diff --git a/bwt.c b/bwt.c
index 689d8f8..fe8007f 100644
--- a/bwt.c
+++ b/bwt.c
@@ -337,3 +337,44 @@ int bwt_smem1(const bwt_t *bwt, int len, const uint8_t *q, int x, int min_intv,
 	if (tmpvec == 0 || tmpvec[1] == 0) free(a[1].a);
 	return ret;
 }
+
+/***************************
+ * SMEM iterator interface *
+ ***************************/
+
+smem_i *smem_itr_init(const bwt_t *bwt)
+{
+	smem_i *itr;
+	itr = calloc(1, sizeof(smem_i));
+	itr->bwt = bwt;
+	itr->tmpvec[0] = calloc(1, sizeof(bwtintv_v));
+	itr->tmpvec[1] = calloc(1, sizeof(bwtintv_v));
+	itr->matches   = calloc(1, sizeof(bwtintv_v));
+	return itr;
+}
+
+void smem_itr_destroy(smem_i *itr)
+{
+	free(itr->tmpvec[0]->a);
+	free(itr->tmpvec[1]->a);
+	free(itr->matches->a);
+	free(itr);
+}
+
+void smem_set_query(smem_i *itr, int min_intv, int len, const uint8_t *query)
+{
+	itr->query = query;
+	itr->start = 0;
+	itr->len = len;
+	itr->min_intv = min_intv;
+}
+
+int smem_next(smem_i *itr)
+{
+	itr->tmpvec[0]->n = itr->tmpvec[1]->n = itr->matches->n = 0;
+	if (itr->start >= itr->len || itr->start < 0) return -1;
+	while (itr->start < itr->len && itr->query[itr->start] > 3) ++itr->start; // skip ambiguous bases
+	if (itr->start == itr->len) return -1;
+	itr->start = bwt_smem1(itr->bwt, itr->len, itr->query, itr->start, itr->min_intv, itr->matches, itr->tmpvec);
+	return itr->start;
+}
diff --git a/bwt.h b/bwt.h
index 1eeaceb..67a256d 100644
--- a/bwt.h
+++ b/bwt.h
@@ -60,6 +60,13 @@ typedef struct {
 
 typedef struct { size_t n, m; bwtintv_t *a; } bwtintv_v;
 
+typedef struct {
+	const bwt_t *bwt;
+	const uint8_t *query;
+	int start, len, min_intv;
+	bwtintv_v *tmpvec[2], *matches;
+} smem_i;
+
 /* For general OCC_INTERVAL, the following is correct:
 #define bwt_bwt(b, k) ((b)->bwt[(k)/OCC_INTERVAL * (OCC_INTERVAL/(sizeof(uint32_t)*8/2) + sizeof(bwtint_t)/4*4) + sizeof(bwtint_t)/4*4 + (k)%OCC_INTERVAL/16])
 #define bwt_occ_intv(b, k) ((b)->bwt + (k)/OCC_INTERVAL * (OCC_INTERVAL/(sizeof(uint32_t)*8/2) + sizeof(bwtint_t)/4*4)
@@ -123,6 +130,13 @@ extern "C" {
 	 */
 	int bwt_smem1(const bwt_t *bwt, int len, const uint8_t *q, int x, int min_intv, bwtintv_v *mem, bwtintv_v *tmpvec[2]);
 
+	// SMEM iterator interface
+
+	smem_i *smem_itr_init(const bwt_t *bwt);
+	void smem_itr_destroy(smem_i *itr);
+	void smem_set_query(smem_i *itr, int min_intv, int len, const uint8_t *query);
+	int smem_next(smem_i *itr);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/fastmap.c b/fastmap.c
index 2c0a823..17db06d 100644
--- a/fastmap.c
+++ b/fastmap.c
@@ -10,50 +10,6 @@ KSEQ_INIT(gzFile, gzread)
 
 extern unsigned char nst_nt4_table[256];
 
