indexer: move the temporary buffers into the indexer object

Storing 4kB or 8kB in the stack is not very gentle. As this part has
to be linear, put the buffer into the indexer object so we allocate it
once in the heap.

src/indexer.c

@@ -55,6 +55,7 @@ struct git_indexer_stream {
 	git_oid hash;
 	git_transfer_progress_callback progress_cb;
 	void *progress_payload;
+	char objbuf[8*1024];
 };
 
 struct delta_info {
@@ -204,18 +205,17 @@ static void hash_header(git_hash_ctx *ctx, git_off_t len, git_otype type)
 	git_hash_update(ctx, buffer, hdrlen);
 }
 
-static int hash_object_stream(git_hash_ctx *ctx, git_packfile_stream *stream)
+static int hash_object_stream(git_indexer_stream *idx, git_packfile_stream *stream)
 {
-	char buffer[8*1024];
 	ssize_t read;
 
-	assert(ctx && stream);
+	assert(idx && stream);
 
 	do {
-		if ((read = git_packfile_stream_read(stream, buffer, sizeof(buffer))) < 0)
+		if ((read = git_packfile_stream_read(stream, idx->objbuf, sizeof(idx->objbuf))) < 0)
 			break;
 
-		git_hash_update(ctx, buffer, read);
+		git_hash_update(&idx->hash_ctx, idx->objbuf, read);
 	} while (read > 0);
 
 	if (read < 0)
@@ -244,15 +244,14 @@ static int advance_delta_offset(git_indexer_stream *idx, git_otype type)
 }
 
 /* Read from the stream and discard any output */
-static int read_object_stream(git_packfile_stream *stream)
+static int read_object_stream(git_indexer_stream *idx, git_packfile_stream *stream)
 {
-	char buffer[4*1024];
 	ssize_t read;
 
 	assert(stream);
 
 	do {
-		read = git_packfile_stream_read(stream, buffer, sizeof(buffer));
+		read = git_packfile_stream_read(stream, idx->objbuf, sizeof(idx->objbuf));
 	} while (read > 0);
 
 	if (read < 0)
@@ -507,9 +506,9 @@ int git_indexer_stream_add(git_indexer_stream *idx, const void *data, size_t siz
 		}
 
 		if (idx->have_delta) {
-			error = read_object_stream(stream);
+			error = read_object_stream(idx, stream);
 		} else {
-			error = hash_object_stream(&idx->hash_ctx, stream);
+			error = hash_object_stream(idx, stream);
 		}
 
 		idx->off = stream->curpos;