diff --git a/src/guf_dbuf.h b/src/guf_dbuf.h
index ae91ba6..7ac729b 100644
--- a/src/guf_dbuf.h
+++ b/src/guf_dbuf.h
@@ -57,9 +57,18 @@ typedef struct GUF_CNT_NAME {
     #endif
 } GUF_CNT_NAME;
 
+/*
+    - Regular iterator: base is always NULL 
+    - Reverse iterator: base points the element after ptr
+        Examples:
+        - rbegin(): base points to end().ptr, and ptr to end().ptr - 1
+        - rend(): base points to begin().ptr and ptr to NULL
+        - reverse iterator for the first element of the container: base points to the second element, ptr points to the first element
+*/
+
 typedef struct GUF_CAT(GUF_CNT_NAME, _iter) {
     GUF_T *ptr;
-    bool reverse;
+    GUF_T *base; 
 } GUF_CAT(GUF_CNT_NAME, _iter);
 
 GUF_FN_KEYWORDS bool GUF_CAT(GUF_CNT_NAME, _valid)(const GUF_CNT_NAME* dbuf);
@@ -132,6 +141,8 @@ GUF_FN_KEYWORDS ptrdiff_t GUF_CAT(GUF_CNT_NAME, _iter_to_idx)(const GUF_CNT_NAME
 GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _find)(GUF_CNT_NAME *dbuf, GUF_CAT(GUF_CNT_NAME, _iter) begin, GUF_CAT(GUF_CNT_NAME, _iter) end, const GUF_T *needle);
 GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _find_val)(GUF_CNT_NAME *dbuf, GUF_CAT(GUF_CNT_NAME, _iter) begin, GUF_CAT(GUF_CNT_NAME, _iter) end, GUF_T needle_val);
 GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _find_if)(GUF_CNT_NAME *dbuf, GUF_CAT(GUF_CNT_NAME, _iter) begin, GUF_CAT(GUF_CNT_NAME, _iter) end, bool (*predicate)(const GUF_T *));
+GUF_FN_KEYWORDS bool GUF_CAT(GUF_CNT_NAME, _contains)(GUF_CNT_NAME *dbuf, const GUF_T *needle);
+GUF_FN_KEYWORDS bool GUF_CAT(GUF_CNT_NAME, _contains_val)(GUF_CNT_NAME *dbuf, GUF_T needle);
 #endif
 
 #if defined(GUF_IMPL) || defined(GUF_IMPL_STATIC)
@@ -761,12 +772,14 @@ GUF_FN_KEYWORDS void GUF_CAT(GUF_CNT_NAME, _try_shrink_to_fit)(GUF_CNT_NAME *dbu
 
 /* Iterator functions */
 
+#define ITER_PTR(it) !it.reverse ? (it.iter.ptr) : (it.rev_iter.ptr - 1)
+
 GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _begin)(const GUF_CNT_NAME* dbuf)
 {
     GUF_ASSERT_RELEASE(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
     return (GUF_CAT(GUF_CNT_NAME, _iter)) {
         .ptr = dbuf->data, 
-        .reverse = false
+        .base = NULL
     };
 }
 
@@ -774,8 +787,8 @@ GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _end)(const G
 {
     GUF_ASSERT_RELEASE(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
     return (GUF_CAT(GUF_CNT_NAME, _iter)) {
-        .ptr = dbuf->data ? dbuf->data + dbuf->size : NULL,
-        .reverse = false
+        .ptr = dbuf->data && dbuf->size ? dbuf->data + dbuf->size : NULL,
+        .base = NULL
     };
 }
 
@@ -783,8 +796,8 @@ GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _rbegin)(cons
 {
     GUF_ASSERT_RELEASE(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
     return (GUF_CAT(GUF_CNT_NAME, _iter)) {
-        .ptr = dbuf->data ? dbuf->data + (dbuf->size > 0 ? dbuf->size - 1 : 0) : NULL,
-        .reverse = true
+        .base = dbuf->data && dbuf->size ? dbuf->data + dbuf->size : NULL,
+        .ptr =  dbuf->data && dbuf->size ? dbuf->data + (dbuf->size - 1) : NULL
     };
 }
 
@@ -792,8 +805,8 @@ GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _rend)(const
 {
     GUF_ASSERT_RELEASE(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
     return (GUF_CAT(GUF_CNT_NAME, _iter)) {
-        .ptr = dbuf->data ? dbuf->data + dbuf->size : NULL, 
-        .reverse = true
+        .base = dbuf->data && dbuf->size ? dbuf->data : NULL,
+        .ptr = NULL    
     };
 }
 
@@ -802,39 +815,64 @@ GUF_FN_KEYWORDS  GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _iter_at_idx
     GUF_ASSERT(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
 
