feat(string): complete string.h + strdup/memccpy

src/string/strspn.c

@@ -0,0 +1,71 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <string.h>
+
+/*
+ * True when c appears anywhere in set (including as the NUL of set — but set
+ * is a string, so scanning stops at that NUL, as intended).
+ */
+static int
+str_in_set(const char *set, char c) // NOLINT(bugprone-easily-swappable-parameters)
+{
+    for (; *set != '\0'; set++)
+    {
+        if (*set == c)
+        {
+            return 1;
+        }
+    }
+    return 0;
+}
+
+/*
+ * Return the length of the initial span of s consisting entirely of bytes
+ * that occur in accept.
+ */
+size_t
+strspn(const char *s, const char *accept) // NOLINT(bugprone-easily-swappable-parameters)
+{
+    size_t n = 0;
+
+    while (s[n] != '\0' && str_in_set(accept, s[n]))
+    {
+        n++;
+    }
+    return n;
+}
+
+/*
+ * Return the length of the initial span of s consisting entirely of bytes
+ * that do NOT occur in reject.
+ */
+size_t
+strcspn(const char *s, const char *reject) // NOLINT(bugprone-easily-swappable-parameters)
+{
+    size_t n = 0;
+
+    while (s[n] != '\0' && !str_in_set(reject, s[n]))
+    {
+        n++;
+    }
+    return n;
+}
+
+/*
+ * Return a pointer to the first byte in s that also occurs in accept, or
+ * NULL when none occurs.
+ */
+char *
+strpbrk(const char *s, const char *accept) // NOLINT(bugprone-easily-swappable-parameters)
+{
+    for (; *s != '\0'; s++)
+    {
+        if (str_in_set(accept, *s))
+        {
+            return (char *)s;
+        }
+    }
+    return NULL;
+}