git/read-cache.c

1053 строки
26 KiB
C

/*
* GIT - The information manager from hell
*
* Copyright (C) Linus Torvalds, 2005
*/
#include "cache.h"
#include "cache-tree.h"
/* Index extensions.
*
* The first letter should be 'A'..'Z' for extensions that are not
* necessary for a correct operation (i.e. optimization data).
* When new extensions are added that _needs_ to be understood in
* order to correctly interpret the index file, pick character that
* is outside the range, to cause the reader to abort.
*/
#define CACHE_EXT(s) ( (s[0]<<24)|(s[1]<<16)|(s[2]<<8)|(s[3]) )
#define CACHE_EXT_TREE 0x54524545 /* "TREE" */
struct cache_entry **active_cache;
static time_t index_file_timestamp;
unsigned int active_nr, active_alloc, active_cache_changed;
struct cache_tree *active_cache_tree;
static void *cache_mmap;
static size_t cache_mmap_size;
/*
* This only updates the "non-critical" parts of the directory
* cache, ie the parts that aren't tracked by GIT, and only used
* to validate the cache.
*/
void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
{
ce->ce_ctime.sec = htonl(st->st_ctime);
ce->ce_mtime.sec = htonl(st->st_mtime);
#ifdef USE_NSEC
ce->ce_ctime.nsec = htonl(st->st_ctim.tv_nsec);
ce->ce_mtime.nsec = htonl(st->st_mtim.tv_nsec);
#endif
ce->ce_dev = htonl(st->st_dev);
ce->ce_ino = htonl(st->st_ino);
ce->ce_uid = htonl(st->st_uid);
ce->ce_gid = htonl(st->st_gid);
ce->ce_size = htonl(st->st_size);
if (assume_unchanged)
ce->ce_flags |= htons(CE_VALID);
}
static int ce_compare_data(struct cache_entry *ce, struct stat *st)
{
int match = -1;
int fd = open(ce->name, O_RDONLY);
if (fd >= 0) {
unsigned char sha1[20];
if (!index_fd(sha1, fd, st, 0, OBJ_BLOB, ce->name))
match = hashcmp(sha1, ce->sha1);
/* index_fd() closed the file descriptor already */
}
return match;
}
static int ce_compare_link(struct cache_entry *ce, size_t expected_size)
{
int match = -1;
char *target;
void *buffer;
unsigned long size;
enum object_type type;
int len;
target = xmalloc(expected_size);
len = readlink(ce->name, target, expected_size);
if (len != expected_size) {
free(target);
return -1;
}
buffer = read_sha1_file(ce->sha1, &type, &size);
if (!buffer) {
free(target);
return -1;
}
if (size == expected_size)
match = memcmp(buffer, target, size);
free(buffer);
free(target);
return match;
}
static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
{
switch (st->st_mode & S_IFMT) {
case S_IFREG:
if (ce_compare_data(ce, st))
return DATA_CHANGED;
break;
case S_IFLNK:
if (ce_compare_link(ce, xsize_t(st->st_size)))
return DATA_CHANGED;
break;
default:
return TYPE_CHANGED;
}
return 0;
}
static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
{
unsigned int changed = 0;
switch (ntohl(ce->ce_mode) & S_IFMT) {
case S_IFREG:
changed |= !S_ISREG(st->st_mode) ? TYPE_CHANGED : 0;
/* We consider only the owner x bit to be relevant for
* "mode changes"
*/
if (trust_executable_bit &&
(0100 & (ntohl(ce->ce_mode) ^ st->st_mode)))
changed |= MODE_CHANGED;
break;
case S_IFLNK:
if (!S_ISLNK(st->st_mode) &&
(has_symlinks || !S_ISREG(st->st_mode)))
changed |= TYPE_CHANGED;
break;
default:
die("internal error: ce_mode is %o", ntohl(ce->ce_mode));
}
if (ce->ce_mtime.sec != htonl(st->st_mtime))
changed |= MTIME_CHANGED;
if (ce->ce_ctime.sec != htonl(st->st_ctime))
changed |= CTIME_CHANGED;
#ifdef USE_NSEC
/*
* nsec seems unreliable - not all filesystems support it, so
* as long as it is in the inode cache you get right nsec
* but after it gets flushed, you get zero nsec.