     GUF_CAT(GUF_CNT_NAME, _iter) it;
-    it.reverse = false;
-    if (idx < 0 || idx >= dbuf->size || !dbuf->data) {
-        it.ptr = GUF_CAT(GUF_CNT_NAME, _end)(dbuf).ptr;
+    it.base = NULL;
+
+    if (!dbuf->data || !dbuf->size) {
+        it.ptr = NULL;
+        return it;
+    }
+
+    if (idx < 0) {
+        it.ptr = dbuf->data;
+    } else if (idx > dbuf->size) {
+        it.ptr = dbuf->data + dbuf->size;
     } else {
         it.ptr = dbuf->data + idx;
     }
+  
     return it;
 }
 
 GUF_FN_KEYWORDS  GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _reverse_iter_at_idx)(const GUF_CNT_NAME* dbuf, ptrdiff_t idx)
 {
     GUF_CAT(GUF_CNT_NAME, _iter) it = GUF_CAT(GUF_CNT_NAME, _iter_at_idx)(dbuf, idx);
-    it.reverse = true;
+
+    if (!dbuf->data || !dbuf->size) {
+        it.base = NULL;
+        it.ptr = NULL;
+        return it;
+    } 
+    
+    if (idx < 0) {
+        it.base = dbuf->data;
+        it.ptr = NULL;
+    } else if (idx >= dbuf->size) {
+        it.base = dbuf->data + dbuf->size;
+        it.ptr = it.base - 1;
+    } else {
+        it.base = dbuf->data + idx + 1;
+        it.ptr = it.base - 1;
+    }
     return it;
 }
 
-static const ptrdiff_t GUF_CAT(GUF_CNT_NAME, _npos) = -1;
+static const ptrdiff_t GUF_CAT(GUF_CNT_NAME, _npos) = PTRDIFF_MIN;
 
-GUF_FN_KEYWORDS ptrdiff_t GUF_CAT(GUF_CNT_NAME, _iter_to_idx)(const GUF_CNT_NAME* dbuf, GUF_CAT(GUF_CNT_NAME, _iter) it)
+GUF_FN_KEYWORDS ptrdiff_t 
+GUF_CAT(GUF_CNT_NAME, _iter_to_idx)(const GUF_CNT_NAME* dbuf, GUF_CAT(GUF_CNT_NAME, _iter) it)
 {
     GUF_ASSERT(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
 
-    GUF_CAT(GUF_CNT_NAME, _iter) begin = GUF_CAT(GUF_CNT_NAME, _begin)(dbuf);
-    GUF_CAT(GUF_CNT_NAME, _iter) end = GUF_CAT(GUF_CNT_NAME, _end)(dbuf);
-
-    if (it.ptr == NULL || begin.ptr == NULL || end.ptr == NULL || it.ptr < begin.ptr || it.ptr > end.ptr || !dbuf->data) {
+    if ((!it.ptr && !it.base) || !dbuf->data || !dbuf->size) {
         return GUF_CAT(GUF_CNT_NAME, _npos);
-    } else if (it.ptr == end.ptr) {
-        return it.reverse ? -1 : dbuf->size;
-    } else {
-        ptrdiff_t idx = it.ptr - begin.ptr;
-        GUF_ASSERT(idx >= 0 && idx <= dbuf->size);
-        return idx;
+    }
+
+    bool is_reverse_it = it.base != NULL;
+
+    if (is_reverse_it) { 
+        return  (ptrdiff_t)(it.base - dbuf->data) - 1;
+    } else { 
+        return (ptrdiff_t)(it.ptr - dbuf->data);
     }
 }
 
@@ -842,62 +880,54 @@ GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _iter_next)(c
 {
     GUF_ASSERT(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
 
-    GUF_T *end_ptr = dbuf->data ? dbuf->data + dbuf->size : NULL;
-
-    if (!dbuf->size || !dbuf->data || !it.ptr) {
-        it.ptr = end_ptr;
+    if (!dbuf->size || !dbuf->data || (!it.base && !it.ptr)) {
+        it.ptr = NULL;
+        it.base = NULL;
         return it;
     }
 
-    if (it.reverse) {
+    const bool is_reverse_it = it.base != NULL;
+
+    if (is_reverse_it) {
         if (step < 0) {
             GUF_ASSERT_RELEASE(step > PTRDIFF_MIN); // Catch overflow.
         }
         step = -step;
     }
 
