split.cc revision 0ae28bd5885b5daa526898fcf7c323dc2c3e1963 
1// Ceres Solver - A fast non-linear least squares minimizer
2// Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
3// http://code.google.com/p/ceres-solver/
4//
5// Redistribution and use in source and binary forms, with or without
6// modification, are permitted provided that the following conditions are met:
7//
8// * Redistributions of source code must retain the above copyright notice,
9//   this list of conditions and the following disclaimer.
10// * Redistributions in binary form must reproduce the above copyright notice,
11//   this list of conditions and the following disclaimer in the documentation
12//   and/or other materials provided with the distribution.
13// * Neither the name of Google Inc. nor the names of its contributors may be
14//   used to endorse or promote products derived from this software without
15//   specific prior written permission.
16//
17// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
18// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
21// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27// POSSIBILITY OF SUCH DAMAGE.
28//
29// Author: keir@google.com (Keir Mierle)
30
31#include <string>
32#include <vector>
33#include <iterator>
34#include "ceres/internal/port.h"
35
36namespace ceres {
37
38// If we know how much to allocate for a vector of strings, we can allocate the
39// vector<string> only once and directly to the right size. This saves in
40// between 33-66 % of memory space needed for the result, and runs faster in the
41// microbenchmarks.
42//
43// The reserve is only implemented for the single character delim.
44//
45// The implementation for counting is cut-and-pasted from
46// SplitStringToIteratorUsing. I could have written my own counting iterator,
47// and use the existing template function, but probably this is more clear and
48// more sure to get optimized to reasonable code.
49static int CalculateReserveForVector(const string& full, const char* delim) {
50  int count = 0;
51  if (delim[0] != '\0' && delim[1] == '\0') {
52    // Optimize the common case where delim is a single character.
53    char c = delim[0];
54    const char* p = full.data();
55    const char* end = p + full.size();
56    while (p != end) {
57      if (*p == c) {  // This could be optimized with hasless(v,1) trick.
58        ++p;
59      } else {
60        while (++p != end && *p != c) {
61          // Skip to the next occurence of the delimiter.
62        }
63        ++count;
64      }
65    }
66  }
67  return count;
68}
69
70template <typename StringType, typename ITR>
71static inline
72void SplitStringToIteratorUsing(const StringType& full,
73                                const char* delim,
74                                ITR& result) {
75  // Optimize the common case where delim is a single character.
76  if (delim[0] != '\0' && delim[1] == '\0') {
77    char c = delim[0];
78    const char* p = full.data();
79    const char* end = p + full.size();
80    while (p != end) {
81      if (*p == c) {
82        ++p;
83      } else {
84        const char* start = p;
85        while (++p != end && *p != c) {
86          // Skip to the next occurence of the delimiter.
87        }
88        *result++ = StringType(start, p - start);
89      }
90    }
91    return;
92  }
93
94  string::size_type begin_index, end_index;
95  begin_index = full.find_first_not_of(delim);
96  while (begin_index != string::npos) {
97    end_index = full.find_first_of(delim, begin_index);
98    if (end_index == string::npos) {
99      *result++ = full.substr(begin_index);
100      return;
101    }
102    *result++ = full.substr(begin_index, (end_index - begin_index));
103    begin_index = full.find_first_not_of(delim, end_index);
104  }
105}
106
107void SplitStringUsing(const string& full,
108                      const char* delim,
109                      vector<string>* result) {
110  result->reserve(result->size() + CalculateReserveForVector(full, delim));
111  back_insert_iterator< vector<string> > it(*result);
112  SplitStringToIteratorUsing(full, delim, it);
113}
114
115}  // namespace ceres
116