Infrastructure to write revisions in fast-export format

repo_tree maintains the exporter's state and provides a facility to to
call fast_export, which writes objects to stdout suitable for
consumption by fast-import.

The exported functions roughly correspond to Subversion FS operations.

 . repo_add, repo_modify, repo_copy, repo_replace, and repo_delete
   update the current commit, based roughly on the corresponding
   Subversion FS operation.

 . repo_commit calls out to fast_export to write the current commit to
   the fast-import stream in stdout.

 . repo_diff is used by the fast_export module to write the changes
   for a commit.

 . repo_reset erases the exporter's state, so valgrind can be happy.

[rr: squelched compiler warnings]
[jn: removed support for maintaining state on-disk, though we may
want to add it back later]

Signed-off-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

5 files changed, 443 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index ea7fc8795d..2017d09934 100644
--- a/Makefile
+++ b/Makefile
@@ -1744,7 +1744,8 @@ ifndef NO_CURL
 endif
 XDIFF_OBJS = xdiff/xdiffi.o xdiff/xprepare.o xdiff/xutils.o xdiff/xemit.o \
 	xdiff/xmerge.o xdiff/xpatience.o
-VCSSVN_OBJS = vcs-svn/string_pool.o vcs-svn/line_buffer.o
+VCSSVN_OBJS = vcs-svn/string_pool.o vcs-svn/line_buffer.o \
+	vcs-svn/repo_tree.o vcs-svn/fast_export.o
 OBJECTS := $(GIT_OBJS) $(XDIFF_OBJS) $(VCSSVN_OBJS)
 
 dep_files := $(foreach f,$(OBJECTS),$(dir $f).depend/$(notdir $f).d)
@@ -1870,7 +1871,7 @@ xdiff-interface.o $(XDIFF_OBJS): \
 
 $(VCSSVN_OBJS): \
 	vcs-svn/obj_pool.h vcs-svn/trp.h vcs-svn/string_pool.h \
-	vcs-svn/line_buffer.h
+	vcs-svn/line_buffer.h vcs-svn/repo_tree.h vcs-svn/fast_export.h
 endif
 
