和内核中的hash table一样，内核中的红黑树比较“裸”。出于效率方面的考虑，并没有把所有的操作都封装起来。
在执行插入操作的时候，需要使用者自己按照搜索二叉树的方法找到想要插入的节点的父节点，然后调用rb_link_node函数将节点插入，再调用rb_insert_color函数对红黑树进行适当的“旋转”。
而在搜索红黑树的时候，则需要使用者自己按照普通二叉树的搜索方法进行搜索。当然，如何比较键值的大小也是使用者自己决定的。
内核的Documentation目录下有一篇rbtree.txt的文档详细的介绍了该如何使用红黑树。
下面是我写的一个使用红黑树的小例子，可在2.6.32下运行。在这个小程序中，coef被当作键值来使用。
#include <linux/init.h>
#include <linux/module.h>
#include <linux/rbtree.h>
struct q_coef
{
u8 coef;
u8 index;
struct rb_node node;
};
#define COEF_NUM 15
u8 coef[15] = {
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13,
};
struct q_coef q_coef[COEF_NUM];
static void q_coef_init(void)
{
int i;
memset(&q_coef, 0, sizeof(q_coef));
for (i = 0 ; i < COEF_NUM ; i++) {
q_coef[i].coef = coef[i];
q_coef[i].index = i + 1;
}
}
struct rb_root q_coef_tree = RB_ROOT;
static int q_coef_insert(struct rb_root *root, struct q_coef *data)
{
struct rb_node **new = &(root->rb_node), *parent = NULL;
/* Figure out where to put new code */
while (*new) {
struct q_coef *this = rb_entry(*new, struct q_coef, node);
parent = *new;
if (data->coef < this->coef)
new = &((*new)->rb_left);
else if (data->coef > this->coef)
new = &((*new)->rb_right);
else
return -1;
}
/* Add new node and rebalance tree. */
rb_link_node(&data->node, parent, new);
rb_insert_color(&data->node, root);
return 0;
}
static struct q_coef *q_coef_search(struct rb_root *root, u8 coef)
{
struct rb_node *node = root->rb_node;
while (node) {
struct q_coef *data = rb_entry(node, struct q_coef, node);
if (coef < data->coef)
node = node->rb_left;
else if (coef > data->coef)
node = node->rb_right;
else
return data;
}
return NULL;
}
static int rbtest_init (void)
{
int i;
struct q_coef *ptr;
struct rb_node *node;
int ret;
q_coef_init();
for (i = 0 ; i < COEF_NUM ; i++) {
ret = q_coef_insert(&q_coef_tree, &q_coef[i]);
if (ret < 0) {
printk(KERN_WARNING "q_coef_insert failed, i=%d\n", i);
return -1;
}
}
printk(KERN_INFO "search by input order:\n");
for (i = 0 ; i < COEF_NUM ; i++) {
ptr = q_coef_search(&q_coef_tree, coef[i]);
if (ptr == NULL) {
printk(KERN_WARNING "q_coef_search failed, i=%d\n", i);
return -1;
}
printk(KERN_INFO "coef[%02d]=0x%02x ptr->coef=0x%02x ptr->index=%02d\n",
i, coef[i], ptr->coef, ptr->index);
}
printk(KERN_INFO "search from first:\n");
for (node = rb_first(&q_coef_tree) ; node ; node = rb_next(node)) {
ptr = rb_entry(node, struct q_coef, node);
printk(KERN_INFO "ptr->coef=0x%02x ptr->index=%02d\n", ptr->coef, ptr->index);
}
printk(KERN_INFO "search from last:\n");
for (node = rb_last(&q_coef_tree) ; node ; node = rb_prev(node)) {
ptr = rb_entry(node, struct q_coef, node);
printk(KERN_INFO "ptr->coef=0x%02x ptr->index=%02d\n", ptr->coef, ptr->index);
}
printk(KERN_INFO "rbtest done\n");
return -1;
}
static void rbtest_exit (void)
{
}
module_init(rbtest_init);
module_exit(rbtest_exit);
MODULE_LICENSE("Dual BSD/GPL");
2010年11月14日星期日
2010年11月12日星期五
GF(2**8)的计算器
实现生成多项式为F(x) = x**8 + x**4 + x**3 + x**2 + 1的伽罗华域的加，减，乘，除，乘方运算。可以带括号。
将下面代码保存为pq.py,chmod +x pq.py，然后./pq.py即可进入计算器。按q退出。
解析算数表达式的程序有些问题，不支持乘方和其他运算混合。
#! /usr/bin/env python
# reference to http://www.cnblogs.com/flyingbread/archive/2007/02/03/638932.html
import re
def is_operator(ch):
if ch == '+' or ch == '-' or ch == '*' or ch == '/' or ch == '**':
return True
else:
return False
def is_parentheses_left(ch):
if ch == '(':
return True
else:
return False
def is_parentheses_right(ch):
if ch == ')':
return True
else:
return False
def opt_priority(ch):
if ch == '+' or ch == '-':
priority = 1
elif ch == '*' or ch == '/':
priority = 2
elif ch == '**':
priority = 3
else:
# maybe '('
priority = 0
return priority
# now we only support 2 operation number
def get_operation_number(ch):
if ch == '+' or ch == '-' or ch == '*' or ch == '/' or ch == '**':
return 2
else:
return 1
# primitive polynomial for GF(2**8)
# F(x) = x**8 + x**4 + x**3 + x**2 + 1
def do_add(a, b):
return a ^ b
def do_sub(a, b):
return a ^ b
gflog = [
0x00, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6, 0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81, 0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,
0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21, 0x35, 0x93, 0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45,
0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9, 0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72, 0xa6,
0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd, 0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88,
0x36, 0xd0, 0x94, 0xce, 0x8f, 0x96, 0xdb, 0xbd, 0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40,
