1 files changed, 143 insertions, 60 deletions

diff --git a/server-info.c b/server-info.c
index e2b2d6a27a..bae2cdfd51 100644
--- a/server-info.c
+++ b/server-info.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "dir.h"
 #include "repository.h"
 #include "refs.h"
 #include "object.h"
@@ -6,82 +7,174 @@
 #include "tag.h"
 #include "packfile.h"
 #include "object-store.h"
+#include "strbuf.h"
+
+struct update_info_ctx {
+	FILE *cur_fp;
+	FILE *old_fp; /* becomes NULL if it differs from cur_fp */
+	struct strbuf cur_sb;
+	struct strbuf old_sb;
+};
+
+static void uic_mark_stale(struct update_info_ctx *uic)
+{
+	fclose(uic->old_fp);
+	uic->old_fp = NULL;
+}
+
+static int uic_is_stale(const struct update_info_ctx *uic)
+{
+	return uic->old_fp == NULL;
+}
+
+static int uic_printf(struct update_info_ctx *uic, const char *fmt, ...)
+{
+	va_list ap;
+	int ret = -1;
+
+	va_start(ap, fmt);
+
+	if (uic_is_stale(uic)) {
+		ret = vfprintf(uic->cur_fp, fmt, ap);
+	} else {
+		ssize_t r;
+		struct strbuf *cur = &uic->cur_sb;
+		struct strbuf *old = &uic->old_sb;
+
+		strbuf_reset(cur);
+		strbuf_vinsertf(cur, 0, fmt, ap);
+
+		strbuf_reset(old);
+		strbuf_grow(old, cur->len);
+		r = fread(old->buf, 1, cur->len, uic->old_fp);
+		if (r != cur->len || memcmp(old->buf, cur->buf, r))
+			uic_mark_stale(uic);
+
+		if (fwrite(cur->buf, 1, cur->len, uic->cur_fp) == cur->len)
+			ret = 0;
+	}
+
+	va_end(ap);
+
+	return ret;
+}
 
 /*
  * Create the file "path" by writing to a temporary file and renaming
  * it into place. The contents of the file come from "generate", which
  * should return non-zero if it encounters an error.
  */
-static int update_info_file(char *path, int (*generate)(FILE *))
+static int update_info_file(char *path,
+			int (*generate)(struct update_info_ctx *),
+			int force)
 {
 	char *tmp = mkpathdup("%s_XXXXXX", path);
 	int ret = -1;
 	int fd = -1;
-	FILE *fp = NULL, *to_close;
+	FILE *to_close;
+	struct update_info_ctx uic = {
+		.cur_fp = NULL,
+		.old_fp = NULL,
+		.cur_sb = STRBUF_INIT,
+		.old_sb = STRBUF_INIT
+	};
 
 	safe_create_leading_directories(path);
 	fd = git_mkstemp_mode(tmp, 0666);
 	if (fd < 0)
 		goto out;
-	to_close = fp = fdopen(fd, "w");
-	if (!fp)
+	to_close = uic.cur_fp = fdopen(fd, "w");
+	if (!uic.cur_fp)
 		goto out;
 	fd = -1;
-	ret = generate(fp);
+
+	/* no problem on ENOENT and old_fp == NULL, it's stale, now */
+	if (!force)
+		uic.old_fp = fopen_or_warn(path, "r");
+
+	/*
+	 * uic_printf will compare incremental comparison against old_fp
+	 * and mark uic as stale if needed
+	 */
+	ret = generate(&uic);
 	if (ret)
 		goto out;
-	fp = NULL;
+
+	/* new file may be shorter than the old one, check here */
+	if (!uic_is_stale(&uic)) {
+		struct stat st;
+		long new_len = ftell(uic.cur_fp);
+		int old_fd = fileno(uic.old_fp);
+
+		if (new_len < 0) {
+			ret = -1;
+			goto out;
+		}
+		if (fstat(old_fd, &st) || (st.st_size != (size_t)new_len))
+			uic_mark_stale(&uic);
+	}
+
+	uic.cur_fp = NULL;
 	if (fclose(to_close))
 		goto out;
-	if (adjust_shared_perm(tmp) < 0)
-		goto out;
-	if (rename(tmp, path) < 0)
-		goto out;
+
+	if (uic_is_stale(&uic)) {
+		if (adjust_shared_perm(tmp) < 0)
+			goto out;
+		if (rename(tmp, path) < 0)
+			goto out;
+	} else {
+		unlink(tmp);
+	}
 	ret = 0;
 
 out:
 	if (ret) {
 		error_errno("unable to update %s", path);
-		if (fp)
-			fclose(fp);
+		if (uic.cur_fp)
+			fclose(uic.cur_fp);
 		else if (fd >= 0)
 			close(fd);
 		unlink(tmp);
 	}
 	free(tmp);
+	if (uic.old_fp)
+		fclose(uic.old_fp);
+	strbuf_release(&uic.old_sb);
+	strbuf_release(&uic.cur_sb);
 	return ret;
 }
 
 static int add_info_ref(const char *path, const struct object_id *oid,
 			int flag, void *cb_data)
 {
-	FILE *fp = cb_data;
+	struct update_info_ctx *uic = cb_data;
 	struct object *o = parse_object(the_repository, oid);
 	if (!o)
 		return -1;
 
-	if (fprintf(fp, "%s	%s\n", oid_to_hex(oid), path) < 0)
+	if (uic_printf(uic, "%s	%s\n", oid_to_hex(oid), path) < 0)
 		return -1;
 
 	if (o->type == OBJ_TAG) {
 		o = deref_tag(the_repository, o, path, 0);
 		if (o)
-			if (fprintf(fp, "%s	%s^{}\n",
+			if (uic_printf(uic, "%s	%s^{}\n",
 				oid_to_hex(&o->oid), path) < 0)
 				return -1;
 	}
 	return 0;
 }
 