 exec_cmd.s exec_cmd.o: EXTRA_CPPFLAGS = \
diff --git a/vcs-svn/fast_export.c b/vcs-svn/fast_export.c
new file mode 100644
index 0000000000..3a6156fc11
--- /dev/null
+++ b/vcs-svn/fast_export.c
@@ -0,0 +1,74 @@
+/*
+ * Licensed under a two-clause BSD-style license.
+ * See LICENSE for details.
+ */
+
+#include "git-compat-util.h"
+#include "fast_export.h"
+#include "line_buffer.h"
+#include "repo_tree.h"
+#include "string_pool.h"
+
+#define MAX_GITSVN_LINE_LEN 4096
+
+static uint32_t first_commit_done;
+
+void fast_export_delete(uint32_t depth, uint32_t *path)
+{
+	putchar('D');
+	putchar(' ');
+	pool_print_seq(depth, path, '/', stdout);
+	putchar('\n');
+}
+
+void fast_export_modify(uint32_t depth, uint32_t *path, uint32_t mode,
+			uint32_t mark)
+{
+	/* Mode must be 100644, 100755, 120000, or 160000. */
+	printf("M %06o :%d ", mode, mark);
+	pool_print_seq(depth, path, '/', stdout);
+	putchar('\n');
+}
+
+static char gitsvnline[MAX_GITSVN_LINE_LEN];
+void fast_export_commit(uint32_t revision, uint32_t author, char *log,
+			uint32_t uuid, uint32_t url,
+			unsigned long timestamp)
+{
+	if (!log)
+		log = "";
+	if (~uuid && ~url) {
+		snprintf(gitsvnline, MAX_GITSVN_LINE_LEN, "\n\ngit-svn-id: %s@%d %s\n",
+				 pool_fetch(url), revision, pool_fetch(uuid));
+	} else {
+		*gitsvnline = '\0';
+	}
+	printf("commit refs/heads/master\n");
+	printf("committer %s <%s@%s> %ld +0000\n",
+		   ~author ? pool_fetch(author) : "nobody",
+		   ~author ? pool_fetch(author) : "nobody",
+		   ~uuid ? pool_fetch(uuid) : "local", timestamp);
+	printf("data %zd\n%s%s\n",
+		   strlen(log) + strlen(gitsvnline), log, gitsvnline);
+	if (!first_commit_done) {
+		if (revision > 1)
+			printf("from refs/heads/master^0\n");
+		first_commit_done = 1;
+	}
+	repo_diff(revision - 1, revision);
+	fputc('\n', stdout);
+
+	printf("progress Imported commit %d.\n\n", revision);
+}
+
+void fast_export_blob(uint32_t mode, uint32_t mark, uint32_t len)
+{
+	if (mode == REPO_MODE_LNK) {
+		/* svn symlink blobs start with "link " */
+		buffer_skip_bytes(5);
+		len -= 5;
+	}
+	printf("blob\nmark :%d\ndata %d\n", mark, len);
+	buffer_copy_bytes(len);
+	fputc('\n', stdout);
+}
diff --git a/vcs-svn/fast_export.h b/vcs-svn/fast_export.h
new file mode 100644
index 0000000000..2aaaea53d5
--- /dev/null
+++ b/vcs-svn/fast_export.h
@@ -0,0 +1,11 @@
+#ifndef FAST_EXPORT_H_
+#define FAST_EXPORT_H_
+
+void fast_export_delete(uint32_t depth, uint32_t *path);
+void fast_export_modify(uint32_t depth, uint32_t *path, uint32_t mode,
+			uint32_t mark);
+void fast_export_commit(uint32_t revision, uint32_t author, char *log,
+			uint32_t uuid, uint32_t url, unsigned long timestamp);
+void fast_export_blob(uint32_t mode, uint32_t mark, uint32_t len);
+
+#endif
diff --git a/vcs-svn/repo_tree.c b/vcs-svn/repo_tree.c
new file mode 100644
index 0000000000..c3d7ee7d24
--- /dev/null
+++ b/vcs-svn/repo_tree.c
@@ -0,0 +1,329 @@
+/*
+ * Licensed under a two-clause BSD-style license.
+ * See LICENSE for details.
+ */
+
+#include "git-compat-util.h"
+
+#include "string_pool.h"
+#include "repo_tree.h"
+#include "obj_pool.h"
+#include "fast_export.h"
+
+#include "trp.h"
+
+struct repo_dirent {
+	uint32_t name_offset;