-    ptrdiff_t it_idx = 0;
-    if (it.ptr == end_ptr && it.reverse) { // Handle rend()
-        it_idx = step - 1;
-    } else if (it.ptr == end_ptr && !it.reverse) { // Handle end()
-        it_idx = dbuf->size + step;
+    if (is_reverse_it) {
+        ptrdiff_t idx = (ptrdiff_t)(it.base - dbuf->data) + step;
+        idx = GUF_CLAMP(idx, 0, dbuf->size);
+        it.base = dbuf->data + idx;
+        it.ptr = idx == 0 ? NULL : it.base - 1;
     } else {
-        GUF_ASSERT_RELEASE(it.ptr >= dbuf->data && it.ptr < end_ptr)
-        it_idx = (ptrdiff_t)(it.ptr - dbuf->data) + step;
+        GUF_ASSERT(it.ptr);
+        ptrdiff_t idx = (ptrdiff_t)(it.ptr - dbuf->data) + step;
+        idx = GUF_CLAMP(idx, 0, dbuf->size);
+        it.ptr = dbuf->data + idx;
     }
-   
-    const ptrdiff_t len = (end_ptr && dbuf->data) ? end_ptr - dbuf->data : 0;
-    GUF_ASSERT_RELEASE(len >= 0);
 
-   if (len == 0 || it_idx >= len || it_idx < 0) {
-        it.ptr = end_ptr;
-    } else {
-        GUF_ASSERT(dbuf->data && it.ptr);
-        it.ptr = dbuf->data + it_idx;
-    }
     return it;
 }
 
-
 #if defined(GUF_T_IS_INTEGRAL_TYPE) || defined(GUF_T_EQ)
 GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _find)(GUF_CNT_NAME *dbuf, GUF_CAT(GUF_CNT_NAME, _iter) begin, GUF_CAT(GUF_CNT_NAME, _iter) end, const GUF_T *needle) 
 {
     GUF_ASSERT_RELEASE(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
     GUF_ASSERT_RELEASE(needle);
-    GUF_CAT(GUF_CNT_NAME, _iter) dbuf_end = GUF_CAT(GUF_CNT_NAME, _end)(dbuf);
-    dbuf_end.reverse = begin.reverse;
 
-    ptrdiff_t begin_idx = GUF_CAT(GUF_CNT_NAME, _iter_to_idx)(dbuf, begin);
-    ptrdiff_t end_idx = GUF_CAT(GUF_CNT_NAME, _iter_to_idx)(dbuf, end);
-    if (!begin.ptr || !end.ptr || !dbuf->data || begin.ptr == dbuf_end.ptr) {
-        return dbuf_end;
-    } else if (!begin.reverse && begin_idx >= end_idx) {
-        return dbuf_end;
-    } else if (begin.reverse && begin_idx <= end_idx) {
-        return dbuf_end;
+    const bool is_reverse_it = begin.base != NULL;
+    GUF_ASSERT_RELEASE(is_reverse_it == (end.base != NULL)); // begin and end must be the same iterator type.
+    const GUF_CAT(GUF_CNT_NAME, _iter) dbuf_end_it = is_reverse_it ? GUF_CAT(GUF_CNT_NAME, _rend)(dbuf) : GUF_CAT(GUF_CNT_NAME, _end)(dbuf);
+
+    if (!dbuf->data || !dbuf->size || (!begin.ptr && !begin.base) || (!end.ptr && !end.base)) {
+        return dbuf_end_it;
+    } 
+    if ((begin.ptr == dbuf_end_it.ptr) || (!is_reverse_it && begin.ptr >= end.ptr) || (is_reverse_it && begin.base <= end.base)) {
+        return dbuf_end_it;
     }
 
-    for (GUF_CAT(GUF_CNT_NAME, _iter) it = begin; it.ptr != end.ptr && it.ptr != dbuf_end.ptr; it = GUF_CAT(GUF_CNT_NAME, _iter_next)(dbuf, it, 1)) {
+    for (GUF_CAT(GUF_CNT_NAME, _iter) it = begin; it.ptr != end.ptr; it = GUF_CAT(GUF_CNT_NAME, _iter_next)(dbuf, it, 1)) {
         #ifdef GUF_T_EQ
             if (GUF_T_EQ(it.ptr, needle)) {
                 return it;
@@ -912,23 +942,36 @@ GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _find)(GUF_CN
 }
 
 GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _find_val)(GUF_CNT_NAME *dbuf, GUF_CAT(GUF_CNT_NAME, _iter) begin, GUF_CAT(GUF_CNT_NAME, _iter) end, GUF_T needle_val) 
-{
+{    
     return GUF_CAT(GUF_CNT_NAME, _find)(dbuf, begin, end, &needle_val);
 }
 
