intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

3 files changed, 61 insertions, 0 deletions

diff --git a/library/cpp/streams/zc_memory_input/ya.make b/library/cpp/streams/zc_memory_input/ya.make
new file mode 100644
index 0000000000..bc94d6f1ed
--- /dev/null
+++ b/library/cpp/streams/zc_memory_input/ya.make
@@ -0,0 +1,12 @@
+LIBRARY()
+
+OWNER(
+    pg
+    g:util
+)
+
+SRCS(
+    zc_memory_input.cpp
+)
+
+END()
diff --git a/library/cpp/streams/zc_memory_input/zc_memory_input.cpp b/library/cpp/streams/zc_memory_input/zc_memory_input.cpp
new file mode 100644
index 0000000000..682099a239
--- /dev/null
+++ b/library/cpp/streams/zc_memory_input/zc_memory_input.cpp
@@ -0,0 +1 @@
+#include "zc_memory_input.h"
diff --git a/library/cpp/streams/zc_memory_input/zc_memory_input.h b/library/cpp/streams/zc_memory_input/zc_memory_input.h
new file mode 100644
index 0000000000..c939d8e426
--- /dev/null
+++ b/library/cpp/streams/zc_memory_input/zc_memory_input.h
@@ -0,0 +1,48 @@
+#pragma once
+
+#include <util/stream/mem.h>
+#include <util/system/defaults.h>
+#include <util/generic/yexception.h>
+
+/// Zero-copy memory input with fixed read
+class TZCMemoryInput: public TMemoryInput {
+public:
+    TZCMemoryInput() {
+    }
+
+    TZCMemoryInput(const char* dataPtr, size_t size)
+        : TMemoryInput(dataPtr, size)
+    {
+    }
+
+    TZCMemoryInput(TMemoryInput& rhs)
+        : TMemoryInput(rhs.Buf(), rhs.Avail())
+    {
+    }
+
+    /// if there's 'size' data read it, otherwise just return false
+    Y_FORCE_INLINE bool ReadFixed(const char*& buf, size_t size) {
+        if (Avail() >= size) {
+            buf = Buf();
+            Reset(Buf() + size, Avail() - size);
+            return true;
+        }
+        return false;
+    }
+
+    template <class T>
+    Y_FORCE_INLINE T LoadPOD() {
+        const char* buf = nullptr;
+        if (!ReadFixed(buf, sizeof(T)))
+            ythrow yexception() << "TZCMemoryInput::LoadPOD failed: not enough data ("
+                                << Avail() << " of " << sizeof(T) << " bytes)";
+        T res;
+        memcpy(&res, buf, sizeof(T));
+        return res;
+    }
+
+    template <class T>
+    Y_FORCE_INLINE void ReadPOD(T& x) {
+        x = LoadPOD<T>();
+    }
+};