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tag: v1.7.2-rc2
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#include "cache.h"
#include "tree-walk.h"
#include "tree.h"

static const char *get_mode(const char *str, unsigned int *modep)
{
unsigned char c;
unsigned int mode = 0;

if (*str == ' ')
return NULL;

while ((c = *str++) != ' ') {
if (c < '0' || c > '7')
return NULL;
mode = (mode << 3) + (c - '0');
}
*modep = mode;
return str;
}

static void decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned long size)
{
const char *path;
unsigned int mode, len;

if (size < 24 || buf[size - 21])
die("corrupt tree file");

path = get_mode(buf, &mode);
if (!path || !*path)
die("corrupt tree file");
len = strlen(path) + 1;

/* Initialize the descriptor entry */
desc->entry.path = path;
desc->entry.mode = mode;
desc->entry.sha1 = (const unsigned char *)(path + len);
}

void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
{
desc->buffer = buffer;
desc->size = size;
if (size)
decode_tree_entry(desc, buffer, size);
}

void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
{
unsigned long size = 0;
void *buf = NULL;

if (sha1) {
buf = read_object_with_reference(sha1, tree_type, &size, NULL);
if (!buf)
die("unable to read tree %s", sha1_to_hex(sha1));
}
init_tree_desc(desc, buf, size);
return buf;
}

static void entry_clear(struct name_entry *a)
{
memset(a, 0, sizeof(*a));
}

static void entry_extract(struct tree_desc *t, struct name_entry *a)
{
*a = t->entry;
}

void update_tree_entry(struct tree_desc *desc)
{
const void *buf = desc->buffer;
const unsigned char *end = desc->entry.sha1 + 20;
unsigned long size = desc->size;
unsigned long len = end - (const unsigned char *)buf;

if (size < len)
die("corrupt tree file");
buf = end;
size -= len;
desc->buffer = buf;
desc->size = size;
if (size)
decode_tree_entry(desc, buf, size);
}

int tree_entry(struct tree_desc *desc, struct name_entry *entry)
{
if (!desc->size)
return 0;

*entry = desc->entry;
update_tree_entry(desc);
return 1;
}

void setup_traverse_info(struct traverse_info *info, const char *base)
{
int pathlen = strlen(base);
static struct traverse_info dummy;

memset(info, 0, sizeof(*info));
if (pathlen && base[pathlen-1] == '/')
pathlen--;
info->pathlen = pathlen ? pathlen + 1 : 0;
info->name.path = base;
info->name.sha1 = (void *)(base + pathlen + 1);
if (pathlen)
info->prev = &dummy;
}

char *make_traverse_path(char *path, const struct traverse_info *info, const struct name_entry *n)
{
int len = tree_entry_len(n->path, n->sha1);
int pathlen = info->pathlen;

path[pathlen + len] = 0;
for (;;) {
memcpy(path + pathlen, n->path, len);
if (!pathlen)
break;
path[--pathlen] = '/';
n = &info->name;
len = tree_entry_len(n->path, n->sha1);
info = info->prev;
pathlen -= len;
}
return path;
}

struct tree_desc_skip {
struct tree_desc_skip *prev;
const void *ptr;
};

struct tree_desc_x {
struct tree_desc d;
struct tree_desc_skip *skip;
};

static int name_compare(const char *a, int a_len,
const char *b, int b_len)
{
int len = (a_len < b_len) ? a_len : b_len;
int cmp = memcmp(a, b, len);
if (cmp)
return cmp;
return (a_len - b_len);
}

static int check_entry_match(const char *a, int a_len, const char *b, int b_len)
{
/*
* The caller wants to pick *a* from a tree or nothing.
* We are looking at *b* in a tree.
*
* (0) If a and b are the same name, we are trivially happy.
*
* There are three possibilities where *a* could be hiding
* behind *b*.
*
* (1) *a* == "t", *b* == "ab" i.e. *b* sorts earlier than *a* no
* matter what.
* (2) *a* == "t", *b* == "t-2" and "t" is a subtree in the tree;
* (3) *a* == "t-2", *b* == "t" and "t-2" is a blob in the tree.
*
* Otherwise we know *a* won't appear in the tree without
* scanning further.
*/

int cmp = name_compare(a, a_len, b, b_len);

/* Most common case first -- reading sync'd trees */
if (!cmp)
return cmp;

if (0 < cmp) {
/* a comes after b; it does not matter if it is case (3)
if (b_len < a_len && !memcmp(a, b, b_len) && a[b_len] < '/')
return 1;
*/
return 1; /* keep looking */
}

/* b comes after a; are we looking at case (2)? */
if (a_len < b_len && !memcmp(a, b, a_len) && b[a_len] < '/')
return 1; /* keep looking */

return -1; /* a cannot appear in the tree */
}

/*
* From the extended tree_desc, extract the first name entry, while
* paying attention to the candidate "first" name. Most importantly,
* when looking for an entry, if there are entries that sorts earlier
* in the tree object representation than that name, skip them and
* process the named entry first. We will remember that we haven't
* processed the first entry yet, and in the later call skip the
* entry we processed early when update_extended_entry() is called.
*
* E.g. if the underlying tree object has these entries:
*
* blob "t-1"
* blob "t-2"
* tree "t"
* blob "t=1"
*
* and the "first" asks for "t", remember that we still need to
* process "t-1" and "t-2" but extract "t". After processing the
* entry "t" from this call, the caller will let us know by calling
* update_extended_entry() that we can remember "t" has been processed
* already.
*/

static void extended_entry_extract(struct tree_desc_x *t,
struct name_entry *a,
const char *first,
int first_len)
{
const char *path;
int len;
struct tree_desc probe;
struct tree_desc_skip *skip;

