//
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// RHSocketUtils+Protobuf.m
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// RHSocketKitDemo
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//
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// Created by zhuruhong on 16/5/26.
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// Copyright © 2016年 zhuruhong. All rights reserved.
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//
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#import "RHSocketUtils+Protobuf.h"
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@implementation RHSocketUtils (Protobuf)
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/**
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* 计算出一帧数据的长度字节个数 (1～5)
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*
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* @param frameData 带解码字节
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*
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* @return 返回一帧数据的长度字节个数, varint32, 返回值为1～5有效，－1为计算失败
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*/
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+ (NSInteger)computeCountOfLengthByte:(NSData *)frameData
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{
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//默认长度字节个数为－1
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NSInteger countOfLengthByte = -1;
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//最大尝试读区个数为4个字节，超过则认为是大数据5个字节
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NSInteger maxCountOfLengthByte = MIN(frameData.length, 4);
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//从第1个字节开始尝试读取计算
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NSInteger testIndex = 0;
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while (testIndex < maxCountOfLengthByte) {
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NSRange lengthRange = NSMakeRange(testIndex, 1);
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NSData *oneByte = [frameData subdataWithRange:lengthRange];
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int8_t oneValue = [RHSocketUtils int8FromBytes:oneByte];
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if ((oneValue & 0x80) == 0) {
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countOfLengthByte = testIndex + 1;
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break;
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}
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testIndex++;//增加长度字节个数
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}//while
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//超过4个字节，则认为是大数据5个字节
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if (testIndex >= 4) {
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countOfLengthByte = 5;
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}
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return countOfLengthByte;
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}
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+ (int64_t)valueWithVarint32Data:(NSData *)data
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{
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NSUInteger dataLen = data.length;
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int64_t value = 0;
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int offset = 0;
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while (offset < dataLen) {
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int32_t tempVal = 0;
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[data getBytes:&tempVal range:NSMakeRange(offset, 1)];
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tempVal = (tempVal & 0x7F);
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value += (tempVal << (7 * offset));
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offset++;
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}//while
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return value;
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}
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+ (NSData *)dataWithRawVarint32:(int64_t)value
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{
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NSMutableData *valData = [[NSMutableData alloc] init];
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while (true) {
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if ((value & ~0x7F) == 0) {//如果最高位是0，只要一个字节表示
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[valData appendBytes:&value length:1];
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break;
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} else {
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int valChar = (value & 0x7F) | 0x80;//先写入低7位，最高位置1
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[valData appendBytes:&valChar length:1];
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value = value >> 7;//再写高7位
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}
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}
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return valData;
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}
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@end
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