0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e, 0x6b, 0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d,
0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b, 0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3, 0xa7, 0x57,
0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d, 0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18,
0xe3, 0xa5, 0x99, 0x77, 0x26, 0xb8, 0xb4, 0x7c, 0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e,
0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd, 0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61,
0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e, 0x84, 0x3c, 0x39, 0x53, 0x47, 0x6d, 0x41, 0xa2,
0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76, 0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6,
0x6c, 0xa1, 0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa, 0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a,
0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0, 0x51, 0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7,
0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8, 0x74, 0xd6, 0xf4, 0xea, 0xa8, 0x50, 0x58, 0xaf,
]
gfilog = [
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26,
0x4c, 0x98, 0x2d, 0x5a, 0xb4, 0x75, 0xea, 0xc9, 0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0,
0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35, 0x6a, 0xd4, 0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23,
0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0, 0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde, 0xa1,
0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc, 0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0,
0xfd, 0xe7, 0xd3, 0xbb, 0x6b, 0xd6, 0xb1, 0x7f, 0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2,
0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88, 0x0d, 0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce,
0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93, 0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33, 0x66, 0xcc,
0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9, 0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54,
0xa8, 0x4d, 0x9a, 0x29, 0x52, 0xa4, 0x55, 0xaa, 0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73,
0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e, 0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff,
0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4, 0x95, 0x37, 0x6e, 0xdc, 0xa5, 0x57, 0xae, 0x41,
0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e, 0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6,
0x51, 0xa2, 0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef, 0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09,
0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5, 0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,
0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83, 0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x00,
]
def do_mul(a, b):
if a == 0 or b == 0:
return 0;
else:
tmp = gflog[a] + gflog[b]
tmp = tmp % 255
return gfilog[tmp]
def do_div(a, b):
if a == 0:
return 0
elif b == 0:
print 'can not div 0'
return 0;
else:
tmp = gflog[a] - gflog[b]
if tmp < 0:
tmp = tmp + 255
return gfilog[tmp]
def do_power(a, b):
count = 0
result = 1
while (count < b):
result = do_mul(result, a)
count += 1
return result
def calc_once(num, ch):
if ch == '+':
ret = do_add(num[1], num[0])
elif ch == '-':
ret = do_sub(num[1], num[0])
elif ch == '*':
ret = do_mul(num[1], num[0])
elif ch == '/':
ret = do_div(num[1], num[0])
elif ch == '**':
ret = do_power(num[1], num[0])
else:
print 'unknow operation'
ret = 0
return ret
# 1. get ch from left to right
# 2. if ch is a number, output it
# 3. if ch is a operator or parenthese:
# a: if ch is '(', push to stack
# b: if ch is ')', pop stack until meet '('
# c: if ch is not parenthese, compare its priority with stack pop
# if ch priority is higher than the stack pop, push ch to stack
# else pop stack, push ch to stack
def midfix_to_posfix(midfix):
stack = []
posfix = []
for ch in midfix:
if is_parentheses_left(ch):
stack.append(ch)
elif is_parentheses_right(ch):
while True:
ch1 = stack.pop()
if is_parentheses_left(ch1):
break
else:
posfix.append(ch1)
elif is_operator(ch):
if len(stack) == 0:
stack.append(ch)
else:
ch1 = stack[-1]
if opt_priority(ch) > opt_priority(ch1):
stack.append(ch)
else:
ch1 = stack.pop()
posfix.append(ch1)
stack.append(ch)
else:
if len(ch) > 2 and ch[0:2] == '0x':
ch = int(ch, 16)
else:
ch = int(ch, 10)
posfix.append(ch)
while len(stack) != 0:
posfix.append(stack.pop())
return posfix
