From: yu.dongliang <18588496441@163.com>
Date: Wed, 16 Oct 2024 07:03:41 +0000 (+0800)
Subject: code for 'deep technology of C'
X-Git-Url: http://baseworks.info/?a=commitdiff_plain;h=refs%2Fheads%2Fmaster;p=c.git

code for 'deep technology of C'
---

bed05fa7d63774c56e5d8aa7674d8bce57a28b45
diff --git a/1.txt b/1.txt
new file mode 100644
index 0000000..242c034
--- /dev/null
+++ b/1.txt
@@ -0,0 +1 @@
+hello_world
diff --git a/fopen.c b/fopen.c
new file mode 100644
index 0000000..62be9a5
--- /dev/null
+++ b/fopen.c
@@ -0,0 +1,26 @@
+/*#include<stdio.h>
+#include<stdint.h>
+*/
+void*   fopen(const char* path, const char* mode);
+int     fclose(void* fp);
+int     fscanf(void* fp, const char* fmt, ...);
+
+int     printf(const char* fmt, ...);
+
+int main()
+{
+	void* fp = fopen("1.txt", "r");
+	if (!fp) {
+		printf("fp: %p\n", fp);
+		return -1;
+	}
+
+	char* s[64];
+
+	int n = fscanf(fp, "%s", s);
+
+	printf("s: %s, n: %d\n", s, n);
+
+	fclose(fp);
+	return 0;
+}
diff --git a/global_var.c b/global_var.c
new file mode 100644
index 0000000..303b7ed
--- /dev/null
+++ b/global_var.c
@@ -0,0 +1,35 @@
+
+int printf(const char* fmt, ...);
+
+/* C 全局数据
+ 
+   1，函数都是全局的，在.text段
+
+   2, 字符串常量
+
+   3，全局变量
+
+   a 和 p 都在 .data段，可写
+----------------------
+   进程的内存排布
+
+   .text    代码段，     R E，可读可执行
+   .rodata  只读数据段， R,
+   .data    数据段，     R, W, 可读可写
+   -------------------
+   堆 heap
+   ------------------ brk，数据段末尾
+   (空白区)
+   ------------------ rsp, 栈顶
+   栈
+   ------------------
+ */
+
+int  a = 123;
+int* p = &a;
+
+int main()
+{
+	printf("a: %d, p: %p\n", a, p);
+	return 0;
+}
diff --git a/hanoi.c b/hanoi.c
new file mode 100644
index 0000000..50ae046
--- /dev/null
+++ b/hanoi.c
@@ -0,0 +1,22 @@
+// 汉诺塔，递归算法
+
+int printf(const char* fmt, ...);
+
+int count = 0;
+
+void hanoi(int n, char a, char b, char c)
+{
+	if (1 == n)
+		printf("count: %d, n: %d, %c->%c\n", count++, n, a, c);
+	else {
+		hanoi(n-1, a, c, b); // 递归
+		printf("count: %d, n: %d, %c->%c\n", count++, n, a, c);
+		hanoi(n-1, b, a, c); // 递归
+	}
+}
+
+int main()
+{
+	hanoi(5, 'A', 'B', 'C');
+	return 0;
+}
diff --git a/hello.c b/hello.c
new file mode 100644
index 0000000..9bf9444
--- /dev/null
+++ b/hello.c
@@ -0,0 +1,19 @@
+
+/* hello world 程序
+ 
+   1，对库函数的调用，printf()
+ 
+   2, 对常量字符串的寻址，"hello world\n"
+
+   常量字符串是只读的，放在.rodata段
+
+   3，分段是为了权限控制（读、写、运行），为了信息安全
+ */
+
+int printf(const char* fmt, ...);
+
+int main()
+{
+	printf("hello world\n");
+	return 0;
+}
diff --git a/macro.c b/macro.c
new file mode 100644
index 0000000..13ab9ba
--- /dev/null
+++ b/macro.c
@@ -0,0 +1,12 @@
+
+int printf(const char* fmt, ...);
+
+#define A(x) #x 
+
+int main()
+{
+	int z = 1;
+
+	printf("%s: %d\n", A(z), z);
+	return 0;
+}
diff --git a/mutex.c b/mutex.c
new file mode 100644
index 0000000..eae664f
--- /dev/null
+++ b/mutex.c
@@ -0,0 +1,61 @@
+#include<stdio.h>
+#include<unistd.h>
+#include<pthread.h>
+
+int xchg(int* mutex)
+{
+	int ret;
+
+	asm volatile(
+		"xchg %0, (%1)\n\t"
+		:"=r"(ret)
+		:"r"(mutex), "0"(1)
+		:
+	);
+
+	return ret;
+}
+
+void lock(int* mutex)
+{
+	while (1 == xchg(mutex))
+		sched_yield();
+}
+
+void unlock(int* mutex)
+{
+	*mutex = 0;
+}
+
+int g_mutex = 0;
+int g_count = 0;
+
+void* thread(void* arg)
+{
+	int i;
+	for (i = 0; i < 1000 * 1000; i++) {
+
+		lock(&g_mutex);
+		g_count++;
+		unlock(&g_mutex);
+	}
+	return 0;
+}
+
+int main()
+{
+	pthread_t tid;
+	pthread_create(&tid, NULL, thread, NULL);
+
+	int i;
+	for (i = 0; i < 1000 * 1000; i++) {
+		lock(&g_mutex);
+		g_count++;
+		unlock(&g_mutex);
+	}
+
+	pthread_join(tid, NULL);
+
+	printf("g_count: %d\n", g_count);
+	return 0;
+}
diff --git a/qsort.c b/qsort.c
new file mode 100644
index 0000000..1a45e31
--- /dev/null
+++ b/qsort.c
@@ -0,0 +1,43 @@
+int printf(const char* fmt, ...);
+
+int sort(int* a, int m, int n)
+{
+	if (m >= n)
+		return 0;
+
+	int i = m;
+	int j = n;
+	int t;
+
+	t = a[i];
+	while (i < j) {
+
+		while (i < j && t <= a[j])
+			j--;
+		a[i]  = a[j];
+		a[j]  = t;
+
+		while (i < j && a[i] <= t)
+			i++;
+		a[j]  = a[i];
+		a[i]  = t;
+	}
+
+	sort(a, m, i - 1);
+	sort(a, i + 1, n);
+	return 0;
+}
+
+int main()
+{
+	int a[20] = {1, 3, 5, 7, 9, 8, 4, 2, 6, 0,
+		11, 13, 15, 17, 19, 18, 16, 14, 12, 10};
+
+	sort(a, 0, 19);
+
+	int i;
+	for (i = 0; i < 20; i++)
+		printf("%d\n", a[i]);
+
+	return 0;
+}