CocoaAsyncSocket网络通信使用之数据编码和解码（二）

CocoaAsyncSocket网络通信使用之数据编码和解码（二）

在上一篇CocoaAsyncSocket网络通信使用之tcp连接（一）中，我们已经利用CocoaAsyncSocket封装了自己的socket
connection。
本篇主要是通过引入编码器和解码器，将可以共用的内容模块化。

简述：
在tcp的应用中，都是以二机制字节的形式来对数据做传输。
一般会针对业务协议构造对应的数据结构／数据对象，然后在使用的时候针对协议转换成二进制数据发送给服务端。
但是我们在不同的app中，不同的业务场景使用不同的tcp协议，这样每次socket模块的重用性就特别差，即使是完全一样的底层内容，也因为实现的时候耦合性太高，而导致需要全部重新开发。为了实现模块化的重用，我仿照mina和netty，引入编码器和解码器。

接口框架设计：

为了后续扩展和自定义实现自己的编码器／解码器，有了以下的设计接口。

数据包

数据包基本接口定义（ RHSocketPacket.h）：

#import <Foundation/Foundation.h>

@protocol RHSocketPacket <NSObject>

@property (nonatomic, assign, readonly) NSInteger tag;
@property (nonatomic, strong, readonly) NSData *data;

- (instancetype)initWithData:(NSData *)data;

@optional

- (void)setTag:(NSInteger)tag;
- (void)setData:(NSData *)data;

@end

数据包内容接口定义（RHSocketPacketContent.h）：(增加timeout超时字段，主要是针对发送的数据包)

#import <Foundation/Foundation.h>
#import "RHSocketPacket.h"

@protocol RHSocketPacketContent <RHSocketPacket>

@property (nonatomic, readonly) NSTimeInterval timeout;

@optional

- (void)setTimeout:(NSTimeInterval)timeout;

@end

tcp编码器

编码器接口定义（ RHSocketEncoderProtocol.h）：

#import <Foundation/Foundation.h>
#import "RHSocketPacketContent.h"

@protocol RHSocketEncoderOutputDelegate <NSObject>

@required

- (void)didEncode:(NSData *)data timeout:(NSTimeInterval)timeout tag:(NSInteger)tag;

@end

@protocol RHSocketEncoderProtocol <NSObject>

@required

- (void)encodePacket:(id<RHSocketPacketContent>)packet encoderOutput:(id<RHSocketEncoderOutputDelegate>)output;

@end

tcp解码器

解码器接口定义（ RHSocketDecoderProtocol.h）：

#import <Foundation/Foundation.h>
#import "RHSocketPacketContent.h"

@protocol RHSocketDecoderOutputDelegate <NSObject>

@required

- (void)didDecode:(id<RHSocketPacketContent>)packet tag:(NSInteger)tag;

@end

@protocol RHSocketDecoderProtocol <NSObject>

@required

- (NSUInteger)decodeData:(NSData *)data decoderOutput:(id<RHSocketDecoderOutputDelegate>)output tag:(long)tag;//这里有返回值，是了为了处理数据包拼包

@end

ok，经过几次调整，程序员内心无数次纠结后，接口定义终于完成了，接下来我们看看怎么组合使用。

前面的socket connection在使用时，还是需要实现delegate的委托方法的，
在不同的app间使用还是需要copy，再实现数据［编码］、［解码］、［分发］，
然后才到对应的场景。其实在［编码］、［分发］之前都是可以模块化独立的，我们就从这里入手。

架构整合调用

首先引入一个service，来帮我们做［连接］、［编码］、［解码］、［分发］的事情。
废话不多说，直接贴代码。

RHSocketService.h文件：

#import <Foundation/Foundation.h>
#import "RHSocketEncoderProtocol.h"
#import "RHSocketDecoderProtocol.h"

extern NSString *const kNotificationSocketServiceState;
extern NSString *const kNotificationSocketPacketRequest;
extern NSString *const kNotificationSocketPacketResponse;

@interface RHSocketService : NSObject <RHSocketEncoderOutputDelegate, RHSocketDecoderOutputDelegate>

@property (nonatomic, copy) NSString *serverHost;
@property (nonatomic, assign) int serverPort;

@property (nonatomic, strong) id<RHSocketEncoderProtocol> encoder;
@property (nonatomic, strong) id<RHSocketDecoderProtocol> decoder;

@property (assign, readonly) BOOL isRunning;

+ (instancetype)sharedInstance;

- (void)startServiceWithHost:(NSString *)host port:(int)port;
- (void)stopService;

- (void)asyncSendPacket:(id<RHSocketPacketContent>)packet;