*/
if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
changed |= MTIME_CHANGED;
if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
changed |= CTIME_CHANGED;
#endif
if (ce->ce_uid != htonl(st->st_uid) ||
ce->ce_gid != htonl(st->st_gid))
changed |= OWNER_CHANGED;
if (ce->ce_ino != htonl(st->st_ino))
changed |= INODE_CHANGED;
#ifdef USE_STDEV
/*
* st_dev breaks on network filesystems where different
* clients will have different views of what "device"
* the filesystem is on
*/
if (ce->ce_dev != htonl(st->st_dev))
changed |= INODE_CHANGED;
#endif
if (ce->ce_size != htonl(st->st_size))
changed |= DATA_CHANGED;
return changed;
}
int ce_match_stat(struct cache_entry *ce, struct stat *st, int options)
{
unsigned int changed;
int ignore_valid = options & 01;
int assume_racy_is_modified = options & 02;
/*
* If it's marked as always valid in the index, it's
* valid whatever the checked-out copy says.
*/
if (!ignore_valid && (ce->ce_flags & htons(CE_VALID)))
return 0;
changed = ce_match_stat_basic(ce, st);
/*
* Within 1 second of this sequence:
* echo xyzzy >file && git-update-index --add file
* running this command:
* echo frotz >file
* would give a falsely clean cache entry. The mtime and
* length match the cache, and other stat fields do not change.
*
* We could detect this at update-index time (the cache entry
* being registered/updated records the same time as "now")
* and delay the return from git-update-index, but that would
* effectively mean we can make at most one commit per second,
* which is not acceptable. Instead, we check cache entries
* whose mtime are the same as the index file timestamp more
* carefully than others.
*/
if (!changed &&
index_file_timestamp &&
index_file_timestamp <= ntohl(ce->ce_mtime.sec)) {
if (assume_racy_is_modified)
changed |= DATA_CHANGED;
else
changed |= ce_modified_check_fs(ce, st);
}
return changed;
}
int ce_modified(struct cache_entry *ce, struct stat *st, int really)
{
int changed, changed_fs;
changed = ce_match_stat(ce, st, really);
if (!changed)
return 0;
/*
* If the mode or type has changed, there's no point in trying
* to refresh the entry - it's not going to match
*/
if (changed & (MODE_CHANGED | TYPE_CHANGED))
return changed;
/* Immediately after read-tree or update-index --cacheinfo,
* the length field is zero. For other cases the ce_size
* should match the SHA1 recorded in the index entry.
