streaming.c - jrn/git - Git at Google

 /*
  * Copyright (c) 2011, Google Inc.
  */
 #include "cache.h"
 #include "streaming.h"

 enum input_source {
 	stream_error = -1,
 	incore = 0,
 	loose = 1,
 	pack_non_delta = 2
 };

 typedef int (*open_istream_fn)(struct git_istream *,
 			       struct object_info *,
 			       const unsigned char *,
 			       enum object_type *);
 typedef int (*close_istream_fn)(struct git_istream *);
 typedef ssize_t (*read_istream_fn)(struct git_istream *, char *, size_t);

 struct stream_vtbl {
 	close_istream_fn close;
 	read_istream_fn read;
 };

 #define open_method_decl(name) \
 	int open_istream_ ##name \
 	(struct git_istream *st, struct object_info *oi, \
 	 const unsigned char *sha1, \
 	 enum object_type *type)

 #define close_method_decl(name) \
 	int close_istream_ ##name \
 	(struct git_istream *st)

 #define read_method_decl(name) \
 	ssize_t read_istream_ ##name \
 	(struct git_istream *st, char *buf, size_t sz)

 /* forward declaration */
 static open_method_decl(incore);
 static open_method_decl(loose);
 static open_method_decl(pack_non_delta);
 static struct git_istream *attach_stream_filter(struct git_istream *st,
 						struct stream_filter *filter);


 static open_istream_fn open_istream_tbl[] = {
 	open_istream_incore,
 	open_istream_loose,
 	open_istream_pack_non_delta,
 };

 #define FILTER_BUFFER (1024*16)

 struct filtered_istream {
 	struct git_istream *upstream;
 	struct stream_filter *filter;
 	char ibuf[FILTER_BUFFER];
 	char obuf[FILTER_BUFFER];
 	int i_end, i_ptr;
 	int o_end, o_ptr;
 	int input_finished;
 };

 struct git_istream {
 	const struct stream_vtbl *vtbl;
 	unsigned long size; /* inflated size of full object */
 	git_zstream z;
 	enum { z_unused, z_used, z_done, z_error } z_state;

 	union {
 		struct {
 			char *buf; /* from read_object() */
 			unsigned long read_ptr;
 		} incore;

 		struct {
 			void *mapped;
 			unsigned long mapsize;
 			char hdr[32];
 			int hdr_avail;
 			int hdr_used;
 		} loose;

 		struct {
 			struct packed_git *pack;
 			off_t pos;
 		} in_pack;

 		struct filtered_istream filtered;
 	} u;
 };

 int close_istream(struct git_istream *st)
 {
 	int r = st->vtbl->close(st);
 	free(st);
 	return r;
 }

 ssize_t read_istream(struct git_istream *st, void *buf, size_t sz)
 {
 	return st->vtbl->read(st, buf, sz);
 }

 static enum input_source istream_source(const unsigned char *sha1,
 					enum object_type *type,
 					struct object_info *oi)
 {
 	unsigned long size;
 	int status;

 	oi->typep = type;
 	oi->sizep = &size;
 	status = sha1_object_info_extended(sha1, oi);
 	if (status < 0)
 		return stream_error;

 	switch (oi->whence) {
 	case OI_LOOSE:
 		return loose;
 	case OI_PACKED:
 		if (!oi->u.packed.is_delta && big_file_threshold < size)
 			return pack_non_delta;
 		/* fallthru */
 	default:
 		return incore;
 	}
 }

 struct git_istream *open_istream(const unsigned char *sha1,
 				 enum object_type *type,
 				 unsigned long *size,
 				 struct stream_filter *filter)
 {
 	struct git_istream *st;
 	struct object_info oi = {NULL};
 	const unsigned char *real = lookup_replace_object(sha1);
 	enum input_source src = istream_source(real, type, &oi);

 	if (src < 0)
 		return NULL;

 	st = xmalloc(sizeof(*st));
 	if (open_istream_tbl[src](st, &oi, real, type)) {
 		if (open_istream_incore(st, &oi, real, type)) {
 			free(st);
 			return NULL;
 		}
 	}
 	if (filter) {
 		/* Add "&& !is_null_stream_filter(filter)" for performance */
 		struct git_istream *nst = attach_stream_filter(st, filter);
 		if (!nst)
 			close_istream(st);
 		st = nst;
 	}

