/*
 * GIT - The information manager from hell
 *
 * Copyright (C) Linus Torvalds, 2005
 *
 * This handles basic git object files - packing, unpacking,
 * creation etc.
 */

#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"
#include "config.h"
#include "convert.h"
#include "dir.h"
#include "environment.h"
#include "fsck.h"
#include "gettext.h"
#include "hex.h"
#include "loose.h"
#include "object-file-convert.h"
#include "object-file.h"
#include "odb.h"
#include "odb/streaming.h"
#include "odb/transaction.h"
#include "pack.h"
#include "packfile.h"
#include "path.h"
#include "read-cache-ll.h"
#include "run-command.h"
#include "setup.h"
#include "strvec.h"
#include "tempfile.h"
#include "tmp-objdir.h"

static int get_conv_flags(unsigned flags)
{
	if (flags & INDEX_RENORMALIZE)
		return CONV_EOL_RENORMALIZE;
	else if (flags & INDEX_WRITE_OBJECT)
		return global_conv_flags_eol | CONV_WRITE_OBJECT;
	else
		return 0;
}

static void fill_loose_path(struct strbuf *buf,
			    const struct object_id *oid,
			    const struct git_hash_algo *algop)
{
	for (size_t i = 0; i < algop->rawsz; i++) {
		static char hex[] = "0123456789abcdef";
		unsigned int val = oid->hash[i];
		strbuf_addch(buf, hex[val >> 4]);
		strbuf_addch(buf, hex[val & 0xf]);
		if (!i)
			strbuf_addch(buf, '/');
	}
}

const char *odb_loose_path(struct odb_source_loose *loose,
			   struct strbuf *buf,
			   const struct object_id *oid)
{
	strbuf_reset(buf);
	strbuf_addstr(buf, loose->base.path);
	strbuf_addch(buf, '/');
	fill_loose_path(buf, oid, loose->base.odb->repo->hash_algo);
	return buf->buf;
}

/* Returns 1 if we have successfully freshened the file, 0 otherwise. */
static int freshen_file(const char *fn, const time_t *mtime)
{
	struct utimbuf times, *timesp = NULL;

	if (mtime) {
		times.actime = *mtime;
		times.modtime = *mtime;
		timesp = &times;
	}

	return !utime(fn, timesp);
}

/*
 * All of the check_and_freshen functions return 1 if the file exists and was
 * freshened (if freshening was requested), 0 otherwise. If they return
 * 0, you should not assume that it is safe to skip a write of the object (it
 * either does not exist on disk, or has a stale mtime and may be subject to
 * pruning).
 */
int check_and_freshen_file(const char *fn, int freshen,
			   const time_t *mtime)
{
	if (access(fn, F_OK))
		return 0;
	if (freshen && !freshen_file(fn, mtime))
		return 0;
	return 1;
}

int format_object_header(char *str, size_t size, enum object_type type,
			 size_t objsize)
{
	const char *name = type_name(type);

	if (!name)
		BUG("could not get a type name for 'enum object_type' value %d", type);

	return xsnprintf(str, size, "%s %"PRIuMAX, name, (uintmax_t)objsize) + 1;
}

int check_object_signature(struct repository *r, const struct object_id *oid,
			   void *buf, unsigned long size,
			   enum object_type type)
{
	const struct git_hash_algo *algo =
		oid->algo ? &hash_algos[oid->algo] : r->hash_algo;
	struct object_id real_oid;

	hash_object_file(algo, buf, size, type, &real_oid);

	return !oideq(oid, &real_oid) ? -1 : 0;
}

int stream_object_signature(struct repository *r,
			    struct odb_stream *st,
			    const struct object_id *oid)
{
	struct object_id real_oid;
	struct git_hash_ctx c;
	char hdr[MAX_HEADER_LEN];
	int hdrlen;

	/* Generate the header */
	hdrlen = format_object_header(hdr, sizeof(hdr), st->type, st->size);

	/* Sha1.. */
	git_hash_init(&c, r->hash_algo);
	git_hash_update(&c, hdr, hdrlen);
	for (;;) {
		char buf[1024 * 16];
		ssize_t readlen = odb_stream_read(st, buf, sizeof(buf));
		if (readlen < 0)
			return -1;
		if (!readlen)
			break;
		git_hash_update(&c, buf, readlen);
	}
	git_hash_final_oid(&real_oid, &c);
	return !oideq(oid, &real_oid) ? -1 : 0;
}

/*
 * Map and close the given loose object fd. The path argument is used for
 * error reporting.
 */
static void *map_fd(int fd, const char *path, unsigned long *size)
{
	void *map = NULL;
	struct stat st;

	if (!fstat(fd, &st)) {
		*size = xsize_t(st.st_size);
		if (!*size) {
			/* mmap() is forbidden on empty files */
			error(_("object file %s is empty"), path);
			close(fd);
			return NULL;
		}
		map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
	}
	close(fd);
	return map;
}

enum unpack_loose_header_result unpack_loose_header(git_zstream *stream,
						    unsigned char *map,
						    unsigned long mapsize,
						    void *buffer,
						    unsigned long bufsiz)
{
	int status;

	/* Get the data stream */
	memset(stream, 0, sizeof(*stream));
	stream->next_in = map;
	stream->avail_in = mapsize;
	stream->next_out = buffer;
	stream->avail_out = bufsiz;

	git_inflate_init(stream);
	obj_read_unlock();
	status = git_inflate(stream, 0);
	obj_read_lock();
	if (status != Z_OK && status != Z_STREAM_END)
		return ULHR_BAD;

	/*
	 * Check if entire header is unpacked in the first iteration.
	 */
	if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
		return ULHR_OK;

