Objective C - 与Android交互时高低位转换：

在与Android交互过程中，因为Android是从低位往高位读，iOS是从高位往低位读，所以交互数据需要进行转换。

/*
 * convert big endian to little endian in C
 */
uint16_t swap_uint16( uint16_t val );
int16_t swap_int16( int16_t val );
uint32_t swap_uint32( uint32_t val );
int32_t swap_int32( int32_t val );
int64_t swap_int64( int64_t val );
uint64_t swap_uint64( uint64_t val );









////////////////////////////////////////////////////////////////////////////////////////////////////
//! Byte swap unsigned short
uint16_t swap_uint16( uint16_t val )
{
    return (val << 8) | (val >> 8 );
}

//! Byte swap short
int16_t swap_int16( int16_t val )
{
    return (val << 8) | ((val >> 8) & 0xFF);
}

//! Byte swap unsigned int
uint32_t swap_uint32( uint32_t val )
{
    val = ((val << 8) & 0xFF00FF00 ) | ((val >> 8) & 0xFF00FF );
    return (val << 16) | (val >> 16);
}

//! Byte swap int
int32_t swap_int32( int32_t val )
{
    val = ((val << 8) & 0xFF00FF00) | ((val >> 8) & 0xFF00FF );
    return (val << 16) | ((val >> 16) & 0xFFFF);
}

int64_t swap_int64( int64_t val )
{
    val = ((val << 8) & 0xFF00FF00FF00FF00ULL ) | ((val >> 8) & 0x00FF00FF00FF00FFULL );
    val = ((val << 16) & 0xFFFF0000FFFF0000ULL ) | ((val >> 16) & 0x0000FFFF0000FFFFULL );
    val = (val << 32) | ((val >> 32) & 0xFFFFFFFFULL);
    return val;
}

uint64_t swap_uint64( uint64_t val )
{
    val = ((val << 8) & 0xFF00FF00FF00FF00ULL ) | ((val >> 8) & 0x00FF00FF00FF00FFULL );
    val = ((val << 16) & 0xFFFF0000FFFF0000ULL ) | ((val >> 16) & 0x0000FFFF0000FFFFULL );
    val = (val << 32) | (val >> 32);
    return val;

}

调用：

UInt64 recordTime = [[NSDate date] timeIntervalSince1970]*1000;
UInt64 value = swap_uint64(recordTime);

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