+	struct trp_node children;
+	uint32_t mode;
+	uint32_t content_offset;
+};
+
+struct repo_dir {
+	struct trp_root entries;
+};
+
+struct repo_commit {
+	uint32_t root_dir_offset;
+};
+
+/* Memory pools for commit, dir and dirent */
+obj_pool_gen(commit, struct repo_commit, 4096)
+obj_pool_gen(dir, struct repo_dir, 4096)
+obj_pool_gen(dirent, struct repo_dirent, 4096)
+
+static uint32_t active_commit;
+static uint32_t mark;
+
+static int repo_dirent_name_cmp(const void *a, const void *b);
+
+/* Treap for directory entries */
+trp_gen(static, dirent_, struct repo_dirent, children, dirent, repo_dirent_name_cmp);
+
+uint32_t next_blob_mark(void)
+{
+	return mark++;
+}
+
+static struct repo_dir *repo_commit_root_dir(struct repo_commit *commit)
+{
+	return dir_pointer(commit->root_dir_offset);
+}
+
+static struct repo_dirent *repo_first_dirent(struct repo_dir *dir)
+{
+	return dirent_first(&dir->entries);
+}
+
+static int repo_dirent_name_cmp(const void *a, const void *b)
+{
+	const struct repo_dirent *dirent1 = a, *dirent2 = b;
+	uint32_t a_offset = dirent1->name_offset;
+	uint32_t b_offset = dirent2->name_offset;
+	return (a_offset > b_offset) - (a_offset < b_offset);
+}
+
+static int repo_dirent_is_dir(struct repo_dirent *dirent)
+{
+	return dirent != NULL && dirent->mode == REPO_MODE_DIR;
+}
+
+static struct repo_dir *repo_dir_from_dirent(struct repo_dirent *dirent)
+{
+	if (!repo_dirent_is_dir(dirent))
+		return NULL;
+	return dir_pointer(dirent->content_offset);
+}
+
+static struct repo_dir *repo_clone_dir(struct repo_dir *orig_dir)
+{
+	uint32_t orig_o, new_o;
+	orig_o = dir_offset(orig_dir);
+	if (orig_o >= dir_pool.committed)
+		return orig_dir;
+	new_o = dir_alloc(1);
+	orig_dir = dir_pointer(orig_o);
+	*dir_pointer(new_o) = *orig_dir;
+	return dir_pointer(new_o);
+}
+
+static struct repo_dirent *repo_read_dirent(uint32_t revision, uint32_t *path)
+{
+	uint32_t name = 0;
+	struct repo_dirent *key = dirent_pointer(dirent_alloc(1));
+	struct repo_dir *dir = NULL;
+	struct repo_dirent *dirent = NULL;
+	dir = repo_commit_root_dir(commit_pointer(revision));
+	while (~(name = *path++)) {
+		key->name_offset = name;
+		dirent = dirent_search(&dir->entries, key);
+		if (dirent == NULL || !repo_dirent_is_dir(dirent))
+			break;
+		dir = repo_dir_from_dirent(dirent);
+	}
+	dirent_free(1);
+	return dirent;
+}
+
+static void repo_write_dirent(uint32_t *path, uint32_t mode,
+			      uint32_t content_offset, uint32_t del)
+{
+	uint32_t name, revision, dir_o = ~0, parent_dir_o = ~0;
+	struct repo_dir *dir;
+	struct repo_dirent *key;
+	struct repo_dirent *dirent = NULL;
+	revision = active_commit;
+	dir = repo_commit_root_dir(commit_pointer(revision));
+	dir = repo_clone_dir(dir);
+	commit_pointer(revision)->root_dir_offset = dir_offset(dir);
+	while (~(name = *path++)) {
+		parent_dir_o = dir_offset(dir);
+
+		key = dirent_pointer(dirent_alloc(1));
+		key->name_offset = name;
+
+		dirent = dirent_search(&dir->entries, key);
+		if (dirent == NULL)
+			dirent = key;
+		else
+			dirent_free(1);
+
+		if (dirent == key) {
+			dirent->mode = REPO_MODE_DIR;
+			dirent->content_offset = 0;
+			dirent_insert(&dir->entries, dirent);
+		}
+