 	*size = st->size;
 	return st;
 }


 /*****************************************************************
  *
  * Common helpers
  *
  *****************************************************************/

 static void close_deflated_stream(struct git_istream *st)
 {
 	if (st->z_state == z_used)
 		git_inflate_end(&st->z);
 }


 /*****************************************************************
  *
  * Filtered stream
  *
  *****************************************************************/

 static close_method_decl(filtered)
 {
 	free_stream_filter(st->u.filtered.filter);
 	return close_istream(st->u.filtered.upstream);
 }

 static read_method_decl(filtered)
 {
 	struct filtered_istream *fs = &(st->u.filtered);
 	size_t filled = 0;

 	while (sz) {
 		/* do we already have filtered output? */
 		if (fs->o_ptr < fs->o_end) {
 			size_t to_move = fs->o_end - fs->o_ptr;
 			if (sz < to_move)
 				to_move = sz;
 			memcpy(buf + filled, fs->obuf + fs->o_ptr, to_move);
 			fs->o_ptr += to_move;
 			sz -= to_move;
 			filled += to_move;
 			continue;
 		}
 		fs->o_end = fs->o_ptr = 0;

 		/* do we have anything to feed the filter with? */
 		if (fs->i_ptr < fs->i_end) {
 			size_t to_feed = fs->i_end - fs->i_ptr;
 			size_t to_receive = FILTER_BUFFER;
 			if (stream_filter(fs->filter,
 					  fs->ibuf + fs->i_ptr, &to_feed,
 					  fs->obuf, &to_receive))
 				return -1;
 			fs->i_ptr = fs->i_end - to_feed;
 			fs->o_end = FILTER_BUFFER - to_receive;
 			continue;
 		}

 		/* tell the filter to drain upon no more input */
 		if (fs->input_finished) {
 			size_t to_receive = FILTER_BUFFER;
 			if (stream_filter(fs->filter,
 					  NULL, NULL,
 					  fs->obuf, &to_receive))
 				return -1;
 			fs->o_end = FILTER_BUFFER - to_receive;
 			if (!fs->o_end)
 				break;
 			continue;
 		}
 		fs->i_end = fs->i_ptr = 0;

 		/* refill the input from the upstream */
 		if (!fs->input_finished) {
 			fs->i_end = read_istream(fs->upstream, fs->ibuf, FILTER_BUFFER);
 			if (fs->i_end < 0)
 				return -1;
 			if (fs->i_end)
 				continue;
 		}
 		fs->input_finished = 1;
 	}
 	return filled;
 }

 static struct stream_vtbl filtered_vtbl = {
 	close_istream_filtered,
 	read_istream_filtered,
 };

 static struct git_istream *attach_stream_filter(struct git_istream *st,
 						struct stream_filter *filter)
 {
 	struct git_istream *ifs = xmalloc(sizeof(*ifs));
 	struct filtered_istream *fs = &(ifs->u.filtered);

 	ifs->vtbl = &filtered_vtbl;
 	fs->upstream = st;
 	fs->filter = filter;
 	fs->i_end = fs->i_ptr = 0;
 	fs->o_end = fs->o_ptr = 0;
 	fs->input_finished = 0;
 	ifs->size = -1; /* unknown */
 	return ifs;
 }

 /*****************************************************************
  *
  * Loose object stream
  *
  *****************************************************************/

 static read_method_decl(loose)
 {
 	size_t total_read = 0;

 	switch (st->z_state) {
 	case z_done:
 		return 0;
 	case z_error:
 		return -1;
 	default:
 		break;
 	}

 	if (st->u.loose.hdr_used < st->u.loose.hdr_avail) {
 		size_t to_copy = st->u.loose.hdr_avail - st->u.loose.hdr_used;
 		if (sz < to_copy)
 			to_copy = sz;
 		memcpy(buf, st->u.loose.hdr + st->u.loose.hdr_used, to_copy);
 		st->u.loose.hdr_used += to_copy;
 		total_read += to_copy;
 	}

 	while (total_read < sz) {
 		int status;

 		st->z.next_out = (unsigned char *)buf + total_read;
 		st->z.avail_out = sz - total_read;
 		status = git_inflate(&st->z, Z_FINISH);