# get data from left to right
# if ch is a number, push to stack
# if ch is a operator, pop the number it needed, do calc, and push result to stack
# if data is paser comlete, pop the stack as result
def calc_posfix(posfix):
stack = []
for ch in posfix:
if is_operator(ch):
num = []
num.append(stack.pop())
if get_operation_number(ch) > 1:
num.append(stack.pop())
stack.append(calc_once(num, ch))
else:
stack.append(ch)
return stack.pop()
def main_loop():
# match all hex and dec number, and +,-,*,/,**
# note: hex must before dec number, and * must before **
print "please do not use ** mix with other operation, it's not support!"
regu_for_exp = re.compile('0x[0-9,a-f]+|[0-9]+|\*\*|\*|\+|\-|\/|\(|\)')
while True:
expression = raw_input('pq>:')
if expression != 'quit' and expression != 'q' and expression != 'exit':
midfix = regu_for_exp.findall(expression)
posfix = midfix_to_posfix(midfix)
result = calc_posfix(posfix)
if result is not None:
print "0x%02x" % result
else:
print result
else:
return
if __name__ == '__main__':
main_loop()
将下面代码保存为pq.py,chmod +x pq.py，然后./pq.py即可进入计算器。按q退出。
解析算数表达式的程序有些问题，不支持乘方和其他运算混合。
#! /usr/bin/env python
# reference to http://www.cnblogs.com/flyingbread/archive/2007/02/03/638932.html
import re
def is_operator(ch):
if ch == '+' or ch == '-' or ch == '*' or ch == '/' or ch == '**':
return True
else:
return False
def is_parentheses_left(ch):
if ch == '(':
return True
else:
return False
def is_parentheses_right(ch):
if ch == ')':
return True
else:
return False
def opt_priority(ch):
if ch == '+' or ch == '-':
priority = 1
elif ch == '*' or ch == '/':
priority = 2
elif ch == '**':
priority = 3
else:
# maybe '('
priority = 0
return priority
# now we only support 2 operation number
def get_operation_number(ch):
if ch == '+' or ch == '-' or ch == '*' or ch == '/' or ch == '**':
return 2
else:
return 1
# primitive polynomial for GF(2**8)
# F(x) = x**8 + x**4 + x**3 + x**2 + 1
def do_add(a, b):
return a ^ b
def do_sub(a, b):
return a ^ b
gflog = [
0x00, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6, 0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81, 0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,
0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21, 0x35, 0x93, 0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45,
0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9, 0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72, 0xa6,
0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd, 0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88,
0x36, 0xd0, 0x94, 0xce, 0x8f, 0x96, 0xdb, 0xbd, 0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40,
0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e, 0x6b, 0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d,
0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b, 0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3, 0xa7, 0x57,
0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d, 0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18,
0xe3, 0xa5, 0x99, 0x77, 0x26, 0xb8, 0xb4, 0x7c, 0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e,
0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd, 0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61,
0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e, 0x84, 0x3c, 0x39, 0x53, 0x47, 0x6d, 0x41, 0xa2,
0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76, 0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6,
0x6c, 0xa1, 0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa, 0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a,
0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0, 0x51, 0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7,
0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8, 0x74, 0xd6, 0xf4, 0xea, 0xa8, 0x50, 0x58, 0xaf,
]
gfilog = [
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26,
0x4c, 0x98, 0x2d, 0x5a, 0xb4, 0x75, 0xea, 0xc9, 0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0,
0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35, 0x6a, 0xd4, 0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23,
0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0, 0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde, 0xa1,
0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc, 0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0,
0xfd, 0xe7, 0xd3, 0xbb, 0x6b, 0xd6, 0xb1, 0x7f, 0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2,
0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88, 0x0d, 0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce,
0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93, 0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33, 0x66, 0xcc,
