Only realloc(pac,...) if it needs to be made larger

Similarly to the realloc(pac,...) within add1(), only bother to call realloc() if appending the reverse complemented sequence requires more space than is currently in the pac/m_pac buffer. Avoids realloc(pac,0) (and a "Failed to allocate 0 bytes at bntseq.c" message from wrap_realloc()) in the corner case of an empty reference FASTA file. Fixes lh3#54.
rbh · rbh · Aug 28, 2017 · Mar 31, 2016 · Mar 31, 2016 · Jun 10, 2016
commit 1972a978133110e36af05a6bc2e27881f51443c4
diff --git a/bntseq.c b/bntseq.c
@@ -299,9 +299,9 @@ int64_t bns_fasta2bntseq(gzFile fp_fa, const char *prefix, int for_only)
 	// read sequences
 	while (kseq_read(seq) >= 0) pac = add1(seq, bns, pac, &m_pac, &m_seqs, &m_holes, &q);
 	if (!for_only) { // add the reverse complemented sequence
-		m_pac = (bns->l_pac * 2 + 3) / 4 * 4;
-		pac = realloc(pac, m_pac/4);
-		memset(pac + (bns->l_pac+3)/4, 0, (m_pac - (bns->l_pac+3)/4*4) / 4);
+		int64_t ll_pac = (bns->l_pac * 2 + 3) / 4 * 4;
+		if (ll_pac > m_pac) pac = realloc(pac, ll_pac/4);
+		memset(pac + (bns->l_pac+3)/4, 0, (ll_pac - (bns->l_pac+3)/4*4) / 4);
 		for (l = bns->l_pac - 1; l >= 0; --l, ++bns->l_pac)
 			_set_pac(pac, bns->l_pac, 3-_get_pac(pac, l));
 	}