bulk-checkin: replace fast-import based implementation

This extends the earlier approach to stream a large file directly from the
filesystem to its own packfile, and allows "git add" to send large files
directly into a single pack. Older code used to spawn fast-import, but the
new bulk-checkin API replaces it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

bulk-checkin.c

@@ -0,0 +1,275 @@
+/*
+ * Copyright (c) 2011, Google Inc.
+ */
+#include "bulk-checkin.h"
+#include "csum-file.h"
+#include "pack.h"
+
+static int pack_compression_level = Z_DEFAULT_COMPRESSION;
+
+static struct bulk_checkin_state {
+	unsigned plugged:1;
+
+	char *pack_tmp_name;
+	struct sha1file *f;
+	off_t offset;
+	struct pack_idx_option pack_idx_opts;
+
+	struct pack_idx_entry **written;
+	uint32_t alloc_written;
+	uint32_t nr_written;
+} state;
+
+static void finish_bulk_checkin(struct bulk_checkin_state *state)
+{
+	unsigned char sha1[20];
+	char packname[PATH_MAX];
+	int i;
+
+	if (!state->f)
+		return;
+
+	if (state->nr_written == 0) {
+		close(state->f->fd);
+		unlink(state->pack_tmp_name);
+		goto clear_exit;
+	} else if (state->nr_written == 1) {
+		sha1close(state->f, sha1, CSUM_FSYNC);
+	} else {
+		int fd = sha1close(state->f, sha1, 0);
+		fixup_pack_header_footer(fd, sha1, state->pack_tmp_name,
+					 state->nr_written, sha1,
+					 state->offset);
+		close(fd);
+	}
+
+	sprintf(packname, "%s/pack/pack-", get_object_directory());
+	finish_tmp_packfile(packname, state->pack_tmp_name,
+			    state->written, state->nr_written,
+			    &state->pack_idx_opts, sha1);
+	for (i = 0; i < state->nr_written; i++)
+		free(state->written[i]);
+
+clear_exit:
+	free(state->written);
+	memset(state, 0, sizeof(*state));
+
+	/* Make objects we just wrote available to ourselves */
+	reprepare_packed_git();
+}
+
+static int already_written(struct bulk_checkin_state *state, unsigned char sha1[])
+{
+	int i;
+
+	/* The object may already exist in the repository */
+	if (has_sha1_file(sha1))
+		return 1;
+
+	/* Might want to keep the list sorted */
+	for (i = 0; i < state->nr_written; i++)
+		if (!hashcmp(state->written[i]->sha1, sha1))
+			return 1;
+
+	/* This is a new object we need to keep */
+	return 0;
+}
+
+/*
+ * Read the contents from fd for size bytes, streaming it to the
+ * packfile in state while updating the hash in ctx. Signal a failure
+ * by returning a negative value when the resulting pack would exceed
+ * the pack size limit and this is not the first object in the pack,
+ * so that the caller can discard what we wrote from the current pack
+ * by truncating it and opening a new one. The caller will then call
+ * us again after rewinding the input fd.
+ *
+ * The already_hashed_to pointer is kept untouched by the caller to
+ * make sure we do not hash the same byte when we are called
+ * again. This way, the caller does not have to checkpoint its hash
+ * status before calling us just in case we ask it to call us again
+ * with a new pack.
+ */
+static int stream_to_pack(struct bulk_checkin_state *state,
+			  git_SHA_CTX *ctx, off_t *already_hashed_to,
+			  int fd, size_t size, enum object_type type,
+			  const char *path, unsigned flags)
+{
+	git_zstream s;
+	unsigned char obuf[16384];
+	unsigned hdrlen;
+	int status = Z_OK;
+	int write_object = (flags & HASH_WRITE_OBJECT);
+	off_t offset = 0;
+
+	memset(&s, 0, sizeof(s));
+	git_deflate_init(&s, pack_compression_level);
+
+	hdrlen = encode_in_pack_object_header(type, size, obuf);
+	s.next_out = obuf + hdrlen;
+	s.avail_out = sizeof(obuf) - hdrlen;
+
+	while (status != Z_STREAM_END) {
+		unsigned char ibuf[16384];
+
+		if (size && !s.avail_in) {
+			ssize_t rsize = size < sizeof(ibuf) ? size : sizeof(ibuf);
+			if (xread(fd, ibuf, rsize) != rsize)
+				die("failed to read %d bytes from '%s'",
+				    (int)rsize, path);
+			offset += rsize;
+			if (*already_hashed_to < offset) {
