        return SNMP_ERR_NOERROR;
        break;
    case MODE_GETNEXT:
        if ((ret = netsnmp_stash_cache_update(handler, reginfo,
                                              reqinfo, requests, cinfo)))
            return ret;
        for(request = requests; request; request = request->next) {
            cnode =
                netsnmp_oid_stash_getnext_node(cinfo->cache,
                                               requests->requestvb->name,
                                               requests->requestvb->name_length);
            if (cnode && cnode->thedata) {
                cdata = cnode->thedata;
                if (cdata->val.string && cdata->name && cdata->name_length) {
                    snmp_set_var_typed_value(request->requestvb, cdata->type,
                                             cdata->val.string, cdata->val_len);
                    snmp_set_var_objid(request->requestvb, cdata->name,
                                       cdata->name_length);
                }
            }
        }
        return SNMP_ERR_NOERROR;
        break;
    default:
        cinfo->cache_valid = 0;
        return netsnmp_call_next_handler(handler, reginfo, reqinfo,
                                         requests);
    }
    return SNMP_ERR_GENERR;     /* should never get here */
}
/** updates a given cache depending on whether it needs to or not.
 */
int
netsnmp_stash_cache_update(netsnmp_mib_handler *handler,
                           netsnmp_handler_registration *reginfo,
                           netsnmp_agent_request_info *reqinfo,
                           netsnmp_request_info *requests,
                           netsnmp_stash_cache_info *cinfo)
{
    int old_mode;
    int ret;
    if (!cinfo->cache_time ||
        atime_ready(cinfo->cache_time, 1000*cinfo->cache_length)) {
        DEBUGMSGTL(("stash_cache",
                    "(re)filling cache (done every %d seconds)n",
                    cinfo->cache_length));
        /* free the old */
        netsnmp_oid_stash_free(&cinfo->cache,
                               (NetSNMPStashFreeNode *) snmp_free_var);
        /* change modes to the GET_STASH mode */
        old_mode = reqinfo->mode;
        reqinfo->mode = MODE_GET_STASH;
        netsnmp_agent_add_list_data(reqinfo,
                                    netsnmp_create_data_list(STASH_CACHE_NAME,
                                                             &cinfo->cache,
                                                             NULL));
        /* have the next handler fill stuff in and switch modes back */
        ret = netsnmp_call_next_handler(handler, reginfo, reqinfo, requests);
        reqinfo->mode = old_mode;
        /* update the cache time */
        if (cinfo->cache_time) {
            atime_setMarker(cinfo->cache_time);
        } else {
            cinfo->cache_time = atime_newMarker();
        }
        return ret;
    }
    return SNMP_ERR_NOERROR;
}
/** initializes the stash_cache helper which then registers a stash_cache
 *  handler as a run-time injectable handler for configuration file
 *  use.
 */
void
netsnmp_init_stash_cache_helper(void)
{
    netsnmp_register_handler_by_name("stash_cache",
                                     netsnmp_get_stash_cache_handler());
}

						