0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9, 0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54,
0xa8, 0x4d, 0x9a, 0x29, 0x52, 0xa4, 0x55, 0xaa, 0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73,
0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e, 0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff,
0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4, 0x95, 0x37, 0x6e, 0xdc, 0xa5, 0x57, 0xae, 0x41,
0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e, 0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6,
0x51, 0xa2, 0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef, 0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09,
0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5, 0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,
0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83, 0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x00,
]
def do_mul(a, b):
if a == 0 or b == 0:
return 0;
else:
tmp = gflog[a] + gflog[b]
tmp = tmp % 255
return gfilog[tmp]
def do_div(a, b):
if a == 0:
return 0
elif b == 0:
print 'can not div 0'
return 0;
else:
tmp = gflog[a] - gflog[b]
if tmp < 0:
tmp = tmp + 255
return gfilog[tmp]
def do_power(a, b):
count = 0
result = 1
while (count < b):
result = do_mul(result, a)
count += 1
return result
def calc_once(num, ch):
if ch == '+':
ret = do_add(num[1], num[0])
elif ch == '-':
ret = do_sub(num[1], num[0])
elif ch == '*':
ret = do_mul(num[1], num[0])
elif ch == '/':
ret = do_div(num[1], num[0])
elif ch == '**':
ret = do_power(num[1], num[0])
else:
print 'unknow operation'
ret = 0
return ret
# 1. get ch from left to right
# 2. if ch is a number, output it
# 3. if ch is a operator or parenthese:
# a: if ch is '(', push to stack
# b: if ch is ')', pop stack until meet '('
# c: if ch is not parenthese, compare its priority with stack pop
# if ch priority is higher than the stack pop, push ch to stack
# else pop stack, push ch to stack
def midfix_to_posfix(midfix):
stack = []
posfix = []
for ch in midfix:
if is_parentheses_left(ch):
stack.append(ch)
elif is_parentheses_right(ch):
while True:
ch1 = stack.pop()
if is_parentheses_left(ch1):
break
else:
posfix.append(ch1)
elif is_operator(ch):
if len(stack) == 0:
stack.append(ch)
else:
ch1 = stack[-1]
if opt_priority(ch) > opt_priority(ch1):
stack.append(ch)
else:
ch1 = stack.pop()
posfix.append(ch1)
stack.append(ch)
else:
if len(ch) > 2 and ch[0:2] == '0x':
ch = int(ch, 16)
else:
ch = int(ch, 10)
posfix.append(ch)
while len(stack) != 0:
posfix.append(stack.pop())
return posfix
# get data from left to right
# if ch is a number, push to stack
# if ch is a operator, pop the number it needed, do calc, and push result to stack
# if data is paser comlete, pop the stack as result
def calc_posfix(posfix):
stack = []
for ch in posfix:
if is_operator(ch):
num = []
num.append(stack.pop())
if get_operation_number(ch) > 1:
num.append(stack.pop())
stack.append(calc_once(num, ch))
else:
stack.append(ch)
return stack.pop()
def main_loop():
# match all hex and dec number, and +,-,*,/,**
# note: hex must before dec number, and * must before **
print "please do not use ** mix with other operation, it's not support!"
regu_for_exp = re.compile('0x[0-9,a-f]+|[0-9]+|\*\*|\*|\+|\-|\/|\(|\)')
while True:
expression = raw_input('pq>:')
if expression != 'quit' and expression != 'q' and expression != 'exit':
midfix = regu_for_exp.findall(expression)
posfix = midfix_to_posfix(midfix)
result = calc_posfix(posfix)
if result is not None:
print "0x%02x" % result
else:
print result
else:
return
if __name__ == '__main__':
main_loop()
2010年11月10日星期三
raid6中gflog与gfilog
写了一篇介绍raid6中gflog与gfilog的文章，用了太多的数学公式，所以用lyx写了，放到网页上似乎不太方便，于是放到了google code上，下面是下载地址：
http://raid6theory.googlecode.com/files/raid6_theory.pdf
http://raid6theory.googlecode.com/files/raid6_theory.pdf
2010年11月3日星期三
创建/sys入口和使用waitqueue的小例子
一个简单的示例程序。创建一个/sys的接口，可以读写，每次回读都是上次写入的内容。每次读写都会触发一次event。
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/kthread.h>
static struct cdev test_cdev;
static dev_t test_devno;
static struct class *test_class;
struct device *test_device;
struct test_thread {
wait_queue_head_t wqueue;
unsigned long flags;
struct task_struct *tsk;
unsigned long timeout;
}test_thread;
#define FROM_SHOW 0
#define FROM_STORE 1
static const struct file_operations test_fops =
{
.owner = THIS_MODULE,
};
static int test_fun(void *arg)
{
struct test_thread *thread = arg;
allow_signal(SIGKILL);
while (!kthread_should_stop()) {
/* We need to wait INTERRUPTIBLE so that
* we don't add to the load-average.
