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combine-diff: cleanup.
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The flag on the surviving lines meant "this parent is not
different" while the parent_map flag on the lost lines meant
"this parent is different", which was confusing.  So swap the
meaning of on-bit in the flag.  Also more heavily comment the
code.

Signed-off-by: Junio C Hamano <junkio@cox.net>
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Junio C Hamano committed Feb 3, 2006
1 parent f16706c commit 46dc941
Showing 1 changed file with 65 additions and 37 deletions.
102 changes: 65 additions & 37 deletions combine-diff.c
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Original file line number Diff line number Diff line change
Expand Up @@ -81,8 +81,8 @@ struct sline {
struct lline *lost_head, **lost_tail;
char *bol;
int len;
/* bit 0 up to (N-1) are on if the parent does _not_
* have this line (i.e. we changed it).
/* bit 0 up to (N-1) are on if the parent has this line (i.e.
* we did not change it).
* bit N is used for "interesting" lines, including context.
*/
unsigned long flag;
Expand Down Expand Up @@ -219,7 +219,6 @@ static void combine_diff(const unsigned char *parent, const char *ourtmp,
char line[MAXLINELEN];
unsigned int lno, ob, on, nb, nn, p_lno;
unsigned long nmask = (1UL << n);
unsigned long pmask = ~nmask;
struct sline *lost_bucket = NULL;

write_temp_blob(parent_tmp, parent);
Expand Down Expand Up @@ -265,7 +264,7 @@ static void combine_diff(const unsigned char *parent, const char *ourtmp,
append_lost(lost_bucket, n, line+1);
break;
case '+':
sline[lno-1].flag &= pmask;
sline[lno-1].flag |= nmask;
lno++;
break;
}
Expand All @@ -291,7 +290,7 @@ static void combine_diff(const unsigned char *parent, const char *ourtmp,
p_lno++; /* '-' means parent had it */
ll = ll->next;
}
if (sline[lno].flag & nmask)
if (!(sline[lno].flag & nmask))
p_lno++; /* no '+' means parent had it */
}
sline[lno].p_lno[n] = p_lno; /* trailer */
Expand All @@ -302,36 +301,46 @@ static char combine_marker = '@';

static int interesting(struct sline *sline, unsigned long all_mask)
{
return ((sline->flag & all_mask) != all_mask || sline->lost_head);
/* If some parents lost lines here, or if we have added to
* some parent, it is interesting.
*/
return ((sline->flag & all_mask) || sline->lost_head);
}

static unsigned long adjust_hunk_tail(struct sline *sline,
unsigned long all_mask,
unsigned long hunk_begin,
unsigned long i)
{
/* i points at the first uninteresting line.
* If the last line of the hunk was interesting
* only because it has some deletion, then
* it is not all that interesting for the
* purpose of giving trailing context lines.
/* i points at the first uninteresting line. If the last line
* of the hunk was interesting only because it has some
* deletion, then it is not all that interesting for the
* purpose of giving trailing context lines. This is because
* we output '-' line and then unmodified sline[i-1] itself in
* that case which gives us one extra context line.
*/
if ((hunk_begin + 1 <= i) &&
((sline[i-1].flag & all_mask) == all_mask))
if ((hunk_begin + 1 <= i) && !(sline[i-1].flag & all_mask))
i--;
return i;
}

static unsigned long next_interesting(struct sline *sline,
unsigned long mark,
unsigned long i,
unsigned long cnt,
int uninteresting)
static unsigned long find_next(struct sline *sline,
unsigned long mark,
unsigned long i,
unsigned long cnt,
int uninteresting)
{
/* We have examined up to i-1 and are about to look at i.
* Find next interesting or uninteresting line. Here,
* "interesting" does not mean interesting(), but marked by
* the give_context() function below (i.e. it includes context
* lines that are not interesting to interesting() function
* that are surrounded by interesting() ones.
*/
while (i < cnt)
if (uninteresting ?
!(sline[i].flag & mark) :
(sline[i].flag & mark))
if (uninteresting
? !(sline[i].flag & mark)
: (sline[i].flag & mark))
return i;
else
i++;
Expand All @@ -344,23 +353,37 @@ static int give_context(struct sline *sline, unsigned long cnt, int num_parent)
unsigned long mark = (1UL<<num_parent);
unsigned long i;

i = next_interesting(sline, mark, 0, cnt, 0);
/* Two groups of interesting lines may have a short gap of
* unintersting lines. Connect such groups to give them a
* bit of context.
*
* We first start from what the interesting() function says,
* and mark them with "mark", and paint context lines with the
* mark. So interesting() would still say false for such context
* lines but they are treated as "interesting" in the end.
*/
i = find_next(sline, mark, 0, cnt, 0);
if (cnt <= i)
return 0;

while (i < cnt) {
unsigned long j = (context < i) ? (i - context) : 0;
unsigned long k;

