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tag: v1.6.0-rc0
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/*
* Helper functions for tree diff generation
*/
#include "cache.h"
#include "diff.h"
#include "diffcore.h"
#include "tree.h"

static char *malloc_base(const char *base, int baselen, const char *path, int pathlen)
{
char *newbase = xmalloc(baselen + pathlen + 2);
memcpy(newbase, base, baselen);
memcpy(newbase + baselen, path, pathlen);
memcpy(newbase + baselen + pathlen, "/", 2);
return newbase;
}

static char *malloc_fullname(const char *base, int baselen, const char *path, int pathlen)
{
char *fullname = xmalloc(baselen + pathlen + 1);
memcpy(fullname, base, baselen);
memcpy(fullname + baselen, path, pathlen);
fullname[baselen + pathlen] = 0;
return fullname;
}

static void show_entry(struct diff_options *opt, const char *prefix, struct tree_desc *desc,
const char *base, int baselen);

static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const char *base, int baselen, struct diff_options *opt)
{
unsigned mode1, mode2;
const char *path1, *path2;
const unsigned char *sha1, *sha2;
int cmp, pathlen1, pathlen2;
char *fullname;

sha1 = tree_entry_extract(t1, &path1, &mode1);
sha2 = tree_entry_extract(t2, &path2, &mode2);

pathlen1 = tree_entry_len(path1, sha1);
pathlen2 = tree_entry_len(path2, sha2);
cmp = base_name_compare(path1, pathlen1, mode1, path2, pathlen2, mode2);
if (cmp < 0) {
show_entry(opt, "-", t1, base, baselen);
return -1;
}
if (cmp > 0) {
show_entry(opt, "+", t2, base, baselen);
return 1;
}
if (!DIFF_OPT_TST(opt, FIND_COPIES_HARDER) && !hashcmp(sha1, sha2) && mode1 == mode2)
return 0;

/*
* If the filemode has changed to/from a directory from/to a regular
* file, we need to consider it a remove and an add.
*/
if (S_ISDIR(mode1) != S_ISDIR(mode2)) {
show_entry(opt, "-", t1, base, baselen);
show_entry(opt, "+", t2, base, baselen);
return 0;
}

if (DIFF_OPT_TST(opt, RECURSIVE) && S_ISDIR(mode1)) {
int retval;
char *newbase = malloc_base(base, baselen, path1, pathlen1);
if (DIFF_OPT_TST(opt, TREE_IN_RECURSIVE)) {
newbase[baselen + pathlen1] = 0;
opt->change(opt, mode1, mode2,
sha1, sha2, newbase);
newbase[baselen + pathlen1] = '/';
}
retval = diff_tree_sha1(sha1, sha2, newbase, opt);
free(newbase);
return retval;
}

fullname = malloc_fullname(base, baselen, path1, pathlen1);
opt->change(opt, mode1, mode2, sha1, sha2, fullname);
free(fullname);
return 0;
}

/*
* Is a tree entry interesting given the pathspec we have?
*
* Return:
* - 2 for "yes, and all subsequent entries will be"
* - 1 for yes
* - zero for no
* - negative for "no, and no subsequent entries will be either"
*/
static int tree_entry_interesting(struct tree_desc *desc, const char *base, int baselen, struct diff_options *opt)
{
const char *path;
const unsigned char *sha1;
unsigned mode;
int i;
int pathlen;
int never_interesting = -1;

if (!opt->nr_paths)
return 1;

sha1 = tree_entry_extract(desc, &path, &mode);

pathlen = tree_entry_len(path, sha1);

for (i = 0; i < opt->nr_paths; i++) {
const char *match = opt->paths[i];
int matchlen = opt->pathlens[i];
int m = -1; /* signals that we haven't called strncmp() */

if (baselen >= matchlen) {
/* If it doesn't match, move along... */
if (strncmp(base, match, matchlen))
continue;

/*
* The base is a subdirectory of a path which
* was specified, so all of them are interesting.
*/
return 2;
}

/* Does the base match? */
if (strncmp(base, match, baselen))
continue;

match += baselen;
matchlen -= baselen;

if (never_interesting) {
/*
* We have not seen any match that sorts later
* than the current path.
*/