 		total_read = st->z.next_out - (unsigned char *)buf;

 		if (status == Z_STREAM_END) {
 			git_inflate_end(&st->z);
 			st->z_state = z_done;
 			break;
 		}
 		if (status != Z_OK && (status != Z_BUF_ERROR || total_read < sz)) {
 			git_inflate_end(&st->z);
 			st->z_state = z_error;
 			return -1;
 		}
 	}
 	return total_read;
 }

 static close_method_decl(loose)
 {
 	close_deflated_stream(st);
 	munmap(st->u.loose.mapped, st->u.loose.mapsize);
 	return 0;
 }

 static struct stream_vtbl loose_vtbl = {
 	close_istream_loose,
 	read_istream_loose,
 };

 static open_method_decl(loose)
 {
 	st->u.loose.mapped = map_sha1_file(sha1, &st->u.loose.mapsize);
 	if (!st->u.loose.mapped)
 		return -1;
 	if (unpack_sha1_header(&st->z,
 			       st->u.loose.mapped,
 			       st->u.loose.mapsize,
 			       st->u.loose.hdr,
 			       sizeof(st->u.loose.hdr)) < 0) {
 		git_inflate_end(&st->z);
 		munmap(st->u.loose.mapped, st->u.loose.mapsize);
 		return -1;
 	}

 	parse_sha1_header(st->u.loose.hdr, &st->size);
 	st->u.loose.hdr_used = strlen(st->u.loose.hdr) + 1;
 	st->u.loose.hdr_avail = st->z.total_out;
 	st->z_state = z_used;

 	st->vtbl = &loose_vtbl;
 	return 0;
 }


 /*****************************************************************
  *
  * Non-delta packed object stream
  *
  *****************************************************************/

 static read_method_decl(pack_non_delta)
 {
 	size_t total_read = 0;

 	switch (st->z_state) {
 	case z_unused:
 		memset(&st->z, 0, sizeof(st->z));
 		git_inflate_init(&st->z);
 		st->z_state = z_used;
 		break;
 	case z_done:
 		return 0;
 	case z_error:
 		return -1;
 	case z_used:
 		break;
 	}

 	while (total_read < sz) {
 		int status;
 		struct pack_window *window = NULL;
 		unsigned char *mapped;

 		mapped = use_pack(st->u.in_pack.pack, &window,
 				  st->u.in_pack.pos, &st->z.avail_in);

 		st->z.next_out = (unsigned char *)buf + total_read;
 		st->z.avail_out = sz - total_read;
 		st->z.next_in = mapped;
 		status = git_inflate(&st->z, Z_FINISH);

 		st->u.in_pack.pos += st->z.next_in - mapped;
 		total_read = st->z.next_out - (unsigned char *)buf;
 		unuse_pack(&window);

 		if (status == Z_STREAM_END) {
 			git_inflate_end(&st->z);
 			st->z_state = z_done;
 			break;
 		}
 		if (status != Z_OK && status != Z_BUF_ERROR) {
 			git_inflate_end(&st->z);
 			st->z_state = z_error;
 			return -1;
 		}
 	}
 	return total_read;
 }

 static close_method_decl(pack_non_delta)
 {
 	close_deflated_stream(st);
 	return 0;
 }

 static struct stream_vtbl pack_non_delta_vtbl = {
 	close_istream_pack_non_delta,
 	read_istream_pack_non_delta,
 };

 static open_method_decl(pack_non_delta)
 {
 	struct pack_window *window;
 	enum object_type in_pack_type;

 	st->u.in_pack.pack = oi->u.packed.pack;
 	st->u.in_pack.pos = oi->u.packed.offset;
 	window = NULL;

 	in_pack_type = unpack_object_header(st->u.in_pack.pack,
 					    &window,
 					    &st->u.in_pack.pos,
 					    &st->size);
 	unuse_pack(&window);
 	switch (in_pack_type) {
 	default:
 		return -1; /* we do not do deltas for now */
 	case OBJ_COMMIT:
 	case OBJ_TREE:
 	case OBJ_BLOB:
 	case OBJ_TAG:
 		break;
 	}
 	st->z_state = z_unused;
 	st->vtbl = &pack_non_delta_vtbl;
 	return 0;
 }


