本文是根據lacewing官網的介紹并結合自己的使用經驗，挑比較常用到的內容提取歸納而成

lacewing簡介

liblacewing是一個跨平臺的，為C/C++提供的高級網絡開源庫，旨在提供一個簡明的類，做到能夠擴展并且可以平臺優化（支持IOCP/EPOLL/KQUEUE等）。

Classes

lacewing::eventpump

eventpump is a default implementation of pump provided by the library, powered by IOCP, kqueue or epoll.

As there is no single model for event handling that would suit every application, eventpump provides several different modes of operation:

• tick polls aggressively, suited to a game loop;

• start_eventloop starts a simple “block forever” event loop, suited to console applications and daemons;

• start_sleepy_ticking enables a threaded callback to request the application call tick as soon as possible, suited to applications with an existing message pump (such as Win32 GUI applications)

lacewing::webserver

webserver aims to provide an embeddable, flexible HTTP server using liblacewing classes as a base.

Ease of embedding makes webserver ideal for things such as remote administration interfaces, and through the use of eventpump, webserver is able to scale well and adapt transparently to different ways of handling I/O.

Features of webserver include:

• Simple hooks for requests, with easy access to GET and POST data
• Support for cookies and sessions
• Support for HTTPS (see host_secure)
• HTTP file upload

webserver uses server as a base for socket communication.

on_get (webserver)

// C++ style void on_get (lacewing::webserver webserver, lacewing::webserver_request request) { /*on_get的響應*/ }webserver->on_get (on_get); /* to register the hook */ // C style void on_get (lw_ws webserver, lw_ws_request) { /*on_get的響應*/ }lw_ws_on_get (webserver, on_get); /* to register the hook */

Description
The on_get hook is triggered for an incoming HTTP GET request.

This hook marks the beginning of the lifetime of a request object. If enable_manual_finish has been called, the request object will be valid until either request::finish is called OR the on_disconnect hook triggers. Otherwise, the request object is only valid until the hook returns.

The application may configure a response in this hook with functions such as request::header, and request::cookie, and write the response data with stream::write and stream::write_file.

Nothing will actually be written to the socket while the request object is still valid. This ensures that an accurate Content-Length header can be generated, and that headers can be changed throughout the lifetime of the request.

on_post (webserver)

// C++ style void on_get (lacewing::webserver webserver, lacewing::webserver_request &request) { }webserver->on_post (on_post); /* to register the hook */ // C style void on_post (lw_ws webserver, lw_ws_request) { }lw_ws_on_post (webserver, on_post); /* to register the hook */

Description
The on_post hook is triggered for an incoming HTTP POST request.

This hook marks the beginning of the lifetime of a request object. If enable_manual_finish has been called, the request object will be valid until either request::finish is called OR the on_disconnect hook triggers. Otherwise, the request object is only valid until the hook returns.

The application may configure a response in this hook with functions such as request::header, and request::cookie, and write the response data with stream::write and stream::write_file.

Nothing will actually be written to the socket while the request object is still valid. This ensures that an accurate Content-Lengthheader can be generated, and that headers can be changed throughout the lifetime of the request.

Methods

file_exists

// C++ style lw_bool file_exists (const char * filename) // C style lw_bool lw_file_exists (const char * filename)

Description
Returns true if the file specified by filename exists, or false otherwise.

This function will also return false if the file specified by filename is a directory. To determine if a directory exists, use path_exists instead.

Parameters
filename
Any absolute or relative filename.

path_exists

// C++ style lw_bool lacewing::path_exists (const char * filename) // C style lw_bool lw_path_exists (const char * filename)

Description
Returns true if the directory specified by filename exists, or false otherwise.

This function will also return false if the path specified by filename is a file. To determine if a file exists, use file_exists instead.

Parameters
filename
Any absolute or relative filename.

file_size

// C++ style size_t lacewing::file_size (const char * filename) // C style size_t lw_file_size (const char * filename)

Description
Returns the size of a file in bytes, or -1 if the file does not exist.

Parameters
filename
Any absolute or relative filename.

md5

// C++ style void lacewing::md5 (char * output, const char * input, size_t length) // C style void lw_md5 (char * output, const char * input, size_t length)

Description
Returns the MD5 hash of a block of data as the raw hash bytes.

The library itself does not include an MD5 implementation - this function is implemented through either OpenSSL or the Windows Cryptography API.

Parameters
output
A buffer of at least 16 bytes to write the hash to.

input
A pointer to the input data.

length [optional]
The length of the input data, or -1 if the data is a null-terminated string.

md5_hex

// C++ style void lacewing::md5_hex (char * output, const char * input, size_t length) // C style void lw_md5_hex (char * output, const char * input, size_t length)

Description
Returns the MD5 hash of a block of data as a hexadecimal digest.

The library itself does not include an MD5 implementation - this function is implemented through either OpenSSL or the Windows Cryptography API.

