Intermediate changes

3 files changed, 74 insertions, 0 deletions

diff --git a/library/cpp/streams/growing_file_input/growing_file_input.cpp b/library/cpp/streams/growing_file_input/growing_file_input.cpp
new file mode 100644
index 00000000000..0bbfa5ade9e
--- /dev/null
+++ b/library/cpp/streams/growing_file_input/growing_file_input.cpp
@@ -0,0 +1,40 @@
+#include "growing_file_input.h"
+
+#include <util/datetime/base.h>
+#include <util/generic/yexception.h>
+
+TGrowingFileInput::TGrowingFileInput(const TString& path)
+    : File_(path, OpenExisting | RdOnly | Seq)
+{
+    if (!File_.IsOpen()) {
+        ythrow TIoException() << "file " << path << " not open";
+    }
+
+    File_.Seek(0, sEnd);
+}
+
+TGrowingFileInput::TGrowingFileInput(const TFile& file)
+    : File_(file)
+{
+    if (!File_.IsOpen()) {
+        ythrow TIoException() << "file (" << file.GetName() << ") not open";
+    }
+
+    File_.Seek(0, sEnd);
+}
+
+size_t TGrowingFileInput::DoRead(void* buf, size_t len) {
+    for (int sleepTime = 1;;) {
+        size_t rr = File_.Read(buf, len);
+
+        if (rr != 0) {
+            return rr;
+        }
+
+        NanoSleep((ui64)sleepTime * 1000000);
+
+        if (sleepTime < 2000) {
+            sleepTime <<= 1;
+        }
+    }
+}
diff --git a/library/cpp/streams/growing_file_input/growing_file_input.h b/library/cpp/streams/growing_file_input/growing_file_input.h
new file mode 100644
index 00000000000..9054a5f3dac
--- /dev/null
+++ b/library/cpp/streams/growing_file_input/growing_file_input.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <util/stream/input.h>
+#include <util/system/file.h>
+
+/**
+ * Growing file input stream.
+ *
+ * File descriptor offsets to the end of the file, when the object is created.
+ *
+ * Read function waites for reading at least one byte.
+ */
+class TGrowingFileInput: public IInputStream {
+public:
+    TGrowingFileInput(const TFile& file);
+    TGrowingFileInput(const TString& path);
+
+private:
+    size_t DoRead(void* buf, size_t len) override;
+
+private:
+    TFile File_;
+};
diff --git a/library/cpp/streams/growing_file_input/ya.make b/library/cpp/streams/growing_file_input/ya.make
new file mode 100644
index 00000000000..69c56fea462
--- /dev/null
+++ b/library/cpp/streams/growing_file_input/ya.make
@@ -0,0 +1,11 @@
+LIBRARY()
+
+SRCS(
+    growing_file_input.cpp
+)
+
+END()
+
+RECURSE_FOR_TESTS(
+    ut
+)