/*
* Does match sort strictly earlier than path
* with their common parts?
*/
m = strncmp(match, path,
(matchlen < pathlen) ? matchlen : pathlen);
if (m < 0)
continue;

/*
* If we come here even once, that means there is at
* least one pathspec that would sort equal to or
* later than the path we are currently looking at.
* In other words, if we have never reached this point
* after iterating all pathspecs, it means all
* pathspecs are either outside of base, or inside the
* base but sorts strictly earlier than the current
* one. In either case, they will never match the
* subsequent entries. In such a case, we initialized
* the variable to -1 and that is what will be
* returned, allowing the caller to terminate early.
*/
never_interesting = 0;
}

if (pathlen > matchlen)
continue;

if (matchlen > pathlen) {
if (match[pathlen] != '/')
continue;
if (!S_ISDIR(mode))
continue;
}

if (m == -1)
/*
* we cheated and did not do strncmp(), so we do
* that here.
*/
m = strncmp(match, path, pathlen);

/*
* If common part matched earlier then it is a hit,
* because we rejected the case where path is not a
* leading directory and is shorter than match.
*/
if (!m)
return 1;
}
return never_interesting; /* No matches */
}

/* A whole sub-tree went away or appeared */
static void show_tree(struct diff_options *opt, const char *prefix, struct tree_desc *desc, const char *base, int baselen)
{
int all_interesting = 0;
while (desc->size) {
int show;

if (all_interesting)
show = 1;
else {
show = tree_entry_interesting(desc, base, baselen,
opt);
if (show == 2)
all_interesting = 1;
}
if (show < 0)
break;
if (show)
show_entry(opt, prefix, desc, base, baselen);
update_tree_entry(desc);
}
}

/* A file entry went away or appeared */
static void show_entry(struct diff_options *opt, const char *prefix, struct tree_desc *desc,
const char *base, int baselen)
{
unsigned mode;
const char *path;
const unsigned char *sha1 = tree_entry_extract(desc, &path, &mode);
int pathlen = tree_entry_len(path, sha1);

if (DIFF_OPT_TST(opt, RECURSIVE) && S_ISDIR(mode)) {
enum object_type type;
char *newbase = malloc_base(base, baselen, path, pathlen);
struct tree_desc inner;
void *tree;
unsigned long size;

tree = read_sha1_file(sha1, &type, &size);
if (!tree || type != OBJ_TREE)
die("corrupt tree sha %s", sha1_to_hex(sha1));

init_tree_desc(&inner, tree, size);
show_tree(opt, prefix, &inner, newbase, baselen + 1 + pathlen);

free(tree);
free(newbase);
} else {
char *fullname = malloc_fullname(base, baselen, path, pathlen);
opt->add_remove(opt, prefix[0], mode, sha1, fullname);
free(fullname);
}
}

static void skip_uninteresting(struct tree_desc *t, const char *base, int baselen, struct diff_options *opt)
{
int all_interesting = 0;
while (t->size) {
int show;

if (all_interesting)
show = 1;
else {
show = tree_entry_interesting(t, base, baselen, opt);
if (show == 2)
all_interesting = 1;
}
if (!show) {
update_tree_entry(t);
continue;
}
/* Skip it all? */
if (show < 0)
t->size = 0;
return;
}
}

int diff_tree(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
{
int baselen = strlen(base);

for (;;) {
if (DIFF_OPT_TST(opt, QUIET) && DIFF_OPT_TST(opt, HAS_CHANGES))
break;
if (opt->nr_paths) {
skip_uninteresting(t1, base, baselen, opt);
skip_uninteresting(t2, base, baselen, opt);
}
if (!t1->size) {
if (!t2->size)
break;
show_entry(opt, "+", t2, base, baselen);
update_tree_entry(t2);
continue;
}
if (!t2->size) {
show_entry(opt, "-", t1, base, baselen);
update_tree_entry(t1);
continue;
}
switch (compare_tree_entry(t1, t2, base, baselen, opt)) {
case -1:
update_tree_entry(t1);
continue;
case 0:
update_tree_entry(t1);
/* Fallthrough */
case 1:
update_tree_entry(t2);
continue;
}
die("git-diff-tree: internal error");
}
return 0;
}

