2 * diff.c : routines for doing diffs
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4 * ====================================================================
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5 * Copyright (c) 2000-2004 CollabNet. All rights reserved.
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7 * This software is licensed as described in the file COPYING, which
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8 * you should have received as part of this distribution. The terms
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9 * are also available at http://subversion.tigris.org/license-1.html.
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10 * If newer versions of this license are posted there, you may use a
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11 * newer version instead, at your option.
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13 * This software consists of voluntary contributions made by many
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14 * individuals. For exact contribution history, see the revision
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15 * history and logs, available at http://subversion.tigris.org/.
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16 * ====================================================================
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21 //#include <apr_pools.h>
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22 #include <apr_general.h>
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24 #include "svn_pools.h"
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25 #include "svn_error.h"
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26 #include "svn_diff.h"
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27 #include "svn_types.h"
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32 * Variance adjustment rules:
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34 * http://subversion.tigris.org/variance-adjusted-patching.html
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36 * ###: Expand this comment to contain the full set of adjustment
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37 * ###: rules instead of pointing to a webpage.
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41 * In the text below consider the following:
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47 * X:Y = diff between X and Y
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48 * X:Y:Z = 3-way diff between X, Y and Z
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49 * P = O:L, possibly adjusted
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51 * diff4 -- Variance adjusted diff algorithm
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53 * 1. Create a diff O:L and call that P.
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55 * 2. Morph P into a 3-way diff by performing the following
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56 * transformation: O:L -> O:O:L.
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58 * 3. Create a diff A:O.
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64 * #. Resolve conflicts...
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67 1. Out-range added line: decrement the line numbers in every hunk in P
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68 that comes after the addition. This undoes the effect of the add, since
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69 the add never happened in D.
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71 2. Out-range deleted line: increment the line numbers in every hunk in P
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72 that comes after the deletion. This undoes the effect of the deletion,
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73 since the deletion never happened in D.
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75 3. Out-range edited line: do nothing. Out-range edits are irrelevant to P.
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77 4. Added line in context range in P: remove the corresponding line from
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78 the context, optionally replacing it with new context based on that
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79 region in M, and adjust line numbers and mappings appropriately.
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81 5. Added line in affected text range in P: this is a dependency problem
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82 -- part of the change T:18-T:19 depends on changes introduced to T after
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83 B branched. There are several possible behaviors, depending on what the
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84 user wants. One is to generate an informative error, stating that
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85 T:18-T:19 depends on some other change (T:N-T:M, where N>=8, M<=18,
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86 and M-N == 1); the exact revisions can be discovered automatically using
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87 the same process as "cvs annotate", though it may take some time to do
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88 so. Another option is to include the change in P, as an insertion of the
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89 "after" version of the text, and adjust line numbers and mappings
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90 accordingly. (And if all this isn't sounding a lot like a directory
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91 merge algorithm, try drinking more of the Kool-Aid.) A third option is
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92 to include it as an insertion, but with metadata (such as CVS-style
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93 conflict markers) indicating that the line attempting to be patched
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94 does not exist in B.
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96 6. Deleted line that is in-range in P: request another universe -- this
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97 situation can't happen in ours.
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99 7. In-range edited line: reverse that edit in the "before" version of the
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100 corresponding line in the appropriate hunk in P, to obtain the version of
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101 the line that will be found in B when P is applied.
