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Add an assertion in, and a commentary for, 'get_nearby_bol_pos'

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* src/xdisp.c:
(get_nearby_bol_pos): Document the function, and add an assertion
on its return value.
This commit is contained in:
Gregory Heytings 2023-05-12 21:56:31 +00:00
parent f0f08eeb05
commit 1e3a66df45
1 changed files with 9 additions and 3 deletions
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12
src/xdisp.c
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@ -3545,7 +3545,7 @@ init_iterator (struct it *it, struct window *w,
The corresponding function 'get_medium_narrowing_zv' (and The corresponding function 'get_medium_narrowing_zv' (and
'medium_narrowing_zv' field in 'struct it') is not used to set the 'medium_narrowing_zv' field in 'struct it') is not used to set the
end limit of a the restriction, which is again unnecessary, but to end limit of the restriction, which is again unnecessary, but to
determine, in 'reseat', whether the iterator has moved far enough determine, in 'reseat', whether the iterator has moved far enough
from its original position, and whether the start position of the from its original position, and whether the start position of the
restriction must be computed anew. restriction must be computed anew.
@ -3613,10 +3613,15 @@ get_medium_narrowing_zv (struct window *w, ptrdiff_t pos)
return min ((pos / len + 1) * len, ZV); return min ((pos / len + 1) * len, ZV);
} }
/* Find the position of the last BOL before POS, unless it is too far
away. The buffer portion in which the search occurs is gradually
enlarged: [POS-500..POS], [POS-5500..POS-500],
[POS-55500..POS-5500], and finally [POS-555500..POS-55500]. Return
BEGV-1 if no BOL was found in [POS-555500..POS]. */
static ptrdiff_t static ptrdiff_t
get_nearby_bol_pos (ptrdiff_t pos) get_nearby_bol_pos (ptrdiff_t pos)
{ {
ptrdiff_t start, pos_bytepos, cur, next, found, bol = BEGV - 1; ptrdiff_t start, pos_bytepos, cur, next, found, bol = BEGV - 1, init_pos = pos;
int dist; int dist;
for (dist = 500; dist <= 500000; dist *= 10) for (dist = 500; dist <= 500000; dist *= 10)
{ {
@ -3633,10 +3638,11 @@ get_nearby_bol_pos (ptrdiff_t pos)
break; break;
} }
if (bol >= BEGV || start == BEGV) if (bol >= BEGV || start == BEGV)
return bol; break;
else else
pos = pos - dist < BEGV ? BEGV : pos - dist; pos = pos - dist < BEGV ? BEGV : pos - dist;
} }
eassert (bol <= init_pos);
return bol; return bol;
} }