<分区>
我有一个已经存在于数据库中的 B 树。现在，下面一段由其他程序员编写的代码试图遍历 B-Tree。但是，我无法理解函数的用途:readInner1(page,slot) 和 readInnerPage(page,slot)。有人可以通过使用这两个函数帮助我理解代码的作用吗？
static inline unsigned readUint32Aligned(const unsigned char* data) { return toHost(*reinterpret_cast<const uint32_t*>(data)); }
/// The page remains accessible during the lifetime of the BufferReference object.
class BufferReference
{
public:
/// The size of a page
static const unsigned pageSize = 16384;
/// A page buffer
struct PageBuffer { char data[pageSize]; };
private:
/// The buffer frame
const BufferFrame* frame;
/// No copying of references
BufferReference(const BufferReference&);
void operator=(const BufferReference&);
public:
/// Constructor
BufferReference();
/// Constructor from a request
BufferReference(const BufferRequest& request);
/// Destructor
/// Access the page
const void* getPage() const;
/// Get the page number
unsigned getPageNo() const;
};
Info1(unsigned root,unsigned value1)
{
// Traverse the B-Tree
#define readInner1(page,slot) readUint32Aligned(page+24+8*(slot))
#define readInnerPage(page,slot) readUint32Aligned(page+24+8*(slot)+4)
BufferReference ref;
ref=readShared(root);
while (true) {
const unsigned char* page=static_cast<const unsigned char*>(ref.getPage());
// Inner node?
if (readUint32Aligned(page+8)==0xFFFFFFFF) {
// Perform a binary search. The test is more complex as we only have the upper bound for ranges
unsigned left=0,right=readUint32Aligned(page+16);
cout<<"\n right="<<right<<"\n";
while (left!=right) {
unsigned middle=(left+right)/2;
printf("\n MIDDLE=%d",middle);
unsigned middle1=readInner1(page,middle);
cout<<"\n middle1="<<middle1<<"\t value1="<<value1<<"\n";
if (value1>middle1) {
left=middle+1;
cout<<"\n left="<<left<<"\n";
} else if ((!middle)||(value1>readInner1(page,middle-1))) {
ref=readShared(readInnerPage(page,middle));
break;
} else {
right=middle;
cout<<"\n right="<<right<<"\n";
}
}
// Unsuccessful search?
if (left==right) {
ref.reset();
return false;
}
} else {
// A leaf node
break;
}
}
#undef readInnerPage
#undef readInner1
}
如果有人能解释一下代码就更好了？