Improve abstraction of ref lock/write.

Created 'struct ref_lock' to contain the data necessary to perform
a ref update.  This change improves writing a ref as the file names
are generated only once (rather than twice) and supports following
symrefs (up to the maximum depth).  Further the ref_lock structure
provides room to extend the update API with ref logging.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/fetch.c b/fetch.c
index 73bde07..8bdaacb 100644 (file)
--- a/fetch.c
+++ b/fetch.c
@@ -204,14 +204,14 @@ static int mark_complete(const char *path, const unsigned char *sha1)
 
 int pull(char *target)
 {
+       struct ref_lock *lock;
        unsigned char sha1[20];
-       int fd = -1;
 
        save_commit_buffer = 0;
        track_object_refs = 0;
-       if (write_ref && current_ref) {
-               fd = lock_ref_sha1(write_ref, current_ref);
-               if (fd < 0)
+       if (write_ref) {
+               lock = lock_ref_sha1(write_ref, current_ref, 1);
+               if (!lock)
                        return -1;
        }
 
@@ -219,20 +219,22 @@ int pull(char *target)
                for_each_ref(mark_complete);
        }
 
-       if (interpret_target(target, sha1))
-               return error("Could not interpret %s as something to pull",
-                            target);
-       if (process(lookup_unknown_object(sha1)))
+       if (interpret_target(target, sha1)) {
+               error("Could not interpret %s as something to pull", target);
+               unlock_ref(lock);
+               return -1;
+       }
+       if (process(lookup_unknown_object(sha1))) {
+               unlock_ref(lock);
                return -1;
-       if (loop())
+       }
+       if (loop()) {
+               unlock_ref(lock);
                return -1;
-       
+       }
+
        if (write_ref) {
-               if (current_ref) {
-                       write_ref_sha1(write_ref, fd, sha1);
-               } else {
-                       write_ref_sha1_unlocked(write_ref, sha1);
-               }
+               return write_ref_sha1(lock, sha1, "git fetch");
        }
        return 0;
 }

diff --git a/refs.c b/refs.c
index 0f3491f..91c8c44 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -198,26 +198,6 @@ int for_each_remote_ref(int (*fn)(const char *path, const unsigned char *sha1))
        return do_for_each_ref("refs/remotes", fn, 13);
 }
 
-static char *ref_file_name(const char *ref)
-{
-       char *base = get_refs_directory();
-       int baselen = strlen(base);
-       int reflen = strlen(ref);
-       char *ret = xmalloc(baselen + 2 + reflen);
-       sprintf(ret, "%s/%s", base, ref);
-       return ret;
-}
-
-static char *ref_lock_file_name(const char *ref)
-{
-       char *base = get_refs_directory();
-       int baselen = strlen(base);
-       int reflen = strlen(ref);
-       char *ret = xmalloc(baselen + 7 + reflen);
-       sprintf(ret, "%s/%s.lock", base, ref);
-       return ret;
-}
-
 int get_ref_sha1(const char *ref, unsigned char *sha1)
 {
        if (check_ref_format(ref))
@@ -225,94 +205,6 @@ int get_ref_sha1(const char *ref, unsigned char *sha1)
        return read_ref(git_path("refs/%s", ref), sha1);
 }
 
