[PATCH 1/2] xdiff: remove "line_hash" field from xrecord_t
From: Phillip Wood <phillip.wood@dunelm.org.uk>
Prior to commit 6a26019c81 (xdiff: split xrecord_t.ha into line_hash and minimal_perfect_hash, 2025-11-18) the "ha" field of xrecord_t initially held the "line_hash" value and once the line had been interned that field was updated to hold the "minimal_perfect_hash". The "line_hash" is only used to intern the line so there is no point in storing it after all the input lines have been interned.
Removing the "line_hash" field from xrecord_t and storing it in xdlclass_t where it is actually used makes it clearer that it is a temporary value and it should not be used once we're calculated the "minimal_perfect_hash". This also reduces the size of xrecord_t by 25% on 64-bit platforms and 40% on 32-bit platforms. While the struct is small we create one instance per input line so any saving is welcome.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
xdiff/xprepare.c | 12 +++++++-----
xdiff/xtypes.h | 1 -
2 files changed, 7 insertions(+), 6 deletions(-)
Show changes to 2 files +7 −6
xdiff/xprepare.c, xdiff/xtypes.h
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 34c82e4f8e1..08e5d3f4dfa 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -34,6 +34,7 @@
#define INVESTIGATE 2
typedef struct s_xdlclass {
+ uint64_t line_hash;
struct s_xdlclass *next;
xrecord_t rec;
long idx;
@@ -92,13 +93,14 @@ static void xdl_free_classifier(xdlclassifier_t *cf) {
}
-static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t *rec) {
+static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t *rec,
+ uint64_t line_hash) {
size_t hi;
xdlclass_t *rcrec;
- hi = XDL_HASHLONG(rec->line_hash, cf->hbits);
+ hi = XDL_HASHLONG(line_hash, cf->hbits);
for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)
- if (rcrec->rec.line_hash == rec->line_hash &&
+ if (rcrec->line_hash == line_hash &&
xdl_recmatch((const char *)rcrec->rec.ptr, (long)rcrec->rec.size,
(const char *)rec->ptr, (long)rec->size, cf->flags))
break;
@@ -112,6 +114,7 @@ static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t
if (XDL_ALLOC_GROW(cf->rcrecs, cf->count, cf->alloc))
return -1;
cf->rcrecs[rcrec->idx] = rcrec;
+ rcrec->line_hash = line_hash;
rcrec->rec = *rec;
rcrec->len1 = rcrec->len2 = 0;
rcrec->next = cf->rchash[hi];
@@ -158,8 +161,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
crec = &xdf->recs[xdf->nrec++];
crec->ptr = prev;
crec->size = cur - prev;
- crec->line_hash = hav;
- if (xdl_classify_record(pass, cf, crec) < 0)
+ if (xdl_classify_record(pass, cf, crec, hav) < 0)
goto abort;
}
}
diff --git a/xdiff/xtypes.h b/xdiff/xtypes.h
index 979586f20a6..50aee779be3 100644
--- a/xdiff/xtypes.h
+++ b/xdiff/xtypes.h
@@ -41,7 +41,6 @@ typedef struct s_chastore {
typedef struct s_xrecord {
uint8_t const *ptr;
size_t size;
- uint64_t line_hash;
size_t minimal_perfect_hash;
} xrecord_t;
--
2.52.0.362.g884e03848a9