@end

RHSocketService.m文件：

#import "RHSocketService.h"
#import "RHSocketConnection.h"
#import "RHSocketDelimiterEncoder.h"
#import "RHSocketDelimiterDecoder.h"

NSString *const kNotificationSocketServiceState = @"kNotificationSocketServiceState";
NSString *const kNotificationSocketPacketRequest = @"kNotificationSocketPacketRequest";
NSString *const kNotificationSocketPacketResponse = @"kNotificationSocketPacketResponse";

@interface RHSocketService () <RHSocketConnectionDelegate>
{
RHSocketConnection *_connection;
}

@end

@implementation RHSocketService

+ (instancetype)sharedInstance
{
static id sharedInstance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}

- (instancetype)init
{
if (self = [super init]) {
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(detectSocketPacketRequest:) name:kNotificationSocketPacketRequest object:nil];
_encoder = [[RHSocketDelimiterEncoder alloc] init];
_decoder = [[RHSocketDelimiterDecoder alloc] init];
}
return self;
}

- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)startServiceWithHost:(NSString *)host port:(int)port
{
NSAssert(_encoder, @"error, _encoder is nil...");
NSAssert(_decoder, @"error, _decoder is nil...");
NSAssert(host.length > 0, @"error, host is nil...");

if (_isRunning) {
return;
}

_serverHost = host;
_serverPort = port;

[self openConnection];
}

- (void)stopService
{
_isRunning = NO;
[self closeConnection];
}

- (void)asyncSendPacket:(id<RHSocketPacketContent>)packet
{
if (!_isRunning) {
NSDictionary *userInfo = @{@"msg":@"Send packet error. Service is stop!"};
NSError *error = [NSError errorWithDomain:@"RHSocketService" code:1 userInfo:userInfo];
[self didDisconnectWithError:error];
return;
}
[_encoder encodePacket:packet encoderOutput:self];
}

#pragma mar -
#pragma mark recevie response data

- (void)detectSocketPacketRequest:(NSNotification *)notif
{
id object = notif.object;
[self asyncSendPacket:object];
}

#pragma mark -
#pragma mark RHSocketConnection method

- (void)openConnection
{
[self closeConnection];
_connection = [[RHSocketConnection alloc] init];
_connection.delegate = self;
[_connection connectWithHost:_serverHost port:_serverPort];
}

- (void)closeConnection
{
if (_connection) {
_connection.delegate = nil;
[_connection disconnect];
_connection = nil;
}
}

#pragma mark -
#pragma mark RHSocketConnectionDelegate method

- (void)didDisconnectWithError:(NSError *)error
{
RHSocketLog(@"didDisconnectWithError: %@", error);
_isRunning = NO;
NSDictionary *userInfo = @{@"isRunning":@(_isRunning), @"error":error};
[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationSocketServiceState object:@(_isRunning) userInfo:userInfo];
}

- (void)didConnectToHost:(NSString *)host port:(UInt16)port
{
_isRunning = YES;
NSDictionary *userInfo = @{@"host":host, @"port":@(port), @"isRunning":@(_isRunning)};
[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationSocketServiceState object:@(_isRunning) userInfo:userInfo];
}

- (void)didReceiveData:(NSData *)data tag:(long)tag
{
NSUInteger remainDataLen = [_decoder decodeData:data decoderOutput:self tag:tag];
if (remainDataLen > 0) {
[_connection readDataWithTimeout:-1 tag:tag];
} else {
[_connection readDataWithTimeout:-1 tag:0];
}
}

#pragma mark -
#pragma mark RHSocketEncoderOutputDelegate method

- (void)didEncode:(NSData *)data timeout:(NSTimeInterval)timeout tag:(NSInteger)tag
{
[_connection writeData:data timeout:timeout tag:tag];
}

#pragma mark -
#pragma mark RHSocketDecoderOutputDelegate method

- (void)didDecode:(id<RHSocketPacketContent>)packet tag:(NSInteger)tag
{
NSDictionary *userInfo = @{@"RHSocketPacketBody":packet, @"tag":@(tag)};
[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationSocketPacketResponse object:nil userInfo:userInfo];
}

@end

测试代码如下：

NSString *host = @"www.baidu.com";
int port = 80;
[[RHSocketService sharedInstance] startServiceWithHost:host port:port];

[RHSocketHttpService sharedInstance].encoder = [[RHSocketHttpEncoder alloc] init];
[RHSocketHttpService sharedInstance].decoder = [[RHSocketHttpDecoder alloc] init];
[[RHSocketHttpService sharedInstance] startServiceWithHost:host port:port];