	/*
	 * We have a header longer than MAX_HEADER_LEN.
	 */
	return ULHR_TOO_LONG;
}

void *unpack_loose_rest(git_zstream *stream,
			void *buffer, unsigned long size,
			const struct object_id *oid)
{
	size_t bytes = strlen(buffer) + 1, n;
	unsigned char *buf = xmallocz(size);
	int status = Z_OK;

	n = stream->total_out - bytes;
	if (n > size)
		n = size;
	memcpy(buf, (char *) buffer + bytes, n);
	bytes = n;
	if (bytes <= size) {
		/*
		 * The above condition must be (bytes <= size), not
		 * (bytes < size).  In other words, even though we
		 * expect no more output and set avail_out to zero,
		 * the input zlib stream may have bytes that express
		 * "this concludes the stream", and we *do* want to
		 * eat that input.
		 *
		 * Otherwise we would not be able to test that we
		 * consumed all the input to reach the expected size;
		 * we also want to check that zlib tells us that all
		 * went well with status == Z_STREAM_END at the end.
		 */
		stream->next_out = buf + bytes;
		stream->avail_out = size - bytes;
		while (status == Z_OK) {
			obj_read_unlock();
			status = git_inflate(stream, Z_FINISH);
			obj_read_lock();
		}
	}

	if (status != Z_STREAM_END) {
		error(_("corrupt loose object '%s'"), oid_to_hex(oid));
		FREE_AND_NULL(buf);
	} else if (stream->avail_in) {
		error(_("garbage at end of loose object '%s'"),
		      oid_to_hex(oid));
		FREE_AND_NULL(buf);
	}

	return buf;
}

/*
 * parse_loose_header() parses the starting "<type> <len>\0" of an
 * object. If it doesn't follow that format -1 is returned. To check
 * the validity of the <type> populate the "typep" in the "struct
 * object_info". It will be OBJ_BAD if the object type is unknown. The
 * parsed <len> can be retrieved via "oi->sizep", and from there
 * passed to unpack_loose_rest().
 *
 * We used to just use "sscanf()", but that's actually way
 * too permissive for what we want to check. So do an anal
 * object header parse by hand.
 */
int parse_loose_header(const char *hdr, struct object_info *oi)
{
	const char *type_buf = hdr;
	size_t size;
	int type, type_len = 0;

	/*
	 * The type can be of any size but is followed by
	 * a space.
	 */
	for (;;) {
		char c = *hdr++;
		if (!c)
			return -1;
		if (c == ' ')
			break;
		type_len++;
	}

	type = type_from_string_gently(type_buf, type_len, 1);
	if (oi->typep)
		*oi->typep = type;

	/*
	 * The length must follow immediately, and be in canonical
	 * decimal format (ie "010" is not valid).
	 */
	size = *hdr++ - '0';
	if (size > 9)
		return -1;
	if (size) {
		for (;;) {
			unsigned long c = *hdr - '0';
			if (c > 9)
				break;
			hdr++;
			size = st_add(st_mult(size, 10), c);
		}
	}

	if (oi->sizep)
		*oi->sizep = size;

	/*
	 * The length must be followed by a zero byte
	 */
	if (*hdr)
		return -1;

	/*
	 * The format is valid, but the type may still be bogus. The
	 * Caller needs to check its oi->typep.
	 */
	return 0;
}

#define CHECK_COLLISION_DEST_VANISHED -2

static int check_collision(const char *source, const char *dest)
{
	char buf_source[4096], buf_dest[4096];
	int fd_source = -1, fd_dest = -1;
	int ret = 0;

	fd_source = open(source, O_RDONLY);
	if (fd_source < 0) {
		ret = error_errno(_("unable to open %s"), source);
		goto out;
	}

	fd_dest = open(dest, O_RDONLY);
	if (fd_dest < 0) {
		if (errno != ENOENT)
			ret = error_errno(_("unable to open %s"), dest);
		else
			ret = CHECK_COLLISION_DEST_VANISHED;
		goto out;
	}

	while (1) {
		ssize_t sz_a, sz_b;

		sz_a = read_in_full(fd_source, buf_source, sizeof(buf_source));
		if (sz_a < 0) {
			ret = error_errno(_("unable to read %s"), source);
			goto out;
		}

		sz_b = read_in_full(fd_dest, buf_dest, sizeof(buf_dest));
		if (sz_b < 0) {
			ret = error_errno(_("unable to read %s"), dest);
			goto out;
		}

		if (sz_a != sz_b || memcmp(buf_source, buf_dest, sz_a)) {
			ret = error(_("files '%s' and '%s' differ in contents"),
				    source, dest);
			goto out;
		}

		if ((size_t) sz_a < sizeof(buf_source))
			break;
	}

out:
	if (fd_source > -1)
		close(fd_source);
	if (fd_dest > -1)
		close(fd_dest);
	return ret;
}

/*
 * Move the just written object into its final resting place.
 */
int finalize_object_file(struct repository *repo,
			 const char *tmpfile, const char *filename)
{
	return finalize_object_file_flags(repo, tmpfile, filename, 0);
}

int finalize_object_file_flags(struct repository *repo,
			       const char *tmpfile, const char *filename,
			       enum finalize_object_file_flags flags)
{
	unsigned retries = 0;
	int ret;
	struct repo_config_values *cfg = repo_config_values(repo);

retry:
	ret = 0;

	if (cfg->object_creation_mode == OBJECT_CREATION_USES_RENAMES)
		goto try_rename;
	else if (link(tmpfile, filename))
		ret = errno;
	else
		unlink_or_warn(tmpfile);