* That means we need to be sure no signals are
* pending
*/
if (signal_pending(current))
flush_signals(current);
wait_event_interruptible_timeout
(thread->wqueue,
test_bit(FROM_SHOW, &thread->flags)
|| test_bit(FROM_STORE, &thread->flags)
|| kthread_should_stop(),
thread->timeout);
printk("thread %s is waken up by %s\n",
thread->tsk->comm,
test_bit(FROM_SHOW, &thread->flags) ? "show" :
test_bit(FROM_STORE, &thread->flags) ? "store" : "kill");
thread->flags = 0;
}
return 0;
}
#define TEST_LEN 4096
static char test_buf[TEST_LEN];
static ssize_t test_show(struct device *ddev,
struct device_attribute *attr, char *buf)
{
int len;
struct test_thread *thread;
thread = dev_get_drvdata(ddev);
len = strlen(test_buf) + 1;
memcpy(buf, test_buf, len);
set_bit(FROM_SHOW, &thread->flags);
wake_up(&thread->wqueue);
return len;
}
static ssize_t test_store(struct device *ddev,
struct device_attribute *attr, const char *buf, size_t count)
{
size_t len;
struct test_thread *thread;
thread = dev_get_drvdata(ddev);
if (count < TEST_LEN - 1)
len = count;
else
len = TEST_LEN - 1;
memcpy(test_buf, buf, len);
test_buf[len] = 0;
set_bit(FROM_STORE, &thread->flags);
wake_up(&thread->wqueue);
return count;
}
static DEVICE_ATTR(test1, 0644, test_show, test_store);
static int test_init(void)
{
int ret;
ret = alloc_chrdev_region(&test_devno, 0, 255, "test");
if (ret) {
printk(KERN_INFO "alloc_chrdev_region failed, ret=%d\n", ret);
return ret;
}
cdev_init(&test_cdev, &test_fops);
test_cdev.owner = THIS_MODULE;
ret = cdev_add(&test_cdev, test_devno, 1);
if (ret) {
printk(KERN_INFO "cdev_add failed, ret=%d\n", ret);
goto free_devno;
}
test_class = class_create(THIS_MODULE, "test_class");
if (IS_ERR(test_class)) {
ret = PTR_ERR(test_class);
printk(KERN_INFO "class_create failed, ret=%d\n", ret);
goto free_cdev;
}
test_device = device_create(test_class, NULL, test_devno, NULL, "test");
if (IS_ERR(test_device)) {
ret = PTR_ERR(test_device);
printk(KERN_INFO "device_create failed, ret=%d\n", ret);
goto free_class;
}
ret = device_create_file(test_device, &dev_attr_test1);
if (ret) {
printk(KERN_INFO "device_create_file failed, ret=%d\n", ret);
goto free_device;
}
init_waitqueue_head(&test_thread.wqueue);
test_thread.timeout = MAX_SCHEDULE_TIMEOUT;
test_thread.flags = 0;
dev_set_drvdata(test_device, &test_thread);
test_thread.tsk = kthread_run(test_fun, &test_thread, "test_thread");
if (IS_ERR(test_thread.tsk)) {
ret = PTR_ERR(test_thread.tsk);
printk(KERN_INFO "kthread_run failed, ret=%d\n", ret);
goto free_file;
}
return 0;
free_file:
device_remove_file(test_device, &dev_attr_test1);
free_device:
device_destroy(test_class, test_devno);
free_class:
class_destroy(test_class);
free_cdev:
cdev_del(&test_cdev);
free_devno:
unregister_chrdev_region(test_devno, 255);
return ret;
}
void test_exit(void)
{
kthread_stop(test_thread.tsk);
device_remove_file(test_device, &dev_attr_test1);
device_destroy(test_class, test_devno);
class_destroy(test_class);
cdev_del(&test_cdev);
unregister_chrdev_region(test_devno, 255);
}
MODULE_LICENSE("GPL");
module_init (test_init);
module_exit (test_exit);
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/kthread.h>
static struct cdev test_cdev;
static dev_t test_devno;
static struct class *test_class;
struct device *test_device;
struct test_thread {
wait_queue_head_t wqueue;
unsigned long flags;
struct task_struct *tsk;
unsigned long timeout;
}test_thread;
#define FROM_SHOW 0
#define FROM_STORE 1
static const struct file_operations test_fops =
{
.owner = THIS_MODULE,
};
static int test_fun(void *arg)
{
struct test_thread *thread = arg;
allow_signal(SIGKILL);
while (!kthread_should_stop()) {
/* We need to wait INTERRUPTIBLE so that
* we don't add to the load-average.
