请求一个C语言的问题

只看该作者 · 2010-1-10 21:06

U8 SDBuffer[512];
U32 tmp；
SDBuffer[0x1c6]=0x61;
SDBuffer[0x1c7]=0;
SDBuffer[0x1c8]=0;
SDBuffer[0x1c9]=0;
为什么tmp = SDBuffer[0x1c9]<<24 + SDBuffer[0x1c8]<<16 + SDBuffer[0x1c7]<<8 + SDBuffer[0x1c6]或者(32)SDBuffer[0x1c9]<<24 + (32)SDBuffer[0x1c8]<<16 + (32)SDBuffer[0x1c7]<<8 + (32)SDBuffer[0x1c6]后tmp都是等于0呢
只有tmp = SDBuffer[0x1c9]*256*256*256 + SDBuffer[0x1c8]*256*256 + SDBuffer[0x1c7]*256+ SDBuffer[0x1c6]或者tmp = (* (U16 *) (buffer + 0x1c6)) + ((* (U16 *) (buffer + 0x1c8)) << 16)后tmp才等于0x61
我用的是32位的ARM