*/
if ((changed & DATA_CHANGED) && ce->ce_size != htonl(0))
return changed;
changed_fs = ce_modified_check_fs(ce, st);
if (changed_fs)
return changed | changed_fs;
return 0;
}
int base_name_compare(const char *name1, int len1, int mode1,
const char *name2, int len2, int mode2)
{
unsigned char c1, c2;
int len = len1 < len2 ? len1 : len2;
int cmp;
cmp = memcmp(name1, name2, len);
if (cmp)
return cmp;
c1 = name1[len];
c2 = name2[len];
if (!c1 && S_ISDIR(mode1))
c1 = '/';
if (!c2 && S_ISDIR(mode2))
c2 = '/';
return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
}
int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
{
int len1 = flags1 & CE_NAMEMASK;
int len2 = flags2 & CE_NAMEMASK;
int len = len1 < len2 ? len1 : len2;
int cmp;
cmp = memcmp(name1, name2, len);
if (cmp)
return cmp;
if (len1 < len2)
return -1;
if (len1 > len2)
return 1;
/* Compare stages */
flags1 &= CE_STAGEMASK;
flags2 &= CE_STAGEMASK;
if (flags1 < flags2)
return -1;
if (flags1 > flags2)
return 1;
return 0;
}
int cache_name_pos(const char *name, int namelen)
{
int first, last;
first = 0;
last = active_nr;
while (last > first) {
int next = (last + first) >> 1;
struct cache_entry *ce = active_cache[next];
int cmp = cache_name_compare(name, namelen, ce->name, ntohs(ce->ce_flags));
if (!cmp)
return next;
if (cmp < 0) {
last = next;
continue;
}
first = next+1;
}
return -first-1;
}
/* Remove entry, return true if there are more entries to go.. */
int remove_cache_entry_at(int pos)
{
active_cache_changed = 1;
active_nr--;
if (pos >= active_nr)
return 0;
memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
return 1;
}
int remove_file_from_cache(const char *path)
{
int pos = cache_name_pos(path, strlen(path));
if (pos < 0)
pos = -pos-1;
while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
remove_cache_entry_at(pos);
return 0;
}
int add_file_to_cache(const char *path, int verbose)
{
int size, namelen;
struct stat st;
struct cache_entry *ce;
if (lstat(path, &st))
die("%s: unable to stat (%s)", path, strerror(errno));
if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode))
die("%s: can only add regular files or symbolic links", path);
namelen = strlen(path);
size = cache_entry_size(namelen);
ce = xcalloc(1, size);
memcpy(ce->name, path, namelen);
ce->ce_flags = htons(namelen);
fill_stat_cache_info(ce, &st);
if (trust_executable_bit && has_symlinks)
ce->ce_mode = create_ce_mode(st.st_mode);
else {
/* If there is an existing entry, pick the mode bits and type
* from it, otherwise assume unexecutable regular file.
*/
struct cache_entry *ent;
int pos = cache_name_pos(path, namelen);
ent = (0 <= pos) ? active_cache[pos] : NULL;
ce->ce_mode = ce_mode_from_stat(ent, st.st_mode);
}
if (index_path(ce->sha1, path, &st, 1))
die("unable to index file %s", path);
if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE))
die("unable to add %s to index",path);
if (verbose)
printf("add '%s'\n", path);
cache_tree_invalidate_path(active_cache_tree, path);
return 0;
}
int ce_same_name(struct cache_entry *a, struct cache_entry *b)
{
int len = ce_namelen(a);
return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
}
int ce_path_match(const struct cache_entry *ce, const char **pathspec)
{
const char *match, *name;
int len;
if (!pathspec)
return 1;
len = ce_namelen(ce);
name = ce->name;
while ((match = *pathspec++) != NULL) {
int matchlen = strlen(match);
if (matchlen > len)
continue;
if (memcmp(name, match, matchlen))
continue;
if (matchlen && name[matchlen-1] == '/')
return 1;
if (name[matchlen] == '/' || !name[matchlen])
return 1;
if (!matchlen)
return 1;
}
return 0;
}
/*
* We fundamentally don't like some paths: we don't want
* dot or dot-dot anywhere, and for obvious reasons don't
* want to recurse into ".git" either.
*
* Also, we don't want double slashes or slashes at the
* end that can make pathnames ambiguous.
*/
static int verify_dotfile(const char *rest)
{
/*
* The first character was '.', but that
* has already been discarded, we now test
* the rest.
*/
switch (*rest) {
/* "." is not allowed */
case '\0': case '/':
return 0;
/*
* ".git" followed by NUL or slash is bad. This
* shares the path end test with the ".." case.