 /*****************************************************************
  *
  * In-core stream
  *
  *****************************************************************/

 static close_method_decl(incore)
 {
 	free(st->u.incore.buf);
 	return 0;
 }

 static read_method_decl(incore)
 {
 	size_t read_size = sz;
 	size_t remainder = st->size - st->u.incore.read_ptr;

 	if (remainder <= read_size)
 		read_size = remainder;
 	if (read_size) {
 		memcpy(buf, st->u.incore.buf + st->u.incore.read_ptr, read_size);
 		st->u.incore.read_ptr += read_size;
 	}
 	return read_size;
 }

 static struct stream_vtbl incore_vtbl = {
 	close_istream_incore,
 	read_istream_incore,
 };

 static open_method_decl(incore)
 {
 	st->u.incore.buf = read_sha1_file_extended(sha1, type, &st->size, 0);
 	st->u.incore.read_ptr = 0;
 	st->vtbl = &incore_vtbl;

 	return st->u.incore.buf ? 0 : -1;
 }


 /****************************************************************
  * Users of streaming interface
  ****************************************************************/

 int stream_blob_to_fd(int fd, unsigned const char *sha1, struct stream_filter *filter,
 		      int can_seek)
 {
 	struct git_istream *st;
 	enum object_type type;
 	unsigned long sz;
 	ssize_t kept = 0;
 	int result = -1;

 	st = open_istream(sha1, &type, &sz, filter);
 	if (!st)
 		return result;
 	if (type != OBJ_BLOB)
 		goto close_and_exit;
 	for (;;) {
 		char buf[1024 * 16];
 		ssize_t wrote, holeto;
 		ssize_t readlen = read_istream(st, buf, sizeof(buf));

 		if (readlen < 0)
 			goto close_and_exit;
 		if (!readlen)
 			break;
 		if (can_seek && sizeof(buf) == readlen) {
 			for (holeto = 0; holeto < readlen; holeto++)
 				if (buf[holeto])
 					break;
 			if (readlen == holeto) {
 				kept += holeto;
 				continue;
 			}
 		}

 		if (kept && lseek(fd, kept, SEEK_CUR) == (off_t) -1)
 			goto close_and_exit;
 		else
 			kept = 0;
 		wrote = write_in_full(fd, buf, readlen);

 		if (wrote != readlen)
 			goto close_and_exit;
 	}
 	if (kept && (lseek(fd, kept - 1, SEEK_CUR) == (off_t) -1 ||
 		     write(fd, "", 1) != 1))
 		goto close_and_exit;
 	result = 0;

  close_and_exit:
 	close_istream(st);
 	return result;
 }
	/*
	* Copyright (c) 2011, Google Inc.
	*/
	#include "cache.h"
	#include "streaming.h"

	enum input_source {
	stream_error = -1,
	incore = 0,
	loose = 1,
	pack_non_delta = 2
	};

	typedef int (open_istream_fn)(struct git_istream ,
	struct object_info *,
	const unsigned char *,
	enum object_type *);
	typedef int (close_istream_fn)(struct git_istream );
	typedef ssize_t (read_istream_fn)(struct git_istream , char *, size_t);

	struct stream_vtbl {
	close_istream_fn close;
	read_istream_fn read;
	};

	#define open_method_decl(name) \
	int open_istream_ ##name \
	(struct git_istream st, struct object_info oi, \
	const unsigned char *sha1, \
	enum object_type *type)

	#define close_method_decl(name) \
	int close_istream_ ##name \
	(struct git_istream *st)

	#define read_method_decl(name) \
	ssize_t read_istream_ ##name \
	(struct git_istream st, char buf, size_t sz)

	/* forward declaration */
	static open_method_decl(incore);
	static open_method_decl(loose);
	static open_method_decl(pack_non_delta);
	static struct git_istream attach_stream_filter(struct git_istream st,
	struct stream_filter *filter);


	static open_istream_fn open_istream_tbl[] = {
	open_istream_incore,
	open_istream_loose,
	open_istream_pack_non_delta,
	};

