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compare-windows: improve resync on single line changes

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* when subsequent lines match, try and skip changes on current line
This commit is contained in:
Charlie Gordon 2026-06-08 17:50:16 +02:00
commit d34d0680d5
1 changed files with 16 additions and 10 deletions
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26
extras.c
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@ -174,7 +174,7 @@ static int eb_skip_spaces(EditBuffer *b, int offset, int *offsetp)
static uint32_t eb_checksum_line(EditBuffer *b, int offset, int *offsetp)
{
uint32_t checksum = 0;
uint32_t checksum = 0U - (offset == b->total_size);
char32_t c;
while ((c = eb_nextc(b, offset, &offset)) != '\n') {
@ -191,7 +191,7 @@ static void compare_resync(EditState *s1, EditState *s2,
EditBuffer *b1 = s1->b;
EditBuffer *b2 = s2->b;
int pos1, pos2, off1, off2;
enum { MAX_LINE_SYNC = 64 };
enum { MAX_BYTE_SYNC = 5, MAX_LINE_SYNC = 64 };
int p1[MAX_LINE_SYNC];
int p2[MAX_LINE_SYNC];
uint32_t chk1[MAX_LINE_SYNC];
@ -208,7 +208,19 @@ static void compare_resync(EditState *s1, EditState *s2,
pos2 = off2;
n++;
}
if (n > 5) {
if (n < MAX_BYTE_SYNC) {
// Try and find identical lines up to MAX_LINE_SYNC - 2 lines apart
off1 = eb_goto_bol(b1, save1);
off2 = eb_goto_bol(b2, save2);
for (i = 0; i < MAX_LINE_SYNC; i++) {
chk1[i] = eb_checksum_line(b1, p1[i] = off1, &off1);
chk2[i] = eb_checksum_line(b2, p2[i] = off2, &off2);
}
if (chk1[1] == chk2[1] && chk1[2] == chk2[2] && chk1[3] == chk2[3])
n = MAX_BYTE_SYNC;
}
if (n >= MAX_BYTE_SYNC) {
// Isolated line change: resync on same line
*offset1_ptr = pos1;
*offset2_ptr = pos2;
if (pos1 - save1 == pos2 - save2) {
@ -218,13 +230,7 @@ static void compare_resync(EditState *s1, EditState *s2,
}
return;
}
// Try and find identical lines up to MAX_LINE_SYNC - 2 lines apart
pos1 = eb_goto_bol(b1, save1);
pos2 = eb_goto_bol(b2, save2);
for (i = 0; i < MAX_LINE_SYNC; i++) {
chk1[i] = eb_checksum_line(b1, p1[i] = pos1, &pos1);
chk2[i] = eb_checksum_line(b2, p2[i] = pos2, &pos2);
}
// Compute minimum change set
for (i = 1; i < 2 * MAX_LINE_SYNC; i++) {
for (j = 0; j <= i && j < MAX_LINE_SYNC - 2; j++) {
int i1 = j;