	/*
	 * Coda hack - coda doesn't like cross-directory links,
	 * so we fall back to a rename, which will mean that it
	 * won't be able to check collisions, but that's not a
	 * big deal.
	 *
	 * The same holds for FAT formatted media.
	 *
	 * When this succeeds, we just return.  We have nothing
	 * left to unlink.
	 */
	if (ret && ret != EEXIST) {
		struct stat st;

	try_rename:
		if (!stat(filename, &st))
			ret = EEXIST;
		else if (!rename(tmpfile, filename))
			goto out;
		else
			ret = errno;
	}
	if (ret) {
		if (ret != EEXIST) {
			int saved_errno = errno;
			unlink_or_warn(tmpfile);
			errno = saved_errno;
			return error_errno(_("unable to write file %s"), filename);
		}
		if (!(flags & FOF_SKIP_COLLISION_CHECK)) {
			ret = check_collision(tmpfile, filename);
			if (ret == CHECK_COLLISION_DEST_VANISHED) {
				if (retries++ > 5)
					return error(_("unable to write repeatedly vanishing file %s"),
						     filename);
				goto retry;
			}
			else if (ret)
				return -1;
		}
		unlink_or_warn(tmpfile);
	}

out:
	if (adjust_shared_perm(repo, filename))
		return error(_("unable to set permission to '%s'"), filename);
	return 0;
}

void hash_object_file(const struct git_hash_algo *algo, const void *buf,
		      size_t len, enum object_type type,
		      struct object_id *oid)
{
	struct git_hash_ctx c;
	char hdr[MAX_HEADER_LEN];
	int hdrlen;

	hdrlen = format_object_header(hdr, sizeof(hdr), type, len);

	git_hash_init(&c, algo);
	git_hash_update(&c, hdr, hdrlen);
	git_hash_update(&c, buf, len);
	git_hash_final_oid(oid, &c);
}

struct transaction_packfile {
	char *pack_tmp_name;
	struct hashfile *f;
	off_t offset;
	struct pack_idx_option pack_idx_opts;

	struct pack_idx_entry **written;
	uint32_t alloc_written;
	uint32_t nr_written;
};

struct odb_transaction_files {
	struct odb_transaction base;
	enum odb_transaction_flags flags;

	struct tmp_objdir *objdir;
	struct transaction_packfile packfile;
	const char *prefix;

	struct tempfile **pack_lockfiles;
	size_t pack_lockfiles_nr;
	size_t pack_lockfiles_alloc;
};

int odb_transaction_files_prepare(struct odb_transaction *base)
{
	struct odb_transaction_files *transaction =
		container_of_or_null(base, struct odb_transaction_files, base);

	/*
	 * We lazily create the temporary object directory
	 * the first time an object might be added, since
	 * callers may not know whether any objects will be
	 * added at the time they call odb_transaction_files_begin.
	 */
	if (!transaction || transaction->objdir)
		return 0;

	transaction->objdir = tmp_objdir_create(base->source->odb->repo, transaction->prefix, 0);
	if (!transaction->objdir)
		return error(_("unable to create temporary object directory"));

	return 0;
}

void odb_transaction_files_fsync(struct odb_transaction *base,
				 int fd, const char *filename)
{
	struct odb_transaction_files *transaction =
		container_of_or_null(base, struct odb_transaction_files, base);

	if (!transaction || !transaction->objdir) {
		fsync_or_die(fd, filename);
		return;
	}

	/*
	 * If we have an active ODB transaction, we issue a call that
	 * cleans the filesystem page cache but avoids a hardware flush
	 * command. Later on we will issue a single hardware flush
	 * before renaming the objects to their final names as part of
	 * flush_batch_fsync.
	 */
	if (git_fsync(fd, FSYNC_WRITEOUT_ONLY) < 0) {
		if (errno == ENOSYS)
			warning(_("core.fsyncMethod = batch is unsupported on this platform"));
		fsync_or_die(fd, filename);
	}
}

/*
 * We can't use the normal fsck_error_function() for index_mem(),
 * because we don't yet have a valid oid for it to report. Instead,
 * report the minimal fsck error here, and rely on the caller to
 * give more context.
 */
static int hash_format_check_report(struct fsck_options *opts UNUSED,
				    void *fsck_report UNUSED,
				    enum fsck_msg_type msg_type UNUSED,
				    enum fsck_msg_id msg_id UNUSED,
				    const char *message)
{
	error(_("object fails fsck: %s"), message);
	return 1;
}

static int index_mem(struct index_state *istate,
		     struct object_id *oid,
		     const void *buf, size_t size,
		     enum object_type type,
		     const char *path, unsigned flags)
{
	struct strbuf nbuf = STRBUF_INIT;
	int ret = 0;
	int write_object = flags & INDEX_WRITE_OBJECT;

	if (!type)
		type = OBJ_BLOB;

	/*
	 * Convert blobs to git internal format
	 */
	if ((type == OBJ_BLOB) && path) {
		if (convert_to_git(istate, path, buf, size, &nbuf,
				   get_conv_flags(flags))) {
			buf = nbuf.buf;
			size = nbuf.len;
		}
	}
	if (flags & INDEX_FORMAT_CHECK) {
		struct fsck_options opts;

		fsck_options_init(&opts, the_repository, FSCK_OPTIONS_DEFAULT);
		opts.strict = 1;
		opts.error_func = hash_format_check_report;
		if (fsck_buffer(null_oid(istate->repo->hash_algo), type, buf, size, &opts))
			die(_("refusing to create malformed object"));
		fsck_finish(&opts);
	}

	if (write_object)
		ret = odb_write_object(istate->repo->objects, buf, size, type, oid);
	else
		hash_object_file(istate->repo->hash_algo, buf, size, type, oid);

	strbuf_release(&nbuf);
	return ret;
}

static int index_stream_convert_blob(struct index_state *istate,
				     struct object_id *oid,
				     int fd,
				     const char *path,
				     unsigned flags)
{
	int ret = 0;
	const int write_object = flags & INDEX_WRITE_OBJECT;
	struct strbuf sbuf = STRBUF_INIT;

	assert(path);
	ASSERT(would_convert_to_git_filter_fd(istate, path));

	convert_to_git_filter_fd(istate, path, fd, &sbuf,
				 get_conv_flags(flags));

	if (write_object)
		ret = odb_write_object(istate->repo->objects, sbuf.buf, sbuf.len, OBJ_BLOB,
				       oid);
	else
		hash_object_file(istate->repo->hash_algo, sbuf.buf, sbuf.len, OBJ_BLOB,
				 oid);
	strbuf_release(&sbuf);
	return ret;
}

static int index_pipe(struct index_state *istate, struct object_id *oid,
		      int fd, enum object_type type,
		      const char *path, unsigned flags)
{
	struct strbuf sbuf = STRBUF_INIT;
	int ret;

	if (strbuf_read(&sbuf, fd, 4096) >= 0)
		ret = index_mem(istate, oid, sbuf.buf, sbuf.len, type, path, flags);
	else
		ret = -1;
	strbuf_release(&sbuf);
	return ret;
}