	#define FILTER_BUFFER (1024*16)

	struct filtered_istream {
	struct git_istream *upstream;
	struct stream_filter *filter;
	char ibuf[FILTER_BUFFER];
	char obuf[FILTER_BUFFER];
	int i_end, i_ptr;
	int o_end, o_ptr;
	int input_finished;
	};

	struct git_istream {
	const struct stream_vtbl *vtbl;
	unsigned long size; /* inflated size of full object */
	git_zstream z;
	enum { z_unused, z_used, z_done, z_error } z_state;

	union {
	struct {
	char buf; / from read_object() */
	unsigned long read_ptr;
	} incore;

	struct {
	void *mapped;
	unsigned long mapsize;
	char hdr[32];
	int hdr_avail;
	int hdr_used;
	} loose;

	struct {
	struct packed_git *pack;
	off_t pos;
	} in_pack;

	struct filtered_istream filtered;
	} u;
	};

	int close_istream(struct git_istream *st)
	{
	int r = st->vtbl->close(st);
	free(st);
	return r;
	}

	ssize_t read_istream(struct git_istream st, void buf, size_t sz)
	{
	return st->vtbl->read(st, buf, sz);
	}

	static enum input_source istream_source(const unsigned char *sha1,
	enum object_type *type,
	struct object_info *oi)
	{
	unsigned long size;
	int status;

	oi->typep = type;
	oi->sizep = &size;
	status = sha1_object_info_extended(sha1, oi);
	if (status < 0)
	return stream_error;

	switch (oi->whence) {
	case OI_LOOSE:
	return loose;
	case OI_PACKED:
	if (!oi->u.packed.is_delta && big_file_threshold < size)
	return pack_non_delta;
	/* fallthru */
	default:
	return incore;
	}
	}

	struct git_istream open_istream(const unsigned char sha1,
	enum object_type *type,
	unsigned long *size,
	struct stream_filter *filter)
	{
	struct git_istream *st;
	struct object_info oi = {NULL};
	const unsigned char *real = lookup_replace_object(sha1);
	enum input_source src = istream_source(real, type, &oi);

	if (src < 0)
	return NULL;

	st = xmalloc(sizeof(*st));
	if (open_istream_tbl[src](st, &oi, real, type)) {
	if (open_istream_incore(st, &oi, real, type)) {
	free(st);
	return NULL;
	}
	}
	if (filter) {
	/* Add "&& !is_null_stream_filter(filter)" for performance */
	struct git_istream *nst = attach_stream_filter(st, filter);
	if (!nst)
	close_istream(st);
	st = nst;
	}

	*size = st->size;
	return st;
	}


	/*****************************************************************
	*
	* Common helpers
	*
	*****************************************************************/

	static void close_deflated_stream(struct git_istream *st)
	{
	if (st->z_state == z_used)
	git_inflate_end(&st->z);
	}


	/*****************************************************************
	*
	* Filtered stream
	*
	*****************************************************************/

	static close_method_decl(filtered)
	{
	free_stream_filter(st->u.filtered.filter);
	return close_istream(st->u.filtered.upstream);
	}

	static read_method_decl(filtered)
	{
	struct filtered_istream *fs = &(st->u.filtered);
	size_t filled = 0;

	while (sz) {
	/* do we already have filtered output? */
	if (fs->o_ptr < fs->o_end) {
	size_t to_move = fs->o_end - fs->o_ptr;
	if (sz < to_move)
	to_move = sz;
	memcpy(buf + filled, fs->obuf + fs->o_ptr, to_move);
	fs->o_ptr += to_move;
	sz -= to_move;
	filled += to_move;
	continue;
	}
	fs->o_end = fs->o_ptr = 0;

	/* do we have anything to feed the filter with? */
	if (fs->i_ptr < fs->i_end) {
	size_t to_feed = fs->i_end - fs->i_ptr;
	size_t to_receive = FILTER_BUFFER;
	if (stream_filter(fs->filter,
	fs->ibuf + fs->i_ptr, &to_feed,
	fs->obuf, &to_receive))
	return -1;
	fs->i_ptr = fs->i_end - to_feed;
	fs->o_end = FILTER_BUFFER - to_receive;
	continue;
	}

	/* tell the filter to drain upon no more input */
	if (fs->input_finished) {
	size_t to_receive = FILTER_BUFFER;
	if (stream_filter(fs->filter,
	NULL, NULL,
	fs->obuf, &to_receive))
	return -1;
	fs->o_end = FILTER_BUFFER - to_receive;
	if (!fs->o_end)
	break;
	continue;
	}
	fs->i_end = fs->i_ptr = 0;

