// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

//

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// modification, are permitted provided that the following conditions are met:

//

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//   this list of conditions and the following disclaimer.

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//   this list of conditions and the following disclaimer in the documentation

//   and/or other materials provided with the distribution.

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//   used to endorse or promote products derived from this software without

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// Author: keir@google.com (Keir Mierle)

#include "ceres/split.h"

#include <iterator>

#include <string>

#include <vector>

#include "ceres/internal/port.h"

namespace ceres {

namespace internal {

using std::string;

using std::vector;

// 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));

  std::back_insert_iterator<vector<string> > it(*result);

  SplitStringToIteratorUsing(full, delim, it);

}

}  // namespace internal

}  // namespace ceres