From 913b45f51b151d8e29f86df67d3e10853d831470 Mon Sep 17 00:00:00 2001 From: Junio C Hamano Date: Thu, 13 Dec 2007 14:24:18 -0800 Subject: [PATCH] xdi_diff: trim common trailing lines This implements earlier Linus's optimization to trim common lines at the end before passing them down to low level xdiff interface for all of our xdiff users. We could later enhance this to also trim common leading lines, but that would need tweaking the output function to add the number of lines trimmed at the beginning to line numbers that appear in the hunk headers. Signed-off-by: Junio C Hamano --- xdiff-interface.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/xdiff-interface.c b/xdiff-interface.c index 69a022c13..f2cd488de 100644 --- a/xdiff-interface.c +++ b/xdiff-interface.c @@ -103,9 +103,41 @@ int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf) return 0; } +/* + * Trim down common substring at the end of the buffers, + * but leave at least ctx lines at the end. + */ +static void trim_common_tail(mmfile_t *a, mmfile_t *b, int ctx) +{ + const int blk = 1024; + long trimmed = 0, recovered = 0; + int i; + char *ap = a->ptr + a->size; + char *bp = b->ptr + b->size; + long smaller = (a->size < b->size) ? a->size : b->size; + + while (blk + trimmed <= smaller && !memcmp(ap - blk, bp - blk, blk)) { + trimmed += blk; + ap -= blk; + bp -= blk; + } + + for (i = 0, recovered = 0; recovered < trimmed && i <= ctx; i++) { + while (recovered < trimmed && ap[recovered] != '\n') + recovered++; + } + a->size -= (trimmed - recovered); + b->size -= (trimmed - recovered); +} + int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *xecb) { - return xdl_diff(mf1, mf2, xpp, xecfg, xecb); + mmfile_t a = *mf1; + mmfile_t b = *mf2; + + trim_common_tail(&a, &b, xecfg->ctxlen); + + return xdl_diff(&a, &b, xpp, xecfg, xecb); } int read_mmfile(mmfile_t *ptr, const char *filename) -- 2.30.2