-static int lock_ref_file(const char *filename, const char *lock_filename,
-                        const unsigned char *old_sha1)
-{
-       int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
-       unsigned char current_sha1[20];
-       int retval;
-       if (fd < 0) {
-               return error("Couldn't open lock file for %s: %s",
-                            filename, strerror(errno));
-       }
-       retval = read_ref(filename, current_sha1);
-       if (old_sha1) {
-               if (retval) {
-                       close(fd);
-                       unlink(lock_filename);
-                       return error("Could not read the current value of %s",
-                                    filename);
-               }
-               if (memcmp(current_sha1, old_sha1, 20)) {
-                       close(fd);
-                       unlink(lock_filename);
-                       error("The current value of %s is %s",
-                             filename, sha1_to_hex(current_sha1));
-                       return error("Expected %s",
-                                    sha1_to_hex(old_sha1));
-               }
-       } else {
-               if (!retval) {
-                       close(fd);
-                       unlink(lock_filename);
-                       return error("Unexpectedly found a value of %s for %s",
-                                    sha1_to_hex(current_sha1), filename);
-               }
-       }
-       return fd;
-}
-
-int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
-{
-       char *filename;
-       char *lock_filename;
-       int retval;
-       if (check_ref_format(ref))
-               return -1;
-       filename = ref_file_name(ref);
-       lock_filename = ref_lock_file_name(ref);
-       retval = lock_ref_file(filename, lock_filename, old_sha1);
-       free(filename);
-       free(lock_filename);
-       return retval;
-}
-
-static int write_ref_file(const char *filename,
-                         const char *lock_filename, int fd,
-                         const unsigned char *sha1)
-{
-       char *hex = sha1_to_hex(sha1);
-       char term = '\n';
-       if (write(fd, hex, 40) < 40 ||
-           write(fd, &term, 1) < 1) {
-               error("Couldn't write %s", filename);
-               close(fd);
-               return -1;
-       }
-       close(fd);
-       rename(lock_filename, filename);
-       return 0;
-}
-
-int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
-{
-       char *filename;
-       char *lock_filename;
-       int retval;
-       if (fd < 0)
-               return -1;
-       if (check_ref_format(ref))
-               return -1;
-       filename = ref_file_name(ref);
-       lock_filename = ref_lock_file_name(ref);
-       if (safe_create_leading_directories(filename))
-               die("unable to create leading directory for %s", filename);
-       retval = write_ref_file(filename, lock_filename, fd, sha1);
-       free(filename);
-       free(lock_filename);
-       return retval;
-}
-
 /*
  * Make sure "ref" is something reasonable to have under ".git/refs/";
  * We do not like it if:
@@ -365,25 +257,119 @@ int check_ref_format(const char *ref)
        }
 }
 