#define SMALL_FILE_SIZE (32*1024)

static int index_core(struct index_state *istate,
		      struct object_id *oid, int fd, size_t size,
		      enum object_type type, const char *path,
		      unsigned flags)
{
	int ret;

	if (!size) {
		ret = index_mem(istate, oid, "", size, type, path, flags);
	} else if (size <= SMALL_FILE_SIZE) {
		char *buf = xmalloc(size);
		ssize_t read_result = read_in_full(fd, buf, size);
		if (read_result < 0)
			ret = error_errno(_("read error while indexing %s"),
					  path ? path : "<unknown>");
		else if ((size_t) read_result != size)
			ret = error(_("short read while indexing %s"),
				    path ? path : "<unknown>");
		else
			ret = index_mem(istate, oid, buf, size, type, path, flags);
		free(buf);
	} else {
		void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
		ret = index_mem(istate, oid, buf, size, type, path, flags);
		munmap(buf, size);
	}
	return ret;
}

static int already_written(struct odb_transaction_files *transaction,
			   struct object_id *oid)
{
	/* The object may already exist in the repository */
	if (odb_has_object(transaction->base.source->odb, oid,
			   ODB_HAS_OBJECT_RECHECK_PACKED | ODB_HAS_OBJECT_FETCH_PROMISOR))
		return 1;

	/* Might want to keep the list sorted */
	for (uint32_t i = 0; i < transaction->packfile.nr_written; i++)
		if (oideq(&transaction->packfile.written[i]->oid, oid))
			return 1;

	/* This is a new object we need to keep */
	return 0;
}

/* Lazily create backing packfile for the state */
static void prepare_packfile_transaction(struct odb_transaction_files *transaction)
{
	struct transaction_packfile *state = &transaction->packfile;
	if (state->f)
		return;

	state->f = create_tmp_packfile(transaction->base.source->odb->repo,
				       &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 hash_stream(struct odb_stream *stream,
		       const struct git_hash_algo *hash_algo,
		       struct object_id *result_oid)
{
	unsigned char buf[16384];
	struct git_hash_ctx ctx;
	unsigned header_len;
	size_t bytes_hashed = 0;

	header_len = format_object_header((char *)buf, sizeof(buf),
					  stream->type, stream->size);
	git_hash_init(&ctx, hash_algo);
	git_hash_update(&ctx, buf, header_len);

	while (1) {
		ssize_t read_result = odb_stream_read(stream, buf,
						      sizeof(buf));
		if (read_result < 0)
			return -1;
		if (!read_result)
			break;

		git_hash_update(&ctx, buf, read_result);
		bytes_hashed += read_result;
	}

	if (bytes_hashed != stream->size)
		return -1;

	git_hash_final_oid(result_oid, &ctx);

	return 0;
}

/*
 * Read the contents from the stream provided, streaming it to the
 * packfile in state while updating the hash in ctx.
 */
static void stream_to_pack(struct transaction_packfile *state,
			   struct git_hash_ctx *ctx,
			   struct odb_stream *stream)
{
	git_zstream s;
	unsigned char ibuf[16384];
	unsigned char obuf[16384];
	unsigned hdrlen;
	int status = Z_OK;
	struct repo_config_values *cfg = repo_config_values(the_repository);
	bool is_finished = false;
	size_t bytes_read = 0;

	git_deflate_init(&s, cfg->pack_compression_level);

	hdrlen = encode_in_pack_object_header(obuf, sizeof(obuf), stream->type, stream->size);
	s.next_out = obuf + hdrlen;
	s.avail_out = sizeof(obuf) - hdrlen;

	while (status != Z_STREAM_END) {
		if (!is_finished && !s.avail_in) {
			ssize_t rsize = odb_stream_read(stream, ibuf,
							sizeof(ibuf));
			if (rsize < 0)
				die("failed to read object data");
			if (!rsize)
				is_finished = true;

			git_hash_update(ctx, ibuf, rsize);

			s.next_in = ibuf;
			s.avail_in = rsize;
			bytes_read += rsize;
		}

		status = git_deflate(&s, is_finished ? Z_FINISH : 0);

		if (!s.avail_out || status == Z_STREAM_END) {
			size_t written = s.next_out - obuf;

			hashwrite(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);
		}
	}

	if (bytes_read != stream->size)
		die("read %" PRIuMAX " bytes of object data, but expected %" PRIuMAX " bytes",
		    (uintmax_t)bytes_read, (uintmax_t)stream->size);

	git_deflate_end(&s);
}

static void flush_packfile_transaction(struct odb_transaction_files *transaction)
{
	struct transaction_packfile *state = &transaction->packfile;
	struct repository *repo = transaction->base.source->odb->repo;
	unsigned char hash[GIT_MAX_RAWSZ];
	struct strbuf packname = STRBUF_INIT;
	char *idx_tmp_name = NULL;

	if (!state->f)
		return;

