音频caf 转 mp3 遇到一段神奇的代码如下:

#pragma mark - caf转mp3
- (void)audio_PCMtoMP3Result:(void(^)(NSData *))result
{
    
    @try {
        int read, write;
        FILE *pcm = fopen([self.cafPathStr cStringUsingEncoding:1], "rb");  //source 被转换的音频文件位置
        fseek(pcm, 4*1024, SEEK_CUR);                                   //skip file header
        FILE *mp3 = fopen([self.mp3PathStr cStringUsingEncoding:1], "wb");  //output 输出生成的Mp3文件位置
        
        const int PCM_SIZE = 8192;
        const int MP3_SIZE = 8192;
        short int pcm_buffer[PCM_SIZE*2];
        unsigned char mp3_buffer[MP3_SIZE];
        
        lame_t lame = lame_init();
        lame_set_in_samplerate(lame, 11025.0);
        lame_set_VBR(lame, vbr_default);
        lame_init_params(lame);
        
        do {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wshorten-64-to-32"

            read = fread(pcm_buffer, 2*sizeof(short int), PCM_SIZE, pcm);
#pragma clang diagnostic pop
            if (read == 0)
                write = lame_encode_flush(lame, mp3_buffer, MP3_SIZE);
            else
                write = lame_encode_buffer_interleaved(lame, pcm_buffer, read, mp3_buffer, MP3_SIZE);
            
            fwrite(mp3_buffer, write, 1, mp3);
            
        } while (read != 0);
        
        lame_close(lame);
        fclose(mp3);
        fclose(pcm);
    }
    @catch (NSException *exception) {
        NSLog(@"%@",[exception description]);
    }
    @finally {
        NSLog(@"MP3生成成功: %@",self.mp3PathStr);
        result([NSData dataWithContentsOfFile:self.mp3PathStr]);
    }
    
}

@try @catch @finally 是个什么鬼东西?

大概分析一下代码逻辑如下:

@try {
 ... 逻辑处理
 ...执行的代码，其中可能有异常。一旦发现异常，则立即跳到catch执行。否则不会执行catch里面的内容
}

@catch {
  ... 异常捕捉
   ...除非try里面执行代码发生了异常，否则这里的代码不会执行
}

@finally{
  ... 逻辑执行结果
  ...不管什么情况都会执行，包括try catch 里面用了return ,可以理解为只要执行了try或者catch，就一定会执行 finally
}