* That means we need to be sure no signals are
* pending
*/
if (signal_pending(current))
flush_signals(current);
wait_event_interruptible_timeout
(thread->wqueue,
test_bit(FROM_SHOW, &thread->flags)
|| test_bit(FROM_STORE, &thread->flags)
|| kthread_should_stop(),
thread->timeout);
printk("thread %s is waken up by %s\n",
thread->tsk->comm,
test_bit(FROM_SHOW, &thread->flags) ? "show" :
test_bit(FROM_STORE, &thread->flags) ? "store" : "kill");
thread->flags = 0;
}
return 0;
}
#define TEST_LEN 4096
static char test_buf[TEST_LEN];
static ssize_t test_show(struct device *ddev,
struct device_attribute *attr, char *buf)
{
int len;
struct test_thread *thread;
thread = dev_get_drvdata(ddev);
len = strlen(test_buf) + 1;
memcpy(buf, test_buf, len);
set_bit(FROM_SHOW, &thread->flags);
wake_up(&thread->wqueue);
return len;
}
static ssize_t test_store(struct device *ddev,
struct device_attribute *attr, const char *buf, size_t count)
{
size_t len;
struct test_thread *thread;
thread = dev_get_drvdata(ddev);
if (count < TEST_LEN - 1)
len = count;
else
len = TEST_LEN - 1;
memcpy(test_buf, buf, len);
test_buf[len] = 0;
set_bit(FROM_STORE, &thread->flags);
wake_up(&thread->wqueue);
return count;
}
static DEVICE_ATTR(test1, 0644, test_show, test_store);
static int test_init(void)
{
int ret;
ret = alloc_chrdev_region(&test_devno, 0, 255, "test");
if (ret) {
printk(KERN_INFO "alloc_chrdev_region failed, ret=%d\n", ret);
return ret;
}
cdev_init(&test_cdev, &test_fops);
test_cdev.owner = THIS_MODULE;
ret = cdev_add(&test_cdev, test_devno, 1);
if (ret) {
printk(KERN_INFO "cdev_add failed, ret=%d\n", ret);
goto free_devno;
}
test_class = class_create(THIS_MODULE, "test_class");
if (IS_ERR(test_class)) {
ret = PTR_ERR(test_class);
printk(KERN_INFO "class_create failed, ret=%d\n", ret);
goto free_cdev;
}
test_device = device_create(test_class, NULL, test_devno, NULL, "test");
if (IS_ERR(test_device)) {
ret = PTR_ERR(test_device);
printk(KERN_INFO "device_create failed, ret=%d\n", ret);
goto free_class;
}
ret = device_create_file(test_device, &dev_attr_test1);
if (ret) {
printk(KERN_INFO "device_create_file failed, ret=%d\n", ret);
goto free_device;
}
init_waitqueue_head(&test_thread.wqueue);
test_thread.timeout = MAX_SCHEDULE_TIMEOUT;
test_thread.flags = 0;
dev_set_drvdata(test_device, &test_thread);
test_thread.tsk = kthread_run(test_fun, &test_thread, "test_thread");
if (IS_ERR(test_thread.tsk)) {
ret = PTR_ERR(test_thread.tsk);
printk(KERN_INFO "kthread_run failed, ret=%d\n", ret);
goto free_file;
}
return 0;
free_file:
device_remove_file(test_device, &dev_attr_test1);
free_device:
device_destroy(test_class, test_devno);
free_class:
class_destroy(test_class);
free_cdev:
cdev_del(&test_cdev);
free_devno:
unregister_chrdev_region(test_devno, 255);
return ret;
}
void test_exit(void)
{
kthread_stop(test_thread.tsk);
device_remove_file(test_device, &dev_attr_test1);
device_destroy(test_class, test_devno);
class_destroy(test_class);
cdev_del(&test_cdev);