	if (state->nr_written == 0) {
		close(state->f->fd);
		free_hashfile(state->f);
		unlink(state->pack_tmp_name);
		goto clear_exit;
	} else if (state->nr_written == 1) {
		finalize_hashfile(state->f, hash, FSYNC_COMPONENT_PACK,
				  CSUM_HASH_IN_STREAM | CSUM_FSYNC | CSUM_CLOSE);
	} else {
		int fd = finalize_hashfile(state->f, hash, FSYNC_COMPONENT_PACK, 0);
		fixup_pack_header_footer(repo->hash_algo, fd, hash, state->pack_tmp_name,
					 state->nr_written, hash,
					 state->offset);
		close(fd);
	}

	strbuf_addf(&packname, "%s/pack/pack-%s.",
		    repo_get_object_directory(transaction->base.source->odb->repo),
		    hash_to_hex_algop(hash, repo->hash_algo));

	stage_tmp_packfiles(repo, &packname, state->pack_tmp_name,
			    state->written, state->nr_written, NULL,
			    &state->pack_idx_opts, hash, &idx_tmp_name);
	rename_tmp_packfile_idx(repo, &packname, &idx_tmp_name);

	for (uint32_t i = 0; i < state->nr_written; i++)
		free(state->written[i]);

clear_exit:
	free(idx_tmp_name);
	free(state->pack_tmp_name);
	free(state->written);
	memset(state, 0, sizeof(*state));

	strbuf_release(&packname);
}

/*
 * This writes the specified object to a packfile. Objects written here
 * during the same transaction are written to the same packfile. The
 * packfile is not flushed until the transaction is flushed. The caller
 * is expected to ensure a valid transaction is setup for objects to be
 * recorded to.
 *
 * This also bypasses the usual "convert-to-git" dance, and that is on
 * purpose. We could write a streaming version of the converting
 * functions and insert that before feeding the data to fast-import
 * (or equivalent in-core API described above). However, that is
 * somewhat complicated, as we do not know the size of the filter
 * result, which we need to know beforehand when writing a git object.
 * Since the primary motivation for trying to stream from the working
 * tree file and to avoid mmaping it in core is to deal with large
 * objects, they generally do not want to get any conversion, and
 * callers should avoid this code path when filters are requested.
 */
static int odb_transaction_files_write_object_stream(struct odb_transaction *base,
						     struct odb_stream *stream,
						     struct object_id *result_oid)
{
	struct odb_transaction_files *transaction = container_of(base,
								 struct odb_transaction_files,
								 base);
	struct transaction_packfile *state = &transaction->packfile;
	struct git_hash_ctx ctx;
	unsigned char obuf[16384];
	unsigned header_len;
	struct hashfile_checkpoint checkpoint;
	struct pack_idx_entry *idx;

	header_len = format_object_header((char *)obuf, sizeof(obuf),
					  stream->type, stream->size);
	git_hash_init(&ctx, transaction->base.source->odb->repo->hash_algo);
	git_hash_update(&ctx, obuf, header_len);

	/*
	 * If writing another object to the packfile could result in it
	 * exceeding the configured size limit, flush the current packfile
	 * transaction.
	 *
	 * Note that this uses the inflated object size as an approximation.
	 * Blob objects written in this manner are not delta-compressed, so
	 * the difference between the inflated and on-disk size is limited
	 * to zlib compression and is sufficient for this check.
	 */
	if (state->nr_written && pack_size_limit_cfg &&
	    pack_size_limit_cfg < state->offset + stream->size) {
		flush_packfile_transaction(transaction);
		odb_reprepare(transaction->base.source->odb);
	}

	CALLOC_ARRAY(idx, 1);
	prepare_packfile_transaction(transaction);
	hashfile_checkpoint_init(state->f, &checkpoint);

	hashfile_checkpoint(state->f, &checkpoint);
	idx->offset = state->offset;
	crc32_begin(state->f);
	stream_to_pack(state, &ctx, stream);
	git_hash_final_oid(result_oid, &ctx);

	idx->crc32 = crc32_end(state->f);
	if (already_written(transaction, result_oid)) {
		hashfile_truncate(state->f, &checkpoint);
		state->offset = checkpoint.offset;
		free(idx);
	} else {
		oidcpy(&idx->oid, result_oid);
		ALLOC_GROW(state->written,
			   state->nr_written + 1,
			   state->alloc_written);
		state->written[state->nr_written++] = idx;
	}

	hashfile_checkpoint_release(&checkpoint);
	return 0;
}

int index_fd(struct index_state *istate, struct object_id *oid,
	     int fd, struct stat *st,
	     enum object_type type, const char *path, unsigned flags)
{
	int ret;

	/*
	 * Call xsize_t() only when needed to avoid potentially unnecessary
	 * die() for large files.
	 */
	if (type == OBJ_BLOB && path && would_convert_to_git_filter_fd(istate, path)) {
		ret = index_stream_convert_blob(istate, oid, fd, path, flags);
	} else if (!S_ISREG(st->st_mode)) {
		ret = index_pipe(istate, oid, fd, type, path, flags);
	} else if ((st->st_size >= 0 &&
		    (size_t)st->st_size <= repo_settings_get_big_file_threshold(istate->repo)) ||
		   type != OBJ_BLOB ||
		   (path && would_convert_to_git(istate, path))) {
		ret = index_core(istate, oid, fd, xsize_t(st->st_size),
				 type, path, flags);
	} else {
		struct odb_stream *stream = odb_stream_from_fd(fd, xsize_t(st->st_size),
							       OBJ_BLOB);

		if (flags & INDEX_WRITE_OBJECT) {
			struct object_database *odb = the_repository->objects;
			struct odb_transaction *transaction = odb->transaction;
			int inflight = !!transaction;

			if (!inflight)
				odb_transaction_begin_or_die(odb, &transaction, 0);
			ret = odb_transaction_write_object_stream(transaction,
								  stream, oid);
			if (!inflight)
				odb_transaction_commit_and_finalize_or_die(transaction);
		} else {
			ret = hash_stream(stream, the_repository->hash_algo, oid);
		}

