reftable/blocksource: consolidate code into a single file

The code that implements block sources is distributed across a couple of
files. Consolidate all of it into "reftable/blocksource.c" and its
accompanying header so that it is easier to locate and more self
contained.

While at it, rename some of the functions to have properly scoped names.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

reftable/block.c

@@ -221,7 +221,7 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block,
 	uint32_t restart_start = 0;
 	uint8_t *restart_bytes = NULL;
 
-	reftable_block_done(&br->block);
+	block_source_return_block(&br->block);
 
 	if (!reftable_is_block_type(typ)) {
 		err =  REFTABLE_FORMAT_ERROR;
@@ -285,7 +285,7 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block,
 		}
 
 		/* We're done with the input data. */
-		reftable_block_done(block);
+		block_source_return_block(block);
 		block->data = br->uncompressed_data;
 		block->len = sz;
 		full_block_size = src_len + block_header_skip - br->zstream->avail_in;
@@ -324,7 +324,7 @@ void block_reader_release(struct block_reader *br)
 	inflateEnd(br->zstream);
 	reftable_free(br->zstream);
 	reftable_free(br->uncompressed_data);
-	reftable_block_done(&br->block);
+	block_source_return_block(&br->block);
 }
 
 uint8_t block_reader_type(const struct block_reader *r)
@@ -570,14 +570,3 @@ void block_writer_release(struct block_writer *bw)
 	reftable_buf_release(&bw->last_key);
 	/* the block is not owned. */
 }
-
-void reftable_block_done(struct reftable_block *blockp)
-{
-	struct reftable_block_source source = blockp->source;
-	if (blockp && source.ops)
-		source.ops->return_block(source.arg, blockp);
-	blockp->data = NULL;
-	blockp->len = 0;
-	blockp->source.ops = NULL;
-	blockp->source.arg = NULL;
-}

reftable/block.h

@@ -142,7 +142,4 @@ size_t header_size(int version);
 /* size of file footer, depending on format version */
 size_t footer_size(int version);
 
-/* returns a block to its source. */
-void reftable_block_done(struct reftable_block *ret);
-
 #endif

reftable/blocksource.c

@@ -13,6 +13,41 @@
 #include "reftable-blocksource.h"
 #include "reftable-error.h"
 
+void block_source_return_block(struct reftable_block *block)
+{
+	struct reftable_block_source source = block->source;
+	if (block && source.ops)
+		source.ops->return_block(source.arg, block);
+	block->data = NULL;
+	block->len = 0;
+	block->source.ops = NULL;
+	block->source.arg = NULL;
+}
+
+void block_source_close(struct reftable_block_source *source)
+{
+	if (!source->ops) {
+		return;
+	}
+
+	source->ops->close(source->arg);
+	source->ops = NULL;
+}
+
+ssize_t block_source_read_block(struct reftable_block_source *source,
+				struct reftable_block *dest, uint64_t off,
+				uint32_t size)
+{
+	ssize_t result = source->ops->read_block(source->arg, dest, off, size);
+	dest->source = *source;
+	return result;
+}
+
+uint64_t block_source_size(struct reftable_block_source *source)
+{
+	return source->ops->size(source->arg);
+}
+
 static void reftable_buf_return_block(void *b REFTABLE_UNUSED, struct reftable_block *dest)
 {
 	if (dest->len)

reftable/blocksource.h

@@ -12,9 +12,34 @@
 #include "system.h"
 
 struct reftable_block_source;
+struct reftable_block;
 struct reftable_buf;
 
-/* Create an in-memory block source for reading reftables */
+/*
+ * Close the block source and the underlying resource. This is a no-op in case
+ * the block source is zero-initialized.
+ */
+void block_source_close(struct reftable_block_source *source);
+
+/*
+ * Read a block of length `size` from the source at the given `off`.
+ */
+ssize_t block_source_read_block(struct reftable_block_source *source,
+				struct reftable_block *dest, uint64_t off,
+				uint32_t size);
+
+/*
+ * Return the total length of the underlying resource.
+ */
+uint64_t block_source_size(struct reftable_block_source *source);
+
+/*
+ * Return a block to its original source, releasing any resources associated
+ * with it.
+ */
+void block_source_return_block(struct reftable_block *block);
+
+/* Create an in-memory block source for reading reftables. */
 void block_source_from_buf(struct reftable_block_source *bs,
 			   struct reftable_buf *buf);
 

reftable/iter.c

@@ -11,6 +11,7 @@
 #include "system.h"
 
 #include "block.h"
+#include "blocksource.h"
 #include "constants.h"
 #include "reftable-error.h"
 #include "table.h"
@@ -113,7 +114,7 @@ static void indexed_table_ref_iter_close(void *p)
 {
 	struct indexed_table_ref_iter *it = p;
 	block_iter_close(&it->cur);
-	reftable_block_done(&it->block_reader.block);
+	block_source_return_block(&it->block_reader.block);
 	reftable_free(it->offsets);
 	reftable_buf_release(&it->oid);
 }
@@ -127,7 +128,7 @@ static int indexed_table_ref_iter_next_block(struct indexed_table_ref_iter *it)
 		return 1;
 	}
 
