thodg/libgit2

diff --git a/.travis.yml b/.travis.yml
index fc51345..68b29b1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,6 +15,7 @@ compiler:
 env:
  global:
   - secure: "YnhS+8n6B+uoyaYfaJ3Lei7cSJqHDPiKJCKFIF2c87YDfmCvAJke8QtE7IzjYDs7UFkTCM4ox+ph2bERUrxZbSCyEkHdjIZpKuMJfYWja/jgMqTMxdyOH9y8JLFbZsSXDIXDwqBlC6vVyl1fP90M35wuWcNTs6tctfVWVofEFbs="
+  - GITTEST_INVASIVE_FS_SIZE=1
  matrix:
   - OPTIONS="-DTHREADSAFE=ON -DCMAKE_BUILD_TYPE=Release"
   - OPTIONS="-DTHREADSAFE=OFF -DBUILD_EXAMPLES=ON"
diff --git a/appveyor.yml b/appveyor.yml
index 8ac6728..d155485 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -3,7 +3,8 @@ branches:
   only:
   - master
 environment:
-  GITTEST_INVASIVE_FILESYSTEM: 1
+  GITTEST_INVASIVE_FS_STRUCTURE: 1
+  GITTEST_INVASIVE_FS_SIZE: 1
 
   matrix:
   - GENERATOR: "Visual Studio 11"
diff --git a/include/git2/filter.h b/include/git2/filter.h
index 5b3f403..dc59e63 100644
--- a/include/git2/filter.h
+++ b/include/git2/filter.h
@@ -39,9 +39,9 @@ typedef enum {
  * Filter option flags.
  */
 typedef enum {
-	GIT_FILTER_OPT_DEFAULT = 0u,
-	GIT_FILTER_OPT_ALLOW_UNSAFE = (1u << 0),
-} git_filter_opt_t;
+	GIT_FILTER_DEFAULT = 0u,
+	GIT_FILTER_ALLOW_UNSAFE = (1u << 0),
+} git_filter_flag_t;
 
 /**
  * A filter that can transform file data
@@ -83,7 +83,7 @@ typedef struct git_filter_list git_filter_list;
  * @param blob The blob to which the filter will be applied (if known)
  * @param path Relative path of the file to be filtered
  * @param mode Filtering direction (WT->ODB or ODB->WT)
- * @param options Combination of `git_filter_opt_t` flags
+ * @param flags Combination of `git_filter_flag_t` flags
  * @return 0 on success (which could still return NULL if no filters are
  *         needed for the requested file), <0 on error
  */
@@ -93,7 +93,7 @@ GIT_EXTERN(int) git_filter_list_load(
 	git_blob *blob, /* can be NULL */
 	const char *path,
 	git_filter_mode_t mode,
-	uint32_t options);
+	uint32_t flags);
 
 /**
  * Apply filter list to a data buffer.
@@ -137,6 +137,22 @@ GIT_EXTERN(int) git_filter_list_apply_to_blob(
 	git_filter_list *filters,
 	git_blob *blob);
 
+GIT_EXTERN(int) git_filter_list_stream_data(
+	git_filter_list *filters,
+	git_buf *data,
+	git_writestream *target);
+
+GIT_EXTERN(int) git_filter_list_stream_file(
+	git_filter_list *filters,
+	git_repository *repo,
+	const char *path,
+	git_writestream *target);
+
+GIT_EXTERN(int) git_filter_list_stream_blob(
+	git_filter_list *filters,
+	git_blob *blob,
+	git_writestream *target);
+
 /**
  * Free a git_filter_list
  *
diff --git a/include/git2/sys/filter.h b/include/git2/sys/filter.h
index 6024827..5fd8d55 100644
--- a/include/git2/sys/filter.h
+++ b/include/git2/sys/filter.h
@@ -123,9 +123,9 @@ GIT_EXTERN(const git_oid *) git_filter_source_id(const git_filter_source *src);
 GIT_EXTERN(git_filter_mode_t) git_filter_source_mode(const git_filter_source *src);
 
