| 121 | |
| 122 | |
| 123 | class Differ(object): |
| 124 | |
| 125 | def __init__(self, timeout=0.1): |
| 126 | # Number of seconds to compute a diff before giving up (0 for infinity). |
| 127 | self.timeout = timeout |
| 128 | |
| 129 | def difference(self, text1, text2, deadline=None): |
| 130 | """ |
| 131 | Find the differences between two texts. Simplifies the problem by |
| 132 | stripping any common prefix or suffix off the texts before diffing. |
| 133 | |
| 134 | Args: |
| 135 | text1: Old string to be diffed. |
| 136 | text2: New string to be diffed. |
| 137 | deadline: Optional time when the diff should be complete by. Used |
| 138 | internally for recursive calls. Users should set timeout instead. |
| 139 | |
| 140 | Returns: |
| 141 | Array of changes. |
| 142 | """ |
| 143 | if text1 == None or text2 == None: |
| 144 | raise ValueError('Illegal empty inputs') |
| 145 | |
| 146 | # Check for equality (speedup). |
| 147 | if text1 == text2: |
| 148 | if text1: |
| 149 | return [(DIFF_EQUAL, text1)] |
| 150 | return [] |
| 151 | |
| 152 | # Set a deadline by which time the diff must be complete. |
| 153 | if deadline == None: |
| 154 | # Unlike in most languages, Python counts time in seconds. |
| 155 | if not self.timeout: |
| 156 | deadline = sys.maxsize |
| 157 | else: |
| 158 | deadline = time.time() + self.timeout |
| 159 | |
| 160 | # Trim off common prefix (speedup). |
| 161 | commonlength = common_prefix(text1, text2) |
| 162 | commonprefix = text1[:commonlength] |
| 163 | text1 = text1[commonlength:] |
| 164 | text2 = text2[commonlength:] |
| 165 | |
| 166 | # Trim off common suffix (speedup). |
| 167 | commonlength = common_suffix(text1, text2) |
| 168 | if commonlength == 0: |
| 169 | commonsuffix = '' |
| 170 | else: |
| 171 | commonsuffix = text1[-commonlength:] |
| 172 | text1 = text1[:-commonlength] |
| 173 | text2 = text2[:-commonlength] |
| 174 | |
| 175 | # Compute the diff on the middle block. |
| 176 | diffs = self.compute(text1, text2, deadline) |
| 177 | |
| 178 | # Restore the prefix and suffix. |
| 179 | if commonprefix: |
| 180 | diffs[:0] = [(DIFF_EQUAL, commonprefix)] |