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[PATCH 13/21] read_raw_ref(): manage own scratch space

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Mar 23, 2016, 10:04 UTC
Message-ID
<2bc5bb4589a7a9e313a4f3ce082af765f11a443d.1458723959.git.mhagger@alum.mit.edu>
In-Reply-To
<cover.1458723959.git.mhagger@alum.mit.edu>

Instead of creating scratch space in resolve_ref_unsafe() and passing it down through resolve_ref_1 to read_raw_ref(), teach read_raw_ref() to manage its own scratch space. This reduces coupling across the functions at the cost of some extra allocations. Also, when read_raw_ref() is implemented for different reference backends, the other implementations might have different scratch space requirements.

Note that we now preserve errno across the calls to strbuf_release(), which calls free() and can thus theoretically overwrite errno.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs/files-backend.c | 76 ++++++++++++++++++++++++++++------------------------
 1 file changed, 41 insertions(+), 35 deletions(-)
diff --git a/refs/files-backend.c b/refs/files-backend.c
index d51e778..f752568 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1421,17 +1421,20 @@ static int resolve_missing_loose_ref(const char *refname,
  *   refname will still be valid and unchanged.
  */
 static int read_raw_ref(const char *refname, unsigned char *sha1,
-			struct strbuf *symref, struct strbuf *sb_path,
-			struct strbuf *sb_contents, int *flags)
+			struct strbuf *symref, int *flags)
 {
+	struct strbuf sb_contents = STRBUF_INIT;
+	struct strbuf sb_path = STRBUF_INIT;
 	const char *path;
 	const char *buf;
 	struct stat st;
 	int fd;
+	int ret = -1;
+	int save_errno;
 
-	strbuf_reset(sb_path);
-	strbuf_git_path(sb_path, "%s", refname);
-	path = sb_path->buf;
+	strbuf_reset(&sb_path);
+	strbuf_git_path(&sb_path, "%s", refname);
+	path = sb_path.buf;
 
 stat_ref:
 	/*
@@ -1446,36 +1449,38 @@ stat_ref:
 
 	if (lstat(path, &st) < 0) {
 		if (errno != ENOENT)
-			return -1;
+			goto out;
 		if (resolve_missing_loose_ref(refname, sha1, flags)) {
 			errno = ENOENT;
-			return -1;
+			goto out;
 		}
-		return 0;
+		ret = 0;
+		goto out;
 	}
 
 	/* Follow "normalized" - ie "refs/.." symlinks by hand */
 	if (S_ISLNK(st.st_mode)) {
-		strbuf_reset(sb_contents);
-		if (strbuf_readlink(sb_contents, path, 0) < 0) {
+		strbuf_reset(&sb_contents);
+		if (strbuf_readlink(&sb_contents, path, 0) < 0) {
 			if (errno == ENOENT || errno == EINVAL)
 				/* inconsistent with lstat; retry */
 				goto stat_ref;
 			else
-				return -1;
+				goto out;
 		}
-		if (starts_with(sb_contents->buf, "refs/") &&
-		    !check_refname_format(sb_contents->buf, 0)) {
-			strbuf_swap(sb_contents, symref);
+		if (starts_with(sb_contents.buf, "refs/") &&
+		    !check_refname_format(sb_contents.buf, 0)) {
+			strbuf_swap(&sb_contents, symref);
 			*flags |= REF_ISSYMREF;
-			return 0;
+			ret = 0;
+			goto out;
 		}
 	}
 
 	/* Is it a directory? */
 	if (S_ISDIR(st.st_mode)) {
 		errno = EISDIR;
-		return -1;
+		goto out;
 	}
 
 	/*
@@ -1488,18 +1493,18 @@ stat_ref:
 			/* inconsistent with lstat; retry */
 			goto stat_ref;
 		else
-			return -1;
+			goto out;
 	}
-	strbuf_reset(sb_contents);
-	if (strbuf_read(sb_contents, fd, 256) < 0) {
+	strbuf_reset(&sb_contents);
+	if (strbuf_read(&sb_contents, fd, 256) < 0) {
 		int save_errno = errno;
 		close(fd);
 		errno = save_errno;
-		return -1;
+		goto out;
 	}
 	close(fd);
-	strbuf_rtrim(sb_contents);
-	buf = sb_contents->buf;
+	strbuf_rtrim(&sb_contents);
+	buf = sb_contents.buf;
 	if (starts_with(buf, "ref:")) {
 		buf += 4;
 		while (isspace(*buf))
@@ -1508,7 +1513,8 @@ stat_ref:
 		strbuf_reset(symref);
 		strbuf_addstr(symref, buf);
 		*flags |= REF_ISSYMREF;
-		return 0;
+		ret = 0;
+		goto out;
 	}
 
 	/*
@@ -1519,10 +1525,17 @@ stat_ref:
 	    (buf[40] != '\0' && !isspace(buf[40]))) {
 		*flags |= REF_ISBROKEN;
 		errno = EINVAL;
-		return -1;
+		goto out;
 	}
 