 /**
- * Get the combination git_filter_opt_t options to be applied
+ * Get the combination git_filter_flag_t options to be applied
  */
-GIT_EXTERN(uint32_t) git_filter_source_options(const git_filter_source *src);
+GIT_EXTERN(uint32_t) git_filter_source_flags(const git_filter_source *src);
 
 /*
  * struct git_filter
@@ -208,6 +208,13 @@ typedef int (*git_filter_apply_fn)(
 	const git_buf *from,
 	const git_filter_source *src);
 
+typedef int (*git_filter_stream_fn)(
+	git_writestream **out,
+	git_filter *self,
+	void **payload,
+	const git_filter_source *src,
+	git_writestream *next);
+
 /**
  * Callback to clean up after filtering has been applied
  *
@@ -247,6 +254,7 @@ struct git_filter {
 	git_filter_shutdown_fn shutdown;
 	git_filter_check_fn    check;
 	git_filter_apply_fn    apply;
+	git_filter_stream_fn   stream;
 	git_filter_cleanup_fn  cleanup;
 };
 
diff --git a/include/git2/types.h b/include/git2/types.h
index 35e1573..c90ac47 100644
--- a/include/git2/types.h
+++ b/include/git2/types.h
@@ -410,6 +410,15 @@ typedef enum {
 	GIT_SUBMODULE_RECURSE_ONDEMAND = 2,
 } git_submodule_recurse_t;
 
+/** A type to write in a streaming fashion, for example, for filters. */
+typedef struct git_writestream git_writestream;
+
+struct git_writestream {
+	int (*write)(git_writestream *stream, const char *buffer, size_t len);
+	int (*close)(git_writestream *stream);
+	void (*free)(git_writestream *stream);
+};
+
 /** @} */
 GIT_END_DECL
 
diff --git a/src/attr.c b/src/attr.c
index 44593da..3842080 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -282,9 +282,8 @@ static int system_attr_file(
 	 * a consumer. This allows them to treat this as a regular `git_buf`,
 	 * but their call to `git_buf_free` will not attempt to free it.
 	 */
-	out->ptr = attr_session->sysdir.ptr;
-	out->size = attr_session->sysdir.size;
-	out->asize = 0;
+	git_buf_attach_notowned(
+		out, attr_session->sysdir.ptr, attr_session->sysdir.size);
 	return 0;
 }
 
diff --git a/src/blob.c b/src/blob.c
index 30d5b70..cf03290 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -199,7 +199,7 @@ int git_blob__create_from_paths(
 			/* Load the filters for writing this file to the ODB */
 			error = git_filter_list_load(
 				&fl, repo, NULL, hint_path,
-				GIT_FILTER_TO_ODB, GIT_FILTER_OPT_DEFAULT);
+				GIT_FILTER_TO_ODB, GIT_FILTER_DEFAULT);
 
 		if (error < 0)
 			/* well, that didn't work */;
@@ -329,15 +329,13 @@ cleanup:
 
 int git_blob_is_binary(const git_blob *blob)
 {
-	git_buf content;
+	git_buf content = GIT_BUF_INIT;
 
 	assert(blob);
 
-	content.ptr   = blob->odb_object->buffer;
-	content.size  =
-		min(blob->odb_object->cached.size, GIT_FILTER_BYTES_TO_CHECK_NUL);
-	content.asize = 0;
-
+	git_buf_attach_notowned(&content, blob->odb_object->buffer,
+		min(blob->odb_object->cached.size,
+		GIT_FILTER_BYTES_TO_CHECK_NUL));
 	return git_buf_text_is_binary(&content);
 }
 
@@ -359,7 +357,7 @@ int git_blob_filtered_content(
 
 	if (!(error = git_filter_list_load(
 			&fl, git_blob_owner(blob), blob, path,
-			GIT_FILTER_TO_WORKTREE, GIT_FILTER_OPT_DEFAULT))) {
+			GIT_FILTER_TO_WORKTREE, GIT_FILTER_DEFAULT))) {
 
 		error = git_filter_list_apply_to_blob(out, fl, blob);
 
diff --git a/src/buffer.c b/src/buffer.c
index 3deb032..f633c5e 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -500,6 +500,20 @@ void git_buf_attach(git_buf *buf, char *ptr, size_t asize)
 	}
 }
 
