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Allow alternate "low-level" emit function from xdl_diff

For some users (e.g. git blame), getting textual patch output is just
extra work, as they can get all the information they need from the low-
level diff structures.  Allow for an alternate low-level emit function
to be defined to allow bypassing the textual patch generation; set
xemitconf_t's emit_func member to enable this.

The (void (*)()) type is pretty ugly, but the alternative would be to
include most of the private xdiff headers in xdiff.h to get the types
required for the "proper" function prototype.  Also, a (void *) won't
work, as ANSI C doesn't allow a function pointer to be cast to an
object pointer.

Signed-off-by: Brian Downing <>
Signed-off-by: Junio C Hamano <>
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1 parent 9ccd0a8 commit ef2e62fe23173586f49a00c6ae953ebbdb0d13ab @bdowning bdowning committed with gitster Oct 25, 2008
Showing with 8 additions and 3 deletions.
  1. +1 −0 xdiff/xdiff.h
  2. +3 −1 xdiff/xdiffi.c
  3. +1 −2 xdiff/xemit.c
  4. +3 −0 xdiff/xemit.h
@@ -87,6 +87,7 @@ typedef struct s_xdemitconf {
unsigned long flags;
find_func_t find_func;
void *find_func_priv;
+ void (*emit_func)();
} xdemitconf_t;
typedef struct s_bdiffparam {
@@ -538,6 +538,8 @@ int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
xdchange_t *xscr;
xdfenv_t xe;
+ emit_func_t ef = xecfg->emit_func ?
+ (emit_func_t)xecfg->emit_func : xdl_emit_diff;
if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
@@ -551,7 +553,7 @@ int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
return -1;
if (xscr) {
- if (xdl_emit_diff(&xe, xscr, ecb, xecfg) < 0) {
+ if (ef(&xe, xscr, ecb, xecfg) < 0) {
@@ -27,7 +27,6 @@
static long xdl_get_rec(xdfile_t *xdf, long ri, char const **rec);
static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *ecb);
-static xdchange_t *xdl_get_hunk(xdchange_t *xscr, xdemitconf_t const *xecfg);
@@ -58,7 +57,7 @@ static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *
* Starting at the passed change atom, find the latest change atom to be included
* inside the differential hunk according to the specified configuration.
-static xdchange_t *xdl_get_hunk(xdchange_t *xscr, xdemitconf_t const *xecfg) {
+xdchange_t *xdl_get_hunk(xdchange_t *xscr, xdemitconf_t const *xecfg) {
xdchange_t *xch, *xchp;
for (xchp = xscr, xch = xscr->next; xch; xchp = xch, xch = xch->next)
@@ -24,7 +24,10 @@
#define XEMIT_H
+typedef int (*emit_func_t)(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
+ xdemitconf_t const *xecfg);
+xdchange_t *xdl_get_hunk(xdchange_t *xscr, xdemitconf_t const *xecfg);
int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
xdemitconf_t const *xecfg);

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