[PATCH 00/11] writing out a huge blob to working tree

@@ -33,9 +33,9 @@ static void show_pack_info(struct packed_git *p, unsigned int flags)
 		if (!sha1)
 			die("internal error pack-check nth-packed-object");
 		offset = nth_packed_object_offset(p, i);
-		type = packed_object_info_detail(p, offset, &size, &store_size,
+		type = typename(packed_object_info_detail(p, offset, &size, &store_size,
 						 &delta_chain_length,
-						 base_sha1);
+						 base_sha1));
 		if (!stat_only)
 			printf("%s ", sha1_to_hex(sha1));
 		if (!delta_chain_length) {

@@ -1020,7 +1020,7 @@ extern off_t find_pack_entry_one(const unsigned char *, struct packed_git *);
 extern void *unpack_entry(struct packed_git *, off_t, enum object_type *, unsigned long *);
 extern unsigned long unpack_object_header_buffer(const unsigned char *buf, unsigned long len, enum object_type *type, unsigned long *sizep);
 extern unsigned long get_size_from_delta(struct packed_git *, struct pack_window **, off_t);
-extern const char *packed_object_info_detail(struct packed_git *, off_t, unsigned long *, unsigned long *, unsigned int *, unsigned char *);
+extern int packed_object_info_detail(struct packed_git *, off_t, unsigned long *, unsigned long *, unsigned int *, unsigned char *);
 
 /* Dumb servers support */
 extern int update_server_info(int);

@@ -1549,7 +1549,7 @@ static int unpack_object_header(struct packed_git *p,
 	return type;
 }
 
-const char *packed_object_info_detail(struct packed_git *p,
+int packed_object_info_detail(struct packed_git *p,
 				      off_t obj_offset,
 				      unsigned long *size,
 				      unsigned long *store_size,

@@ -1580,7 +1580,7 @@ const char *packed_object_info_detail(struct packed_git *p,
 		case OBJ_BLOB:
 		case OBJ_TAG:
 			unuse_pack(&w_curs);
-			return typename(type);
+			return type;
 		case OBJ_OFS_DELTA:
 			obj_offset = get_delta_base(p, &w_curs, &curpos, type, obj_offset);
 			if (!obj_offset)

@@ -552,6 +552,7 @@ LIB_H += sha1-lookup.h
 LIB_H += sideband.h
 LIB_H += sigchain.h
 LIB_H += strbuf.h
+LIB_H += streaming.h
 LIB_H += string-list.h
 LIB_H += submodule.h
 LIB_H += tag.h

@@ -657,6 +658,7 @@ LIB_OBJS += shallow.o
 LIB_OBJS += sideband.o
 LIB_OBJS += sigchain.o
 LIB_OBJS += strbuf.o
+LIB_OBJS += streaming.o
 LIB_OBJS += string-list.o
 LIB_OBJS += submodule.o
 LIB_OBJS += symlinks.o

@@ -0,0 +1,196 @@
+#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 *, unsigned long *);
+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, unsigned long *sz)
+
+#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 open_istream_fn open_istream_tbl[] = {
+	open_istream_incore,
+	open_istream_loose,
+	open_istream_pack_non_delta,
+};
+
+struct git_istream {
+	enum input_source source;
+	const struct stream_vtbl *vtbl;
+	union {
+		struct {
+			char *buf; /* from read_object() */
+			unsigned long sz;
+			unsigned long read_ptr;
+		} incore;
+
+		struct {
+			int fd; /* open for reading */
+			/* NEEDSWORK: what else? */
+		} loose;
+
+		struct {
+			int fd; /* open for reading */
+			/* NEEDSWORK: what else? */
+		} in_pack;
+	} u;
+};
+
+int close_istream(struct git_istream *st)
+{
+	return st->vtbl->close(st);
+}
+
+ssize_t read_istream(struct git_istream *st, char *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->sizep = &size;
+	oi->want_deltainfo = 1;
+
+	status = sha1_object_info_extended(sha1, oi);
+	if (status < 0)
+		return stream_error;
+	*type = status;
+
+	switch (oi->whence) {
+	case OI_LOOSE:
+		return loose;
+	case OI_PACKED:
+		if (!oi->u.packed.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 *sz)
+{
+	struct git_istream *st;
+	struct object_info oi;
+	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));
+	st->source = src;
+	if (open_istream_tbl[src](st, &oi, real, type, sz)) {
+		if (open_istream_incore(st, &oi, real, type, sz)) {
+			free(st);
+			st = NULL;
+		}
+	}
+	return st;
+}
+
+/*****************************************************************
+ *
+ * Loose object stream
+ *
+ *****************************************************************/
+
+static open_method_decl(loose)
+{
+	return -1; /* for now */
+}
+
+
+/*****************************************************************
+ *
+ * Non-delta packed object stream
+ *
+ *****************************************************************/
+
+static open_method_decl(pack_non_delta)
+{
+	return -1; /* for now */
+}
+
+
+/*****************************************************************
+ *
+ * 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->u.incore.sz - 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, sz, 0);
+	st->u.incore.read_ptr = 0;
+	st->u.incore.sz = *sz;
+	st->vtbl = &incore_vtbl;
+
+	if (!st->u.incore.buf) {
+		free(st->u.incore.buf);
+		return -1;
+	}
+	return 0;
+}