代码调用方法和过程说明：
1-通过startServiceWithHost方法，可实现对服务器的连接。
2-客户端给服务端发送数据，在连接成功后，可以调用asyncSendPacket方法发送数据包。也可以通过notification发送kNotificationSocketPacketRequest通知，发送数据包。在发送数据的过程中，会通过编码器，编码完成后通过connection发送给服务端。
3-服务端向客户端推送数据，会触发didReceiveData方法的回调，通过解码器，解码完成后发出通知给对应的分发器（分发器针对业务调整实现）

代码中是默认的解码器和编码器，针对数据中的分隔符处理，也可以自定义分隔符和数据帧的最大值，代码如下：

分隔符编码器

RHSocketDelimiterEncoder.h文件：

#import <Foundation/Foundation.h>
#import "RHSocketEncoderProtocol.h"

/**
*  针对数据包分隔符编码器
*  默认数据包中每帧最大值为8192（maxFrameSize == 8192）
*  默认数据包每帧分隔符为0xff（delimiter == 0xff）
*/
@interface RHSocketDelimiterEncoder : NSObject <RHSocketEncoderProtocol>

@property (nonatomic, assign) NSUInteger maxFrameSize;
@property (nonatomic, assign) uint8_t delimiter;

@end

RHSocketDelimiterEncoder.m文件：

#import "RHSocketDelimiterEncoder.h"
#import "RHSocketConfig.h"

@implementation RHSocketDelimiterEncoder

- (instancetype)init
{
if (self = [super init]) {
_maxFrameSize = 8192;
_delimiter = 0xff;
}
return self;
}

- (void)encodePacket:(id<RHSocketPacketContent>)packet encoderOutput:(id<RHSocketEncoderOutputDelegate>)output
{
NSData *data = [packet data];
NSMutableData *sendData = [NSMutableData dataWithData:data];
[sendData appendBytes:&_delimiter length:1];
NSAssert(sendData.length < _maxFrameSize, @"Encode frame is too long...");

NSTimeInterval timeout = [packet timeout];
NSInteger tag = [packet tag];
RHSocketLog(@"tag:%ld, timeout: %f, data: %@", (long)tag, timeout, sendData);
[output didEncode:sendData timeout:timeout tag:tag];
}

@end

分隔符解码器
RHSocketDelimiterDecoder.h文件：

#import <Foundation/Foundation.h>
#import "RHSocketDecoderProtocol.h"

/**
*  针对数据包分隔符解码器
*  默认数据包中每帧最大值为8192（maxFrameSize == 8192）
*  默认数据包每帧分隔符为0xff（delimiter == 0xff）
*/
@interface RHSocketDelimiterDecoder : NSObject <RHSocketDecoderProtocol>

@property (nonatomic, assign) NSUInteger maxFrameSize;
@property (nonatomic, assign) uint8_t delimiter;

@end

RHSocketDelimiterDecoder.m文件：

#import "RHSocketDelimiterDecoder.h"
#import "RHPacketBody.h"

@interface RHSocketDelimiterDecoder ()
{
NSMutableData *_receiveData;
}

@end

@implementation RHSocketDelimiterDecoder

- (instancetype)init
{
if (self = [super init]) {
_maxFrameSize = 8192;
_delimiter = 0xff;
}
return self;
}

- (NSUInteger)decodeData:(NSData *)data decoderOutput:(id<RHSocketDecoderOutputDelegate>)output tag:(long)tag
{
@synchronized(self) {
if (_receiveData) {
[_receiveData appendData:data];
} else {
_receiveData = [NSMutableData dataWithData:data];
}

NSUInteger dataLen = _receiveData.length;
NSInteger headIndex = 0;

for (NSInteger i=0; i<dataLen; i++) {
NSAssert(i < _maxFrameSize, @"Decode frame is too long...");
uint8_t byte;
[_receiveData getBytes:&byte range:NSMakeRange(i, 1)];
if (byte == _delimiter) {
NSInteger packetLen = i - headIndex;
NSData *packetData = [_receiveData subdataWithRange:NSMakeRange(headIndex, packetLen)];
RHPacketBody *body = [[RHPacketBody alloc] initWithData:packetData];
[output didDecode:body tag:0];
headIndex = i + 1;
}
}

NSData *remainData = [_receiveData subdataWithRange:NSMakeRange(headIndex, dataLen-headIndex)];
[_receiveData setData:remainData];

return _receiveData.length;
}//@synchronized
}

@end

总结：

目前没来得及提供服务器代码，不过socket框架已经基本完整，可以根据不同的协议扩展实现自定义的编码器和解码器。
测试代码中访问的是百度的首页，为http协议，需要额外实现http协议的编码器和解码器。
下一篇，我们来实现针对http的简单编码器和解码器。

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