add assignment operator and unify memory pools

The unification of memory pools also fixed some memory leaks and
hopefully reduced the mallocs of identifier strings significantly by
giving them the same pool as the token stream.

util.c

@@ -49,6 +49,38 @@ void set_err(const char *fmt, ...) {
 	va_end(va);
 }
 
+Pool *pool_new(size_t init_cap) {
+	Pool *p = malloc(sizeof(Pool) + init_cap);
+	p->len = 0;
+	p->cap = init_cap;
+	p->data = p + 1;
+	p->next = NULL;
+	return p;
+}
+
+void pool_term(Pool *p) {
+	for (Pool *i = p; i != NULL;) {
+		Pool *next = i->next;
+		free(i);
+		i = next;
+	}
+}
+
+void *pool_alloc(Pool *p, size_t bytes) {
+	for (Pool *i = p;; i = i->next) {
+		if (i->len + bytes < i->cap) {
+			void *ret = (uint8_t*)i->data + i->len;
+			i->len += bytes;
+			return ret;
+		}
+		if (!i->next) {
+			i->next = pool_new(bytes + i->cap * 2);
+			i->next->len = bytes;
+			return i->next->data;
+		}
+	}
+}
+
 char *sndup(const char *s, size_t n) {
 	char *ret = malloc(n+1);
 	if (ret) {
@@ -58,6 +90,13 @@ char *sndup(const char *s, size_t n) {
 	return ret;
 }
 
+char *psndup(Pool *p, const char *s, size_t n) {
+	char *ret = pool_alloc(p, n+1);
+	memcpy(ret, s, n);
+	ret[n] = 0;
+	return ret;
+}
+
 intmax_t stoimax(const char *s, size_t n, size_t base, ssize_t *endpos) {
 	for (size_t i = 0; i < n; i++) { if (s[i] == 0) { n = i; break; } }
 	intmax_t res = 0;