+GUF_FN_KEYWORDS bool GUF_CAT(GUF_CNT_NAME, _contains)(GUF_CNT_NAME *dbuf, const GUF_T *needle)
+{
+    GUF_CAT(GUF_CNT_NAME, _iter) beg = GUF_CAT(GUF_CNT_NAME, _begin)(dbuf);
+    GUF_CAT(GUF_CNT_NAME, _iter) end = GUF_CAT(GUF_CNT_NAME, _end)(dbuf);
+    return GUF_CAT(GUF_CNT_NAME, _find)(dbuf, beg, end, needle).ptr != end.ptr;
+}
+
+GUF_FN_KEYWORDS bool GUF_CAT(GUF_CNT_NAME, _contains_val)(GUF_CNT_NAME *dbuf, GUF_T needle)
+{
+    return GUF_CAT(GUF_CNT_NAME, _contains)(dbuf, &needle);
+}
+
 GUF_FN_KEYWORDS GUF_CAT(GUF_CNT_NAME, _iter) GUF_CAT(GUF_CNT_NAME, _find_if)(GUF_CNT_NAME *dbuf, GUF_CAT(GUF_CNT_NAME, _iter) begin, GUF_CAT(GUF_CNT_NAME, _iter) end, bool (*predicate)(const GUF_T *)) 
 {
     GUF_ASSERT_RELEASE(GUF_CAT(GUF_CNT_NAME, _valid)(dbuf));
     GUF_ASSERT_RELEASE(predicate);
 
-    GUF_CAT(GUF_CNT_NAME, _iter) dbuf_end = GUF_CAT(GUF_CNT_NAME, _end)(dbuf);
-    dbuf_end.reverse = begin.reverse;
-    if (!begin.ptr || !end.ptr || !dbuf->data) {
-        return dbuf_end;
-    } else if (!begin.reverse && begin.ptr >= end.ptr) {
-        return dbuf_end;
-    } else if (begin.reverse && begin.ptr <= end.ptr) {
-        return dbuf_end;
+    const bool is_reverse_it = begin.base != NULL;
+    GUF_ASSERT_RELEASE(is_reverse_it == (end.base != NULL)); // begin and end must be the same iterator type.
+    const GUF_CAT(GUF_CNT_NAME, _iter) dbuf_end_it = is_reverse_it ? GUF_CAT(GUF_CNT_NAME, _rend)(dbuf) : GUF_CAT(GUF_CNT_NAME, _end)(dbuf);
+    
+    if (!dbuf->data || !dbuf->size || (!begin.ptr && !begin.base) || (!end.ptr && !end.base)) {
+        return dbuf_end_it;
+    } 
+    if ((begin.ptr == dbuf_end_it.ptr) || (!is_reverse_it && begin.ptr >= end.ptr) || (is_reverse_it && begin.base <= end.base)) {
+        return dbuf_end_it;
     }
 
     for (GUF_CAT(GUF_CNT_NAME, _iter) it = begin; it.ptr != end.ptr; GUF_CAT(GUF_CNT_NAME, _iter_next)(dbuf, it, 1)) {
diff --git a/src/guf_test.c b/src/guf_test.c
index 41dca98..aca8bad 100644
--- a/src/guf_test.c
+++ b/src/guf_test.c
@@ -75,8 +75,8 @@ int main(void)
     dbuf_heap_cstr_push_val_cpy(&strings, "Boz 4");
 
     char *findme = "Baz 3";
-    dbuf_heap_cstr_iter beg = dbuf_heap_cstr_rbegin(&strings);
-    dbuf_heap_cstr_iter end = dbuf_heap_cstr_rend(&strings);
+    dbuf_heap_cstr_iter beg = dbuf_heap_cstr_begin(&strings);
+    dbuf_heap_cstr_iter end = dbuf_heap_cstr_end(&strings);
     dbuf_heap_cstr_iter fnd_it = dbuf_heap_cstr_find(&strings, beg, end, &findme);
     if (fnd_it.ptr != dbuf_heap_cstr_end(&strings).ptr) {
         printf("%s found in range [%td, %td) at idx %td\n", findme, dbuf_heap_cstr_iter_to_idx(&strings, beg), dbuf_heap_cstr_iter_to_idx(&strings, end), dbuf_heap_cstr_iter_to_idx(&strings, fnd_it));
@@ -84,6 +84,12 @@ int main(void)
         printf("%s not found in range [%td, %td) at idx %td\n", findme, dbuf_heap_cstr_iter_to_idx(&strings, beg), dbuf_heap_cstr_iter_to_idx(&strings, end), dbuf_heap_cstr_iter_to_idx(&strings, fnd_it));
     }
 
+    if (dbuf_heap_cstr_contains_val(&strings, "Baz 3")) {
+        printf("contains\n");
+    } else {
+        printf("does not contain\n");
+    }
+
     GUF_CNT_FOREACH(&strings, dbuf_heap_cstr, it) {
         printf("%s\n", *it.ptr);
     }