/*
* Does it look like the resulting diff might be due to a rename?
* - single entry
* - not a valid previous file
*/
static inline int diff_might_be_rename(void)
{
return diff_queued_diff.nr == 1 &&
!DIFF_FILE_VALID(diff_queued_diff.queue[0]->one);
}

static void try_to_follow_renames(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
{
struct diff_options diff_opts;
struct diff_queue_struct *q = &diff_queued_diff;
struct diff_filepair *choice;
const char *paths[1];
int i;

/* Remove the file creation entry from the diff queue, and remember it */
choice = q->queue[0];
q->nr = 0;

diff_setup(&diff_opts);
DIFF_OPT_SET(&diff_opts, RECURSIVE);
diff_opts.detect_rename = DIFF_DETECT_RENAME;
diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
diff_opts.single_follow = opt->paths[0];
diff_opts.break_opt = opt->break_opt;
paths[0] = NULL;
diff_tree_setup_paths(paths, &diff_opts);
if (diff_setup_done(&diff_opts) < 0)
die("unable to set up diff options to follow renames");
diff_tree(t1, t2, base, &diff_opts);
diffcore_std(&diff_opts);
diff_tree_release_paths(&diff_opts);

/* Go through the new set of filepairing, and see if we find a more interesting one */
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];

/*
* Found a source? Not only do we use that for the new
* diff_queued_diff, we will also use that as the path in
* the future!
*/
if ((p->status == 'R' || p->status == 'C') && !strcmp(p->two->path, opt->paths[0])) {
/* Switch the file-pairs around */
q->queue[i] = choice;
choice = p;

/* Update the path we use from now on.. */
diff_tree_release_paths(opt);
opt->paths[0] = xstrdup(p->one->path);
diff_tree_setup_paths(opt->paths, opt);
break;
}
}

/*
* Then, discard all the non-relevane file pairs...
*/
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
diff_free_filepair(p);
}

/*
* .. and re-instate the one we want (which might be either the
* original one, or the rename/copy we found)
*/
q->queue[0] = choice;
q->nr = 1;
}

int diff_tree_sha1(const unsigned char *old, const unsigned char *new, const char *base, struct diff_options *opt)
{
void *tree1, *tree2;
struct tree_desc t1, t2;
unsigned long size1, size2;
int retval;

tree1 = read_object_with_reference(old, tree_type, &size1, NULL);
if (!tree1)
die("unable to read source tree (%s)", sha1_to_hex(old));
tree2 = read_object_with_reference(new, tree_type, &size2, NULL);
if (!tree2)
die("unable to read destination tree (%s)", sha1_to_hex(new));
init_tree_desc(&t1, tree1, size1);
init_tree_desc(&t2, tree2, size2);
retval = diff_tree(&t1, &t2, base, opt);
if (DIFF_OPT_TST(opt, FOLLOW_RENAMES) && diff_might_be_rename()) {
init_tree_desc(&t1, tree1, size1);
init_tree_desc(&t2, tree2, size2);
try_to_follow_renames(&t1, &t2, base, opt);
}
free(tree1);
free(tree2);
return retval;
}

int diff_root_tree_sha1(const unsigned char *new, const char *base, struct diff_options *opt)
{
int retval;
void *tree;
unsigned long size;
struct tree_desc empty, real;

tree = read_object_with_reference(new, tree_type, &size, NULL);
if (!tree)
die("unable to read root tree (%s)", sha1_to_hex(new));
init_tree_desc(&real, tree, size);

init_tree_desc(&empty, "", 0);
retval = diff_tree(&empty, &real, base, opt);
free(tree);
return retval;
}

static int count_paths(const char **paths)
{
int i = 0;
while (*paths++)
i++;
return i;
}

void diff_tree_release_paths(struct diff_options *opt)
{
free(opt->pathlens);
}

void diff_tree_setup_paths(const char **p, struct diff_options *opt)
{
opt->nr_paths = 0;
opt->pathlens = NULL;
opt->paths = NULL;

if (p) {
int i;

opt->paths = p;
opt->nr_paths = count_paths(p);
if (opt->nr_paths == 0) {
opt->pathlens = NULL;
return;
}
opt->pathlens = xmalloc(opt->nr_paths * sizeof(int));
for (i=0; i < opt->nr_paths; i++)
opt->pathlens[i] = strlen(p[i]);
}
}
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