/* Paint a few lines before the first interesting line. */
while (j < i)
sline[j++].flag |= mark;

again:
j = next_interesting(sline, mark, i, cnt, 1);
/* we know up to i is to be included. where does the
* next uninteresting one start?
*/
j = find_next(sline, mark, i, cnt, 1);
if (cnt <= j)
break; /* the rest are all interesting */

/* lookahead context lines */
k = next_interesting(sline, mark, j, cnt, 0);
k = find_next(sline, mark, j, cnt, 0);
j = adjust_hunk_tail(sline, all_mask, i, j);

if (k < j + context) {
Expand All @@ -374,7 +397,8 @@ static int give_context(struct sline *sline, unsigned long cnt, int num_parent)
}

/* j is the first uninteresting line and there is
* no overlap beyond it within context lines.
* no overlap beyond it within context lines. Paint
* the trailing edge a bit.
*/
i = k;
k = (j + context < cnt) ? j + context : cnt;
Expand Down Expand Up @@ -461,7 +485,7 @@ static int make_hunks(struct sline *sline, unsigned long cnt,
same_diff = 0;
has_interesting = 0;
for (j = i; j < hunk_end && !has_interesting; j++) {
unsigned long this_diff = ~sline[j].flag & all_mask;
unsigned long this_diff = sline[j].flag & all_mask;
struct lline *ll = sline[j].lost_head;
if (this_diff) {
/* This has some changes. Is it the
Expand Down Expand Up @@ -532,6 +556,7 @@ static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent)
while (lno < hunk_end) {
struct lline *ll;
int j;
unsigned long p_mask;
sl = &sline[lno++];
ll = sl->lost_head;
while (ll) {
Expand All @@ -544,11 +569,13 @@ static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent)
puts(ll->line);
ll = ll->next;
}
p_mask = 1;
for (j = 0; j < num_parent; j++) {
if ((1UL<<j) & sl->flag)
putchar(' ');
else
if (p_mask & sl->flag)
putchar('+');
else
putchar(' ');
p_mask <<= 1;
}
printf("%.*s\n", sl->len, sl->bol);
}
Expand All @@ -574,8 +601,8 @@ static void reuse_combine_diff(struct sline *sline, unsigned long cnt,
ll->parent_map |= imask;
ll = ll->next;
}
if (!(sline->flag & jmask))
sline->flag &= ~imask;
if (sline->flag & jmask)
sline->flag |= imask;
sline++;
}
}
Expand Down Expand Up @@ -641,7 +668,7 @@ int show_combined_diff(struct combine_diff_path *elem, int num_parent,
if (*cp == '\n') {
sline[lno].lost_tail = &sline[lno].lost_head;
sline[lno].len = cp - sline[lno].bol;
sline[lno].flag = (1UL<<num_parent) - 1;
sline[lno].flag = 0;
lno++;
if (lno < cnt)
sline[lno].bol = cp + 1;
Expand All @@ -650,7 +677,7 @@ int show_combined_diff(struct combine_diff_path *elem, int num_parent,
if (result[size-1] != '\n') {
sline[cnt-1].lost_tail = &sline[cnt-1].lost_head;
sline[cnt-1].len = size - (sline[cnt-1].bol - result);
sline[cnt-1].flag = (1UL<<num_parent) - 1;
sline[cnt-1].flag = 0;
}

sline[0].p_lno = xcalloc((cnt+1) * num_parent, sizeof(unsigned long));
Expand All @@ -673,11 +700,11 @@ int show_combined_diff(struct combine_diff_path *elem, int num_parent,

show_hunks = make_hunks(sline, cnt, num_parent, dense);

if (header && (show_hunks || show_empty)) {
shown_header++;
puts(header);
}
if (show_hunks) {
if (header) {
shown_header++;
puts(header);
}
printf("diff --%s ", dense ? "cc" : "combined");
if (quote_c_style(elem->path, NULL, NULL, 0))
quote_c_style(elem->path, NULL, stdout, 0);
Expand Down Expand Up @@ -709,6 +736,7 @@ int show_combined_diff(struct combine_diff_path *elem, int num_parent,
}
}
}
free(sline[0].p_lno);
free(sline);
return shown_header;
}
Expand Down

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