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| 1 | +/* |
| 2 | + * Copyright (C) 2005 Junio C Hamano |
| 3 | + */ |
| 4 | +#include "cache.h" |
| 5 | +#include "diff.h" |
| 6 | +#include "diffcore.h" |
| 7 | +#include "delta.h" |
| 8 | +#include "count-delta.h" |
| 9 | + |
| 10 | +static int very_different(struct diff_filespec *src, |
| 11 | + struct diff_filespec *dst, |
| 12 | + int min_score) |
| 13 | +{ |
| 14 | + /* dst is recorded as a modification of src. Are they so |
| 15 | + * different that we are better off recording this as a pair |
| 16 | + * of delete and create? min_score is the minimum amount of |
| 17 | + * new material that must exist in the dst and not in src for |
| 18 | + * the pair to be considered a complete rewrite, and recommended |
| 19 | + * to be set to a very high value, 99% or so. |
| 20 | + * |
| 21 | + * The value we return represents the amount of new material |
| 22 | + * that is in dst and not in src. We return 0 when we do not |
| 23 | + * want to get the filepair broken. |
| 24 | + */ |
| 25 | + void *delta; |
| 26 | + unsigned long delta_size, base_size; |
| 27 | + |
| 28 | + if (!S_ISREG(src->mode) || !S_ISREG(dst->mode)) |
| 29 | + return 0; /* leave symlink rename alone */ |
| 30 | + |
| 31 | + if (diff_populate_filespec(src, 1) || diff_populate_filespec(dst, 1)) |
| 32 | + return 0; /* error but caught downstream */ |
| 33 | + |
| 34 | + delta_size = ((src->size < dst->size) ? |
| 35 | + (dst->size - src->size) : (src->size - dst->size)); |
| 36 | + |
| 37 | + /* Notice that we use max of src and dst as the base size, |
| 38 | + * unlike rename similarity detection. This is so that we do |
| 39 | + * not mistake a large addition as a complete rewrite. |
| 40 | + */ |
| 41 | + base_size = ((src->size < dst->size) ? dst->size : src->size); |
| 42 | + |
| 43 | + /* |
| 44 | + * If file size difference is too big compared to the |
| 45 | + * base_size, we declare this a complete rewrite. |
| 46 | + */ |
| 47 | + if (base_size * min_score < delta_size * MAX_SCORE) |
| 48 | + return MAX_SCORE; |
| 49 | + |
| 50 | + if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0)) |
| 51 | + return 0; /* error but caught downstream */ |
| 52 | + |
| 53 | + delta = diff_delta(src->data, src->size, |
| 54 | + dst->data, dst->size, |
| 55 | + &delta_size); |
| 56 | + |
| 57 | + /* A delta that has a lot of literal additions would have |
| 58 | + * big delta_size no matter what else it does. |
| 59 | + */ |
| 60 | + if (base_size * min_score < delta_size * MAX_SCORE) |
| 61 | + return MAX_SCORE; |
| 62 | + |
| 63 | + /* Estimate the edit size by interpreting delta. */ |
| 64 | + delta_size = count_delta(delta, delta_size); |
| 65 | + free(delta); |
| 66 | + if (delta_size == UINT_MAX) |
| 67 | + return 0; /* error in delta computation */ |
| 68 | + |
| 69 | + if (base_size < delta_size) |
| 70 | + return MAX_SCORE; |
| 71 | + |
| 72 | + return delta_size * MAX_SCORE / base_size; |
| 73 | +} |
| 74 | + |
| 75 | +void diffcore_break(int min_score) |
| 76 | +{ |
| 77 | + struct diff_queue_struct *q = &diff_queued_diff; |
| 78 | + struct diff_queue_struct outq; |
| 79 | + int i; |
| 80 | + |
| 81 | + if (!min_score) |
| 82 | + min_score = DEFAULT_BREAK_SCORE; |
| 83 | + |
| 84 | + outq.nr = outq.alloc = 0; |
| 85 | + outq.queue = NULL; |
| 86 | + |
| 87 | + for (i = 0; i < q->nr; i++) { |
| 88 | + struct diff_filepair *p = q->queue[i]; |
| 89 | + int score; |
| 90 | + |
| 91 | + /* We deal only with in-place edit of non directory. |
| 92 | + * We do not break anything else. |
| 93 | + */ |
| 94 | + if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two) && |
| 95 | + !S_ISDIR(p->one->mode) && !S_ISDIR(p->two->mode) && |
| 96 | + !strcmp(p->one->path, p->two->path)) { |
| 97 | + score = very_different(p->one, p->two, min_score); |
| 98 | + if (min_score <= score) { |
| 99 | + /* Split this into delete and create */ |
| 100 | + struct diff_filespec *null_one, *null_two; |
| 101 | + struct diff_filepair *dp; |
| 102 | + |
| 103 | + /* deletion of one */ |
| 104 | + null_one = alloc_filespec(p->one->path); |
| 105 | + dp = diff_queue(&outq, p->one, null_one); |
| 106 | + dp->score = score; |
| 107 | + dp->broken_pair = 1; |
| 108 | + |
| 109 | + /* creation of two */ |
| 110 | + null_two = alloc_filespec(p->two->path); |
| 111 | + dp = diff_queue(&outq, null_two, p->two); |
| 112 | + dp->score = score; |
| 113 | + dp->broken_pair = 1; |
| 114 | + |
| 115 | + free(p); /* not diff_free_filepair(), we are |
| 116 | + * reusing one and two here. |
| 117 | + */ |
| 118 | + continue; |
| 119 | + } |
| 120 | + } |
| 121 | + diff_q(&outq, p); |
| 122 | + } |
| 123 | + free(q->queue); |
| 124 | + *q = outq; |
| 125 | + |
| 126 | + return; |
| 127 | +} |
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