+		if (dirent_offset(dirent) < dirent_pool.committed) {
+			dir_o = repo_dirent_is_dir(dirent) ?
+					dirent->content_offset : ~0;
+			dirent_remove(&dir->entries, dirent);
+			dirent = dirent_pointer(dirent_alloc(1));
+			dirent->name_offset = name;
+			dirent->mode = REPO_MODE_DIR;
+			dirent->content_offset = dir_o;
+			dirent_insert(&dir->entries, dirent);
+		}
+
+		dir = repo_dir_from_dirent(dirent);
+		dir = repo_clone_dir(dir);
+		dirent->content_offset = dir_offset(dir);
+	}
+	if (dirent == NULL)
+		return;
+	dirent->mode = mode;
+	dirent->content_offset = content_offset;
+	if (del && ~parent_dir_o)
+		dirent_remove(&dir_pointer(parent_dir_o)->entries, dirent);
+}
+
+uint32_t repo_copy(uint32_t revision, uint32_t *src, uint32_t *dst)
+{
+	uint32_t mode = 0, content_offset = 0;
+	struct repo_dirent *src_dirent;
+	src_dirent = repo_read_dirent(revision, src);
+	if (src_dirent != NULL) {
+		mode = src_dirent->mode;
+		content_offset = src_dirent->content_offset;
+		repo_write_dirent(dst, mode, content_offset, 0);
+	}
+	return mode;
+}
+
+void repo_add(uint32_t *path, uint32_t mode, uint32_t blob_mark)
+{
+	repo_write_dirent(path, mode, blob_mark, 0);
+}
+
+uint32_t repo_replace(uint32_t *path, uint32_t blob_mark)
+{
+	uint32_t mode = 0;
+	struct repo_dirent *src_dirent;
+	src_dirent = repo_read_dirent(active_commit, path);
+	if (src_dirent != NULL) {
+		mode = src_dirent->mode;
+		repo_write_dirent(path, mode, blob_mark, 0);
+	}
+	return mode;
+}
+
+void repo_modify(uint32_t *path, uint32_t mode, uint32_t blob_mark)
+{
+	struct repo_dirent *src_dirent;
+	src_dirent = repo_read_dirent(active_commit, path);
+	if (src_dirent != NULL && blob_mark == 0)
+		blob_mark = src_dirent->content_offset;
+	repo_write_dirent(path, mode, blob_mark, 0);
+}
+
+void repo_delete(uint32_t *path)
+{
+	repo_write_dirent(path, 0, 0, 1);
+}
+
+static void repo_git_add_r(uint32_t depth, uint32_t *path, struct repo_dir *dir);
+
+static void repo_git_add(uint32_t depth, uint32_t *path, struct repo_dirent *dirent)
+{
+	if (repo_dirent_is_dir(dirent))
+		repo_git_add_r(depth, path, repo_dir_from_dirent(dirent));
+	else
+		fast_export_modify(depth, path,
+				   dirent->mode, dirent->content_offset);
+}
+
+static void repo_git_add_r(uint32_t depth, uint32_t *path, struct repo_dir *dir)
+{
+	struct repo_dirent *de = repo_first_dirent(dir);
+	while (de) {
+		path[depth] = de->name_offset;
+		repo_git_add(depth + 1, path, de);
+		de = dirent_next(&dir->entries, de);
+	}
+}
+
+static void repo_diff_r(uint32_t depth, uint32_t *path, struct repo_dir *dir1,
+			struct repo_dir *dir2)
+{
+	struct repo_dirent *de1, *de2;
+	de1 = repo_first_dirent(dir1);
+	de2 = repo_first_dirent(dir2);
+
+	while (de1 && de2) {
+		if (de1->name_offset < de2->name_offset) {
+			path[depth] = de1->name_offset;
+			fast_export_delete(depth + 1, path);
+			de1 = dirent_next(&dir1->entries, de1);
+			continue;
+		}
+		if (de1->name_offset > de2->name_offset) {
+			path[depth] = de2->name_offset;
+			repo_git_add(depth + 1, path, de2);
+			de2 = dirent_next(&dir2->entries, de2);
+			continue;
+		}
+		path[depth] = de1->name_offset;
+
+		if (de1->mode == de2->mode &&
+		    de1->content_offset == de2->content_offset) {
