exercise 2.02 2.03

chapter_2/exercise_2_02.c

@@ -0,0 +1,42 @@
+#include <stdio.h>
+
+#define MAXLINE 32
+
+int _getline(char line[], int maxline);
+
+/* Write a loop equivalent to the for loop above without using && or ||. */
+int main()
+{
+    char s[MAXLINE];
+    while (_getline(s, MAXLINE)) {
+        printf("%s", s);
+    }
+    return 0;
+}
+
+int _getline(char s[], int lim)
+{
+    int c, i;
+
+    i = 0;
+    for (;;) {
+        if (i < lim - 1) {
+            if ((c = getchar()) != EOF) {
+                if (c != '\n') {
+                    s[i] = c;
+                    ++i;
+                    continue;
+                }
+            }
+        }
+        break;
+    }
+
+    if (c == '\n') {
+        s[i] = c;
+        ++i;
+    }
+
+    s[i] = '\0';
+    return i;
+}

chapter_2/exercise_2_03.c

@@ -0,0 +1,38 @@
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int htoi(char s[], int limit);
+
+int main()
+{
+    printf("  0xff - %d\n", htoi("0xff", INT_MAX));
+    printf("0x88fe - %d\n", htoi("0x88fe", INT_MAX));
+    return 0;
+}
+
+int htoi(char s[], int limit)
+{
+    if (s[0] != '0' || (s[1] != 'x' && s[1] != 'X')) {
+        fprintf(stderr, "hex format error\n");
+        exit(1);
+    }
+
+    int res = 0;
+    int base = 1;
+    for (size_t i = strnlen(s, limit) - 1; i >= 2; --i, base *= 0x10) {
+        if ('0' <= s[i] && s[i] <= '9') {
+            res += (s[i] - '0') * base;
+        } else if ('a' <= s[i] && s[i] <= 'f') {
+            res += (s[i] - 'a' + 10) * base;
+        } else if ('A' <= s[i] && s[i] <= 'F') {
+            res += (s[i] - 'A' + 10) * base;
+        } else {
+            fprintf(stderr, "hex format error\n");
+            exit(1);
+        }
+    }
+
+    return res;
+}