-	reftable_block_done(&it->block_reader.block);
+	block_source_return_block(&it->block_reader.block);
 
 	off = it->offsets[it->offset_idx++];
 	err = table_init_block_reader(it->table, &it->block_reader, off,

reftable/reftable-blocksource.h

@@ -11,7 +11,8 @@
 
 #include <stdint.h>
 
-/* block_source is a generic wrapper for a seekable readable file.
+/*
+ * Generic wrapper for a seekable readable file.
  */
 struct reftable_block_source {
 	struct reftable_block_source_vtable *ops;

reftable/table.c

@@ -10,35 +10,12 @@
 
 #include "system.h"
 #include "block.h"
+#include "blocksource.h"
 #include "constants.h"
 #include "iter.h"
 #include "record.h"
 #include "reftable-error.h"
 
-uint64_t block_source_size(struct reftable_block_source *source)
-{
-	return source->ops->size(source->arg);
-}
-
-ssize_t block_source_read_block(struct reftable_block_source *source,
-				struct reftable_block *dest, uint64_t off,
-				uint32_t size)
-{
-	ssize_t result = source->ops->read_block(source->arg, dest, off, size);
-	dest->source = *source;
-	return result;
-}
-
-void block_source_close(struct reftable_block_source *source)
-{
-	if (!source->ops) {
-		return;
-	}
-
-	source->ops->close(source->arg);
-	source->ops = NULL;
-}
-
 static struct reftable_table_offsets *
 table_offsets_for(struct reftable_table *t, uint8_t typ)
 {
@@ -249,7 +226,7 @@ int table_init_block_reader(struct reftable_table *t, struct block_reader *br,
 	}
 
 	if (block_size > guess_block_size) {
-		reftable_block_done(&block);
+		block_source_return_block(&block);
 		err = table_get_block(t, &block, next_off, block_size);
 		if (err < 0) {
 			goto done;
@@ -259,7 +236,7 @@ int table_init_block_reader(struct reftable_table *t, struct block_reader *br,
 	err = block_reader_init(br, &block, header_off, t->block_size,
 				hash_size(t->hash_id));
 done:
-	reftable_block_done(&block);
+	block_source_return_block(&block);
 
 	return err;
 }
@@ -666,8 +643,8 @@ int reftable_table_new(struct reftable_table **out,
 	*out = t;
 
 done:
-	reftable_block_done(&footer);
-	reftable_block_done(&header);
+	block_source_return_block(&footer);
+	block_source_return_block(&header);
 	if (err) {
 		if (t)
 			reftable_free(t->name);

reftable/table.h

@@ -14,13 +14,6 @@
 #include "reftable-iterator.h"
 #include "reftable-table.h"
 
-uint64_t block_source_size(struct reftable_block_source *source);
-
-ssize_t block_source_read_block(struct reftable_block_source *source,
-				struct reftable_block *dest, uint64_t off,
-				uint32_t size);
-void block_source_close(struct reftable_block_source *source);
-
 /* metadata for a block type */
 struct reftable_table_offsets {
 	int is_present;

t/unit-tests/t-reftable-block.c

@@ -100,7 +100,7 @@ static void t_ref_block_read_write(void)
 	block_reader_release(&br);
 	block_iter_close(&it);
 	reftable_record_release(&rec);
-	reftable_block_done(&br.block);
+	block_source_return_block(&br.block);
 	reftable_buf_release(&want);
 	reftable_buf_release(&buf);
 	for (i = 0; i < N; i++)
@@ -190,7 +190,7 @@ static void t_log_block_read_write(void)
 	block_reader_release(&br);
 	block_iter_close(&it);
 	reftable_record_release(&rec);
-	reftable_block_done(&br.block);
+	block_source_return_block(&br.block);
 	reftable_buf_release(&want);
 	reftable_buf_release(&buf);
 	for (i = 0; i < N; i++)
@@ -273,7 +273,7 @@ static void t_obj_block_read_write(void)
 	block_reader_release(&br);
 	block_iter_close(&it);
 	reftable_record_release(&rec);
-	reftable_block_done(&br.block);
+	block_source_return_block(&br.block);
 	reftable_buf_release(&want);
 	reftable_buf_release(&buf);
 	for (i = 0; i < N; i++)
@@ -365,7 +365,7 @@ static void t_index_block_read_write(void)
 	block_reader_release(&br);
 	block_iter_close(&it);
 	reftable_record_release(&rec);
-	reftable_block_done(&br.block);
+	block_source_return_block(&br.block);
 	reftable_buf_release(&want);
 	reftable_buf_release(&buf);
 	for (i = 0; i < N; i++)

t/unit-tests/t-reftable-readwrite.c

@@ -32,13 +32,13 @@ static void t_buffer(void)
 	n = block_source_read_block(&source, &out, 0, sizeof(in));
 	check_int(n, ==, sizeof(in));
 	check(!memcmp(in, out.data, n));
-	reftable_block_done(&out);
+	block_source_return_block(&out);
 
 	n = block_source_read_block(&source, &out, 1, 2);
 	check_int(n, ==, 2);
 	check(!memcmp(out.data, "el", 2));
 
-	reftable_block_done(&out);
+	block_source_return_block(&out);
 	block_source_close(&source);
 	reftable_buf_release(&buf);
 }