@@ -0,0 +1,12 @@
+#ifndef STREAMING_H
+#define STREAMING_H 1
+#include "cache.h"
+
+/* opaque */
+struct git_istream;
+
+extern struct git_istream *open_istream(const unsigned char *, enum object_type *, unsigned long *);
+extern int close_istream(struct git_istream *);
+extern ssize_t read_istream(struct git_istream *, char *, size_t);
+
+#endif /* STREAMING_H */

@@ -91,6 +91,29 @@ static void *read_blob_entry(struct cache_entry *ce, unsigned long *size)
 	return NULL;
 }
 
+static int open_output_fd(char *path, struct cache_entry *ce, int to_tempfile)
+{
+	int symlink = (ce->ce_mode & S_IFMT) != S_IFREG;
+	if (to_tempfile) {
+		strcpy(path, symlink
+		       ? ".merge_link_XXXXXX" : ".merge_file_XXXXXX");
+		return mkstemp(path);
+	} else {
+		return create_file(path, !symlink ? ce->ce_mode : 0666);
+	}
+}
+
+static int fstat_output(int fd, const struct checkout *state, struct stat *st)
+{
+	/* use fstat() only when path == ce->name */
+	if (fstat_is_reliable() &&
+	    state->refresh_cache && !state->base_dir_len) {
+		fstat(fd, st);
+		return 1;
+	}
+	return 0;
+}
+
 static int write_entry(struct cache_entry *ce, char *path, const struct checkout *state, int to_tempfile)
 {
 	unsigned int ce_mode_s_ifmt = ce->ce_mode & S_IFMT;

@@ -128,17 +151,7 @@ static int write_entry(struct cache_entry *ce, char *path, const struct checkout
 			size = newsize;
 		}
 
-		if (to_tempfile) {
-			if (ce_mode_s_ifmt == S_IFREG)
-				strcpy(path, ".merge_file_XXXXXX");
-			else
-				strcpy(path, ".merge_link_XXXXXX");
-			fd = mkstemp(path);
-		} else if (ce_mode_s_ifmt == S_IFREG) {
-			fd = create_file(path, ce->ce_mode);
-		} else {
-			fd = create_file(path, 0666);
-		}
+		fd = open_output_fd(path, ce, to_tempfile);
 		if (fd < 0) {
 			free(new);
 			return error("unable to create file %s (%s)",

@@ -146,12 +159,8 @@ static int write_entry(struct cache_entry *ce, char *path, const struct checkout
 		}
 
 		wrote = write_in_full(fd, new, size);
-		/* use fstat() only when path == ce->name */
-		if (fstat_is_reliable() &&
-		    state->refresh_cache && !to_tempfile && !state->base_dir_len) {
-			fstat(fd, &st);
-			fstat_done = 1;
-		}
+		if (!to_tempfile)
+			fstat_done = fstat_output(fd, state, &st);
 		close(fd);
 		free(new);
 		if (wrote != size)

@@ -1021,6 +1021,7 @@ extern void *unpack_entry(struct packed_git *, off_t, enum object_type *, unsign
 extern unsigned long unpack_object_header_buffer(const unsigned char *buf, unsigned long len, enum object_type *type, unsigned long *sizep);
 extern unsigned long get_size_from_delta(struct packed_git *, struct pack_window **, off_t);
 extern int packed_object_info_detail(struct packed_git *, off_t, unsigned long *, unsigned long *, unsigned int *, unsigned char *);
+extern int unpack_object_header(struct packed_git *, struct pack_window **, off_t *, unsigned long *);
 
 struct object_info {
 	/* Request */

@@ -1523,10 +1523,10 @@ static int packed_delta_info(struct packed_git *p,
 	return type;
 }
 