		odb_stream_close(stream);
	}

	close(fd);
	return ret;
}

int index_path(struct index_state *istate, struct object_id *oid,
	       const char *path, struct stat *st, unsigned flags)
{
	int fd;
	struct strbuf sb = STRBUF_INIT;
	int rc = 0;

	switch (st->st_mode & S_IFMT) {
	case S_IFREG:
		fd = open(path, O_RDONLY);
		if (fd < 0)
			return error_errno("open(\"%s\")", path);
		if (index_fd(istate, oid, fd, st, OBJ_BLOB, path, flags) < 0)
			return error(_("%s: failed to insert into database"),
				     path);
		break;
	case S_IFLNK:
		if (strbuf_readlink(&sb, path, st->st_size))
			return error_errno("readlink(\"%s\")", path);
		if (!(flags & INDEX_WRITE_OBJECT))
			hash_object_file(istate->repo->hash_algo, sb.buf, sb.len,
					 OBJ_BLOB, oid);
		else if (odb_write_object(istate->repo->objects, sb.buf, sb.len, OBJ_BLOB, oid))
			rc = error(_("%s: failed to insert into database"), path);
		strbuf_release(&sb);
		break;
	case S_IFDIR:
		if (repo_resolve_gitlink_ref(istate->repo, path, "HEAD", oid))
			return error(_("'%s' does not have a commit checked out"), path);
		if (&hash_algos[oid->algo] != istate->repo->hash_algo)
			return error(_("cannot add a submodule of a different hash algorithm"));
		break;
	default:
		return error(_("%s: unsupported file type"), path);
	}
	return rc;
}

int read_pack_header(int fd, struct pack_header *header)
{
	if (read_in_full(fd, header, sizeof(*header)) != sizeof(*header))
		/* "eof before pack header was fully read" */
		return PH_ERROR_EOF;

	if (header->hdr_signature != htonl(PACK_SIGNATURE))
		/* "protocol error (pack signature mismatch detected)" */
		return PH_ERROR_PACK_SIGNATURE;
	if (!pack_version_ok(header->hdr_version))
		/* "protocol error (pack version unsupported)" */
		return PH_ERROR_PROTOCOL;
	return 0;
}

int for_each_file_in_obj_subdir(unsigned int subdir_nr,
				struct strbuf *path,
				const struct git_hash_algo *algop,
				each_loose_object_fn obj_cb,
				each_loose_cruft_fn cruft_cb,
				each_loose_subdir_fn subdir_cb,
				void *data)
{
	size_t origlen, baselen;
	DIR *dir;
	struct dirent *de;
	int r = 0;
	struct object_id oid;

	if (subdir_nr > 0xff)
		BUG("invalid loose object subdirectory: %x", subdir_nr);

	origlen = path->len;
	strbuf_complete(path, '/');
	strbuf_addf(path, "%02x", subdir_nr);

	dir = opendir(path->buf);
	if (!dir) {
		if (errno != ENOENT)
			r = error_errno(_("unable to open %s"), path->buf);
		strbuf_setlen(path, origlen);
		return r;
	}

	oid.hash[0] = subdir_nr;
	strbuf_addch(path, '/');
	baselen = path->len;

	while ((de = readdir_skip_dot_and_dotdot(dir))) {
		size_t namelen;

		namelen = strlen(de->d_name);
		strbuf_setlen(path, baselen);
		strbuf_add(path, de->d_name, namelen);
		if (namelen == algop->hexsz - 2 &&
		    !hex_to_bytes(oid.hash + 1, de->d_name,
				  algop->rawsz - 1)) {
			oid_set_algo(&oid, algop);
			memset(oid.hash + algop->rawsz, 0,
			       GIT_MAX_RAWSZ - algop->rawsz);
			if (obj_cb) {
				r = obj_cb(&oid, path->buf, data);
				if (r)
					break;
			}
			continue;
		}

		if (cruft_cb) {
			r = cruft_cb(de->d_name, path->buf, data);
			if (r)
				break;
		}
	}
	closedir(dir);

	strbuf_setlen(path, baselen - 1);
	if (!r && subdir_cb)
		r = subdir_cb(subdir_nr, path->buf, data);

	strbuf_setlen(path, origlen);

	return r;
}

int for_each_loose_file_in_source(struct odb_source *source,
				  each_loose_object_fn obj_cb,
				  each_loose_cruft_fn cruft_cb,
				  each_loose_subdir_fn subdir_cb,
				  void *data)
{
	struct strbuf buf = STRBUF_INIT;
	int r;

	strbuf_addstr(&buf, source->path);
	for (int i = 0; i < 256; i++) {
		r = for_each_file_in_obj_subdir(i, &buf, source->odb->repo->hash_algo,
						obj_cb, cruft_cb, subdir_cb, data);
		if (r)
			break;
	}

	strbuf_release(&buf);
	return r;
}

static int check_stream_oid(git_zstream *stream,
			    const char *hdr,
			    unsigned long size,
			    const char *path,
			    const struct object_id *expected_oid,
			    const struct git_hash_algo *algop)
{
	struct git_hash_ctx c;
	struct object_id real_oid;
	unsigned char buf[4096];
	unsigned long total_read;
	int status = Z_OK;

	git_hash_init(&c, algop);
	git_hash_update(&c, hdr, stream->total_out);

	/*
	 * We already read some bytes into hdr, but the ones up to the NUL
	 * do not count against the object's content size.
	 */
	total_read = stream->total_out - strlen(hdr) - 1;

