//-------------------------------------------------------------------------------------------------------------------
// bwrite() -- Write b's contents to disk. Must be B_BUSY.
//-------------------------------------------------------------------------------------------------------------------
void bwrite(struct buf *b)
{
if ((b->flags & B_BUSY) == 0) panic("bwrite");
b->flags |= B_DIRTY;
iderw(b);
}
// Return a B_BUSY buf with the contents of the indicated disk sector.
struct buf*
bread(uint dev, uint sector)
{
struct buf *b;
b = bget(dev, sector);
if(!(b->flags & B_VALID))
iderw(b);
return b;
}
// Return a B_BUSY buf with the contents of the indicated block.
struct buf*
bread(uint dev, uint blockno)
{
struct buf *b;
b = bget(dev, blockno);
if(!(b->flags & B_VALID)) {
iderw(b);
}
return b;
}
// Return a B_BUSY buf with the contents of the indicated block.
struct buf*
bread(uint dev, uint blockno)
{
struct buf *b;
//回收回来的要么是一个已经存在的，但可能是dirty的数据。也有可能是个什么都没有的。
//0和dirty是不一样的。dirty是写回去，0是直接从硬盘里面读数据的。
b = bget(dev, blockno);
if(!(b->flags & B_VALID)) {
iderw(b);
}
return b;
}
int main()
{
char tmp[512] = "abcd";
struct buf *b;
b = (struct buf *)malloc(sizeof(struct buf));
memmove(b->data,tmp,512);
b->dev = 1;
b->blockno = 1;
b->flags = 0;
iderw(b);
printf("The is %s\n",b->data);
return 0;
//Test the write [0,0] abcd
b->dev = 0;
b->blockno = 0;
b->flags = B_DIRTY;
iderw(b);
//Test the write [0,1] abcd
b->flags = B_DIRTY;
b->blockno = 1;
iderw(b);
idedump(0,0);
idedump(0,1);
memset(b->data,'z',512);
printf("The buf b is %s:\n",b->data);
//这种情况下，lseek会失败的。
//b->blockno = 2;
iderw(b);
printf("The [0,1] is %s:\n",b->data);
b->flags = B_DIRTY;
memset(b->data,'a',512);
b->blockno = 0;
iderw(b);
idedump(0,0);
idedump(0,1);
printf("-------------------------\n");
idedump(0,3);
b->blockno = 3;
iderw(b);
printf("The buf b is %s:\n",b->data);
// lseek if beyond the len of file,lseek is success,but will read the 0 data.
}
// Write b's contents to disk. Must be B_BUSY.
void
bwrite(struct buf *b)
{
b->flags |= B_DIRTY;
iderw(b);
}