+void git_buf_attach_notowned(git_buf *buf, const char *ptr, size_t size)
+{
+	if (git_buf_is_allocated(buf))
+		git_buf_free(buf);
+
+	if (!size) {
+		git_buf_init(buf, 0);
+	} else {
+		buf->ptr = (char *)ptr;
+		buf->asize = 0;
+		buf->size = size;
+	}
+}
+
 int git_buf_join_n(git_buf *buf, char separator, int nbuf, ...)
 {
 	va_list ap;
diff --git a/src/buffer.h b/src/buffer.h
index 52342e3..093ed9b 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -74,6 +74,12 @@ extern void git_buf_swap(git_buf *buf_a, git_buf *buf_b);
 extern char *git_buf_detach(git_buf *buf);
 extern void git_buf_attach(git_buf *buf, char *ptr, size_t asize);
 
+/* Populates a `git_buf` where the contents are not "owned" by the
+ * buffer, and calls to `git_buf_free` will not free the given buf.
+ */
+extern void git_buf_attach_notowned(
+	git_buf *buf, const char *ptr, size_t size);
+
 /**
  * Test if there have been any reallocation failures with this git_buf.
  *
diff --git a/src/checkout.c b/src/checkout.c
index 880af3d..f71be26 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -17,6 +17,7 @@
 #include "git2/diff.h"
 #include "git2/submodule.h"
 #include "git2/sys/index.h"
+#include "git2/sys/filter.h"
 
 #include "refs.h"
 #include "repository.h"
@@ -1371,39 +1372,37 @@ static int mkpath2file(
 	return error;
 }
 
-static int buffer_to_file(
-	checkout_data *data,
-	struct stat *st,
-	git_buf *buf,
-	const char *path,
-	mode_t file_mode)
-{
-	int error;
-
-	if ((error = mkpath2file(data, path, data->opts.dir_mode)) < 0)
-		return error;
+struct checkout_stream {
+	git_writestream base;
+	const char *path;
+	int fd;
+	int open;
+};
 
-	if ((error = git_futils_writebuffer(
-			buf, path, data->opts.file_open_flags, file_mode)) < 0)
-		return error;
+static int checkout_stream_write(
+	git_writestream *s, const char *buffer, size_t len)
+{
+	struct checkout_stream *stream = (struct checkout_stream *)s;
+	int ret;
 
-	if (st) {
-		data->perfdata.stat_calls++;
+	if ((ret = p_write(stream->fd, buffer, len)) < 0)
+		giterr_set(GITERR_OS, "Could not write to '%s'", stream->path);
 
-		if ((error = p_stat(path, st)) < 0) {
-			giterr_set(GITERR_OS, "Error statting '%s'", path);
-			return error;
-		}
-	}
+	return ret;
+}
 
-	if (GIT_PERMS_IS_EXEC(file_mode)) {
-		data->perfdata.chmod_calls++;
+static int checkout_stream_close(git_writestream *s)
+{
+	struct checkout_stream *stream = (struct checkout_stream *)s;
+	assert(stream && stream->open);
 
-		if ((error = p_chmod(path, file_mode)) < 0)
-			giterr_set(GITERR_OS, "Failed to set permissions on '%s'", path);
-	}
+	stream->open = 0;
+	return p_close(stream->fd);
+}
 
-	return error;
+static void checkout_stream_free(git_writestream *s)
+{
+	GIT_UNUSED(s);
 }
 
 static int blob_content_to_file(
@@ -1411,36 +1410,83 @@ static int blob_content_to_file(
 	struct stat *st,
 	git_blob *blob,
 	const char *path,
-	const char * hint_path,
+	const char *hint_path,
 	mode_t entry_filemode)
 {
+	int flags = data->opts.file_open_flags;
 	mode_t file_mode = data->opts.file_mode ?
 		data->opts.file_mode : entry_filemode;
-	git_buf out = GIT_BUF_INIT;
+	git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
+	struct checkout_stream writer;
+	mode_t mode;
 	git_filter_list *fl = NULL;
+	int fd;
 	int error = 0;
 
 	if (hint_path == NULL)
 		hint_path = path;
 
