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。将能够共用的内容模块化。

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。

通常会针对业务协议构造相应的数据结构／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。

可是我们在不同的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。即使是全然一样的底层内容，也由于实现的时候耦合性太高。而导致须要所有又一次开发。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：

为了兴许扩展和自己定义实现自己的编码器／解码器。有了下面的设计接口。

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）：(添加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，程序猿内心无数次纠结后，接口定义最终完毕了，接下来我们看看怎么组合使用。

前面的socket connection在使用时，还是须要实现delegate的托付方法的，

在不同的app间使用还是须要copy，再实现数据［编码］、［解码］、［分发］，

然后才到相应的场景。

事实上在［编码］、［分发］之前都是能够模块化独立的，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

測试代码例如以下：

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server的连接。

2-client给服务端发送数据，在连接成功后。能够调用asyncSendPacket方法发送数据包。也能够通过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，编码完毕后通过connection发送给服务端。

3-服务端向client推送数据，会触发didReceiveData方法的回调，通过解码器，解码完毕后发出通知给相应的分发器（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，也能够自己定义分隔符和数据帧的最大值。代码例如以下：

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：

眼下没来得及提供server代码，只是socket框架已经基本完整，能够依据不同的协议扩展实现自己定义的编码器和解码器。

測试代码中訪问的是百度的首页，为http协议，须要额外实现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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