reftable: generic interface to tables

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

5 files changed, 402 insertions, 0 deletions

diff --git a/reftable/generic.c b/reftable/generic.c
new file mode 100644
index 0000000000..7a8a738d86
--- /dev/null
+++ b/reftable/generic.c
@@ -0,0 +1,169 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "basics.h"
+#include "record.h"
+#include "generic.h"
+#include "reftable-iterator.h"
+#include "reftable-generic.h"
+
+int reftable_table_seek_ref(struct reftable_table *tab,
+			    struct reftable_iterator *it, const char *name)
+{
+	struct reftable_ref_record ref = {
+		.refname = (char *)name,
+	};
+	struct reftable_record rec = { NULL };
+	reftable_record_from_ref(&rec, &ref);
+	return tab->ops->seek_record(tab->table_arg, it, &rec);
+}
+
+int reftable_table_seek_log(struct reftable_table *tab,
+			    struct reftable_iterator *it, const char *name)
+{
+	struct reftable_log_record log = {
+		.refname = (char *)name,
+		.update_index = ~((uint64_t)0),
+	};
+	struct reftable_record rec = { NULL };
+	reftable_record_from_log(&rec, &log);
+	return tab->ops->seek_record(tab->table_arg, it, &rec);
+}
+
+int reftable_table_read_ref(struct reftable_table *tab, const char *name,
+			    struct reftable_ref_record *ref)
+{
+	struct reftable_iterator it = { NULL };
+	int err = reftable_table_seek_ref(tab, &it, name);
+	if (err)
+		goto done;
+
+	err = reftable_iterator_next_ref(&it, ref);
+	if (err)
+		goto done;
+
+	if (strcmp(ref->refname, name) ||
+	    reftable_ref_record_is_deletion(ref)) {
+		reftable_ref_record_release(ref);
+		err = 1;
+		goto done;
+	}
+
+done:
+	reftable_iterator_destroy(&it);
+	return err;
+}
+
+int reftable_table_print(struct reftable_table *tab) {
+	struct reftable_iterator it = { NULL };
+	struct reftable_ref_record ref = { NULL };
+	struct reftable_log_record log = { NULL };
+	uint32_t hash_id = reftable_table_hash_id(tab);
+	int err = reftable_table_seek_ref(tab, &it, "");
+	if (err < 0) {
+		return err;
+	}
+
+	while (1) {
+		err = reftable_iterator_next_ref(&it, &ref);
+		if (err > 0) {
+			break;
+		}
+		if (err < 0) {
+			return err;
+		}
+		reftable_ref_record_print(&ref, hash_id);
+	}
+	reftable_iterator_destroy(&it);
+	reftable_ref_record_release(&ref);
+
+	err = reftable_table_seek_log(tab, &it, "");
+	if (err < 0) {
+		return err;
+	}
+	while (1) {
+		err = reftable_iterator_next_log(&it, &log);
+		if (err > 0) {
+			break;
+		}
+		if (err < 0) {
+			return err;
+		}
+		reftable_log_record_print(&log, hash_id);
+	}
+	reftable_iterator_destroy(&it);
+	reftable_log_record_release(&log);
+	return 0;
+}
+
+uint64_t reftable_table_max_update_index(struct reftable_table *tab)
+{
+	return tab->ops->max_update_index(tab->table_arg);
+}
+
+uint64_t reftable_table_min_update_index(struct reftable_table *tab)
+{
+	return tab->ops->min_update_index(tab->table_arg);
+}
+
+uint32_t reftable_table_hash_id(struct reftable_table *tab)
+{
+	return tab->ops->hash_id(tab->table_arg);
+}
+
+void reftable_iterator_destroy(struct reftable_iterator *it)
+{
+	if (!it->ops) {
+		return;
+	}
+	it->ops->close(it->iter_arg);
+	it->ops = NULL;
+	FREE_AND_NULL(it->iter_arg);
+}
+
+int reftable_iterator_next_ref(struct reftable_iterator *it,
+			       struct reftable_ref_record *ref)
+{
+	struct reftable_record rec = { NULL };
+	reftable_record_from_ref(&rec, ref);
+	return iterator_next(it, &rec);
+}
+
+int reftable_iterator_next_log(struct reftable_iterator *it,
+			       struct reftable_log_record *log)