-	if (!data->opts.disable_filters)
-		error = git_filter_list__load_with_attr_session(
-			&fl, data->repo, &data->attr_session, blob, hint_path,
-			GIT_FILTER_TO_WORKTREE, GIT_FILTER_OPT_DEFAULT);
+	if ((error = mkpath2file(data, path, data->opts.dir_mode)) < 0)
+		return error;
 
-	if (!error)
-		error = git_filter_list_apply_to_blob(&out, fl, blob);
+	if (flags <= 0)
+		flags = O_CREAT | O_TRUNC | O_WRONLY;
+	if (!(mode = file_mode))
+		mode = GIT_FILEMODE_BLOB;
+
+	if ((fd = p_open(path, flags, mode)) < 0) {
+		giterr_set(GITERR_OS, "Could not open '%s' for writing", path);
+		return fd;
+	}
+
+	filter_opts.attr_session = &data->attr_session;
+	filter_opts.temp_buf = &data->tmp;
+
+	if (!data->opts.disable_filters &&
+		(error = git_filter_list__load_ext(
+			&fl, data->repo, blob, hint_path,
+			GIT_FILTER_TO_WORKTREE, &filter_opts)))
+		return error;
+
+	/* setup the writer */
+	memset(&writer, 0, sizeof(struct checkout_stream));
+	writer.base.write = checkout_stream_write;
+	writer.base.close = checkout_stream_close;
+	writer.base.free = checkout_stream_free;
+	writer.path = path;
+	writer.fd = fd;
+	writer.open = 1;
+
+	error = git_filter_list_stream_blob(fl, blob, (git_writestream *)&writer);
+
+	assert(writer.open == 0);
 
 	git_filter_list_free(fl);
 
-	if (!error) {
-		error = buffer_to_file(data, st, &out, path, file_mode);
-		st->st_mode = entry_filemode;
+	if (error < 0)
+		return error;
+
+	if (GIT_PERMS_IS_EXEC(mode)) {
+		data->perfdata.chmod_calls++;
+
+		if ((error = p_chmod(path, mode)) < 0) {
+			giterr_set(GITERR_OS, "Failed to set permissions on '%s'", path);
+			return error;
+		}
+	}
+
+	if (st) {
+		data->perfdata.stat_calls++;
 
-		git_buf_free(&out);
+		if ((error = p_stat(path, st)) < 0) {
+			giterr_set(GITERR_OS, "Error statting '%s'", path);
+			return error;
+		}
+
+		st->st_mode = entry_filemode;
 	}
 
-	return error;
+	return 0;
 }
 
 static int blob_content_to_link(
@@ -1958,6 +2004,7 @@ static int checkout_write_merge(
 	git_merge_file_result result = {0};
 	git_filebuf output = GIT_FILEBUF_INIT;
 	git_filter_list *fl = NULL;
+	git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
 	int error = 0;
 
 	if (data->opts.checkout_strategy & GIT_CHECKOUT_CONFLICT_STYLE_DIFF3)
@@ -2007,9 +2054,12 @@ static int checkout_write_merge(
 		in_data.ptr = (char *)result.ptr;
 		in_data.size = result.len;
 
-		if ((error = git_filter_list__load_with_attr_session(
-				&fl, data->repo, &data->attr_session, NULL, git_buf_cstr(&path_workdir),
-				GIT_FILTER_TO_WORKTREE, GIT_FILTER_OPT_DEFAULT)) < 0 ||
+		filter_opts.attr_session = &data->attr_session;
+		filter_opts.temp_buf = &data->tmp;
+
+		if ((error = git_filter_list__load_ext(
+				&fl, data->repo, NULL, git_buf_cstr(&path_workdir),
+				GIT_FILTER_TO_WORKTREE, &filter_opts)) < 0 ||
 			(error = git_filter_list_apply_to_data(&out_data, fl, &in_data)) < 0)
 			goto done;
 	} else {
diff --git a/src/crlf.c b/src/crlf.c
index c0a7399..b5d1dbf 100644
--- a/src/crlf.c
+++ b/src/crlf.c
@@ -302,7 +302,7 @@ static int crlf_check(
 			return error;
 
