From 83c4a22d73f9801ced3c29e664e2c000535a0965 Mon Sep 17 00:00:00 2001
From: Maxim Mamontov <faust.madf@gmail.com>
Date: Wed, 8 Apr 2015 22:47:33 +0300
Subject: [PATCH] Added blockio library.

---
 stglibs/common.lib/blockio.cpp           | 102 +++++++++++++++++++++++
 stglibs/common.lib/include/stg/blockio.h |  43 ++++++++++
 2 files changed, 145 insertions(+)
 create mode 100644 stglibs/common.lib/blockio.cpp
 create mode 100644 stglibs/common.lib/include/stg/blockio.h

diff --git a/stglibs/common.lib/blockio.cpp b/stglibs/common.lib/blockio.cpp
new file mode 100644
index 00000000..04fd1d81
--- /dev/null
+++ b/stglibs/common.lib/blockio.cpp
@@ -0,0 +1,102 @@
+#include "stg/blockio.h"
+
+namespace
+{
+
+void* adjust(void* base, size_t shift)
+{
+    char* ptr = static_cast<char*>(base);
+    return ptr + shift;
+}
+
+} // namspace anonymous
+
+using STG::BlockReader;
+using STG::BlockWriter;
+
+BlockReader::BlockReader(const IOVec& ioVec)
+    : m_dest(ioVec),
+      m_remainder(0)
+{
+    for (size_t i = 0; i < m_dest.size(); ++i)
+        m_remainder += m_dest[i].iov_len;
+}
+
+bool BlockReader::read(int socket)
+{
+    if (m_remainder == 0)
+        return true;
+
+    size_t offset = m_dest.size() - 1;
+    size_t toRead = m_remainder;
+    while (offset > 0) {
+        if (toRead < m_dest[offset].iov_len)
+            break;
+        toRead -= m_dest[offset].iov_len;
+        --offset;
+    }
+
+    IOVec dest(m_dest.size() - offset);
+    for (size_t i = 0; i < dest.size(); ++i) {
+        if (i == 0) {
+            dest[0].iov_len = toRead;
+            dest[0].iov_base = adjust(m_dest[offset].iov_base, m_dest[offset].iov_len - toRead);
+        } else {
+            dest[i] = m_dest[offset + i];
+        }
+    }
+
+    ssize_t res = readv(socket, dest.data(), dest.size());
+    if (res < 0)
+        return false;
+    if (res == 0)
+        return m_remainder == 0;
+    if (res < static_cast<ssize_t>(m_remainder))
+        m_remainder -= res;
+    else
+        m_remainder = 0;
+    return true;
+}
+
+BlockWriter::BlockWriter(const IOVec& ioVec)
+    : m_source(ioVec),
+      m_remainder(0)
+{
+    for (size_t i = 0; i < m_source.size(); ++i)
+        m_remainder += m_source[i].iov_len;
+}
+
+bool BlockWriter::write(int socket)
+{
+    if (m_remainder == 0)
+        return true;
+
+    size_t offset = m_source.size() - 1;
+    size_t toWrite = m_remainder;
+    while (offset > 0) {
+        if (toWrite < m_source[offset].iov_len)
+            break;
+        toWrite -= m_source[offset].iov_len;
+        --offset;
+    }
+
+    IOVec source(m_source.size() - offset);
+    for (size_t i = 0; i < source.size(); ++i) {
+        if (i == 0) {
+            source[0].iov_len = toWrite;
+            source[0].iov_base = adjust(m_source[offset].iov_base, m_source[offset].iov_len - toWrite);
+        } else {
+            source[i] = m_source[offset + i];
+        }
+    }
+    ssize_t res = writev(socket, source.data(), source.size());
+    if (res < 0)
+        return false;
+    if (res == 0)
+        return m_remainder == 0;
+    if (res < static_cast<ssize_t>(m_remainder))
+        m_remainder -= res;
+    else
+        m_remainder = 0;
+    return true;
+}
diff --git a/stglibs/common.lib/include/stg/blockio.h b/stglibs/common.lib/include/stg/blockio.h
new file mode 100644
index 00000000..3879e39e
--- /dev/null
+++ b/stglibs/common.lib/include/stg/blockio.h
@@ -0,0 +1,43 @@
+#ifndef __STG_STGLIBS_BLOCK_IO_H__
+#define __STG_STGLIBS_BLOCK_IO_H__
+
+#include <vector>
+
+#include <sys/uio.h>
+
+namespace STG
+{
+
+typedef std::vector<iovec> IOVec;
+
+class BlockReader
+{
+    public:
+        BlockReader(const IOVec& ioVec);
+
+        bool read(int socket);
+        bool done() const { return m_remainder == 0; }
+        size_t remainder() const { return m_remainder; }
+
+    private:
+        IOVec m_dest;
+        size_t m_remainder;
+};
+
+class BlockWriter
+{
+    public:
+        BlockWriter(const IOVec& ioVec);
+
+        bool write(int socket);
+        bool done() const { return m_remainder == 0; }
+        size_t remainder() const { return m_remainder; }
+
+    private:
+        IOVec m_source;
+        size_t m_remainder;
+};
+
+} // namespace STG
+
+#endif
-- 
2.43.2