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xdiffi: fix typos and touch up comments #380

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99 changes: 55 additions & 44 deletions xdiff/xdiffi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -38,9 +38,9 @@ typedef struct s_xdpsplit {
* Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
* the forward diagonal starting from (off1, off2) and the backward diagonal
* 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
* cases using this algorithm is full, so a little bit of heuristic is needed
* to cut the search and to return a suboptimal point.
* returns the furthest point of reach. We might encounter expensive edge cases
* using this algorithm, so a little bit of heuristic is needed to cut the
* search and to return a suboptimal point.
*/
static long xdl_split(unsigned long const *ha1, long off1, long lim1,
unsigned long const *ha2, long off2, long lim2,
Expand All @@ -63,11 +63,13 @@ static long xdl_split(unsigned long const *ha1, long off1, long lim1,
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
* 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
* avoid extra conditions check inside the core loop.
* avoid extra conditions in the check inside the core loop.
*/
if (fmin > dmin)
kvdf[--fmin - 1] = -1;
Expand Down Expand Up @@ -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
* 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
* avoid extra conditions check inside the core loop.
* avoid extra conditions in the check inside the core loop.
*/
if (bmin > dmin)
kvdb[--bmin - 1] = XDL_LINE_MAX;
Expand Down Expand Up @@ -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
* 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
* corner (i1 + i2) penalized with the distance from the
* mid diagonal itself. If this value is above the current
Expand Down Expand Up @@ -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
* the furthest reaching path using the (i1 + i2) measure.
* Enough is enough. We spent too much time here and now we
* collect the furthest reaching path using the (i1 + i2)
* measure.
*/
if (ec >= xenv->mxcost) {
long fbest, fbest1, bbest, bbest1;
Expand Down Expand Up @@ -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
* the box splitting function. Note that the real job (marking changed lines)
* is done in the two boundary reaching checks.
* Rule: "Divide et Impera" (divide & conquer). Recursively split the box in
* sub-boxes by calling the box splitting function. Note that the real job
* (marking changed lines) is done in the two boundary reaching checks.
*/
int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
diffdata_t *dd2, long off2, long lim2,
Expand Down Expand Up @@ -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.
*/
ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
Expand Down Expand Up @@ -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.
* 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
* an int.
* human-readable text, and also ensures that the output of get_indent fits
* within an int.
*/
#define MAX_INDENT 200

Expand Down Expand Up @@ -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
* value. This avoids requiring O(N^2) work for pathological cases, and also
* ensures that the output of score_split fits in an int.
* If more than this number of consecutive blank rows are found, just return
* this value. This avoids requiring O(N^2) work for pathological cases, and
* also ensures that the output of score_split fits in an int.
*/
#define MAX_BLANKS 20

Expand All @@ -443,8 +450,8 @@ struct split_measurement {
int end_of_file;

/*
* How much is the line immediately following the split indented (or -1 if
* the line is blank):
* How much is the line immediately following the split indented (or -1
* if the line is blank):
*/
int indent;

Expand All @@ -454,8 +461,8 @@ struct split_measurement {
int pre_blank;

/*
* How much is the nearest non-blank line above the split indented (or -1
* if there is no such line)?
* How much is the nearest non-blank line above the split indented (or
* -1 if there is no such line)?
*/
int pre_indent;

Expand Down Expand Up @@ -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
* stored in m. The weight factors were determined empirically using the tools and
* corpus described in
* stored in m. The weight factors were determined empirically using the tools
* and corpus described in
*
* https://github.com/mhagger/diff-slider-tools
*
* Also see that project if you want to improve the weights based on, for example,
* a larger or more diverse corpus.
* Also see that project if you want to improve the weights based on, for
* example, a larger or more diverse corpus.
*/
static void score_add_split(const struct split_measurement *m, struct split_score *s)
{
Expand Down Expand Up @@ -809,13 +816,16 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
group_init(xdfo, &go);

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)
goto next;

/*
* 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 {
groupsize = g.end - g.start;
Expand Down Expand Up @@ -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
* freedom to produce a more intuitive diff.
*
* The group is currently shifted as far down as possible, so the
* heuristics below only have to handle upwards shifts.
* The group is currently shifted as far down as possible, so
* the heuristics below only have to handle upwards shifts.
*/

if (g.end == earliest_end) {
/* no shifting was possible */
} else if (end_matching_other != -1) {
/*
* Move the possibly merged group of changes back to line
* up with the last group of changes from the other file
* that it can align with.
* Move the possibly merged group of changes back to
* line up with the last group of changes from the
* other file that it can align with.
*/
while (go.end == go.start) {
if (group_slide_up(xdf, &g, flags))
Expand All @@ -879,14 +889,15 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
} else if (flags & XDF_INDENT_HEURISTIC) {
/*
* Indent heuristic: a group of pure add/delete lines
* implies two splits, one between the end of the "before"
* context and the start of the group, and another between
* the end of the group and the beginning of the "after"
* context. Some splits are aesthetically better and some
* are worse. We compute a badness "score" for each split,
* and add the scores for the two splits to define a
* "score" for each position that the group can be shifted
* to. Then we pick the shift with the lowest score.
* implies two splits, one between the end of the
* "before" context and the start of the group, and
* another between the end of the group and the
* beginning of the "after" context. Some splits are
* aesthetically better and some are worse. We compute
* a badness "score" for each split, and add the scores
* for the two splits to define a "score" for each
* position that the group can be shifted to. Then we
* pick the shift with the lowest score.
*/
long shift, best_shift = -1;
struct split_score best_score;
Expand Down