unregister_chrdev_region(test_devno, 255);
}
MODULE_LICENSE("GPL");
module_init (test_init);
module_exit (test_exit);
2010年11月1日星期一
在加载驱动时自动创建设备节点
在网上找了些自动创建设备节点的办法，但由于内核接口的变化，已经无法使用了。下面这个程序是可以在2.6.32内核上使用的：
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
static struct cdev test_cdev;
static dev_t test_devno;
static struct class *test_class;
struct device *test_device;
static const struct file_operations test_fops =
{
.owner = THIS_MODULE,
};
static int test_init(void)
{
int ret;
ret = alloc_chrdev_region(&test_devno, 0, 255, "test");
if (ret) {
printk(KERN_INFO "alloc_chrdev_region failed, ret=%d\n", ret);
return ret;
}
cdev_init(&test_cdev, &test_fops);
test_cdev.owner = THIS_MODULE;
ret = cdev_add(&test_cdev, test_devno, 1);
if (ret) {
printk(KERN_INFO "cdev_add failed, ret=%d\n", ret);
goto free_devno;
}
test_class = class_create(THIS_MODULE, "test_class");
if (IS_ERR(test_class)) {
ret = PTR_ERR(test_class);
printk(KERN_INFO "class_create failed, ret=%d\n", ret);
goto free_cdev;
}
test_device = device_create(test_class, NULL, test_devno, NULL, "test");
if (IS_ERR(test_device)) {
ret = PTR_ERR(test_device);
printk(KERN_INFO "device_create failed, ret=%d\n", ret);
goto free_class;
}
return 0;
free_class:
class_destroy(test_class);
free_cdev:
cdev_del(&test_cdev);
free_devno:
unregister_chrdev_region(test_devno, 255);
return ret;
}
void test_exit(void)
{
device_destroy(test_class, test_devno);
class_destroy(test_class);
cdev_del(&test_cdev);
unregister_chrdev_region(test_devno, 255);
}
MODULE_LICENSE("GPL");
module_init (test_init);
module_exit (test_exit);
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
static struct cdev test_cdev;
static dev_t test_devno;
static struct class *test_class;
struct device *test_device;
static const struct file_operations test_fops =
{
.owner = THIS_MODULE,
};
static int test_init(void)
{
int ret;
ret = alloc_chrdev_region(&test_devno, 0, 255, "test");
if (ret) {
printk(KERN_INFO "alloc_chrdev_region failed, ret=%d\n", ret);
return ret;
}
cdev_init(&test_cdev, &test_fops);
test_cdev.owner = THIS_MODULE;
ret = cdev_add(&test_cdev, test_devno, 1);
if (ret) {
printk(KERN_INFO "cdev_add failed, ret=%d\n", ret);
goto free_devno;
}
test_class = class_create(THIS_MODULE, "test_class");
if (IS_ERR(test_class)) {
ret = PTR_ERR(test_class);
printk(KERN_INFO "class_create failed, ret=%d\n", ret);
goto free_cdev;
}
test_device = device_create(test_class, NULL, test_devno, NULL, "test");
if (IS_ERR(test_device)) {
ret = PTR_ERR(test_device);
printk(KERN_INFO "device_create failed, ret=%d\n", ret);
goto free_class;
}
return 0;
free_class:
class_destroy(test_class);
free_cdev:
cdev_del(&test_cdev);
free_devno:
unregister_chrdev_region(test_devno, 255);
return ret;
}
void test_exit(void)
{
device_destroy(test_class, test_devno);
class_destroy(test_class);
cdev_del(&test_cdev);
unregister_chrdev_region(test_devno, 255);
}
MODULE_LICENSE("GPL");
module_init (test_init);
module_exit (test_exit);
订阅：
博文 (Atom)