 		/* downgrade FAIL to WARN if ALLOW_UNSAFE option is used */
-		if ((git_filter_source_options(src) & GIT_FILTER_OPT_ALLOW_UNSAFE) &&
+		if ((git_filter_source_flags(src) & GIT_FILTER_ALLOW_UNSAFE) &&
 			ca.safe_crlf == GIT_SAFE_CRLF_FAIL)
 			ca.safe_crlf = GIT_SAFE_CRLF_WARN;
 	}
diff --git a/src/diff.c b/src/diff.c
index 07eae03..815351b 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -600,7 +600,7 @@ int git_diff__oid_for_entry(
 		error = -1;
 	} else if (!(error = git_filter_list_load(
 		&fl, diff->repo, NULL, entry.path,
-		GIT_FILTER_TO_ODB, GIT_FILTER_OPT_ALLOW_UNSAFE)))
+		GIT_FILTER_TO_ODB, GIT_FILTER_ALLOW_UNSAFE)))
 	{
 		int fd = git_futils_open_ro(full_path.ptr);
 		if (fd < 0)
diff --git a/src/diff_driver.c b/src/diff_driver.c
index 7313ab5..049e6ef 100644
--- a/src/diff_driver.c
+++ b/src/diff_driver.c
@@ -418,14 +418,13 @@ void git_diff_driver_update_options(
 int git_diff_driver_content_is_binary(
 	git_diff_driver *driver, const char *content, size_t content_len)
 {
-	git_buf search;
-
-	search.ptr   = (char *)content;
-	search.size  = min(content_len, GIT_FILTER_BYTES_TO_CHECK_NUL);
-	search.asize = 0;
+	git_buf search = GIT_BUF_INIT;
 
 	GIT_UNUSED(driver);
 
+	git_buf_attach_notowned(&search, content,
+		min(content_len, GIT_FILTER_BYTES_TO_CHECK_NUL));
+
 	/* TODO: provide encoding / binary detection callbacks that can
 	 * be UTF-8 aware, etc.  For now, instead of trying to be smart,
 	 * let's just use the simple NUL-byte detection that core git uses.
diff --git a/src/diff_file.c b/src/diff_file.c
index 96be094..f7061ae 100644
--- a/src/diff_file.c
+++ b/src/diff_file.c
@@ -302,7 +302,7 @@ static int diff_file_content_load_workdir_file(
 
 	if ((error = git_filter_list_load(
 			&fl, fc->repo, NULL, fc->file->path,
-			GIT_FILTER_TO_ODB, GIT_FILTER_OPT_ALLOW_UNSAFE)) < 0)
+			GIT_FILTER_TO_ODB, GIT_FILTER_ALLOW_UNSAFE)) < 0)
 		goto cleanup;
 
 	/* if there are no filters, try to mmap the file */
diff --git a/src/filter.c b/src/filter.c
index 7b54a76..4fbf84f 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -23,7 +23,7 @@ struct git_filter_source {
 	git_oid         oid;  /* zero if unknown (which is likely) */
 	uint16_t        filemode; /* zero if unknown */
 	git_filter_mode_t mode;
-	uint32_t        options;
+	uint32_t        flags;
 };
 
 typedef struct {
@@ -34,6 +34,7 @@ typedef struct {
 struct git_filter_list {
 	git_array_t(git_filter_entry) filters;
 	git_filter_source source;
+	git_buf *temp_buf;
 	char path[GIT_FLEX_ARRAY];
 };
 
@@ -371,9 +372,9 @@ git_filter_mode_t git_filter_source_mode(const git_filter_source *src)
 	return src->mode;
 }
 
-uint32_t git_filter_source_options(const git_filter_source *src)
+uint32_t git_filter_source_flags(const git_filter_source *src)
 {
-	return src->options;
+	return src->flags;
 }
 
 static int filter_list_new(
@@ -393,7 +394,7 @@ static int filter_list_new(
 	fl->source.repo = src->repo;
 	fl->source.path = fl->path;
 	fl->source.mode = src->mode;
-	fl->source.options = src->options;
+	fl->source.flags = src->flags;
 