Parameters
output
A buffer of at least 33 bytes to write the hash digest to.

input
A pointer to the input data.

length [optional]
The length of the input data, or -1 if the data is a null-terminated string.

random

// C++ style lw_bool lacewing::random (char * buffer, size_t size) // C style lw_bool lw_random (char * buffer, size_t size)

Description
Generates size bytes of random data, returning true on success or false on failure.

Parameters
buffer
A buffer of at least size bytes to store the generated random data.

size
The number of bytes of random data to generate.

sha1

// C++ style void lacewing::sha1 (char * output, const char * input, size_t length) // C style void lw_sha1 (char * output, const char * input, size_t length)

Description
Returns the SHA1 hash of a block of data as the raw hash bytes.

The library itself does not include an SHA1 implementation - this function is implemented through either OpenSSL or the Windows Cryptography API.

Parameters
output
A buffer of at least 20 bytes to write the hash to.

input
A pointer to the input data.

length [optional]
The length of the input data, or -1 if the data is a null-terminated string.

sha1_hex

// C++ style void lacewing::sha1 (char * output, const char * input, size_t length) // C style void lw_sha1 (char * output, const char * input, size_t length)

Description
Returns the SHA1 hash of a block of data as a hexadecimal digest.

The library itself does not include an SHA1 implementation - this function is implemented through either OpenSSL or the Windows Cryptography API.

Parameters
output
A buffer of at least 41 bytes to write the hash digest to.

input
A pointer to the input data.

length [optional]
The length of the input data, or -1 if the data is a null-terminated string.

temp_path

// C++ style void lacewing::temp_path (char * buffer) // C style void lw_temp_path (char * buffer)

Description
Determines the correct place to store temporary files on the current system.

The path retrieved will have a trailing slash.

Parameters
buffer
A buffer of at least 512 bytes to write the path to.

Examples

simple webserver

Outputs "Hello world" and lacewing::version in response to any request

#include <lacewing.h>void on_get (lw_ws webserver, lw_ws_req req) {lw_stream_writef (req, "Hello world from %s", lw_version ()); }int main (int argc, char * argv[]) {lw_pump pump = lw_eventpump_new ();lw_ws webserver = lw_ws_new (pump);lw_ws_on_get (webserver, on_get);lw_ws_host (webserver, 8081);lw_eventpump_start_eventloop (pump);lw_ws_delete (webserver);lw_pump_delete (pump);return 0; }

ajax

即“Asynchronous Javascript And XML”(異步 JavaScript 和 XML),Simple long-poll AJAX example using jQuery

#include <lacewing.h>#include <string.h> #include <iostream> #include <list>using namespace std;list <lacewing::webserver_request> waiting;void on_get (lacewing::webserver, lacewing::webserver_request request) {request->write_file ("ajax.html");request->finish (); }void on_post (lacewing::webserver, lacewing::webserver_request request) {if (!strcmp (request->url (), "poll")){waiting.push_back (request);return;}if (!strcmp (request->url (), "message")){const char * message = request->POST ("message");request->writef ("Message from %s: %s\n",request->address ()->tostring (),message);/* Complete all waiting requests with the message */for(list <lacewing::webserver_request>::iterator it= waiting.begin (); it != waiting.end (); ++ it){lacewing::webserver_request waiting_req = *it;waiting_req->write (message);waiting_req->finish ();}waiting.clear ();request->finish ();return;} }void on_disconnect (lacewing::webserver, lacewing::webserver_request request) {for (list <lacewing::webserver_request>::iterator it= waiting.begin(); it != waiting.end (); ++ it){if(*it == request){waiting.erase (it);break;}} }int main (int argc, char * argv[]) {lacewing::eventpump eventpump = lacewing::eventpump_new ();lacewing::webserver webserver = lacewing::webserver_new (eventpump);/* Enabling this means we will have to call request->finish() to complete* a request. Until request->finish() is called, requests will just hang,* which is exactly what we want for long-poll AJAX.*/webserver->enable_manual_finish ();webserver->on_get (on_get);webserver->on_post (on_post);webserver->on_disconnect (on_disconnect);webserver->host (8080); eventpump->start_eventloop();lacewing::webserver_delete (webserver);lacewing::pump_delete (eventpump);return 0; } <html><head><title>liblacewing AJAX example</title><script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js" type="text/javascript"></script><script type="text/javascript">$(document).ready(function(){$('#broadcast').click(function(){var message = $('#message').val();$('#message').val('');$.post('message', { message: message });});(function doPoll(){$.post('poll', function(message){if(!message)return;$('#messages').prepend($('<li></li>').text(message));doPoll();});})();});</script></head><body><label for="message">Type something to broadcast to everyone</label><input type="text" id="message" /><button id="broadcast">Broadcast!</button><br />Messages:<p><ul id="messages"></ul></p></body> </html>

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