	/* refill the input from the upstream */
	if (!fs->input_finished) {
	fs->i_end = read_istream(fs->upstream, fs->ibuf, FILTER_BUFFER);
	if (fs->i_end < 0)
	return -1;
	if (fs->i_end)
	continue;
	}
	fs->input_finished = 1;
	}
	return filled;
	}

	static struct stream_vtbl filtered_vtbl = {
	close_istream_filtered,
	read_istream_filtered,
	};

	static struct git_istream attach_stream_filter(struct git_istream st,
	struct stream_filter *filter)
	{
	struct git_istream ifs = xmalloc(sizeof(ifs));
	struct filtered_istream *fs = &(ifs->u.filtered);

	ifs->vtbl = &filtered_vtbl;
	fs->upstream = st;
	fs->filter = filter;
	fs->i_end = fs->i_ptr = 0;
	fs->o_end = fs->o_ptr = 0;
	fs->input_finished = 0;
	ifs->size = -1; /* unknown */
	return ifs;
	}

	/*****************************************************************
	*
	* Loose object stream
	*
	*****************************************************************/

	static read_method_decl(loose)
	{
	size_t total_read = 0;

	switch (st->z_state) {
	case z_done:
	return 0;
	case z_error:
	return -1;
	default:
	break;
	}

	if (st->u.loose.hdr_used < st->u.loose.hdr_avail) {
	size_t to_copy = st->u.loose.hdr_avail - st->u.loose.hdr_used;
	if (sz < to_copy)
	to_copy = sz;
	memcpy(buf, st->u.loose.hdr + st->u.loose.hdr_used, to_copy);
	st->u.loose.hdr_used += to_copy;
	total_read += to_copy;
	}

	while (total_read < sz) {
	int status;

	st->z.next_out = (unsigned char *)buf + total_read;
	st->z.avail_out = sz - total_read;
	status = git_inflate(&st->z, Z_FINISH);

	total_read = st->z.next_out - (unsigned char *)buf;

	if (status == Z_STREAM_END) {
	git_inflate_end(&st->z);
	st->z_state = z_done;
	break;
	}
	if (status != Z_OK && (status != Z_BUF_ERROR \|\| total_read < sz)) {
	git_inflate_end(&st->z);
	st->z_state = z_error;
	return -1;
	}
	}
	return total_read;
	}

	static close_method_decl(loose)
	{
	close_deflated_stream(st);
	munmap(st->u.loose.mapped, st->u.loose.mapsize);
	return 0;
	}

	static struct stream_vtbl loose_vtbl = {
	close_istream_loose,
	read_istream_loose,
	};

	static open_method_decl(loose)
	{
	st->u.loose.mapped = map_sha1_file(sha1, &st->u.loose.mapsize);
	if (!st->u.loose.mapped)
	return -1;
	if (unpack_sha1_header(&st->z,
	st->u.loose.mapped,
	st->u.loose.mapsize,
	st->u.loose.hdr,
	sizeof(st->u.loose.hdr)) < 0) {
	git_inflate_end(&st->z);
	munmap(st->u.loose.mapped, st->u.loose.mapsize);
	return -1;
	}

	parse_sha1_header(st->u.loose.hdr, &st->size);
	st->u.loose.hdr_used = strlen(st->u.loose.hdr) + 1;
	st->u.loose.hdr_avail = st->z.total_out;
	st->z_state = z_used;

	st->vtbl = &loose_vtbl;
	return 0;
	}


	/*****************************************************************
	*
	* Non-delta packed object stream
	*
	*****************************************************************/

	static read_method_decl(pack_non_delta)
	{
	size_t total_read = 0;

	switch (st->z_state) {
	case z_unused:
	memset(&st->z, 0, sizeof(st->z));
	git_inflate_init(&st->z);
	st->z_state = z_used;
	break;
	case z_done:
	return 0;
	case z_error:
	return -1;
	case z_used:
	break;
	}

	while (total_read < sz) {
	int status;
	struct pack_window *window = NULL;
	unsigned char *mapped;