-static int generate_info_refs(FILE *fp)
+static int generate_info_refs(struct update_info_ctx *uic)
 {
-	return for_each_ref(add_info_ref, fp);
+	return for_each_ref(add_info_ref, uic);
 }
 
 static int update_info_refs(int force)
 {
 	char *path = git_pathdup("info/refs");
-	int ret = update_info_file(path, generate_info_refs);
+	int ret = update_info_file(path, generate_info_refs, force);
 	free(path);
 	return ret;
 }
@@ -91,19 +184,15 @@ static struct pack_info {
 	struct packed_git *p;
 	int old_num;
 	int new_num;
-	int nr_alloc;
 } **info;
 static int num_pack;
-static const char *objdir;
-static int objdirlen;
 
 static struct pack_info *find_pack_by_name(const char *name)
 {
 	int i;
 	for (i = 0; i < num_pack; i++) {
 		struct packed_git *p = info[i]->p;
-		/* skip "/pack/" after ".git/objects" */
-		if (!strcmp(p->pack_name + objdirlen + 6, name))
+		if (!strcmp(pack_basename(p), name))
 			return info[i];
 	}
 	return NULL;
@@ -112,9 +201,9 @@ static struct pack_info *find_pack_by_name(const char *name)
 /* Returns non-zero when we detect that the info in the
  * old file is useless.
  */
-static int parse_pack_def(const char *line, int old_cnt)
+static int parse_pack_def(const char *packname, int old_cnt)
 {
-	struct pack_info *i = find_pack_by_name(line + 2);
+	struct pack_info *i = find_pack_by_name(packname);
 	if (i) {
 		i->old_num = old_cnt;
 		return 0;
@@ -131,39 +220,40 @@ static int parse_pack_def(const char *line, int old_cnt)
 static int read_pack_info_file(const char *infofile)
 {
 	FILE *fp;
-	char line[1000];
+	struct strbuf line = STRBUF_INIT;
 	int old_cnt = 0;
+	int stale = 1;
 
 	fp = fopen_or_warn(infofile, "r");
 	if (!fp)
 		return 1; /* nonexistent is not an error. */
 
-	while (fgets(line, sizeof(line), fp)) {
-		int len = strlen(line);
-		if (len && line[len-1] == '\n')
-			line[--len] = 0;
+	while (strbuf_getline(&line, fp) != EOF) {
+		const char *arg;
 
-		if (!len)
+		if (!line.len)
 			continue;
 
-		switch (line[0]) {
-		case 'P': /* P name */
-			if (parse_pack_def(line, old_cnt++))
+		if (skip_prefix(line.buf, "P ", &arg)) {
+			/* P name */
+			if (parse_pack_def(arg, old_cnt++))
 				goto out_stale;
-			break;
-		case 'D': /* we used to emit D but that was misguided. */
-		case 'T': /* we used to emit T but nobody uses it. */
+		} else if (line.buf[0] == 'D') {
+			/* we used to emit D but that was misguided. */
+			goto out_stale;
+		} else if (line.buf[0] == 'T') {
+			/* we used to emit T but nobody uses it. */
 			goto out_stale;
-		default:
-			error("unrecognized: %s", line);
-			break;
+		} else {
+			error("unrecognized: %s", line.buf);
 		}
 	}
-	fclose(fp);
-	return 0;
+	stale = 0;
+
  out_stale:
+	strbuf_release(&line);
 	fclose(fp);
-	return 1;
+	return stale;
 }
 
 static int compare_info(const void *a_, const void *b_)
@@ -194,28 +284,21 @@ static void init_pack_info(const char *infofile, int force)
 {
 	struct packed_git *p;
 	int stale;
-	int i = 0;
-
-	objdir = get_object_directory();
-	objdirlen = strlen(objdir);
+	int i;
+	size_t alloc = 0;
 
 	for (p = get_all_packs(the_repository); p; p = p->next) {
 		/* we ignore things on alternate path since they are
 		 * not available to the pullers in general.
 		 */
-		if (!p->pack_local)
-			continue;
-		i++;
-	}
-	num_pack = i;
-	info = xcalloc(num_pack, sizeof(struct pack_info *));
-	for (i = 0, p = get_all_packs(the_repository); p; p = p->next) {
-		if (!p->pack_local)
+		if (!p->pack_local || !file_exists(p->pack_name))
 			continue;
+
+		i = num_pack++;
+		ALLOC_GROW(info, num_pack, alloc);
 		info[i] = xcalloc(1, sizeof(struct pack_info));
 		info[i]->p = p;
 		info[i]->old_num = -1;
-		i++;
 	}
 
 	if (infofile && !force)
@@ -241,14 +324,14 @@ static void free_pack_info(void)
 	free(info);
 }
 
-static int write_pack_info_file(FILE *fp)
+static int write_pack_info_file(struct update_info_ctx *uic)
 {
 	int i;
 	for (i = 0; i < num_pack; i++) {
-		if (fprintf(fp, "P %s\n", info[i]->p->pack_name + objdirlen + 6) < 0)
+		if (uic_printf(uic, "P %s\n", pack_basename(info[i]->p)) < 0)
 			return -1;
 	}
-	if (fputc('\n', fp) == EOF)
+	if (uic_printf(uic, "\n") < 0)
 		return -1;
 	return 0;
 }
@@ -259,7 +342,7 @@ static int update_info_packs(int force)
 	int ret;
 
 	init_pack_info(infofile, force);
-	ret = update_info_file(infofile, write_pack_info_file);
+	ret = update_info_file(infofile, write_pack_info_file, force);
 	free_pack_info();
 	free(infofile);
 	return ret;