*/
case 'g':
if (rest[1] != 'i')
break;
if (rest[2] != 't')
break;
rest += 2;
/* fallthrough */
case '.':
if (rest[1] == '\0' || rest[1] == '/')
return 0;
}
return 1;
}
int verify_path(const char *path)
{
char c;
goto inside;
for (;;) {
if (!c)
return 1;
if (c == '/') {
inside:
c = *path++;
switch (c) {
default:
continue;
case '/': case '\0':
break;
case '.':
if (verify_dotfile(path))
continue;
}
return 0;
}
c = *path++;
}
}
/*
* Do we have another file that has the beginning components being a
* proper superset of the name we're trying to add?
*/
static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replace)
{
int retval = 0;
int len = ce_namelen(ce);
int stage = ce_stage(ce);
const char *name = ce->name;
while (pos < active_nr) {
struct cache_entry *p = active_cache[pos++];
if (len >= ce_namelen(p))
break;
if (memcmp(name, p->name, len))
break;
if (ce_stage(p) != stage)
continue;
if (p->name[len] != '/')
continue;
if (!ce_stage(p) && !p->ce_mode)
continue;
retval = -1;
if (!ok_to_replace)
break;
remove_cache_entry_at(--pos);
}
return retval;
}
/*
* Do we have another file with a pathname that is a proper
* subset of the name we're trying to add?
*/
static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace)
{
int retval = 0;
int stage = ce_stage(ce);
const char *name = ce->name;
const char *slash = name + ce_namelen(ce);
for (;;) {
int len;
for (;;) {
if (*--slash == '/')
break;
if (slash <= ce->name)
return retval;
}
len = slash - name;
pos = cache_name_pos(name, ntohs(create_ce_flags(len, stage)));
if (pos >= 0) {
/*
* Found one, but not so fast. This could
* be a marker that says "I was here, but
* I am being removed". Such an entry is
* not a part of the resulting tree, and
* it is Ok to have a directory at the same
* path.
*/
if (stage || active_cache[pos]->ce_mode) {
retval = -1;
if (!ok_to_replace)
break;
remove_cache_entry_at(pos);
continue;
}
}
else
pos = -pos-1;
/*
* Trivial optimization: if we find an entry that
* already matches the sub-directory, then we know
* we're ok, and we can exit.
*/
while (pos < active_nr) {
struct cache_entry *p = active_cache[pos];
if ((ce_namelen(p) <= len) ||
(p->name[len] != '/') ||
memcmp(p->name, name, len))
break; /* not our subdirectory */
if (ce_stage(p) == stage && (stage || p->ce_mode))
/* p is at the same stage as our entry, and
* is a subdirectory of what we are looking
* at, so we cannot have conflicts at our
* level or anything shorter.
*/
return retval;
pos++;
}
}
return retval;
}
/* We may be in a situation where we already have path/file and path
* is being added, or we already have path and path/file is being
* added. Either one would result in a nonsense tree that has path
* twice when git-write-tree tries to write it out. Prevent it.
*
* If ok-to-replace is specified, we remove the conflicting entries
* from the cache so the caller should recompute the insert position.
* When this happens, we return non-zero.
*/
static int check_file_directory_conflict(const struct cache_entry *ce, int pos, int ok_to_replace)
{
int retval;
/*
* When ce is an "I am going away" entry, we allow it to be added
*/
if (!ce_stage(ce) && !ce->ce_mode)
return 0;
/*
* We check if the path is a sub-path of a subsequent pathname
* first, since removing those will not change the position
* in the array.
*/
retval = has_file_name(ce, pos, ok_to_replace);
/*
* Then check if the path might have a clashing sub-directory
* before it.
*/
return retval + has_dir_name(ce, pos, ok_to_replace);
}
int add_cache_entry(struct cache_entry *ce, int option)
{
int pos;
int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
/* existing match? Just replace it. */
if (pos >= 0) {
active_cache_changed = 1;
active_cache[pos] = ce;
return 0;
}
pos = -pos-1;
/*
* Inserting a merged entry ("stage 0") into the index
* will always replace all non-merged entries..