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106 adjust_diff(svn_diff_t *diff, svn_diff_t *adjust)
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109 apr_off_t range_start;
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110 apr_off_t range_end;
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111 apr_off_t adjustment;
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113 for (; adjust; adjust = adjust->next)
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115 range_start = adjust->modified_start;
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116 range_end = range_start + adjust->modified_length;
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117 adjustment = adjust->original_length - adjust->modified_length;
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119 /* No change in line count, so no modifications. [3, 7] */
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120 if (adjustment == 0)
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123 for (hunk = diff; hunk; hunk = hunk->next)
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125 /* Changes are in the range before this hunk. Adjust the start
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126 * of the hunk. [1, 2]
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128 if (hunk->modified_start >= range_end)
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130 hunk->modified_start += adjustment;
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134 /* Changes are in the range beyond this hunk. No adjustments
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137 if (hunk->modified_start + hunk->modified_length <= range_start)
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140 /* From here on changes are in the range of this hunk. */
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142 /* This is a context hunk. Adjust the length. [4]
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144 if (hunk->type == svn_diff__type_diff_modified)
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146 hunk->modified_length += adjustment;
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150 /* Mark as conflicted. This happens in the reverse case when a line
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151 * is added in range and in the forward case when a line is deleted
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152 * in range. [5 (reverse), 6 (forward)]
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154 if (adjustment < 0)
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155 hunk->type = svn_diff__type_conflict;
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157 /* Adjust the length of this hunk (reverse the change). [5, 6] */
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158 hunk->modified_length -= adjustment;
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164 svn_diff_diff4(svn_diff_t **diff,
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166 const svn_diff_fns_t *vtable,
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169 svn_diff__tree_t *tree;
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170 svn_diff__position_t *position_list[4];
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171 svn_diff__lcs_t *lcs_ol;
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172 svn_diff__lcs_t *lcs_adjust;
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173 svn_diff_t *diff_ol;
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174 svn_diff_t *diff_adjust;
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176 apr_pool_t *subpool;
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177 apr_pool_t *subpool2;
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178 apr_pool_t *subpool3;
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182 subpool = svn_pool_create(pool);
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183 subpool2 = svn_pool_create(subpool);
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184 subpool3 = svn_pool_create(subpool2);
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186 svn_diff__tree_create(&tree, subpool3);
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188 SVN_ERR(svn_diff__get_tokens(&position_list[0],
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190 diff_baton, vtable,
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191 svn_diff_datasource_original,
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194 SVN_ERR(svn_diff__get_tokens(&position_list[1],
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196 diff_baton, vtable,
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197 svn_diff_datasource_modified,
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200 SVN_ERR(svn_diff__get_tokens(&position_list[2],
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202 diff_baton, vtable,
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203 svn_diff_datasource_latest,
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206 SVN_ERR(svn_diff__get_tokens(&position_list[3],
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208 diff_baton, vtable,
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209 svn_diff_datasource_ancestor,
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212 /* Get rid of the tokens, we don't need them to calc the diff */
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213 if (vtable->token_discard_all != NULL)
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214 vtable->token_discard_all(diff_baton);
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216 /* We don't need the nodes in the tree either anymore, nor the tree itself */
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217 svn_pool_clear(subpool3);
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219 /* Get the lcs for original - latest */
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220 lcs_ol = svn_diff__lcs(position_list[0], position_list[2], subpool3);
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221 diff_ol = svn_diff__diff(lcs_ol, 1, 1, TRUE, pool);
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223 svn_pool_clear(subpool3);
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225 for (hunk = diff_ol; hunk; hunk = hunk->next)
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227 hunk->latest_start = hunk->modified_start;
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228 hunk->latest_length = hunk->modified_length;
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229 hunk->modified_start = hunk->original_start;
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230 hunk->modified_length = hunk->original_length;
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232 if (hunk->type == svn_diff__type_diff_modified)
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233 hunk->type = svn_diff__type_diff_latest;
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235 hunk->type = svn_diff__type_diff_modified;
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238 /* Get the lcs for common ancestor - original
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239 * Do reverse adjustements
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241 lcs_adjust = svn_diff__lcs(position_list[3], position_list[2], subpool3);
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242 diff_adjust = svn_diff__diff(lcs_adjust, 1, 1, FALSE, subpool3);
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243 adjust_diff(diff_ol, diff_adjust);
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245 svn_pool_clear(subpool3);
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247 /* Get the lcs for modified - common ancestor
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248 * Do forward adjustments
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250 lcs_adjust = svn_diff__lcs(position_list[1], position_list[3], subpool3);
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251 diff_adjust = svn_diff__diff(lcs_adjust, 1, 1, FALSE, subpool3);
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252 adjust_diff(diff_ol, diff_adjust);
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254 /* Get rid of the position lists for original and ancestor, and delete
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257 svn_pool_destroy(subpool2);
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259 /* Now we try and resolve the conflicts we encountered */
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260 for (hunk = diff_ol; hunk; hunk = hunk->next)
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262 if (hunk->type == svn_diff__type_conflict)
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264 svn_diff__resolve_conflict(hunk, &position_list[1],
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265 &position_list[2], pool);
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269 svn_pool_destroy(subpool);
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273 return SVN_NO_ERROR;
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