+				size_t hsize = offset - *already_hashed_to;
+				if (rsize < hsize)
+					hsize = rsize;
+				if (hsize)
+					git_SHA1_Update(ctx, ibuf, hsize);
+				*already_hashed_to = offset;
+			}
+			s.next_in = ibuf;
+			s.avail_in = rsize;
+			size -= rsize;
+		}
+
+		status = git_deflate(&s, size ? 0 : Z_FINISH);
+
+		if (!s.avail_out || status == Z_STREAM_END) {
+			if (write_object) {
+				size_t written = s.next_out - obuf;
+
+				/* would we bust the size limit? */
+				if (state->nr_written &&
+				    pack_size_limit_cfg &&
+				    pack_size_limit_cfg < state->offset + written) {
+					git_deflate_abort(&s);
+					return -1;
+				}
+
+				sha1write(state->f, obuf, written);
+				state->offset += written;
+			}
+			s.next_out = obuf;
+			s.avail_out = sizeof(obuf);
+		}
+
+		switch (status) {
+		case Z_OK:
+		case Z_BUF_ERROR:
+		case Z_STREAM_END:
+			continue;
+		default:
+			die("unexpected deflate failure: %d", status);
+		}
+	}
+	git_deflate_end(&s);
+	return 0;
+}
+
+/* Lazily create backing packfile for the state */
+static void prepare_to_stream(struct bulk_checkin_state *state,
+			      unsigned flags)
+{
+	if (!(flags & HASH_WRITE_OBJECT) || state->f)
+		return;
+
+	state->f = create_tmp_packfile(&state->pack_tmp_name);
+	reset_pack_idx_option(&state->pack_idx_opts);
+
+	/* Pretend we are going to write only one object */
+	state->offset = write_pack_header(state->f, 1);
+	if (!state->offset)
+		die_errno("unable to write pack header");
+}
+
+static int deflate_to_pack(struct bulk_checkin_state *state,
+			   unsigned char result_sha1[],
+			   int fd, size_t size,
+			   enum object_type type, const char *path,
+			   unsigned flags)
+{
+	off_t seekback, already_hashed_to;
+	git_SHA_CTX ctx;
+	unsigned char obuf[16384];
+	unsigned header_len;
+	struct sha1file_checkpoint checkpoint;
+	struct pack_idx_entry *idx = NULL;
+
+	seekback = lseek(fd, 0, SEEK_CUR);
+	if (seekback == (off_t) -1)
+		return error("cannot find the current offset");
+
+	header_len = sprintf((char *)obuf, "%s %" PRIuMAX,
+			     typename(type), (uintmax_t)size) + 1;
+	git_SHA1_Init(&ctx);
+	git_SHA1_Update(&ctx, obuf, header_len);
+
+	/* Note: idx is non-NULL when we are writing */
+	if ((flags & HASH_WRITE_OBJECT) != 0)
+		idx = xcalloc(1, sizeof(*idx));
+
+	already_hashed_to = 0;
+
+	while (1) {
+		prepare_to_stream(state, flags);
+		if (idx) {
+			sha1file_checkpoint(state->f, &checkpoint);
+			idx->offset = state->offset;
+			crc32_begin(state->f);
+		}
+		if (!stream_to_pack(state, &ctx, &already_hashed_to,
+				    fd, size, type, path, flags))
+			break;
+		/*
+		 * Writing this object to the current pack will make
+		 * it too big; we need to truncate it, start a new
+		 * pack, and write into it.
+		 */
+		if (!idx)
+			die("BUG: should not happen");
+		sha1file_truncate(state->f, &checkpoint);
+		state->offset = checkpoint.offset;
+		finish_bulk_checkin(state);
+		if (lseek(fd, seekback, SEEK_SET) == (off_t) -1)
+			return error("cannot seek back");
+	}
+	git_SHA1_Final(result_sha1, &ctx);
+	if (!idx)
+		return 0;
+
+	idx->crc32 = crc32_end(state->f);
+	if (already_written(state, result_sha1)) {
+		sha1file_truncate(state->f, &checkpoint);
+		state->offset = checkpoint.offset;
+		free(idx);
+	} else {
+		hashcpy(idx->sha1, result_sha1);
+		ALLOC_GROW(state->written,
+			   state->nr_written + 1,
+			   state->alloc_written);
+		state->written[state->nr_written++] = idx;
+	}
+	return 0;
+}
+
+int index_bulk_checkin(unsigned char *sha1,
+		       int fd, size_t size, enum object_type type,
+		       const char *path, unsigned flags)
+{
+	int status = deflate_to_pack(&state, sha1, fd, size, type,
+				     path, flags);
+	if (!state.plugged)
+		finish_bulk_checkin(&state);
+	return status;
+}
+
+void plug_bulk_checkin(void)
+{
+	state.plugged = 1;
+}
+
+void unplug_bulk_checkin(void)
+{
+	state.plugged = 0;
+	if (state.f)
+		finish_bulk_checkin(&state);
+}