 	*out = fl;
 	return 0;
@@ -448,24 +449,23 @@ int git_filter_list_new(
 	git_filter_list **out,
 	git_repository *repo,
 	git_filter_mode_t mode,
-	uint32_t options)
+	uint32_t flags)
 {
 	git_filter_source src = { 0 };
 	src.repo = repo;
 	src.path = NULL;
 	src.mode = mode;
-	src.options = options;
+	src.flags = flags;
 	return filter_list_new(out, &src);
 }
 
-int git_filter_list__load_with_attr_session(
+int git_filter_list__load_ext(
 	git_filter_list **filters,
 	git_repository *repo,
-	git_attr_session *attr_session,
 	git_blob *blob, /* can be NULL */
 	const char *path,
 	git_filter_mode_t mode,
-	uint32_t options)
+	git_filter_options *filter_opts)
 {
 	int error = 0;
 	git_filter_list *fl = NULL;
@@ -480,7 +480,8 @@ int git_filter_list__load_with_attr_session(
 	src.repo = repo;
 	src.path = path;
 	src.mode = mode;
-	src.options = options;
+	src.flags = filter_opts->flags;
+
 	if (blob)
 		git_oid_cpy(&src.oid, git_blob_id(blob));
 
@@ -493,7 +494,7 @@ int git_filter_list__load_with_attr_session(
 
 		if (fdef->nattrs > 0) {
 			error = filter_list_check_attributes(
-				&values, repo, attr_session, fdef, &src);
+				&values, repo, filter_opts->attr_session, fdef, &src);
 
 			if (error == GIT_ENOTFOUND) {
 				error = 0;
@@ -516,8 +517,12 @@ int git_filter_list__load_with_attr_session(
 		else if (error < 0)
 			break;
 		else {
-			if (!fl && (error = filter_list_new(&fl, &src)) < 0)
-				return error;
+			if (!fl) {
+				if ((error = filter_list_new(&fl, &src)) < 0)
+					return error;
+
+				fl->temp_buf = filter_opts->temp_buf;
+			}
 
 			fe = git_array_alloc(fl->filters);
 			GITERR_CHECK_ALLOC(fe);
@@ -542,10 +547,14 @@ int git_filter_list_load(
 	git_blob *blob, /* can be NULL */
 	const char *path,
 	git_filter_mode_t mode,
-	uint32_t options)
+	uint32_t flags)
 {
-	return git_filter_list__load_with_attr_session(
-		filters, repo, NULL, blob, path, mode, options);
+	git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
+
+	filter_opts.flags = flags;
+
+	return git_filter_list__load_ext(
+		filters, repo, blob, path, mode, &filter_opts);
 }
 
 void git_filter_list_free(git_filter_list *fl)
@@ -600,84 +609,72 @@ size_t git_filter_list_length(const git_filter_list *fl)
 	return fl ? git_array_size(fl->filters) : 0;
 }
 
-static int filter_list_out_buffer_from_raw(
-	git_buf *out, const void *ptr, size_t size)
+struct buf_stream {
+	git_writestream parent;
+	git_buf *target;
+	bool complete;
+};
+
+static int buf_stream_write(
+	git_writestream *s, const char *buffer, size_t len)
 {
-	if (git_buf_is_allocated(out))
-		git_buf_free(out);
+	struct buf_stream *buf_stream = (struct buf_stream *)s;
+	assert(buf_stream);
 
-	if (!size) {
-		git_buf_init(out, 0);
-	} else {
-		out->ptr   = (char *)ptr;
-		out->asize = 0;
-		out->size  = size;
-	}
+	assert(buf_stream->complete == 0);
 
