Question

#include <stdio.h>
#include <map>
#include <set>
#include <string>
#include <iostream>
struct map_pair
{
int key;
const char *value;
};

struct tree_node
{
int M_color; // 0 - Red, 1 - Black
struct tree_node *M_parent;
struct tree_node *M_left;
struct tree_node *M_right;
};
struct tree_struct
{
int M_key_compare;
struct tree_node M_header;
size_t M_node_count;
};
void dump_tree_node (struct tree_node *n, bool is_set, bool traverse, bool dump_keys_and_values)
{
printf ("ptr=0x%p M_left=0x%p M_parent=0x%p M_right=0x%p M_color=%d\n",
n, n->M_left, n->M_parent, n->M_right, n->M_color);
void *point_after_struct=((char*)n)+sizeof(struct tree_node);
if (dump_keys_and_values)
{
if (is_set)
printf ("key=%d\n", *(int*)point_after_struct);
else
{
struct map_pair *p=(struct map_pair *)point_after_struct;
printf ("key=%d value=[%s]\n", p->key, p->value);
};
};
if (traverse==false)
return;
if (n->M_left)
dump_tree_node (n->M_left, is_set, traverse, dump_keys_and_values);
if (n->M_right)
dump_tree_node (n->M_right, is_set, traverse, dump_keys_and_values);
};
const char* ALOT_OF_TABS="\t\t\t\t\t\t\t\t\t\t\t";
void dump_as_tree (int tabs, struct tree_node *n, bool is_set)
{
void *point_after_struct=((char*)n)+sizeof(struct tree_node);
if (is_set)
printf ("%d\n", *(int*)point_after_struct);
else
{
struct map_pair *p=(struct map_pair *)point_after_struct;
printf ("%d [%s]\n", p->key, p->value);
}
if (n->M_left)
{
printf ("%.*sL-------", tabs, ALOT_OF_TABS);
dump_as_tree (tabs+1, n->M_left, is_set);
};
if (n->M_right)
{
printf ("%.*sR-------", tabs, ALOT_OF_TABS);
dump_as_tree (tabs+1, n->M_right, is_set);
};
};
void dump_map_and_set(struct tree_struct *m, bool is_set)
{
printf ("ptr=0x%p, M_key_compare=0x%x, M_header=0x%p, M_node_count=%d\n",
m, m->M_key_compare, &m->M_header, m->M_node_count);
dump_tree_node (m->M_header.M_parent, is_set, true, true);
printf ("As a tree:\n");
printf ("root----");
dump_as_tree (1, m->M_header.M_parent, is_set);
};
int main()
{
// map
std::map<int, const char*> m;
m[10]="ten";
m[20]="twenty";
m[3]="three";
m[101]="one hundred one";
m[100]="one hundred";
m[12]="twelve";
m[107]="one hundred seven";
m[0]="zero";
m[1]="one";
m[6]="six";
m[99]="ninety-nine";
m[5]="five";
m[11]="eleven";
m[1001]="one thousand one";
m[1010]="one thousand ten";
m[2]="two";
m[9]="nine";
printf ("dumping m as map:\n");
dump_map_and_set ((struct tree_struct *)(void*)&m, false);
std::map<int, const char*>::iterator it1=m.begin();
printf ("m.begin():\n");
dump_tree_node ((struct tree_node *)*(void**)&it1, false, false, true);
it1=m.end();
printf ("m.end():\n");
dump_tree_node ((struct tree_node *)*(void**)&it1, false, false, false);
// set
std::set<int> s;
s.insert(123);
s.insert(456);
s.insert(11);
s.insert(12);
s.insert(100);
s.insert(1001);
printf ("dumping s as set:\n");
dump_map_and_set ((struct tree_struct *)(void*)&s, true);
std::set<int>::iterator it2=s.begin();
printf ("s.begin():\n");
dump_tree_node ((struct tree_node *)*(void**)&it2, true, false, true);
it2=s.end();
printf ("s.end():\n");
dump_tree_node ((struct tree_node *)*(void**)&it2, true, false, false);
};