-	return 0;
+	ret = 0;
+
+out:
+	save_errno = errno;
+	strbuf_release(&sb_path);
+	strbuf_release(&sb_contents);
+	errno = save_errno;
+	return ret;
 }
 
 /* This function needs to return a meaningful errno on failure */
@@ -1530,9 +1543,7 @@ static const char *resolve_ref_1(const char *refname,
 				 int resolve_flags,
 				 unsigned char *sha1,
 				 int *flags,
-				 struct strbuf *sb_refname,
-				 struct strbuf *sb_path,
-				 struct strbuf *sb_contents)
+				 struct strbuf *sb_refname)
 {
 	int symref_count;
 
@@ -1559,8 +1570,7 @@ static const char *resolve_ref_1(const char *refname,
 	for (symref_count = 0; symref_count < MAXDEPTH; symref_count++) {
 		int read_flags = 0;
 
-		if (read_raw_ref(refname, sha1, sb_refname,
-				 sb_path, sb_contents, &read_flags)) {
+		if (read_raw_ref(refname, sha1, sb_refname, &read_flags)) {
 			*flags |= read_flags;
 			if (errno != ENOENT || (resolve_flags & RESOLVE_REF_READING))
 				return NULL;
@@ -1604,8 +1614,6 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
 			       unsigned char *sha1, int *flags)
 {
 	static struct strbuf sb_refname = STRBUF_INIT;
-	struct strbuf sb_contents = STRBUF_INIT;
-	struct strbuf sb_path = STRBUF_INIT;
 	int unused_flags;
 	const char *ret;
 
@@ -1613,9 +1621,7 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
 		flags = &unused_flags;
 
 	ret = resolve_ref_1(refname, resolve_flags, sha1, flags,
-			    &sb_refname, &sb_path, &sb_contents);
-	strbuf_release(&sb_path);
-	strbuf_release(&sb_contents);
+			    &sb_refname);
 	return ret;
 }
 

-- 
2.8.0.rc3
Previous: Michael HaggertyNext: Michael Haggerty
Message 14 of 31 in “replacement for dt/refs-backend-lmdb v7 patch 04/33”
  1. 00/21 replacement for dt/refs-backend-lmdb v7 patch 04/33Michael Haggerty, Mar 23, 2016
  2. 01/21 t1430: test the output and error of some commands more carefullyMichael Haggerty, Mar 23, 2016
  3. 02/21 t1430: clean up broken refs/tags/shadowMichael Haggerty, Mar 23, 2016
  4. 03/21 t1430: don't rely on symbolic-ref for creating broken symrefsMichael Haggerty, Mar 23, 2016
  5. 04/21 t1430: test for-each-ref in the presence of badly-named refsMichael Haggerty, Mar 23, 2016
  6. 05/21 t1430: improve test coverage of deletion of badly-named refsMichael Haggerty, Mar 23, 2016
  7. 06/21 resolve_missing_loose_ref(): simplify semanticsMichael Haggerty, Mar 23, 2016
  8. 07/21 resolve_ref_unsafe(): use for loop to count up to MAXDEPTHMichael Haggerty, Mar 23, 2016
  9. 08/21 resolve_ref_unsafe(): ensure flags is always setMichael Haggerty, Mar 23, 2016
  10. 09/21 resolve_ref_1(): eliminate local variableMichael Haggerty, Mar 23, 2016
  11. 10/21 resolve_ref_1(): reorder codeMichael Haggerty, Mar 23, 2016
  12. 11/21 resolve_ref_1(): eliminate local variable "bad_name"Michael Haggerty, Mar 23, 2016
  13. 12/21 files-backend: break out ref readingMichael Haggerty, Mar 23, 2016
  14. 13/21 read_raw_ref(): manage own scratch spaceMichael Haggerty, Mar 23, 2016
  15. 14/21 Inline resolve_ref_1() into resolve_ref_unsafe()Michael Haggerty, Mar 23, 2016
  16. 15/21 read_raw_ref(): change flags parameter to unsigned intMichael Haggerty, Mar 23, 2016
  17. 16/21 fsck_head_link(): remove unneeded flag variableMichael Haggerty, Mar 23, 2016
  18. 17/21 cmd_merge(): remove unneeded flag variableMichael Haggerty, Mar 23, 2016
  19. 18/21 get_default_remote(): remove unneeded flag variableMichael Haggerty, Mar 23, 2016
  20. 19/21 checkout_paths(): remove unneeded flag variableMichael Haggerty, Mar 23, 2016
  21. 20/21 check_aliased_update(): check that dst_name is non-NULLMichael Haggerty, Mar 23, 2016
  22. 21/21 show_head_ref(): check the result of resolve_ref_namespace()Michael Haggerty, Mar 23, 2016
  23. David TurnerMar 24, 2016
  24. Michael HaggertyMar 27, 2016
  25. David TurnerMar 29, 2016
  26. Michael HaggertyMar 30, 2016
  27. David TurnerMar 30, 2016
  28. Michael HaggertyMar 31, 2016
  29. David TurnerMar 31, 2016
  30. Stefan BellerApr 1, 2016
  31. David TurnerApr 1, 2016

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