-static int unpack_object_header(struct packed_git *p,
-				struct pack_window **w_curs,
-				off_t *curpos,
-				unsigned long *sizep)
+int unpack_object_header(struct packed_git *p,
+			 struct pack_window **w_curs,
+			 off_t *curpos,
+			 unsigned long *sizep)
 {
 	unsigned char *base;
 	unsigned int left;

@@ -1031,7 +1031,8 @@ struct object_info {
 	enum {
 		OI_CACHED,
 		OI_LOOSE,
-		OI_PACKED
+		OI_PACKED,
+		OI_DBCACHED,
 	} whence;
 	union {
 		/*

@@ -1695,6 +1695,13 @@ static unsigned long pack_entry_hash(struct packed_git *p, off_t base_offset)
 	return hash % MAX_DELTA_CACHE;
 }
 
+static int in_delta_base_cache(struct packed_git *p, off_t base_offset)
+{
+	unsigned long hash = pack_entry_hash(p, base_offset);
+	struct delta_base_cache_entry *ent = delta_base_cache + hash;
+	return (ent->data && ent->p == p && ent->base_offset == base_offset);
+}
+
 static void *cache_or_unpack_entry(struct packed_git *p, off_t base_offset,
 	unsigned long *base_size, enum object_type *type, int keep_cache)
 {

@@ -2141,6 +2148,8 @@ int sha1_object_info_extended(const unsigned char *sha1, struct object_info *oi)
 	if (status < 0) {
 		mark_bad_packed_object(e.p, sha1);
 		status = sha1_object_info_extended(sha1, oi);
+	} else if (in_delta_base_cache(e.p, e.offset)) {
+		oi->whence = OI_CACHED;
 	} else {
 		oi->whence = OI_PACKED;
 		oi->u.packed.offset = e.offset;

@@ -1022,6 +1022,35 @@ extern unsigned long unpack_object_header_buffer(const unsigned char *buf, unsig
 extern unsigned long get_size_from_delta(struct packed_git *, struct pack_window **, off_t);
 extern int packed_object_info_detail(struct packed_git *, off_t, unsigned long *, unsigned long *, unsigned int *, unsigned char *);
 
+struct object_info {
+	/* Request */
+	unsigned long *sizep;
+	int want_deltainfo;
+
+	/* Response */
+	enum {
+		OI_CACHED,
+		OI_LOOSE,
+		OI_PACKED
+	} whence;
+	union {
+		/*
+		 * struct {
+		 * 	... Nothing to expose in this case
+		 * } cached;
+		 * struct {
+		 * 	... Nothing to expose in this case
+		 * } loose;
+		 */
+		struct {
+			off_t offset;
+			unsigned int delta;
+			struct packed_git *pack;
+		} packed;
+	} u;
+};
+extern int sha1_object_info_extended(const unsigned char *, struct object_info *);
+
 /* Dumb servers support */
 extern int update_server_info(int);
 

@@ -2093,7 +2093,8 @@ static int sha1_loose_object_info(const unsigned char *sha1, unsigned long *size
 	return status;
 }
 
-int sha1_object_info(const unsigned char *sha1, unsigned long *sizep)
+/* returns enum object_type or negative */
+int sha1_object_info_extended(const unsigned char *sha1, struct object_info *oi)
 {
 	struct cached_object *co;
 	struct pack_entry e;

@@ -2101,16 +2102,19 @@ int sha1_object_info(const unsigned char *sha1, unsigned long *sizep)
 
 	co = find_cached_object(sha1);
 	if (co) {
-		if (sizep)
-			*sizep = co->size;
+		if (oi->sizep)
+			*(oi->sizep) = co->size;
+		oi->whence = OI_CACHED;
 		return co->type;
 	}
 
 	if (!find_pack_entry(sha1, &e)) {
 		/* Most likely it's a loose object. */
-		status = sha1_loose_object_info(sha1, sizep);
-		if (status >= 0)
+		status = sha1_loose_object_info(sha1, oi->sizep);
+		if (status >= 0) {
+			oi->whence = OI_LOOSE;
 			return status;
+		}
 
 		/* Not a loose object; someone else may have just packed it. */
 		reprepare_packed_git();

@@ -2118,15 +2122,43 @@ int sha1_object_info(const unsigned char *sha1, unsigned long *sizep)
 			return status;
 	}
 