/*
* Extract the first entry from the tree_desc, but skip the
* ones that we already returned in earlier rounds.
*/
while (1) {
if (!t->d.size) {
entry_clear(a);
break; /* not found */
}
entry_extract(&t->d, a);
for (skip = t->skip; skip; skip = skip->prev)
if (a->path == skip->ptr)
break; /* found */
if (!skip)
break;
/* We have processed this entry already. */
update_tree_entry(&t->d);
}

if (!first || !a->path)
return;

/*
* The caller wants "first" from this tree, or nothing.
*/
path = a->path;
len = tree_entry_len(a->path, a->sha1);
switch (check_entry_match(first, first_len, path, len)) {
case -1:
entry_clear(a);
case 0:
return;
default:
break;
}

/*
* We need to look-ahead -- we suspect that a subtree whose
* name is "first" may be hiding behind the current entry "path".
*/
probe = t->d;
while (probe.size) {
entry_extract(&probe, a);
path = a->path;
len = tree_entry_len(a->path, a->sha1);
switch (check_entry_match(first, first_len, path, len)) {
case -1:
entry_clear(a);
case 0:
return;
default:
update_tree_entry(&probe);
break;
}
/* keep looking */
}
entry_clear(a);
}

static void update_extended_entry(struct tree_desc_x *t, struct name_entry *a)
{
if (t->d.entry.path == a->path) {
update_tree_entry(&t->d);
} else {
/* we have returned this entry early */
struct tree_desc_skip *skip = xmalloc(sizeof(*skip));
skip->ptr = a->path;
skip->prev = t->skip;
t->skip = skip;
}
}

static void free_extended_entry(struct tree_desc_x *t)
{
struct tree_desc_skip *p, *s;

for (s = t->skip; s; s = p) {
p = s->prev;
free(s);
}
}

int traverse_trees(int n, struct tree_desc *t, struct traverse_info *info)
{
int ret = 0;
struct name_entry *entry = xmalloc(n*sizeof(*entry));
int i;
struct tree_desc_x *tx = xcalloc(n, sizeof(*tx));

for (i = 0; i < n; i++)
tx[i].d = t[i];

for (;;) {
unsigned long mask, dirmask;
const char *first = NULL;
int first_len = 0;
struct name_entry *e;
int len;

for (i = 0; i < n; i++) {
e = entry + i;
extended_entry_extract(tx + i, e, NULL, 0);
}

/*
* A tree may have "t-2" at the current location even
* though it may have "t" that is a subtree behind it,
* and another tree may return "t". We want to grab
* all "t" from all trees to match in such a case.
*/
for (i = 0; i < n; i++) {
e = entry + i;
if (!e->path)
continue;
len = tree_entry_len(e->path, e->sha1);
if (!first) {
first = e->path;
first_len = len;
continue;
}
if (name_compare(e->path, len, first, first_len) < 0) {
first = e->path;
first_len = len;
}
}

if (first) {
for (i = 0; i < n; i++) {
e = entry + i;
extended_entry_extract(tx + i, e, first, first_len);
/* Cull the ones that are not the earliest */
if (!e->path)
continue;
len = tree_entry_len(e->path, e->sha1);
if (name_compare(e->path, len, first, first_len))
entry_clear(e);
}
}

/* Now we have in entry[i] the earliest name from the trees */
mask = 0;
dirmask = 0;
for (i = 0; i < n; i++) {
if (!entry[i].path)
continue;
mask |= 1ul << i;
if (S_ISDIR(entry[i].mode))
dirmask |= 1ul << i;
}
if (!mask)
break;
ret = info->fn(n, mask, dirmask, entry, info);
if (ret < 0)
break;
mask &= ret;
ret = 0;
for (i = 0; i < n; i++)
if (mask & (1ul << i))
update_extended_entry(tx + i, entry + i);
}
free(entry);
for (i = 0; i < n; i++)
free_extended_entry(tx + i);
free(tx);
return ret;
}

static int find_tree_entry(struct tree_desc *t, const char *name, unsigned char *result, unsigned *mode)
{
int namelen = strlen(name);
while (t->size) {
const char *entry;
const unsigned char *sha1;
int entrylen, cmp;

sha1 = tree_entry_extract(t, &entry, mode);
update_tree_entry(t);
entrylen = tree_entry_len(entry, sha1);
if (entrylen > namelen)
continue;
cmp = memcmp(name, entry, entrylen);
if (cmp > 0)
continue;
if (cmp < 0)
break;
if (entrylen == namelen) {
hashcpy(result, sha1);
return 0;
}
if (name[entrylen] != '/')
continue;
if (!S_ISDIR(*mode))
break;
if (++entrylen == namelen) {
hashcpy(result, sha1);
return 0;
}
return get_tree_entry(sha1, name + entrylen, result, mode);
}
return -1;
}

int get_tree_entry(const unsigned char *tree_sha1, const char *name, unsigned char *sha1, unsigned *mode)
{
int retval;
void *tree;
unsigned long size;
struct tree_desc t;
unsigned char root[20];

tree = read_object_with_reference(tree_sha1, tree_type, &size, root);
if (!tree)
return -1;

if (name[0] == '\0') {
hashcpy(sha1, root);
free(tree);
return 0;
}

init_tree_desc(&t, tree, size);
retval = find_tree_entry(&t, name, sha1, mode);
free(tree);
return retval;
}
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