	/*
	 * This size comparison must be "<=" to read the final zlib packets;
	 * see the comment in unpack_loose_rest for details.
	 */
	while (total_read <= size &&
	       (status == Z_OK ||
		(status == Z_BUF_ERROR && !stream->avail_out))) {
		stream->next_out = buf;
		stream->avail_out = sizeof(buf);
		if (size - total_read < stream->avail_out)
			stream->avail_out = size - total_read;
		status = git_inflate(stream, Z_FINISH);
		git_hash_update(&c, buf, stream->next_out - buf);
		total_read += stream->next_out - buf;
	}

	if (status != Z_STREAM_END) {
		error(_("corrupt loose object '%s'"), oid_to_hex(expected_oid));
		git_hash_discard(&c);
		return -1;
	}
	if (stream->avail_in) {
		error(_("garbage at end of loose object '%s'"),
		      oid_to_hex(expected_oid));
		git_hash_discard(&c);
		return -1;
	}

	git_hash_final_oid(&real_oid, &c);
	if (!oideq(expected_oid, &real_oid)) {
		error(_("hash mismatch for %s (expected %s)"), path,
		      oid_to_hex(expected_oid));
		return -1;
	}

	return 0;
}

int read_loose_object(struct repository *repo,
		      const char *path,
		      const struct object_id *expected_oid,
		      struct object_id *real_oid,
		      void **contents,
		      struct object_info *oi)
{
	int ret = -1;
	int fd;
	void *map = NULL;
	unsigned long mapsize;
	git_zstream stream;
	char hdr[MAX_HEADER_LEN];
	size_t *size = oi->sizep;

	fd = git_open(path);
	if (fd >= 0)
		map = map_fd(fd, path, &mapsize);
	if (!map) {
		error_errno(_("unable to mmap %s"), path);
		goto out;
	}

	if (unpack_loose_header(&stream, map, mapsize, hdr, sizeof(hdr)) != ULHR_OK) {
		error(_("unable to unpack header of %s"), path);
		goto out_inflate;
	}

	if (parse_loose_header(hdr, oi) < 0) {
		error(_("unable to parse header of %s"), path);
		goto out_inflate;
	}

	if (*oi->typep < 0) {
		error(_("unable to parse type from header '%s' of %s"),
		      hdr, path);
		goto out_inflate;
	}

	if (*oi->typep == OBJ_BLOB &&
	    *size > repo_settings_get_big_file_threshold(repo)) {
		if (check_stream_oid(&stream, hdr, *size, path, expected_oid,
				     repo->hash_algo) < 0)
			goto out_inflate;
	} else {
		*contents = unpack_loose_rest(&stream, hdr, *size, expected_oid);
		if (!*contents) {
			error(_("unable to unpack contents of %s"), path);
			goto out_inflate;
		}
		hash_object_file(repo->hash_algo,
				 *contents, *size,
				 *oi->typep, real_oid);
		if (!oideq(expected_oid, real_oid))
			goto out_inflate;
	}

	ret = 0; /* everything checks out */

out_inflate:
	git_inflate_end(&stream);
out:
	if (map)
		munmap(map, mapsize);
	return ret;
}

static int odb_transaction_files_commit(struct odb_transaction *base)
{
	struct odb_transaction_files *transaction =
		container_of(base, struct odb_transaction_files, base);
	int have_packfile = !!transaction->packfile.f;

	flush_packfile_transaction(transaction);

	if (transaction->objdir) {
		struct strbuf temp_path = STRBUF_INIT;
		struct tempfile *temp;

		/*
		 * Issue a full hardware flush against a temporary file to ensure
		 * that all objects are durable before any renames occur. The code in
		 * odb_transaction_files_fsync has already issued a writeout
		 * request, but it has not flushed any writeback cache in the storage
		 * hardware or any filesystem logs. This fsync call acts as a barrier
		 * to ensure that the data in each new object file is durable before
		 * the final name is visible.
		 */
		strbuf_addf(&temp_path, "%s/bulk_fsync_XXXXXX",
			    repo_get_object_directory(transaction->base.source->odb->repo));
		temp = xmks_tempfile(temp_path.buf);
		fsync_or_die(get_tempfile_fd(temp), get_tempfile_path(temp));
		delete_tempfile(&temp);
		strbuf_release(&temp_path);

		/*
		 * Make the object files visible in the primary ODB after their data is
		 * fully durable.
		 */
		if (tmp_objdir_migrate(transaction->objdir))
			return error(_("unable to migrate temporary objects"));

		transaction->objdir = NULL;
	}

	if (have_packfile)
		odb_reprepare(transaction->base.source->odb);

	return 0;
}

static const char *parse_pack_header(struct pack_header *hdr, int pack_fd)
{
	switch (read_pack_header(pack_fd, hdr)) {
	case PH_ERROR_EOF:
		return "eof before pack header was fully read";

	case PH_ERROR_PACK_SIGNATURE:
		return "protocol error (pack signature mismatch detected)";

	case PH_ERROR_PROTOCOL:
		return "protocol error (pack version unsupported)";

	default:
		return "unknown error in parse_pack_header";

	case 0:
		return NULL;
	}
}

static void push_header_arg(struct strvec *args, struct pack_header *hdr)
{
	strvec_pushf(args, "--pack_header=%"PRIu32",%"PRIu32,
		     ntohl(hdr->hdr_version), ntohl(hdr->hdr_entries));
}

static unsigned int get_unpack_limit(struct repository *repo,
				     enum odb_transaction_flags flags)
{
	unsigned int limit = 0;

	if (flags & ODB_TRANSACTION_RECEIVE) {
		limit = 100;
		repo_config_get_uint(repo, "transfer.unpacklimit", &limit);
		repo_config_get_uint(repo, "receive.unpacklimit", &limit);
	}

	return limit;
}

static int odb_transaction_files_write_pack(struct odb_transaction *base,
					    int pack_fd, struct strbuf *err_msg,
					    const struct odb_transaction_write_pack_opts *opts)
{
	struct odb_transaction_files *transaction =
		container_of(base, struct odb_transaction_files, base);
	struct repository *repo = base->source->odb->repo;
	struct child_process child = CHILD_PROCESS_INIT;
	struct pack_header hdr;
	const char *hdr_err;
	int err_fd = opts->err_fd;
	int status;

