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diff --git a/internal/ceres/split.cc b/internal/ceres/split.cc
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
+// http://code.google.com/p/ceres-solver/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+//   this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors may be
+//   used to endorse or promote products derived from this software without
+//   specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: keir@google.com (Keir Mierle)
+
+#include <string>
+#include <vector>
+#include <iterator>
+#include "ceres/internal/port.h"
+
+namespace ceres {
+
+// If we know how much to allocate for a vector of strings, we can allocate the
+// vector<string> only once and directly to the right size. This saves in
+// between 33-66 % of memory space needed for the result, and runs faster in the
+// microbenchmarks.
+//
+// The reserve is only implemented for the single character delim.
+//
+// The implementation for counting is cut-and-pasted from
+// SplitStringToIteratorUsing. I could have written my own counting iterator,
+// and use the existing template function, but probably this is more clear and
+// more sure to get optimized to reasonable code.
+static int CalculateReserveForVector(const string& full, const char* delim) {
+  int count = 0;
+  if (delim[0] != '\0' && delim[1] == '\0') {
+    // Optimize the common case where delim is a single character.
+    char c = delim[0];
+    const char* p = full.data();
+    const char* end = p + full.size();
+    while (p != end) {
+      if (*p == c) {  // This could be optimized with hasless(v,1) trick.
+        ++p;
+      } else {
+        while (++p != end && *p != c) {
+          // Skip to the next occurence of the delimiter.
+        }
+        ++count;
+      }
+    }
+  }
+  return count;
+}
+
+template <typename StringType, typename ITR>
+static inline
+void SplitStringToIteratorUsing(const StringType& full,
+                                const char* delim,
+                                ITR& result) {
+  // Optimize the common case where delim is a single character.
+  if (delim[0] != '\0' && delim[1] == '\0') {
+    char c = delim[0];
+    const char* p = full.data();
+    const char* end = p + full.size();
+    while (p != end) {
+      if (*p == c) {
+        ++p;
+      } else {
+        const char* start = p;
+        while (++p != end && *p != c) {
+          // Skip to the next occurence of the delimiter.
+        }
+        *result++ = StringType(start, p - start);
+      }
+    }
+    return;
+  }
+
+  string::size_type begin_index, end_index;
+  begin_index = full.find_first_not_of(delim);
+  while (begin_index != string::npos) {
+    end_index = full.find_first_of(delim, begin_index);
+    if (end_index == string::npos) {
+      *result++ = full.substr(begin_index);
+      return;
+    }
+    *result++ = full.substr(begin_index, (end_index - begin_index));
+    begin_index = full.find_first_not_of(delim, end_index);
+  }
+}
+
+void SplitStringUsing(const string& full,
+                      const char* delim,
+                      vector<string>* result) {
+  result->reserve(result->size() + CalculateReserveForVector(full, delim));
+  back_insert_iterator< vector<string> > it(*result);
+  SplitStringToIteratorUsing(full, delim, it);
+}
+
+}  // namespace ceres