*/
if (pos < active_nr && ce_stage(ce) == 0) {
while (ce_same_name(active_cache[pos], ce)) {
ok_to_add = 1;
if (!remove_cache_entry_at(pos))
break;
}
}
if (!ok_to_add)
return -1;
if (!verify_path(ce->name))
return -1;
if (!skip_df_check &&
check_file_directory_conflict(ce, pos, ok_to_replace)) {
if (!ok_to_replace)
return error("'%s' appears as both a file and as a directory", ce->name);
pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
pos = -pos-1;
}
/* Make sure the array is big enough .. */
if (active_nr == active_alloc) {
active_alloc = alloc_nr(active_alloc);
active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
}
/* Add it in.. */
active_nr++;
if (active_nr > pos)
memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
active_cache[pos] = ce;
active_cache_changed = 1;
return 0;
}
/*
* "refresh" does not calculate a new sha1 file or bring the
* cache up-to-date for mode/content changes. But what it
* _does_ do is to "re-match" the stat information of a file
* with the cache, so that you can refresh the cache for a
* file that hasn't been changed but where the stat entry is
* out of date.
*
* For example, you'd want to do this after doing a "git-read-tree",
* to link up the stat cache details with the proper files.
*/
static struct cache_entry *refresh_cache_ent(struct cache_entry *ce, int really, int *err)
{
struct stat st;
struct cache_entry *updated;
int changed, size;
if (lstat(ce->name, &st) < 0) {
if (err)
*err = errno;
return NULL;
}
changed = ce_match_stat(ce, &st, really);
if (!changed) {
if (really && assume_unchanged &&
!(ce->ce_flags & htons(CE_VALID)))
; /* mark this one VALID again */
else
return ce;
}
if (ce_modified(ce, &st, really)) {
if (err)
*err = EINVAL;
return NULL;
}
size = ce_size(ce);
updated = xmalloc(size);
memcpy(updated, ce, size);
fill_stat_cache_info(updated, &st);
/* In this case, if really is not set, we should leave
* CE_VALID bit alone. Otherwise, paths marked with
* --no-assume-unchanged (i.e. things to be edited) will
* reacquire CE_VALID bit automatically, which is not
* really what we want.
*/
if (!really && assume_unchanged && !(ce->ce_flags & htons(CE_VALID)))
updated->ce_flags &= ~htons(CE_VALID);
return updated;
}
int refresh_cache(unsigned int flags)
{
int i;
int has_errors = 0;
int really = (flags & REFRESH_REALLY) != 0;
int allow_unmerged = (flags & REFRESH_UNMERGED) != 0;
int quiet = (flags & REFRESH_QUIET) != 0;
int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
for (i = 0; i < active_nr; i++) {
struct cache_entry *ce, *new;
int cache_errno = 0;
ce = active_cache[i];
if (ce_stage(ce)) {
while ((i < active_nr) &&
! strcmp(active_cache[i]->name, ce->name))
i++;
i--;
if (allow_unmerged)
continue;
printf("%s: needs merge\n", ce->name);
has_errors = 1;
continue;
}
new = refresh_cache_ent(ce, really, &cache_errno);
if (new == ce)
continue;
if (!new) {
if (not_new && cache_errno == ENOENT)
continue;
if (really && cache_errno == EINVAL) {
/* If we are doing --really-refresh that
* means the index is not valid anymore.
