Add tail

Author: bajdcc

README.md

@@ -327,7 +327,7 @@ int main(int argc, char **argv) {
     - [x] pwd, whoami
     - [x] VFS: cd, mkdir, touch, cat, ls(-l), ll, rm, tree, write, append
     - [x] wc
-    - [x] head
+    - [x] head, tail
     - [x] ps(`cat /sys/pc`)
     - [x] badapple（黑白动画）
 - [ ] 虚拟文件系统

code/bin/tail.cpp

@@ -0,0 +1,104 @@
+#include "/include/io"
+#include "/include/fs"
+#include "/include/memory"
+#include "/include/shell"
+#include "/include/string"
+#include "/include/xtoa_atoi"
+struct string {
+    char *text;
+    int capacity;
+    int length;
+};
+string new_string() {
+    string s;
+    s.text = malloc(16);
+    s.capacity = 16;
+    s.length = 0;
+    return s;
+}
+struct node {
+    string text;
+    node *prev;
+    node *next;
+};
+void destroy(node *tmp) {
+    free(tmp->text.text);
+    free(tmp);
+}
+void push(node **head, node **last, string s, int not_remove) {
+    node *new_node = (node *) malloc(sizeof(node));
+    new_node->text = s;
+    new_node->prev = 0;
+    new_node->next = *head;
+    if (new_node->next)
+        new_node->next->prev = new_node;
+    if (not_remove == 1) {
+        if (!*last)
+            *last = new_node;
+    } else {
+        node *tmp = *last;
+        destroy(tmp);
+        *last = (*last)->prev;
+        (*last)->next = 0;
+    }
+    *head = new_node;
+}
+void append_char(string *s, char c) {
+    if (s->length >= s->capacity - 1) {
+        s->capacity <<= 1;
+        char *new_text = malloc(s->capacity);
+        strcpy(new_text, s->text);
+        free(s->text);
+        s->text = new_text;
+    }
+    (s->text)[s->length++] = c;
+    (s->text)[s->length] = 0;
+}
+void print(node *last) {
+    while (last) {
+        put_string((last->text).text);
+        put_string("\n");
+        last = last->prev;
+    }
+}
+void tail(int n) {
+    int c, i = 0, cmd = 0;
+    node *list = (node *) 0;
+    node *last = (node *) 0;
+    string s = new_string();
+    input_lock();
+    while ((c = input_char()) != -1) {
+        if (((char) c) == '\033') {
+            append_char(&s, c);
+            cmd = 1 - cmd;
+        } else if (cmd == 0) {
+            if (((char) c) == '\n') {
+                push(&list, &last, s, i < n);
+                s = new_string();
+                ++i;
+            } else {
+                append_char(&s, c);
+            }
+        } else {
+            append_char(&s, c);
+        }
+    }
+    push(&list, &last, s, i < n);
+    input_unlock();
+    print(last);
+}
+int main(int argc, char **argv) {
+    if (argc == 1) { // tail
+        shell("pipe");
+    } else if (argc == 2) { // tail XX
+        int n = atoi32(argv[1]);
+        if (n <= 0)
+            return 1;
+        tail(n);
+    } else {
+        set_fg(240, 0, 0);
+        put_string("[Error] Invalid argument.");
+        restore_fg();
+    }
+    return 0;
+}

code/include/io.cpp

@@ -11,7 +11,7 @@ int put_char(char c) {
     interrupt 0;
 }
 int put_string(char *text) {
-    while (put_char(*text++));
+    while (*text) put_char(*text++);
 }
 int put_int(int number) {
     number;