-typedef struct {
-	const bwt_t *bwt;
-	const uint8_t *query;
-	int start, len, min_intv;
-	bwtintv_v *tmpvec[2], *matches;
-} smem_i;
-
-smem_i *smem_iter_init(const bwt_t *bwt, int min_intv)
-{
-	smem_i *iter;
-	iter = calloc(1, sizeof(smem_i));
-	iter->bwt = bwt;
-	iter->tmpvec[0] = calloc(1, sizeof(bwtintv_v));
-	iter->tmpvec[1] = calloc(1, sizeof(bwtintv_v));
-	iter->matches   = calloc(1, sizeof(bwtintv_v));
-	iter->min_intv = min_intv > 0? min_intv : 1;
-	return iter;
-}
-
-void smem_iter_destroy(smem_i *iter)
-{
-	free(iter->tmpvec[0]->a);
-	free(iter->tmpvec[1]->a);
-	free(iter->matches->a);
-	free(iter);
-}
-
-void smem_set_query(smem_i *iter, int len, const uint8_t *query)
-{
-	iter->query = query;
-	iter->start = 0;
-	iter->len = len;
-}
-
-int smem_next(smem_i *iter)
-{
-	iter->tmpvec[0]->n = iter->tmpvec[1]->n = iter->matches->n = 0;
-	if (iter->start >= iter->len || iter->start < 0) return -1;
-	while (iter->start < iter->len && iter->query[iter->start] > 3) ++iter->start; // skip ambiguous bases
-	if (iter->start == iter->len) return -1;
-	iter->start = bwt_smem1(iter->bwt, iter->len, iter->query, iter->start, iter->min_intv, iter->matches, iter->tmpvec);
-	return iter->start;
-}
-
 int main_fastmap(int argc, char *argv[])
 {
 	int c, i, min_iwidth = 20, min_len = 17, print_seq = 0, min_intv = 1;
@@ -62,7 +18,7 @@ int main_fastmap(int argc, char *argv[])
 	gzFile fp;
 	bwt_t *bwt;
 	bntseq_t *bns;
-	smem_i *iter;
+	smem_i *itr;
 
 	while ((c = getopt(argc, argv, "w:l:sm:")) >= 0) {
 		switch (c) {
@@ -88,7 +44,7 @@ int main_fastmap(int argc, char *argv[])
 		free(tmp);
 		bns = bns_restore(argv[optind]);
 	}
-	iter = smem_iter_init(bwt, min_intv);
+	itr = smem_itr_init(bwt);
 	while (kseq_read(seq) >= 0) {
 		printf("SQ\t%s\t%ld", seq->name.s, seq->seq.l);
 		if (print_seq) {
@@ -97,10 +53,10 @@ int main_fastmap(int argc, char *argv[])
 		} else putchar('\n');
 		for (i = 0; i < seq->seq.l; ++i)
 			seq->seq.s[i] = nst_nt4_table[(int)seq->seq.s[i]];
-		smem_set_query(iter, seq->seq.l, (uint8_t*)seq->seq.s);
-		while (smem_next(iter) > 0) {
-			for (i = 0; i < iter->matches->n; ++i) {
-				bwtintv_t *p = &iter->matches->a[i];
+		smem_set_query(itr, min_intv, seq->seq.l, (uint8_t*)seq->seq.s);
+		while (smem_next(itr) > 0) {
+			for (i = 0; i < itr->matches->n; ++i) {
+				bwtintv_t *p = &itr->matches->a[i];
 				if ((uint32_t)p->info - (p->info>>32) < min_len) continue;
 				printf("EM\t%d\t%d\t%ld", (uint32_t)(p->info>>32), (uint32_t)p->info, (long)p->x[2]);
 				if (p->x[2] <= min_iwidth) {
@@ -120,7 +76,7 @@ int main_fastmap(int argc, char *argv[])
 		puts("//");
 	}
 
-	smem_iter_destroy(iter);
+	smem_itr_destroy(itr);
 	bns_destroy(bns);
 	bwt_destroy(bwt);
 	kseq_destroy(seq);