*/
ce->ce_flags &= ~htons(CE_VALID);
active_cache_changed = 1;
}
if (quiet)
continue;
printf("%s: needs update\n", ce->name);
has_errors = 1;
continue;
}
active_cache_changed = 1;
/* You can NOT just free active_cache[i] here, since it
* might not be necessarily malloc()ed but can also come
* from mmap(). */
active_cache[i] = new;
}
return has_errors;
}
struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really)
{
return refresh_cache_ent(ce, really, NULL);
}
static int verify_hdr(struct cache_header *hdr, unsigned long size)
{
SHA_CTX c;
unsigned char sha1[20];
if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
return error("bad signature");
if (hdr->hdr_version != htonl(2))
return error("bad index version");
SHA1_Init(&c);
SHA1_Update(&c, hdr, size - 20);
SHA1_Final(sha1, &c);
if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
return error("bad index file sha1 signature");
return 0;
}
static int read_index_extension(const char *ext, void *data, unsigned long sz)
{
switch (CACHE_EXT(ext)) {
case CACHE_EXT_TREE:
active_cache_tree = cache_tree_read(data, sz);
break;
default:
if (*ext < 'A' || 'Z' < *ext)
return error("index uses %.4s extension, which we do not understand",
ext);
fprintf(stderr, "ignoring %.4s extension\n", ext);
break;
}
return 0;
}
int read_cache(void)
{
return read_cache_from(get_index_file());
}
/* remember to discard_cache() before reading a different cache! */
int read_cache_from(const char *path)
{
int fd, i;
struct stat st;
unsigned long offset;
struct cache_header *hdr;
errno = EBUSY;
if (cache_mmap)
return active_nr;
errno = ENOENT;
index_file_timestamp = 0;
fd = open(path, O_RDONLY);
if (fd < 0) {
if (errno == ENOENT)
return 0;
die("index file open failed (%s)", strerror(errno));
}
if (!fstat(fd, &st)) {
cache_mmap_size = xsize_t(st.st_size);
errno = EINVAL;
if (cache_mmap_size >= sizeof(struct cache_header) + 20)
cache_mmap = xmmap(NULL, cache_mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
else
die("index file smaller than expected");
} else
die("cannot stat the open index (%s)", strerror(errno));
close(fd);
hdr = cache_mmap;
if (verify_hdr(hdr, cache_mmap_size) < 0)
goto unmap;
active_nr = ntohl(hdr->hdr_entries);
active_alloc = alloc_nr(active_nr);
active_cache = xcalloc(active_alloc, sizeof(struct cache_entry *));
offset = sizeof(*hdr);
for (i = 0; i < active_nr; i++) {
struct cache_entry *ce = (struct cache_entry *) ((char *) cache_mmap + offset);
offset = offset + ce_size(ce);
active_cache[i] = ce;
}
index_file_timestamp = st.st_mtime;
while (offset <= cache_mmap_size - 20 - 8) {
/* After an array of active_nr index entries,
* there can be arbitrary number of extended
* sections, each of which is prefixed with
* extension name (4-byte) and section length
* in 4-byte network byte order.
*/
unsigned long extsize;
memcpy(&extsize, (char *) cache_mmap + offset + 4, 4);
extsize = ntohl(extsize);
if (read_index_extension(((const char *) cache_mmap) + offset,
(char *) cache_mmap + offset + 8,
extsize) < 0)
goto unmap;
offset += 8;
offset += extsize;
}
return active_nr;
unmap:
munmap(cache_mmap, cache_mmap_size);
errno = EINVAL;
die("index file corrupt");
}
int discard_cache(void)
{
int ret;
active_nr = active_cache_changed = 0;
index_file_timestamp = 0;
cache_tree_free(&active_cache_tree);
if (cache_mmap == NULL)
return 0;
ret = munmap(cache_mmap, cache_mmap_size);
cache_mmap = NULL;
cache_mmap_size = 0;
/* no need to throw away allocated active_cache */
return ret;
}
#define WRITE_BUFFER_SIZE 8192
static unsigned char write_buffer[WRITE_BUFFER_SIZE];
static unsigned long write_buffer_len;
static int ce_write_flush(SHA_CTX *context, int fd)
{
unsigned int buffered = write_buffer_len;
if (buffered) {
SHA1_Update(context, write_buffer, buffered);