	mapped = use_pack(st->u.in_pack.pack, &window,
	st->u.in_pack.pos, &st->z.avail_in);

	st->z.next_out = (unsigned char *)buf + total_read;
	st->z.avail_out = sz - total_read;
	st->z.next_in = mapped;
	status = git_inflate(&st->z, Z_FINISH);

	st->u.in_pack.pos += st->z.next_in - mapped;
	total_read = st->z.next_out - (unsigned char *)buf;
	unuse_pack(&window);

	if (status == Z_STREAM_END) {
	git_inflate_end(&st->z);
	st->z_state = z_done;
	break;
	}
	if (status != Z_OK && status != Z_BUF_ERROR) {
	git_inflate_end(&st->z);
	st->z_state = z_error;
	return -1;
	}
	}
	return total_read;
	}

	static close_method_decl(pack_non_delta)
	{
	close_deflated_stream(st);
	return 0;
	}

	static struct stream_vtbl pack_non_delta_vtbl = {
	close_istream_pack_non_delta,
	read_istream_pack_non_delta,
	};

	static open_method_decl(pack_non_delta)
	{
	struct pack_window *window;
	enum object_type in_pack_type;

	st->u.in_pack.pack = oi->u.packed.pack;
	st->u.in_pack.pos = oi->u.packed.offset;
	window = NULL;

	in_pack_type = unpack_object_header(st->u.in_pack.pack,
	&window,
	&st->u.in_pack.pos,
	&st->size);
	unuse_pack(&window);
	switch (in_pack_type) {
	default:
	return -1; /* we do not do deltas for now */
	case OBJ_COMMIT:
	case OBJ_TREE:
	case OBJ_BLOB:
	case OBJ_TAG:
	break;
	}
	st->z_state = z_unused;
	st->vtbl = &pack_non_delta_vtbl;
	return 0;
	}


	/*****************************************************************
	*
	* In-core stream
	*
	*****************************************************************/

	static close_method_decl(incore)
	{
	free(st->u.incore.buf);
	return 0;
	}

	static read_method_decl(incore)
	{
	size_t read_size = sz;
	size_t remainder = st->size - st->u.incore.read_ptr;

	if (remainder <= read_size)
	read_size = remainder;
	if (read_size) {
	memcpy(buf, st->u.incore.buf + st->u.incore.read_ptr, read_size);
	st->u.incore.read_ptr += read_size;
	}
	return read_size;
	}

	static struct stream_vtbl incore_vtbl = {
	close_istream_incore,
	read_istream_incore,
	};

	static open_method_decl(incore)
	{
	st->u.incore.buf = read_sha1_file_extended(sha1, type, &st->size, 0);
	st->u.incore.read_ptr = 0;
	st->vtbl = &incore_vtbl;

	return st->u.incore.buf ? 0 : -1;
	}


	/****************************************************************
	* Users of streaming interface
	****************************************************************/

	int stream_blob_to_fd(int fd, unsigned const char sha1, struct stream_filter filter,
	int can_seek)
	{
	struct git_istream *st;
	enum object_type type;
	unsigned long sz;
	ssize_t kept = 0;
	int result = -1;

	st = open_istream(sha1, &type, &sz, filter);
	if (!st)
	return result;
	if (type != OBJ_BLOB)
	goto close_and_exit;
	for (;;) {
	char buf[1024 * 16];
	ssize_t wrote, holeto;
	ssize_t readlen = read_istream(st, buf, sizeof(buf));

	if (readlen < 0)
	goto close_and_exit;
	if (!readlen)
	break;
	if (can_seek && sizeof(buf) == readlen) {
	for (holeto = 0; holeto < readlen; holeto++)
	if (buf[holeto])
	break;
	if (readlen == holeto) {
	kept += holeto;
	continue;
	}
	}

	if (kept && lseek(fd, kept, SEEK_CUR) == (off_t) -1)
	goto close_and_exit;
	else
	kept = 0;
	wrote = write_in_full(fd, buf, readlen);

	if (wrote != readlen)
	goto close_and_exit;
	}
	if (kept && (lseek(fd, kept - 1, SEEK_CUR) == (off_t) -1 \|\|
	write(fd, "", 1) != 1))
	goto close_and_exit;
	result = 0;

	close_and_exit:
	close_istream(st);
	return result;
	}