-	status = packed_object_info(e.p, e.offset, sizep);
+	if (!oi->want_deltainfo) {
+		status = packed_object_info(e.p, e.offset, oi->sizep);
+	} else {
+		unsigned long size, store_size;
+		unsigned int delta_chain_length;
+		unsigned char base_sha1[20];
+		status = packed_object_info_detail(e.p, e.offset,
+						   &size, &store_size,
+						   &delta_chain_length,
+						   base_sha1);
+		if (0 <= status) {
+			if (oi->sizep)
+				*oi->sizep = size;
+			oi->u.packed.delta = delta_chain_length;
+		}
+	}
 	if (status < 0) {
 		mark_bad_packed_object(e.p, sha1);
-		status = sha1_object_info(sha1, sizep);
+		status = sha1_object_info_extended(sha1, oi);
+	} else {
+		oi->whence = OI_PACKED;
+		oi->u.packed.offset = e.offset;
+		oi->u.packed.pack = e.p;
 	}
 
 	return status;
 }
 
+int sha1_object_info(const unsigned char *sha1, unsigned long *sizep)
+{
+	struct object_info oi;
+
+	oi.sizep = sizep;
+	oi.want_deltainfo = 0;
+	return sha1_object_info_extended(sha1, &oi);
+}
+
 static void *read_packed_sha1(const unsigned char *sha1,
 			      enum object_type *type, unsigned long *size)
 {

@@ -1157,6 +1157,7 @@ extern int convert_to_git(const char *path, const char *src, size_t len,
                           struct strbuf *dst, enum safe_crlf checksafe);
 extern int convert_to_working_tree(const char *path, const char *src, size_t len, struct strbuf *dst);
 extern int renormalize_buffer(const char *path, const char *src, size_t len, struct strbuf *dst);
+extern int can_bypass_conversion(const char *path);
 
 /* add */
 /*

@@ -813,3 +813,26 @@ int renormalize_buffer(const char *path, const char *src, size_t len, struct str
 	}
 	return ret | convert_to_git(path, src, len, dst, 0);
 }
+
+/*
+ * You would be crazy to set CRLF, smuge/clean or ident to
+ * a large binary blob you would want us not to slurp into
+ * the memory!
+ */
+int can_bypass_conversion(const char *path)
+{
+	struct conv_attrs ca;
+	enum crlf_action crlf_action;
+
+	convert_attrs(&ca, path);
+
+	if (ca.ident ||
+	    (ca.drv && (ca.drv->smudge || ca.drv->clean)))
+		return 0;
+
+	crlf_action = input_crlf_action(ca.crlf_action, ca.eol_attr);
+	if ((crlf_action == CRLF_BINARY) ||
+	    (crlf_action == CRLF_GUESS && auto_crlf == AUTO_CRLF_FALSE))
+		return 1;
+	return 0;
+}

@@ -1,6 +1,7 @@
 #include "cache.h"
 #include "blob.h"
 #include "dir.h"
+#include "streaming.h"
 
 static void create_directories(const char *path, int path_len,
 			       const struct checkout *state)

@@ -114,6 +115,50 @@ static int fstat_output(int fd, const struct checkout *state, struct stat *st)
 	return 0;
 }
 
+static int streaming_write_entry(struct cache_entry *ce, char *path,
+				 const struct checkout *state, int to_tempfile,
+				 int *fstat_done, struct stat *statbuf)
+{
+	struct git_istream *st;
+	enum object_type type;
+	unsigned long sz;
+	int result = -1;
+	int fd = -1;
+
+	st = open_istream(ce->sha1, &type, &sz);
+	if (!st)
+		return -1;
+	if (type != OBJ_BLOB)
+		goto close_and_exit;
+
+	fd = open_output_fd(path, ce, to_tempfile);
+	if (fd < 0)
+		goto close_and_exit;
+
+	for (;;) {
+		char buf[10240];
+		ssize_t wrote;
+		ssize_t readlen = read_istream(st, buf, sizeof(buf));
+
+		if (!readlen)
+			break;
+
+		wrote = write_in_full(fd, buf, readlen);
+
+		if (wrote != readlen)
+			goto close_and_exit;
+	}
+	*fstat_done = fstat_output(fd, state, statbuf);
+
+close_and_exit:
+	close_istream(st);
+	if (0 <= fd)
+		result |= close(fd);
+	if (result && 0 <= fd)
+		unlink(path);
+	return result;
+}
+
 static int write_entry(struct cache_entry *ce, char *path, const struct checkout *state, int to_tempfile)
 {
 	unsigned int ce_mode_s_ifmt = ce->ce_mode & S_IFMT;