+{
+	struct reftable_record rec = { NULL };
+	reftable_record_from_log(&rec, log);
+	return iterator_next(it, &rec);
+}
+
+int iterator_next(struct reftable_iterator *it, struct reftable_record *rec)
+{
+	return it->ops->next(it->iter_arg, rec);
+}
+
+static int empty_iterator_next(void *arg, struct reftable_record *rec)
+{
+	return 1;
+}
+
+static void empty_iterator_close(void *arg)
+{
+}
+
+static struct reftable_iterator_vtable empty_vtable = {
+	.next = &empty_iterator_next,
+	.close = &empty_iterator_close,
+};
+
+void iterator_set_empty(struct reftable_iterator *it)
+{
+	assert(!it->ops);
+	it->iter_arg = NULL;
+	it->ops = &empty_vtable;
+}
diff --git a/reftable/generic.h b/reftable/generic.h
new file mode 100644
index 0000000000..98886a0640
--- /dev/null
+++ b/reftable/generic.h
@@ -0,0 +1,32 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef GENERIC_H
+#define GENERIC_H
+
+#include "record.h"
+#include "reftable-generic.h"
+
+/* generic interface to reftables */
+struct reftable_table_vtable {
+	int (*seek_record)(void *tab, struct reftable_iterator *it,
+			   struct reftable_record *);
+	uint32_t (*hash_id)(void *tab);
+	uint64_t (*min_update_index)(void *tab);
+	uint64_t (*max_update_index)(void *tab);
+};
+
+struct reftable_iterator_vtable {
+	int (*next)(void *iter_arg, struct reftable_record *rec);
+	void (*close)(void *iter_arg);
+};
+
+void iterator_set_empty(struct reftable_iterator *it);
+int iterator_next(struct reftable_iterator *it, struct reftable_record *rec);
+
+#endif
diff --git a/reftable/reftable-generic.h b/reftable/reftable-generic.h
new file mode 100644
index 0000000000..d239751a77
--- /dev/null
+++ b/reftable/reftable-generic.h
@@ -0,0 +1,47 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef REFTABLE_GENERIC_H
+#define REFTABLE_GENERIC_H
+
+#include "reftable-iterator.h"
+
+struct reftable_table_vtable;
+
+/*
+ * Provides a unified API for reading tables, either merged tables, or single
+ * readers. */
+struct reftable_table {
+	struct reftable_table_vtable *ops;
+	void *table_arg;
+};
+
+int reftable_table_seek_log(struct reftable_table *tab,
+			    struct reftable_iterator *it, const char *name);
+
+int reftable_table_seek_ref(struct reftable_table *tab,
+			    struct reftable_iterator *it, const char *name);
+
+/* returns the hash ID from a generic reftable_table */
+uint32_t reftable_table_hash_id(struct reftable_table *tab);
+
+/* returns the max update_index covered by this table. */
+uint64_t reftable_table_max_update_index(struct reftable_table *tab);
+
+/* returns the min update_index covered by this table. */
+uint64_t reftable_table_min_update_index(struct reftable_table *tab);
+
+/* convenience function to read a single ref. Returns < 0 for error, 0
+   for success, and 1 if ref not found. */
+int reftable_table_read_ref(struct reftable_table *tab, const char *name,
+			    struct reftable_ref_record *ref);
+
+/* dump table contents onto stdout for debugging */
+int reftable_table_print(struct reftable_table *tab);
+
+#endif
diff --git a/reftable/reftable-iterator.h b/reftable/reftable-iterator.h
new file mode 100644
index 0000000000..d3eee7af35
--- /dev/null
+++ b/reftable/reftable-iterator.h
@@ -0,0 +1,39 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef REFTABLE_ITERATOR_H
+#define REFTABLE_ITERATOR_H
+
+#include "reftable-record.h"
+
+struct reftable_iterator_vtable;
+
+/* iterator is the generic interface for walking over data stored in a
+ * reftable.
