MMap: fix readline

Author: steve-s

graalpython/com.oracle.graal.python.test/src/tests/test_mmap.py

@@ -206,6 +206,21 @@ def test_getitem():
     assert m[slice(-10, 100)] == b'\x02\x03\x04\x05\x06\x07\x08\t\n\x0b'
 
 
+def test_readline():
+    m = mmap.mmap(-1, 9)
+    for i in range(0, 9):
+        m[i] = i
+    m[4] = b'\n'[0]
+    assert m.readline() == b'\x00\x01\x02\x03\n'
+    assert m.readline() == b'\x05\x06\x07\x08'
+
+    m = mmap.mmap(-1, 1024 + 3)
+    m[1024] = b'\n'[0]
+    m[1025] = b'a'[0]
+    m[1026] = b'b'[0]
+    assert m.readline() == (b'\x00' * 1024) + b'\n'
+    assert m.readline() == b'ab'
+
 
 def test_main():
     #run_unittest(MmapTests, LargeMmapTests)

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/mmap/MMapBuiltins.java

@@ -457,24 +457,22 @@ Object readline(VirtualFrame frame, PMMap self,
             // small buffer
             ByteSequenceStorage res = new ByteSequenceStorage(16);
             byte[] buffer = new byte[BUFFER_SIZE];
-            long pos = self.getPos();
             int nread;
-            outer: while (pos < self.getLength()) {
+            outer: while (self.getPos() < self.getLength()) {
                 try {
-                    nread = posixLib.mmapReadBytes(getPosixSupport(), self.getPosixSupportHandle(), pos, buffer, buffer.length);
+                    nread = posixLib.mmapReadBytes(getPosixSupport(), self.getPosixSupportHandle(), self.getPos(), buffer, (int) Math.min(self.getRemaining(), buffer.length));
                 } catch (PosixException e) {
                     throw raiseOSErrorFromPosixException(frame, e);
                 }
                 for (int i = 0; i < nread; i++) {
                     byte b = buffer[i];
-                    if (b != '\n') {
-                        appendNode.execute(res, b, BytesLikeNoGeneralizationNode.SUPPLIER);
-                    } else {
-                        self.setPos(pos + i - 1);
+                    appendNode.execute(res, b, BytesLikeNoGeneralizationNode.SUPPLIER);
+                    if (b == '\n') {
+                        self.setPos(self.getPos() + i + 1);
                         break outer;
                     }
                 }
-                pos += nread;
+                self.setPos(self.getPos() + nread);
             }
             return factory().createBytes(res);
         }