if (write_in_full(fd, write_buffer, buffered) != buffered)
return -1;
write_buffer_len = 0;
}
return 0;
}
static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
{
while (len) {
unsigned int buffered = write_buffer_len;
unsigned int partial = WRITE_BUFFER_SIZE - buffered;
if (partial > len)
partial = len;
memcpy(write_buffer + buffered, data, partial);
buffered += partial;
if (buffered == WRITE_BUFFER_SIZE) {
write_buffer_len = buffered;
if (ce_write_flush(context, fd))
return -1;
buffered = 0;
}
write_buffer_len = buffered;
len -= partial;
data = (char *) data + partial;
}
return 0;
}
static int write_index_ext_header(SHA_CTX *context, int fd,
unsigned int ext, unsigned int sz)
{
ext = htonl(ext);
sz = htonl(sz);
return ((ce_write(context, fd, &ext, 4) < 0) ||
(ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
}
static int ce_flush(SHA_CTX *context, int fd)
{
unsigned int left = write_buffer_len;
if (left) {
write_buffer_len = 0;
SHA1_Update(context, write_buffer, left);
}
/* Flush first if not enough space for SHA1 signature */
if (left + 20 > WRITE_BUFFER_SIZE) {
if (write_in_full(fd, write_buffer, left) != left)
return -1;
left = 0;
}
/* Append the SHA1 signature at the end */
SHA1_Final(write_buffer + left, context);
left += 20;
return (write_in_full(fd, write_buffer, left) != left) ? -1 : 0;
}
static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
{
/*
* The only thing we care about in this function is to smudge the
* falsely clean entry due to touch-update-touch race, so we leave
* everything else as they are. We are called for entries whose
* ce_mtime match the index file mtime.
*/
struct stat st;
if (lstat(ce->name, &st) < 0)
return;
if (ce_match_stat_basic(ce, &st))
return;
if (ce_modified_check_fs(ce, &st)) {
/* This is "racily clean"; smudge it. Note that this
* is a tricky code. At first glance, it may appear
* that it can break with this sequence:
*
* $ echo xyzzy >frotz
* $ git-update-index --add frotz
* $ : >frotz
* $ sleep 3
* $ echo filfre >nitfol
* $ git-update-index --add nitfol
*
* but it does not. When the second update-index runs,
* it notices that the entry "frotz" has the same timestamp
* as index, and if we were to smudge it by resetting its
* size to zero here, then the object name recorded
* in index is the 6-byte file but the cached stat information
* becomes zero --- which would then match what we would
* obtain from the filesystem next time we stat("frotz").
*
* However, the second update-index, before calling
* this function, notices that the cached size is 6
* bytes and what is on the filesystem is an empty
* file, and never calls us, so the cached size information
* for "frotz" stays 6 which does not match the filesystem.
*/
ce->ce_size = htonl(0);
}
}
int write_cache(int newfd, struct cache_entry **cache, int entries)
{
SHA_CTX c;
struct cache_header hdr;
int i, removed;
for (i = removed = 0; i < entries; i++)
if (!cache[i]->ce_mode)
removed++;
hdr.hdr_signature = htonl(CACHE_SIGNATURE);
hdr.hdr_version = htonl(2);
hdr.hdr_entries = htonl(entries - removed);
SHA1_Init(&c);
if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
return -1;
for (i = 0; i < entries; i++) {
struct cache_entry *ce = cache[i];
if (!ce->ce_mode)
continue;
if (index_file_timestamp &&
index_file_timestamp <= ntohl(ce->ce_mtime.sec))
ce_smudge_racily_clean_entry(ce);
if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
return -1;
}
/* Write extension data here */
if (active_cache_tree) {
unsigned long sz;
void *data = cache_tree_write(active_cache_tree, &sz);
if (data &&
!write_index_ext_header(&c, newfd, CACHE_EXT_TREE, sz) &&
!ce_write(&c, newfd, data, sz))
free(data);
else {
free(data);
return -1;
}
}
return ce_flush(&c, newfd);
}