+ */
+struct reftable_iterator {
+	struct reftable_iterator_vtable *ops;
+	void *iter_arg;
+};
+
+/* reads the next reftable_ref_record. Returns < 0 for error, 0 for OK and > 0:
+ * end of iteration.
+ */
+int reftable_iterator_next_ref(struct reftable_iterator *it,
+			       struct reftable_ref_record *ref);
+
+/* reads the next reftable_log_record. Returns < 0 for error, 0 for OK and > 0:
+ * end of iteration.
+ */
+int reftable_iterator_next_log(struct reftable_iterator *it,
+			       struct reftable_log_record *log);
+
+/* releases resources associated with an iterator. */
+void reftable_iterator_destroy(struct reftable_iterator *it);
+
+#endif
diff --git a/reftable/reftable.c b/reftable/reftable.c
new file mode 100644
index 0000000000..0e4607a7cd
--- /dev/null
+++ b/reftable/reftable.c
@@ -0,0 +1,115 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "basics.h"
+#include "record.h"
+#include "generic.h"
+#include "reftable-iterator.h"
+#include "reftable-generic.h"
+
+int reftable_table_seek_ref(struct reftable_table *tab,
+			    struct reftable_iterator *it, const char *name)
+{
+	struct reftable_ref_record ref = {
+		.refname = (char *)name,
+	};
+	struct reftable_record rec = { NULL };
+	reftable_record_from_ref(&rec, &ref);
+	return tab->ops->seek_record(tab->table_arg, it, &rec);
+}
+
+int reftable_table_read_ref(struct reftable_table *tab, const char *name,
+			    struct reftable_ref_record *ref)
+{
+	struct reftable_iterator it = { NULL };
+	int err = reftable_table_seek_ref(tab, &it, name);
+	if (err)
+		goto done;
+
+	err = reftable_iterator_next_ref(&it, ref);
+	if (err)
+		goto done;
+
+	if (strcmp(ref->refname, name) ||
+	    reftable_ref_record_is_deletion(ref)) {
+		reftable_ref_record_release(ref);
+		err = 1;
+		goto done;
+	}
+
+done:
+	reftable_iterator_destroy(&it);
+	return err;
+}
+
+uint64_t reftable_table_max_update_index(struct reftable_table *tab)
+{
+	return tab->ops->max_update_index(tab->table_arg);
+}
+
+uint64_t reftable_table_min_update_index(struct reftable_table *tab)
+{
+	return tab->ops->min_update_index(tab->table_arg);
+}
+
+uint32_t reftable_table_hash_id(struct reftable_table *tab)
+{
+	return tab->ops->hash_id(tab->table_arg);
+}
+
+void reftable_iterator_destroy(struct reftable_iterator *it)
+{
+	if (!it->ops) {
+		return;
+	}
+	it->ops->close(it->iter_arg);
+	it->ops = NULL;
+	FREE_AND_NULL(it->iter_arg);
+}
+
+int reftable_iterator_next_ref(struct reftable_iterator *it,
+			       struct reftable_ref_record *ref)
+{
+	struct reftable_record rec = { NULL };
+	reftable_record_from_ref(&rec, ref);
+	return iterator_next(it, &rec);
+}
+
+int reftable_iterator_next_log(struct reftable_iterator *it,
+			       struct reftable_log_record *log)
+{
+	struct reftable_record rec = { NULL };
+	reftable_record_from_log(&rec, log);
+	return iterator_next(it, &rec);
+}
+
+int iterator_next(struct reftable_iterator *it, struct reftable_record *rec)
+{
+	return it->ops->next(it->iter_arg, rec);
+}
+
+static int empty_iterator_next(void *arg, struct reftable_record *rec)
+{
+	return 1;
+}
+
+static void empty_iterator_close(void *arg)
+{
+}
+
+static struct reftable_iterator_vtable empty_vtable = {
+	.next = &empty_iterator_next,
+	.close = &empty_iterator_close,
+};
+
+void iterator_set_empty(struct reftable_iterator *it)
+{
+	assert(!it->ops);
+	it->iter_arg = NULL;
+	it->ops = &empty_vtable;
+}