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xdiffi: fix typos and touch up comments

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Inspired by the thoroughly stale https://github.com/git/git/pull/159,
this patch fixes a couple of typos, rewraps and clarifies some comments.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johannes Schindelin 2019-10-08 11:27:52 -07:00 committed by Junio C Hamano
parent 5fa0f5238b
commit 03d3b1297c
1 changed files with 55 additions and 44 deletions
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99
xdiff/xdiffi.c
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@ -38,9 +38,9 @@ typedef struct s_xdpsplit {
* Basically considers a "box" (off1, off2, lim1, lim2) and scan from both * Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
* the forward diagonal starting from (off1, off2) and the backward diagonal * the forward diagonal starting from (off1, off2) and the backward diagonal
* starting from (lim1, lim2). If the K values on the same diagonal crosses * starting from (lim1, lim2). If the K values on the same diagonal crosses
* returns the furthest point of reach. We might end up having to expensive * returns the furthest point of reach. We might encounter expensive edge cases
* cases using this algorithm is full, so a little bit of heuristic is needed * using this algorithm, so a little bit of heuristic is needed to cut the
* to cut the search and to return a suboptimal point. * search and to return a suboptimal point.
*/ */
static long xdl_split(unsigned long const *ha1, long off1, long lim1, static long xdl_split(unsigned long const *ha1, long off1, long lim1,
unsigned long const *ha2, long off2, long lim2, unsigned long const *ha2, long off2, long lim2,
@ -63,11 +63,13 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
int got_snake = 0; int got_snake = 0;
/* /*
* We need to extent the diagonal "domain" by one. If the next * We need to extend the diagonal "domain" by one. If the next
* values exits the box boundaries we need to change it in the * values exits the box boundaries we need to change it in the
* opposite direction because (max - min) must be a power of two. * opposite direction because (max - min) must be a power of
* two.
*
* Also we initialize the external K value to -1 so that we can * Also we initialize the external K value to -1 so that we can
* avoid extra conditions check inside the core loop. * avoid extra conditions in the check inside the core loop.
*/ */
if (fmin > dmin) if (fmin > dmin)
kvdf[--fmin - 1] = -1; kvdf[--fmin - 1] = -1;
@ -98,11 +100,13 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
} }
/* /*
* We need to extent the diagonal "domain" by one. If the next * We need to extend the diagonal "domain" by one. If the next
* values exits the box boundaries we need to change it in the * values exits the box boundaries we need to change it in the
* opposite direction because (max - min) must be a power of two. * opposite direction because (max - min) must be a power of
* two.
*
* Also we initialize the external K value to -1 so that we can * Also we initialize the external K value to -1 so that we can
* avoid extra conditions check inside the core loop. * avoid extra conditions in the check inside the core loop.
*/ */
if (bmin > dmin) if (bmin > dmin)
kvdb[--bmin - 1] = XDL_LINE_MAX; kvdb[--bmin - 1] = XDL_LINE_MAX;
@ -138,7 +142,7 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
/* /*
* If the edit cost is above the heuristic trigger and if * If the edit cost is above the heuristic trigger and if
* we got a good snake, we sample current diagonals to see * we got a good snake, we sample current diagonals to see
* if some of the, have reached an "interesting" path. Our * if some of them have reached an "interesting" path. Our
* measure is a function of the distance from the diagonal * measure is a function of the distance from the diagonal
* corner (i1 + i2) penalized with the distance from the * corner (i1 + i2) penalized with the distance from the
* mid diagonal itself. If this value is above the current * mid diagonal itself. If this value is above the current
@ -196,8 +200,9 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
} }
/* /*
* Enough is enough. We spent too much time here and now we collect * Enough is enough. We spent too much time here and now we
* the furthest reaching path using the (i1 + i2) measure. * collect the furthest reaching path using the (i1 + i2)
* measure.
*/ */
if (ec >= xenv->mxcost) { if (ec >= xenv->mxcost) {
long fbest, fbest1, bbest, bbest1; long fbest, fbest1, bbest, bbest1;
@ -244,9 +249,9 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
/* /*
* Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling * Rule: "Divide et Impera" (divide & conquer). Recursively split the box in
* the box splitting function. Note that the real job (marking changed lines) * sub-boxes by calling the box splitting function. Note that the real job
* is done in the two boundary reaching checks. * (marking changed lines) is done in the two boundary reaching checks.
*/ */
int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1, int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
diffdata_t *dd2, long off2, long lim2, diffdata_t *dd2, long off2, long lim2,
@ -323,7 +328,9 @@ int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
} }
/* /*
* Allocate and setup K vectors to be used by the differential algorithm. * Allocate and setup K vectors to be used by the differential
* algorithm.
*
* One is to store the forward path and one to store the backward path. * One is to store the forward path and one to store the backward path.
*/ */
ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3; ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
@ -394,8 +401,8 @@ static int recs_match(xrecord_t *rec1, xrecord_t *rec2, long flags)
/* /*
* If a line is indented more than this, get_indent() just returns this value. * If a line is indented more than this, get_indent() just returns this value.