+			; /* No change. */
+		} else if (repo_dirent_is_dir(de1) && repo_dirent_is_dir(de2)) {
+			repo_diff_r(depth + 1, path,
+				    repo_dir_from_dirent(de1),
+				    repo_dir_from_dirent(de2));
+		} else if (!repo_dirent_is_dir(de1) && !repo_dirent_is_dir(de2)) {
+			repo_git_add(depth + 1, path, de2);
+		} else {
+			fast_export_delete(depth + 1, path);
+			repo_git_add(depth + 1, path, de2);
+		}
+		de1 = dirent_next(&dir1->entries, de1);
+		de2 = dirent_next(&dir2->entries, de2);
+	}
+	while (de1) {
+		path[depth] = de1->name_offset;
+		fast_export_delete(depth + 1, path);
+		de1 = dirent_next(&dir1->entries, de1);
+	}
+	while (de2) {
+		path[depth] = de2->name_offset;
+		repo_git_add(depth + 1, path, de2);
+		de2 = dirent_next(&dir2->entries, de2);
+	}
+}
+
+static uint32_t path_stack[REPO_MAX_PATH_DEPTH];
+
+void repo_diff(uint32_t r1, uint32_t r2)
+{
+	repo_diff_r(0,
+		    path_stack,
+		    repo_commit_root_dir(commit_pointer(r1)),
+		    repo_commit_root_dir(commit_pointer(r2)));
+}
+
+void repo_commit(uint32_t revision, uint32_t author, char *log, uint32_t uuid,
+		 uint32_t url, unsigned long timestamp)
+{
+	fast_export_commit(revision, author, log, uuid, url, timestamp);
+	dirent_commit();
+	dir_commit();
+	active_commit = commit_alloc(1);
+	commit_pointer(active_commit)->root_dir_offset =
+		commit_pointer(active_commit - 1)->root_dir_offset;
+}
+
+static void mark_init(void)
+{
+	uint32_t i;
+	mark = 0;
+	for (i = 0; i < dirent_pool.size; i++)
+		if (!repo_dirent_is_dir(dirent_pointer(i)) &&
+		    dirent_pointer(i)->content_offset > mark)
+			mark = dirent_pointer(i)->content_offset;
+	mark++;
+}
+
+void repo_init(void)
+{
+	mark_init();
+	if (commit_pool.size == 0) {
+		/* Create empty tree for commit 0. */
+		commit_alloc(1);
+		commit_pointer(0)->root_dir_offset = dir_alloc(1);
+		dir_pointer(0)->entries.trp_root = ~0;
+		dir_commit();
+	}
+	/* Preallocate next commit, ready for changes. */
+	active_commit = commit_alloc(1);
+	commit_pointer(active_commit)->root_dir_offset =
+		commit_pointer(active_commit - 1)->root_dir_offset;
+}
+
+void repo_reset(void)
+{
+	pool_reset();
+	commit_reset();
+	dir_reset();
+	dirent_reset();
+}
diff --git a/vcs-svn/repo_tree.h b/vcs-svn/repo_tree.h
new file mode 100644
index 0000000000..5476175922
--- /dev/null
+++ b/vcs-svn/repo_tree.h
@@ -0,0 +1,26 @@
+#ifndef REPO_TREE_H_
+#define REPO_TREE_H_
+
+#include "git-compat-util.h"
+
+#define REPO_MODE_DIR 0040000
+#define REPO_MODE_BLB 0100644
+#define REPO_MODE_EXE 0100755
+#define REPO_MODE_LNK 0120000
+
+#define REPO_MAX_PATH_LEN 4096
+#define REPO_MAX_PATH_DEPTH 1000
+
+uint32_t next_blob_mark(void);
+uint32_t repo_copy(uint32_t revision, uint32_t *src, uint32_t *dst);
+void repo_add(uint32_t *path, uint32_t mode, uint32_t blob_mark);
+uint32_t repo_replace(uint32_t *path, uint32_t blob_mark);
+void repo_modify(uint32_t *path, uint32_t mode, uint32_t blob_mark);
+void repo_delete(uint32_t *path);
+void repo_commit(uint32_t revision, uint32_t author, char *log, uint32_t uuid,
+		 uint32_t url, long unsigned timestamp);
+void repo_diff(uint32_t r1, uint32_t r2);
+void repo_init(void);
+void repo_reset(void);
+
+#endif