	hdr_err = parse_pack_header(&hdr, pack_fd);
	if (hdr_err) {
		if (err_fd > 0)
			close(err_fd);
		strbuf_addstr(err_msg, hdr_err);
		return -1;
	}

	if (opts->shallow_file) {
		strvec_push(&child.args, "--shallow-file");
		strvec_push(&child.args, opts->shallow_file);
	}

	odb_transaction_env(base, &child.env);

	if (ntohl(hdr.hdr_entries) < get_unpack_limit(repo, transaction->flags)) {
		strvec_push(&child.args, "unpack-objects");
		push_header_arg(&child.args, &hdr);
		if (opts->quiet)
			strvec_push(&child.args, "-q");
		if (opts->fsck_objects)
			strvec_pushf(&child.args, "--strict%s",
				     opts->fsck_msg_types);
		if (opts->max_input_size)
			strvec_pushf(&child.args, "--max-input-size=%"PRIuMAX,
				     (uintmax_t)opts->max_input_size);
		child.no_stdout = 1;
		child.in = pack_fd;
		child.err = err_fd;
		child.git_cmd = 1;
		status = run_command(&child);
		if (status) {
			strbuf_addstr(err_msg, "unpack-objects abnormal exit");
			return -1;
		}
	} else {
		char hostname[HOST_NAME_MAX + 1];
		char *lockfile;

		strvec_pushl(&child.args, "index-pack", "--stdin", NULL);
		push_header_arg(&child.args, &hdr);

		if (xgethostname(hostname, sizeof(hostname)))
			xsnprintf(hostname, sizeof(hostname), "localhost");
		strvec_pushf(&child.args,
			     "--keep=receive-pack %"PRIuMAX" on %s",
			     (uintmax_t)getpid(),
			     hostname);

		if (!opts->quiet && err_fd)
			strvec_push(&child.args, "--show-resolving-progress");
		if (err_fd)
			strvec_push(&child.args, "--report-end-of-input");
		if (opts->fsck_objects)
			strvec_pushf(&child.args, "--strict%s",
				     opts->fsck_msg_types);
		if (!opts->reject_thin)
			strvec_push(&child.args, "--fix-thin");
		if (opts->max_input_size)
			strvec_pushf(&child.args, "--max-input-size=%"PRIuMAX,
				     (uintmax_t)opts->max_input_size);
		child.out = -1;
		child.in = pack_fd;
		child.err = err_fd;
		child.git_cmd = 1;
		status = start_command(&child);
		if (status) {
			strbuf_addstr(err_msg, "index-pack fork failed");
			return -1;
		}

		/*
		 * The lockfile filepath is expected to be the final location of
		 * the ".keep" file after being migrated to the main ODB source.
		 * This ensures the lockfile can be found and removed later
		 * after the ODB transaction has been committed.
		 */
		lockfile = index_pack_lockfile(base->source, child.out, NULL);
		if (lockfile) {
			ALLOC_GROW(transaction->pack_lockfiles,
				   transaction->pack_lockfiles_nr + 1,
				   transaction->pack_lockfiles_alloc);
			transaction->pack_lockfiles[transaction->pack_lockfiles_nr++] =
				register_tempfile(lockfile);
			free(lockfile);
		}
		close(child.out);

		status = finish_command(&child);
		if (status) {
			strbuf_addstr(err_msg, "index-pack abnormal exit");
			return -1;
		}

		odb_source_prepare(base->source, ODB_PREPARE_FLUSH_CACHES);
	}

	return 0;
}

static int odb_transaction_files_finalize(struct odb_transaction *base)
{
	struct odb_transaction_files *transaction =
		container_of(base, struct odb_transaction_files, base);
	int ret = 0;

	for (size_t i = 0; i < transaction->pack_lockfiles_nr; i++)
		ret |= delete_tempfile(&transaction->pack_lockfiles[i]);

	free(transaction->pack_lockfiles);

	return ret;
}

static int odb_transaction_files_env(struct odb_transaction *base,
				     struct strvec *env)
{
	struct odb_transaction_files *transaction =
		container_of(base, struct odb_transaction_files, base);
	int ret;

	ret = odb_transaction_files_prepare(&transaction->base);
	if (!ret)
		strvec_pushv(env, tmp_objdir_env(transaction->objdir));

	return ret;
}

int odb_transaction_files_begin(struct odb_source *source,
				struct odb_transaction **out,
				enum odb_transaction_flags flags)
{
	struct odb_transaction_files *transaction;

	transaction = xcalloc(1, sizeof(*transaction));
	transaction->base.source = source;
	transaction->base.commit = odb_transaction_files_commit;
	transaction->base.finalize = odb_transaction_files_finalize;
	transaction->base.write_object_stream = odb_transaction_files_write_object_stream;
	transaction->base.write_pack = odb_transaction_files_write_pack;
	transaction->base.env = odb_transaction_files_env;
	transaction->flags = flags;

	transaction->prefix = "bulk-fsync";
	if (flags & ODB_TRANSACTION_RECEIVE) {
		/*
		 * ODB transactions for git-receive-pack(1) eagerly create a
		 * temporary directory and use a different temporary directory
		 * prefix.
		 *
		 * NEEDSWORK: This transaction flag is only used by the "files"
		 * backend to special case temporary directory set up and
		 * handling. Ideally transaction users should not have to care
		 * though. To avoid this, we could eagerly create the temporary
		 * directory and use the same prefix name for all transactions.
		 */
		transaction->prefix = "incoming";
		if (odb_transaction_files_prepare(&transaction->base)) {
			free(transaction);
			return -1;
		}
	}

	*out = &transaction->base;

	return 0;
}