-	return 0;
+	return git_buf_put(buf_stream->target, buffer, len);
 }
 
-int git_filter_list_apply_to_data(
-	git_buf *tgt, git_filter_list *fl, git_buf *src)
+static int buf_stream_close(git_writestream *s)
 {
-	int error = 0;
-	uint32_t i;
-	git_buf *dbuffer[2], local = GIT_BUF_INIT;
-	unsigned int si = 0;
+	struct buf_stream *buf_stream = (struct buf_stream *)s;
+	assert(buf_stream);
 
-	git_buf_sanitize(tgt);
-	git_buf_sanitize(src);
+	assert(buf_stream->complete == 0);
+	buf_stream->complete = 1;
 
-	if (!fl)
-		return filter_list_out_buffer_from_raw(tgt, src->ptr, src->size);
+	return 0;
+}
 
-	dbuffer[0] = src;
-	dbuffer[1] = tgt;
+static void buf_stream_free(git_writestream *s)
+{
+	GIT_UNUSED(s);
+}
 
-	/* if `src` buffer is reallocable, then use it, otherwise copy it */
-	if (!git_buf_is_allocated(src)) {
-		if (git_buf_set(&local, src->ptr, src->size) < 0)
-			return -1;
-		dbuffer[0] = &local;
-	}
+static void buf_stream_init(struct buf_stream *writer, git_buf *target)
+{
+	memset(writer, 0, sizeof(struct buf_stream));
 
-	for (i = 0; i < git_array_size(fl->filters); ++i) {
-		unsigned int di = 1 - si;
-		uint32_t fidx = (fl->source.mode == GIT_FILTER_TO_WORKTREE) ?
-			i : git_array_size(fl->filters) - 1 - i;
-		git_filter_entry *fe = git_array_get(fl->filters, fidx);
-
-		dbuffer[di]->size = 0;
-
-		/* Apply the filter from dbuffer[src] to the other buffer;
-		 * if the filtering is canceled by the user mid-filter,
-		 * we skip to the next filter without changing the source
-		 * of the double buffering (so that the text goes through
-		 * cleanly).
-		 */
+	writer->parent.write = buf_stream_write;
+	writer->parent.close = buf_stream_close;
+	writer->parent.free = buf_stream_free;
+	writer->target = target;
 
-		error = fe->filter->apply(
-			fe->filter, &fe->payload, dbuffer[di], dbuffer[si], &fl->source);
+	git_buf_clear(target);
+}
 
-		if (error == GIT_PASSTHROUGH) {
-			/* PASSTHROUGH means filter decided not to process the buffer */
-			error = 0;
-		} else if (!error) {
-			git_buf_sanitize(dbuffer[di]); /* force NUL termination */
-			si = di; /* swap buffers */
-		} else {
-			tgt->size = 0;
-			goto cleanup;
-		}
+int git_filter_list_apply_to_data(
+	git_buf *tgt, git_filter_list *filters, git_buf *src)
+{
+	struct buf_stream writer;
+	int error;
+
+	git_buf_sanitize(tgt);
+	git_buf_sanitize(src);
+
+	if (!filters) {
+		git_buf_attach_notowned(tgt, src->ptr, src->size);
+		return 0;
 	}
 
-	/* Ensure that the output ends up in dbuffer[1] (i.e. the dest) */
-	if (si != 1)
-		git_buf_swap(dbuffer[0], dbuffer[1]);
+	buf_stream_init(&writer, tgt);
 
-cleanup:
-	git_buf_free(&local); /* don't leak if we allocated locally */
+	if ((error = git_filter_list_stream_data(filters, src,
+		(git_writestream *)&writer)) < 0)
+			return error;
 
+	assert(writer.complete);
 	return error;
 }
 
@@ -687,28 +684,21 @@ int git_filter_list_apply_to_file(
 	git_repository *repo,
 	const char *path)
 {
+	struct buf_stream writer;
 	int error;
-	const char *base = repo ? git_repository_workdir(repo) : NULL;
-	git_buf abspath = GIT_BUF_INIT, raw = GIT_BUF_INIT;
 
-	if (!(error = git_path_join_unrooted(&abspath, path, base, NULL)) &&
-		!(error = git_futils_readbuffer(&raw, abspath.ptr)))
-	{
-		error = git_filter_list_apply_to_data(out, filters, &raw);
+	buf_stream_init(&writer, out);
 
