lesson 22

22-malloc/libc/string.c

@@ -1 +0,0 @@
-../../21-shell/libc/string.c

22-malloc/libc/string.c

@@ -0,0 +1,77 @@
+#include "string.h"
+#include "../cpu/type.h"
+
+/**
+ * K&R implementation
+ */
+void int_to_ascii(int n, char str[]) {
+    int i, sign;
+    if ((sign = n) < 0) n = -n;
+    i = 0;
+    do {
+        str[i++] = n % 10 + '0';
+    } while ((n /= 10) > 0);
+
+    if (sign < 0) str[i++] = '-';
+    str[i] = '\0';
+
+    reverse(str);
+}
+
+void hex_to_ascii(int n, char str[]) {
+    append(str, '0');
+    append(str, 'x');
+    char zeros = 0;
+
+    s32 tmp;
+    int i;
+    for (i = 28; i > 0; i -= 4) {
+        tmp = (n >> i) & 0xF;
+        if (tmp == 0 && zeros == 0) continue;
+        zeros = 1;
+        if (tmp > 0xA) append(str, tmp - 0xA + 'a');
+        else append(str, tmp + '0');
+    }
+
+    tmp = n & 0xF;
+    if (tmp >= 0xA) append(str, tmp - 0xA + 'a');
+    else append(str, tmp + '0');
+}
+
+/* K&R */
+void reverse(char s[]) {
+    int c, i, j;
+    for (i = 0, j = strlen(s)-1; i < j; i++, j--) {
+        c = s[i];
+        s[i] = s[j];
+        s[j] = c;
+    }
+}
+
+/* K&R */
+int strlen(char s[]) {
+    int i = 0;
+    while (s[i] != '\0') ++i;
+    return i;
+}
+
+void append(char s[], char n) {
+    int len = strlen(s);
+    s[len] = n;
+    s[len+1] = '\0';
+}
+
+void backspace(char s[]) {
+    int len = strlen(s);
+    s[len-1] = '\0';
+}
+
+/* K&R 
+ * Returns <0 if s1<s2, 0 if s1==s2, >0 if s1>s2 */
+int strcmp(char s1[], char s2[]) {
+    int i;
+    for (i = 0; s1[i] == s2[i]; i++) {
+        if (s1[i] == '\0') return 0;
+    }
+    return s1[i] - s2[i];
+}