-int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
+static struct ref_lock* verify_lock(struct ref_lock *lock,
+       const unsigned char *old_sha1, int mustexist)
+{
+       char buf[40];
+       int nr, fd = open(lock->ref_file, O_RDONLY);
+       if (fd < 0 && (mustexist || errno != ENOENT)) {
+               error("Can't verify ref %s", lock->ref_file);
+               unlock_ref(lock);
+               return NULL;
+       }
+       nr = read(fd, buf, 40);
+       close(fd);
+       if (nr != 40 || get_sha1_hex(buf, lock->old_sha1) < 0) {
+               error("Can't verify ref %s", lock->ref_file);
+               unlock_ref(lock);
+               return NULL;
+       }
+       if (memcmp(lock->old_sha1, old_sha1, 20)) {
+               error("Ref %s is at %s but expected %s", lock->ref_file,
+                       sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
+               unlock_ref(lock);
+               return NULL;
+       }
+       return lock;
+}
+
+static struct ref_lock* lock_ref_sha1_basic(const char *path,
+       int plen,
+       const unsigned char *old_sha1, int mustexist)
+{
+       struct ref_lock *lock;
+
+       lock = xcalloc(1, sizeof(struct ref_lock));
+       lock->lock_fd = -1;
+
+       plen = strlen(path) - plen;
+       path = resolve_ref(path, lock->old_sha1, mustexist);
+       if (!path) {
+               error("Can't read ref %s", path);
+               unlock_ref(lock);
+               return NULL;
+       }
+
+       lock->ref_file = strdup(path);
+       lock->lock_file = strdup(mkpath("%s.lock", lock->ref_file));
+
+       if (safe_create_leading_directories(lock->lock_file))
+               die("unable to create directory for %s", lock->lock_file);
+       lock->lock_fd = open(lock->lock_file,
+               O_WRONLY | O_CREAT | O_EXCL, 0666);
+       if (lock->lock_fd < 0) {
+               error("Couldn't open lock file %s: %s",
+                       lock->lock_file, strerror(errno));
+               unlock_ref(lock);
+               return NULL;
+       }
+
+       return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
+}
+
+struct ref_lock* lock_ref_sha1(const char *ref,
+       const unsigned char *old_sha1, int mustexist)
 {
-       char *filename;
-       char *lock_filename;
-       int fd;
-       int retval;
        if (check_ref_format(ref))
+               return NULL;
+       return lock_ref_sha1_basic(git_path("refs/%s", ref),
+               strlen(ref), old_sha1, mustexist);
+}
+
+struct ref_lock* lock_any_ref_for_update(const char *ref,
+       const unsigned char *old_sha1, int mustexist)
+{
+       return lock_ref_sha1_basic(git_path("%s", ref),
+               strlen(ref), old_sha1, mustexist);
+}
+
+void unlock_ref (struct ref_lock *lock)
+{
+       if (lock->lock_fd >= 0) {
+               close(lock->lock_fd);
+               unlink(lock->lock_file);
+       }
+       if (lock->ref_file)
+               free(lock->ref_file);
+       if (lock->lock_file)
+               free(lock->lock_file);
+       free(lock);
+}
+
+int write_ref_sha1(struct ref_lock *lock,
+       const unsigned char *sha1, const char *logmsg)
+{
+       static char term = '\n';
+
+       if (!lock)
                return -1;
-       filename = ref_file_name(ref);
-       lock_filename = ref_lock_file_name(ref);
-       if (safe_create_leading_directories(filename))
-               die("unable to create leading directory for %s", filename);
-       fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
-       if (fd < 0) {
-               error("Writing %s", lock_filename);
-               perror("Open");
+       if (!memcmp(lock->old_sha1, sha1, 20)) {
+               unlock_ref(lock);
+               return 0;
        }
-       retval = write_ref_file(filename, lock_filename, fd, sha1);
-       free(filename);
-       free(lock_filename);
-       return retval;
+       if (write(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
+           write(lock->lock_fd, &term, 1) != 1
+               || close(lock->lock_fd) < 0) {
+               error("Couldn't write %s", lock->lock_file);
+               unlock_ref(lock);
+               return -1;
+       }
+       if (rename(lock->lock_file, lock->ref_file) < 0) {
+               error("Couldn't set %s", lock->ref_file);
+               unlock_ref(lock);
+               return -1;
+       }
+       lock->lock_fd = -1;
+       unlock_ref(lock);
+       return 0;
 }

diff --git a/refs.h b/refs.h
index fa816c1..b7e9df2 100644 (file)
--- a/refs.h
+++ b/refs.h
@@ -1,6 +1,13 @@
 #ifndef REFS_H
 #define REFS_H
 
+struct ref_lock {
+       char *ref_file;
+       char *lock_file;
+       unsigned char old_sha1[20];
+       int lock_fd;
+};
+
 /*
  * Calls the specified function for each ref file until it returns nonzero,
  * and returns the value
@@ -14,16 +21,17 @@ extern int for_each_remote_ref(int (*fn)(const char *path, const unsigned char *
 /** Reads the refs file specified into sha1 **/
 extern int get_ref_sha1(const char *ref, unsigned char *sha1);
 
-/** Locks ref and returns the fd to give to write_ref_sha1() if the ref
- * has the given value currently; otherwise, returns -1.
- **/
-extern int lock_ref_sha1(const char *ref, const unsigned char *old_sha1);
+/** Locks a "refs/" ref returning the lock on success and NULL on failure. **/
+extern struct ref_lock* lock_ref_sha1(const char *ref, const unsigned char *old_sha1, int mustexist);
+
+/** Locks any ref (for 'HEAD' type refs). */
+extern struct ref_lock* lock_any_ref_for_update(const char *ref, const unsigned char *old_sha1, int mustexist);
 
-/** Writes sha1 into the refs file specified, locked with the given fd. **/
-extern int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1);
+/** Release any lock taken but not written. **/
+extern void unlock_ref (struct ref_lock *lock);
 
-/** Writes sha1 into the refs file specified. **/
-extern int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1);
+/** Writes sha1 into the ref specified by the lock. **/
+extern int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1, const char *msg);
 
 /** Returns 0 if target has the right format for a ref. **/
 extern int check_ref_format(const char *target);