From 8c0e4a5c1f168a419b3a236a94815c97164bddbc Mon Sep 17 00:00:00 2001
From: "Wu, Ke" <wuke@cs.umd.edu>
Date: Sun, 12 Oct 2014 16:30:02 -0400
Subject: Cherry picked Mr.MIRA compatibility mode code

---
 utils/b64featvector.cc | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 utils/b64featvector.cc

(limited to 'utils/b64featvector.cc')

diff --git a/utils/b64featvector.cc b/utils/b64featvector.cc
new file mode 100644
index 00000000..c7d08b29
--- /dev/null
+++ b/utils/b64featvector.cc
@@ -0,0 +1,55 @@
+#include "b64featvector.h"
+
+#include <sstream>
+#include <boost/scoped_array.hpp>
+#include "b64tools.h"
+#include "fdict.h"
+
+using namespace std;
+
+static inline void EncodeFeatureWeight(const string &featname, weight_t weight,
+                                       ostream *output) {
+  output->write(featname.data(), featname.size() + 1);
+  output->write(reinterpret_cast<char *>(&weight), sizeof(weight_t));
+}
+
+string EncodeFeatureVector(const SparseVector<weight_t> &vec) {
+  string b64;
+  {
+    ostringstream base64_strm;
+    {
+      ostringstream strm;
+      for (SparseVector<weight_t>::const_iterator it = vec.begin();
+           it != vec.end(); ++it)
+        if (it->second != 0)
+          EncodeFeatureWeight(FD::Convert(it->first), it->second, &strm);
+      string data(strm.str());
+      B64::b64encode(data.data(), data.size(), &base64_strm);
+    }
+    b64 = base64_strm.str();
+  }
+  return b64;
+}
+
+void DecodeFeatureVector(const string &data, SparseVector<weight_t> *vec) {
+  vec->clear();
+  if (data.empty()) return;
+  // Decode data
+  size_t b64_len = data.size(), len = b64_len / 4 * 3;
+  boost::scoped_array<char> buf(new char[len]);
+  bool res =
+      B64::b64decode(reinterpret_cast<const unsigned char *>(data.data()),
+                     b64_len, buf.get(), len);
+  assert(res);
+  // Apply updates
+  size_t cur = 0;
+  while (cur < len) {
+    string feat_name(buf.get() + cur);
+    if (feat_name.empty()) break;  // Encountered trailing \0
+    int feat_id = FD::Convert(feat_name);
+    weight_t feat_delta =
+        *reinterpret_cast<weight_t *>(buf.get() + cur + feat_name.size() + 1);
+    (*vec)[feat_id] = feat_delta;
+    cur += feat_name.size() + 1 + sizeof(weight_t);
+  }
+}
-- 
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