code:mmwrite - ikarishinjieva/unixV6-code-analyze-chs GitHub Wiki

9041

9042 mmwrite(dev)

9043 {

9044     register c, bn, on;

9045     int a, d;

9046

9047     if(dev.d_minor == 2) {

9048          c = u.u_count;

9049          u.u_count = 0;

9050          u.u_base =+ c;

9051          dpadd(u.u_offset, c);

9052          return;

9053     }

• "无底洞"模式，只修改参数

9054     for(;;) {

9055          bn = lshift(u.u_offset, -6);

9056          on = u.u_offset[1] & 077;

• bn ← 块号
• on ← 块内偏移

9057          if ((c=cpass())<0 || u.u_error!=0)

9058           break;

9059          a = UISA->r[0];

9060          d = UISD->r[0];

9061          spl7();

9062          UISA->r[0] = bn;

9063          UISD->r[0] = 077406;

• LIONS 源代码为 9059          a = UISA[[skill:r|->r]][0] = bn;

9060 &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;d = UISD->r[0] = 077406; 9061 &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;spl7(); 9062 &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;UISA->r[0]; 9063 &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;UISD->r[0]; 疑为笔误

9064          if(dev.d_minor == 1)

9065          UISA->r[0] = (ka6-6)->r[(bn>>7)&07]

9066                               + (bn & 0177);

• 若 模式为 写入核心态内存，则将 UISA[0] 置核心态地址

9067          suibyte(on, c);

• 以 UISA0/UISD0 寻址，第0块第on个字节

9068          UISA->r[0] = a;

9069          UISD->r[0] = d;

9070          spl0();

9071     }

9072 }

9073 /* ------------------------- */

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• code:cdevsw