* This avoids having to do absurd amounts of work for data that are not * This avoids having to do absurd amounts of work for data that are not
* human-readable text, and also ensures that the output of get_indent fits within * human-readable text, and also ensures that the output of get_indent fits
* an int. * within an int.
*/ */
#define MAX_INDENT 200 #define MAX_INDENT 200
@ -429,9 +436,9 @@ static int get_indent(xrecord_t *rec)
} }
/* /*
* If more than this number of consecutive blank rows are found, just return this * If more than this number of consecutive blank rows are found, just return
* value. This avoids requiring O(N^2) work for pathological cases, and also * this value. This avoids requiring O(N^2) work for pathological cases, and
* ensures that the output of score_split fits in an int. * also ensures that the output of score_split fits in an int.
*/ */
#define MAX_BLANKS 20 #define MAX_BLANKS 20
@ -443,8 +450,8 @@ struct split_measurement {
int end_of_file; int end_of_file;
/* /*
* How much is the line immediately following the split indented (or -1 if * How much is the line immediately following the split indented (or -1
* the line is blank): * if the line is blank):
*/ */
int indent; int indent;
@ -454,8 +461,8 @@ struct split_measurement {
int pre_blank; int pre_blank;
/* /*
* How much is the nearest non-blank line above the split indented (or -1 * How much is the nearest non-blank line above the split indented (or
* if there is no such line)? * -1 if there is no such line)?
*/ */
int pre_indent; int pre_indent;
@ -581,13 +588,13 @@ static void measure_split(const xdfile_t *xdf, long split,
/* /*
* Compute a badness score for the hypothetical split whose measurements are * Compute a badness score for the hypothetical split whose measurements are
* stored in m. The weight factors were determined empirically using the tools and * stored in m. The weight factors were determined empirically using the tools
* corpus described in * and corpus described in
* *
* https://github.com/mhagger/diff-slider-tools * https://github.com/mhagger/diff-slider-tools
* *
* Also see that project if you want to improve the weights based on, for example, * Also see that project if you want to improve the weights based on, for
* a larger or more diverse corpus. * example, a larger or more diverse corpus.
*/ */
static void score_add_split(const struct split_measurement *m, struct split_score *s) static void score_add_split(const struct split_measurement *m, struct split_score *s)
{ {
@ -809,13 +816,16 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
group_init(xdfo, &go); group_init(xdfo, &go);
while (1) { while (1) {
/* If the group is empty in the to-be-compacted file, skip it: */ /*
* If the group is empty in the to-be-compacted file, skip it:
*/
if (g.end == g.start) if (g.end == g.start)
goto next; goto next;
/* /*
* Now shift the change up and then down as far as possible in * Now shift the change up and then down as far as possible in
* each direction. If it bumps into any other changes, merge them. * each direction. If it bumps into any other changes, merge
* them.
*/ */
do { do {
groupsize = g.end - g.start; groupsize = g.end - g.start;
@ -858,17 +868,17 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
* If the group can be shifted, then we can possibly use this * If the group can be shifted, then we can possibly use this
* freedom to produce a more intuitive diff. * freedom to produce a more intuitive diff.
* *
* The group is currently shifted as far down as possible, so the * The group is currently shifted as far down as possible, so
* heuristics below only have to handle upwards shifts. * the heuristics below only have to handle upwards shifts.
*/ */
if (g.end == earliest_end) { if (g.end == earliest_end) {
/* no shifting was possible */ /* no shifting was possible */
} else if (end_matching_other != -1) { } else if (end_matching_other != -1) {
/* /*
* Move the possibly merged group of changes back to line * Move the possibly merged group of changes back to
* up with the last group of changes from the other file * line up with the last group of changes from the
* that it can align with. * other file that it can align with.
*/ */
while (go.end == go.start) { while (go.end == go.start) {
if (group_slide_up(xdf, &g, flags)) if (group_slide_up(xdf, &g, flags))
@ -879,14 +889,15 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
} else if (flags & XDF_INDENT_HEURISTIC) { } else if (flags & XDF_INDENT_HEURISTIC) {
/* /*
* Indent heuristic: a group of pure add/delete lines * Indent heuristic: a group of pure add/delete lines
* implies two splits, one between the end of the "before" * implies two splits, one between the end of the
* context and the start of the group, and another between * "before" context and the start of the group, and
* the end of the group and the beginning of the "after" * another between the end of the group and the
* context. Some splits are aesthetically better and some * beginning of the "after" context. Some splits are
* are worse. We compute a badness "score" for each split, * aesthetically better and some are worse. We compute
* and add the scores for the two splits to define a * a badness "score" for each split, and add the scores
* "score" for each position that the group can be shifted * for the two splits to define a "score" for each
* to. Then we pick the shift with the lowest score. * position that the group can be shifted to. Then we
* pick the shift with the lowest score.
*/ */
long shift, best_shift = -1; long shift, best_shift = -1;
struct split_score best_score; struct split_score best_score;