From 4ca29d9593b4890441dc163999302a870b76162a Mon Sep 17 00:00:00 2001
From: Alex Zolotarev <deathbaba@gmail.com>
Date: Mon, 7 Nov 2011 05:55:11 +0300
Subject: [mac] Added chunks download strategy

---
 platform/chunks_download_strategy.cpp | 92 +++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 platform/chunks_download_strategy.cpp

(limited to 'platform/chunks_download_strategy.cpp')

diff --git a/platform/chunks_download_strategy.cpp b/platform/chunks_download_strategy.cpp
new file mode 100644
index 0000000000..ff22ab3f1b
--- /dev/null
+++ b/platform/chunks_download_strategy.cpp
@@ -0,0 +1,92 @@
+#include "chunks_download_strategy.hpp"
+
+#include "../std/algorithm.hpp"
+
+#define INVALID_CHUNK -1
+
+
+namespace downloader
+{
+
+ChunksDownloadStrategy::RangeT const ChunksDownloadStrategy::INVALID_RANGE = RangeT(-1, -1);
+
+ChunksDownloadStrategy::ChunksDownloadStrategy(vector<string> const & urls, int64_t fileSize, int64_t chunkSize)
+  : m_chunkSize(chunkSize)
+{
+  // init servers list
+  for (size_t i = 0; i < urls.size(); ++i)
+    m_servers.push_back(make_pair(urls[i], INVALID_RANGE));
+
+  // init chunks which should be downloaded
+  // @TODO implement download resume by saving chunks to download for specified file
+  for (int64_t i = 0; i < fileSize; i += chunkSize)
+  {
+    m_chunksToDownload.insert(RangeT(i, min(i + chunkSize - 1,
+                                            fileSize - 1)));
+  }
+}
+
+void ChunksDownloadStrategy::ChunkFinished(bool successfully, int64_t begRange, int64_t endRange)
+{
+  RangeT const chunk(begRange, endRange);
+  // find server which was downloading this chunk
+  for (ServersT::iterator it = m_servers.begin(); it != m_servers.end(); ++it)
+  {
+    if (it->second == chunk)
+    {
+      if (successfully)
+        it->second = INVALID_RANGE;
+      else
+      {
+        // remove failed server and mark chunk as not downloaded
+        m_servers.erase(it);
+        m_chunksToDownload.insert(chunk);
+      }
+      break;
+    }
+  }
+}
+
+ChunksDownloadStrategy::ResultT ChunksDownloadStrategy::NextChunk(string & outUrl,
+                                                                  int64_t & begRange,
+                                                                  int64_t & endRange)
+{
+  if (m_servers.empty())
+    return EDownloadFailed;
+
+  if (m_chunksToDownload.empty())
+  {
+    // no more chunks to download
+    bool allChunksAreFinished = true;
+    for (size_t i = 0; i < m_servers.size(); ++i)
+    {
+      if (m_servers[i].second != INVALID_RANGE)
+        allChunksAreFinished = false;
+    }
+    if (allChunksAreFinished)
+      return EDownloadSucceeded;
+    else
+      return ENoFreeServers;
+  }
+  else
+  {
+    RangeT const nextChunk = *m_chunksToDownload.begin();
+    for (size_t i = 0; i < m_servers.size(); ++i)
+    {
+      if (m_servers[i].second == INVALID_RANGE)
+      {
+        // found not used server
+        m_servers[i].second = nextChunk;
+        outUrl = m_servers[i].first;
+        begRange = nextChunk.first;
+        endRange = nextChunk.second;
+        m_chunksToDownload.erase(m_chunksToDownload.begin());
+        return ENextChunk;
+      }
+    }
+    // if we're here, all servers are busy downloading
+    return ENoFreeServers;
+  }
+}
+
+} // namespace downloader
-- 
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