如何读取 evbuffer 并将其放入 libevent 中的字符串 (char*)
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【中文标题】如何读取 evbuffer 并将其放入 libevent 中的字符串 (char*)【英文标题】:How to read evbuffer and put it into a string (char*) in libevent 【发布时间】:2012-08-10 14:30:05 【问题描述】:我正在使用 libevent 及其 http API 来编写一个能够编写 C servlet 的简单 HTTP 服务器。此 servlet 与 GET 一起工作正常,但现在我正在使用 POST 发送一些数据,我想读取传入的事件缓冲区 evb。我想打印/检查 evb 中存在的数据,但我不能。你知道如何将数据放入 char* 变量中的 evb (evbuffer) 中吗?我只看到了操作缓冲区的方法,但没有看到它。我试过了:
evb->
这是代码:
#include <stdio.h>
#include "servlet.h"
void servlet(struct evhttp_request *req, struct evbuffer *evb)
time_t now;
time(&now);
evbuffer_add_printf(evb, "<html>\n <head>\n"
" <title>%s</title>\n"
" </head>\n"
" <body>\n"
" <h1>%s</h1>\n"
" <p>Current time is: %s</p>",
"C servlet engine", "C servlet", ctime(&now));
evhttp_add_header(evhttp_request_get_output_headers(req),
"Content-Type", "text/html");
evhttp_send_reply(req, 200, "OK", evb);
I am trying this
void servlet(struct evhttp_request *req, struct evbuffer *evb)
size_t len = evbuffer_get_length(evhttp_request_get_input_buffer(req));
struct evbuffer *in_evb = evhttp_request_get_input_buffer(req);
char *data;
evbuffer_copyout(in_evb, data, len);
但我得到总线错误:10(我在 Mac 上)
【问题讨论】:
【参考方案1】:听起来你想用
ev_ssize_t evbuffer_copyout(struct evbuffer *buf, void *data, size_t datalen)
它将缓冲区内容(最多datalen
字节)复制到内存区域data
。
它记录在libevent book
【讨论】:
是的,我正在尝试该功能,但出现 Bus error: 10 see my update。 你需要为数据变量分配内存,例如:data = malloc(len) 我必须初始化数据变量 char *data = malloc(len);【参考方案2】:这是一个有效的方法:
static void echo_read_cb(struct bufferevent *bev, void *ctx)
/* This callback is invoked when there is data to read on bev. */
struct evbuffer *input = bufferevent_get_input(bev);
struct evbuffer *output = bufferevent_get_output(bev);
size_t len = evbuffer_get_length(input);
char *data;
data = malloc(len);
evbuffer_copyout(input, data, len);
printf("we got some data: %s\n", data);
/* Copy all the data from the input buffer to the output buffer. */
evbuffer_add_buffer(output, input);
free(data);
【讨论】:
【参考方案3】:根据libevent的buffer.h中的源码,我们应该使用
int evbuffer_remove(struct evbuffer *buf, void *data, size_t datlen);
而不是
ev_ssize_t evbuffer_copyout(struct evbuffer *buf, void *data_out, size_t datlen);
这是从buffer.h借来的代码
/**
Read data from an evbuffer and drain the bytes read.
If more bytes are requested than are available in the evbuffer, we
only extract as many bytes as were available.
@param buf the evbuffer to be read from
@param data the destination buffer to store the result
@param datlen the maximum size of the destination buffer
@return the number of bytes read, or -1 if we can't drain the buffer.
*/
int evbuffer_remove(struct evbuffer *buf, void *data, size_t datlen);
/**
Read data from an evbuffer, and leave the buffer unchanged.
If more bytes are requested than are available in the evbuffer, we
only extract as many bytes as were available.
@param buf the evbuffer to be read from
@param data_out the destination buffer to store the result
@param datlen the maximum size of the destination buffer
@return the number of bytes read, or -1 if we can't drain the buffer.
*/
ev_ssize_t evbuffer_copyout(struct evbuffer *buf, void *data_out, size_t datlen);
【讨论】:
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