Fix a bug in BAM random reader.

src/cljam/bam/reader.clj

@@ -95,23 +95,26 @@
 
 (defn- read-to-finish
   [^BAMReader rdr
+   ^Long start
    ^Long finish
    ^clojure.lang.IFn read-fn]
   (let [r ^BGZFInputStream (.reader rdr)]
-    (when (and (not (zero? (.available r)))
-               (> finish (.getFilePointer r)))
-      (cons (read-fn rdr (.refs rdr))
-            (lazy-seq (read-to-finish rdr finish read-fn))))))
+    (when (< start finish)
+      (.seek r start)
+      (when-not (zero? (.available r))
+        (let [result (read-fn rdr (.refs rdr))
+              curr (.getFilePointer r)]
+          (cons result
+                (lazy-seq (read-to-finish rdr curr finish read-fn))))))))
 
 (defn- read-alignments-first-only
   "It should be equivalent to [(first (filter window @candidates))]"
   [^BAMReader rdr spans window read-fn]
   (loop [left-spans spans]
     (when-let [span (first left-spans)]
       (let [[^Long begin ^Long finish] span]
-        (.seek ^BGZFInputStream (.reader rdr) begin)
         (or
-          (loop [left (read-to-finish rdr finish read-fn)]
+          (loop [left (read-to-finish rdr begin finish read-fn)]
             (when-let [one (first left)]
               (if (window one)
                 [one]
@@ -138,8 +141,7 @@
                   :deep read-alignment
                   :pointer pointer-read-alignment)
         candidates (flatten (map (fn [[^Long begin ^Long finish]]
-                                   (.seek ^BGZFInputStream (.reader rdr) begin)
-                                   (read-to-finish rdr finish read-fn)) spans))]
+                                   (read-to-finish rdr begin finish read-fn)) spans))]
     (if (= deep-or-shallow :first-only)
       (read-alignments-first-only rdr spans window read-fn)
       (filter window candidates))))
@@ -182,8 +184,7 @@
                         (<= start left)
                         (>= end left))))
         candidates (flatten (map (fn [[^Long begin ^Long finish]]
-                                   (.seek ^BGZFInputStream (.reader rdr) begin)
-                                   (read-to-finish rdr finish read-coordinate-alignment-block)) spans))]
+                                   (read-to-finish rdr begin finish read-coordinate-alignment-block)) spans))]
     (filter window candidates)))
 
 (defn load-headers

test/cljam/t_bam_indexer.clj

@@ -46,6 +46,20 @@
       ;; (it will use https://gitlab.xcoo.jp/chrovis/cljam/issues/8 later)
       )))
 
+(with-state-changes [(before :facts (do (prepare-cache!)
+                                        (fs/copy small-bam-file temp-file-sorted)))
+                     (after :facts (clean-cache!))]
+  (fact "about BAM indexer (small file)"
+    (bai/create-index
+     temp-file-sorted (str temp-file-sorted ".bai")) => anything
+    (fs/exists? (str temp-file-sorted ".bai")) => truthy
+    (with-open [r (bam/reader temp-file-sorted)]
+      ;; Random read with different number of spans.
+      (count (io/read-alignments r {:chr "chr1" :start 23000000 :end 25000000 :depth :deep})) => 14858
+      (count (io/read-alignments r {:chr "chr1" :start 23000000 :end 24500000 :depth :deep})) => 11424
+      (count (io/read-alignments r {:chr "chr1" :start 23000000 :end 24000000 :depth :deep})) => 10010
+      (count (io/read-alignments r {:chr "chr1" :start 23000000 :end 23500000 :depth :deep})) => 3806)))
+
 (with-state-changes [(before :facts (do (prepare-cache!)
                                         (fs/copy medium-bam-file
                                                  temp-file-sorted)))

test/cljam/t_common.clj

@@ -63,6 +63,7 @@
 
 (def test-bam-file "test-resources/test.bam")
 (def test-sorted-bam-file "test-resources/test.sorted.bam")
+(def small-bam-file "test-resources/small.bam")
 (def medium-bam-file "test-resources/medium.bam")
 (def large-bam-file (cavia/resource mycavia "large.bam"))