@@ -124,6 +169,12 @@ static int write_entry(struct cache_entry *ce, char *path, const struct checkout
 	size_t wrote, newsize = 0;
 	struct stat st;
 
+	if ((ce_mode_s_ifmt == S_IFREG) &&
+	    can_bypass_conversion(path) &&
+	    !streaming_write_entry(ce, path, state, to_tempfile,
+				   &fstat_done, &st))
+		goto finish;
+
 	switch (ce_mode_s_ifmt) {
 	case S_IFREG:
 	case S_IFLNK:

@@ -176,6 +227,7 @@ static int write_entry(struct cache_entry *ce, char *path, const struct checkout
 		return error("unknown file mode for %s in index", path);
 	}
 
+finish:
 	if (state->refresh_cache) {
 		if (!fstat_done)
 			lstat(ce->name, &st);

@@ -123,6 +123,7 @@ static int streaming_write_entry(struct cache_entry *ce, char *path,
 	enum object_type type;
 	unsigned long sz;
 	int result = -1;
+	ssize_t kept = 0;
 	int fd = -1;
 
 	st = open_istream(ce->sha1, &type, &sz);

@@ -137,17 +138,32 @@ static int streaming_write_entry(struct cache_entry *ce, char *path,
 
 	for (;;) {
 		char buf[10240];
-		ssize_t wrote;
+		ssize_t wrote, holeto;
 		ssize_t readlen = read_istream(st, buf, sizeof(buf));
 
 		if (!readlen)
 			break;
+		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;
 	*fstat_done = fstat_output(fd, state, statbuf);
 
 close_and_exit:

@@ -55,8 +55,11 @@ struct git_istream {
 		} incore;
 
 		struct {
-			int fd; /* open for reading */
-			/* NEEDSWORK: what else? */
+			void *mapped;
+			unsigned long mapsize;
+			char hdr[32];
+			int hdr_avail;
+			int hdr_used;
 		} loose;
 
 		struct {

@@ -149,9 +152,85 @@ static void close_deflated_stream(struct git_istream *st)
  *
  *****************************************************************/
 
+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) {
+			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)
 {
-	return -1; /* for now */
+	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;
+	}
+
+	/* bypass parse_sha1_header() as we know it is already valid */
+	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;
 }
 
 

@@ -780,6 +780,8 @@ extern int hash_sha1_file(const void *buf, unsigned long len, const char *type,
 extern int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *return_sha1);
 extern int pretend_sha1_file(void *, unsigned long, enum object_type, unsigned char *);
 extern int force_object_loose(const unsigned char *sha1, time_t mtime);
+extern void *map_sha1_file(const unsigned char *sha1, unsigned long *size);
+extern int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz);
 
 /* global flag to enable extra checks when accessing packed objects */
 extern int do_check_packed_object_crc;

@@ -1186,7 +1186,7 @@ static int open_sha1_file(const unsigned char *sha1)
 	return -1;
 }
 
-static void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
+void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 {
 	void *map;
 	int fd;

@@ -1245,7 +1245,7 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 	return used;
 }
 
-static int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
+int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
 {
 	unsigned long size, used;
 	static const char valid_loose_object_type[8] = {

@@ -60,10 +60,13 @@ struct git_istream {
 		} loose;
 
 		struct {
-			int fd; /* open for reading */
-			/* NEEDSWORK: what else? */
+			struct packed_git *pack;
+			off_t pos;
+			unsigned long sz;
 		} in_pack;
 	} u;
+	z_stream z;
+	enum { z_unused, z_used, z_done, z_error } z_state;
 };
 
 int close_istream(struct git_istream *st)

@@ -126,6 +129,20 @@ struct git_istream *open_istream(const unsigned char *sha1,
 	return st;
 }
 
+
+/*****************************************************************
+ *
+ * Common helpers
+ *
+ *****************************************************************/
+
+static void close_deflated_stream(struct git_istream *st)
+{
+	if (st->z_state == z_used)
+		git_inflate_end(&st->z);
+}
+
+
 /*****************************************************************
  *
  * Loose object stream

@@ -144,9 +161,93 @@ static open_method_decl(loose)
  *
  *****************************************************************/
 
+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)
 {
-	return -1; /* for now */
+	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->u.in_pack.sz);
+	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;
 }