dumping m as map:
ptr=0x0028FE3C, M_key_compare=0x402b70, M_header=0x0028FE40, M_node_count=17
ptr=0x007A4988 M_left=0x007A4C00 M_parent=0x0028FE40 M_right=0x007A4B80 M_color=1
key=10 value=[ten]
ptr=0x007A4C00 M_left=0x007A4BE0 M_parent=0x007A4988 M_right=0x007A4C60 M_color=1
key=1 value=[one]
ptr=0x007A4BE0 M_left=0x00000000 M_parent=0x007A4C00 M_right=0x00000000 M_color=1
key=0 value=[zero]
ptr=0x007A4C60 M_left=0x007A4B40 M_parent=0x007A4C00 M_right=0x007A4C20 M_color=0
key=5 value=[five]
ptr=0x007A4B40 M_left=0x007A4CE0 M_parent=0x007A4C60 M_right=0x00000000 M_color=1
key=3 value=[three]
ptr=0x007A4CE0 M_left=0x00000000 M_parent=0x007A4B40 M_right=0x00000000 M_color=0
key=2 value=[two]
ptr=0x007A4C20 M_left=0x00000000 M_parent=0x007A4C60 M_right=0x007A4D00 M_color=1
key=6 value=[six]
ptr=0x007A4D00 M_left=0x00000000 M_parent=0x007A4C20 M_right=0x00000000 M_color=0
key=9 value=[nine]
ptr=0x007A4B80 M_left=0x007A49A8 M_parent=0x007A4988 M_right=0x007A4BC0 M_color=1
key=100 value=[one hundred]
ptr=0x007A49A8 M_left=0x007A4BA0 M_parent=0x007A4B80 M_right=0x007A4C40 M_color=0
key=20 value=[twenty]
ptr=0x007A4BA0 M_left=0x007A4C80 M_parent=0x007A49A8 M_right=0x00000000 M_color=1
key=12 value=[twelve]
ptr=0x007A4C80 M_left=0x00000000 M_parent=0x007A4BA0 M_right=0x00000000 M_color=0
key=11 value=[eleven]
ptr=0x007A4C40 M_left=0x00000000 M_parent=0x007A49A8 M_right=0x00000000 M_color=1
key=99 value=[ninety-nine]
ptr=0x007A4BC0 M_left=0x007A4B60 M_parent=0x007A4B80 M_right=0x007A4CA0 M_color=0
key=107 value=[one hundred seven]
ptr=0x007A4B60 M_left=0x00000000 M_parent=0x007A4BC0 M_right=0x00000000 M_color=1
key=101 value=[one hundred one]
ptr=0x007A4CA0 M_left=0x00000000 M_parent=0x007A4BC0 M_right=0x007A4CC0 M_color=1
key=1001 value=[one thousand one]
ptr=0x007A4CC0 M_left=0x00000000 M_parent=0x007A4CA0 M_right=0x00000000 M_color=0
key=1010 value=[one thousand ten]
As a tree:
root----10 [ten]
L-------1 [one]
L-------0 [zero]
R-------5 [five]
L-------3 [three]
L-------2 [two]
R-------6 [six]
R-------9 [nine]
R-------100 [one hundred]
L-------20 [twenty]
L-------12 [twelve]
L-------11 [eleven]
R-------99 [ninety-nine]
R-------107 [one hundred seven]
L-------101 [one hundred one]
R-------1001 [one thousand one]
R-------1010 [one thousand ten]
m.begin():
ptr=0x007A4BE0 M_left=0x00000000 M_parent=0x007A4C00 M_right=0x00000000 M_color=1
key=0 value=[zero]
m.end():
ptr=0x0028FE40 M_left=0x007A4BE0 M_parent=0x007A4988 M_right=0x007A4CC0 M_color=0
dumping s as set:
ptr=0x0028FE20, M_key_compare=0x8, M_header=0x0028FE24, M_node_count=6
ptr=0x007A1E80 M_left=0x01D5D890 M_parent=0x0028FE24 M_right=0x01D5D850 M_color=1
key=123
ptr=0x01D5D890 M_left=0x01D5D870 M_parent=0x007A1E80 M_right=0x01D5D8B0 M_color=1
key=12
ptr=0x01D5D870 M_left=0x00000000 M_parent=0x01D5D890 M_right=0x00000000 M_color=0
key=11
ptr=0x01D5D8B0 M_left=0x00000000 M_parent=0x01D5D890 M_right=0x00000000 M_color=0
key=100
ptr=0x01D5D850 M_left=0x00000000 M_parent=0x007A1E80 M_right=0x01D5D8D0 M_color=1
key=456
ptr=0x01D5D8D0 M_left=0x00000000 M_parent=0x01D5D850 M_right=0x00000000 M_color=0
key=1001
As a tree:
root----123
L-------12
L-------11
R-------100
R-------456
R-------1001
s.begin():
ptr=0x01D5D870 M_left=0x00000000 M_parent=0x01D5D890 M_right=0x00000000 M_color=0
key=11
s.end():
ptr=0x0028FE24 M_left=0x01D5D870 M_parent=0x007A1E80 M_right=0x01D5D8D0 M_color=0

GCC 的实现也很类似。唯一一的不同点就是没有 Isnil 元素，因此占用的空间要小于 MSVC 的实现。跟节点也是作为.end() 迭代器指向的位置，同时也不包含键和值。