-		git_buf_free(&raw);
-	}
+	if ((error = git_filter_list_stream_file(
+		filters, repo, path, (git_writestream *)&writer)) < 0)
+			return error;
 
-	git_buf_free(&abspath);
+	assert(writer.complete);
 	return error;
 }
 
-int git_filter_list_apply_to_blob(
-	git_buf *out,
-	git_filter_list *filters,
-	git_blob *blob)
+static int buf_from_blob(git_buf *out, git_blob *blob)
 {
-	git_buf in = GIT_BUF_INIT;
 	git_off_t rawsize = git_blob_rawsize(blob);
 
 	if (!git__is_sizet(rawsize)) {
@@ -716,12 +706,250 @@ int git_filter_list_apply_to_blob(
 		return -1;
 	}
 
-	in.ptr   = (char *)git_blob_rawcontent(blob);
-	in.asize = 0;
-	in.size  = (size_t)rawsize;
+	git_buf_attach_notowned(out, git_blob_rawcontent(blob), (size_t)rawsize);
+	return 0;
+}
+
+int git_filter_list_apply_to_blob(
+	git_buf *out,
+	git_filter_list *filters,
+	git_blob *blob)
+{
+	struct buf_stream writer;
+	int error;
+
+	buf_stream_init(&writer, out);
+
+	if ((error = git_filter_list_stream_blob(
+		filters, blob, (git_writestream *)&writer)) < 0)
+			return error;
+
+	assert(writer.complete);
+	return error;
+}
+
+struct proxy_stream {
+	git_writestream parent;
+	git_filter *filter;
+	const git_filter_source *source;
+	void **payload;
+	git_buf input;
+	git_buf temp_buf;
+	git_buf *output;
+	git_writestream *target;
+};
+
+static int proxy_stream_write(
+	git_writestream *s, const char *buffer, size_t len)
+{
+	struct proxy_stream *proxy_stream = (struct proxy_stream *)s;
+	assert(proxy_stream);
+
+	return git_buf_put(&proxy_stream->input, buffer, len);
+}
+
+static int proxy_stream_close(git_writestream *s)
+{
+	struct proxy_stream *proxy_stream = (struct proxy_stream *)s;
+	git_buf *writebuf;
+	int error;
+
+	assert(proxy_stream);
+
+	error = proxy_stream->filter->apply(
+		proxy_stream->filter,
+		proxy_stream->payload,
+		proxy_stream->output,
+		&proxy_stream->input,
+		proxy_stream->source);
+
+	if (error == GIT_PASSTHROUGH) {
+		writebuf = &proxy_stream->input;
+	} else if (error == 0) {
+		git_buf_sanitize(proxy_stream->output);
+		writebuf = proxy_stream->output;
+	} else {
+		return error;
+	}
+
+	if ((error = proxy_stream->target->write(
+			proxy_stream->target, writebuf->ptr, writebuf->size)) == 0)
+		error = proxy_stream->target->close(proxy_stream->target);
+
+	return error;
+}
+
+static void proxy_stream_free(git_writestream *s)
+{
+	struct proxy_stream *proxy_stream = (struct proxy_stream *)s;
+	assert(proxy_stream);
+
+	git_buf_free(&proxy_stream->input);
+	git_buf_free(&proxy_stream->temp_buf);
+	git__free(proxy_stream);
+}
+
+static int proxy_stream_init(
+	git_writestream **out,
+	git_filter *filter,
+	git_buf *temp_buf,
+	void **payload,
+	const git_filter_source *source,
+	git_writestream *target)
+{
+	struct proxy_stream *proxy_stream = git__calloc(1, sizeof(struct proxy_stream));
+	GITERR_CHECK_ALLOC(proxy_stream);
+
+	proxy_stream->parent.write = proxy_stream_write;
+	proxy_stream->parent.close = proxy_stream_close;
+	proxy_stream->parent.free = proxy_stream_free;
+	proxy_stream->filter = filter;
+	proxy_stream->payload = payload;
+	proxy_stream->source = source;
+	proxy_stream->target = target;
+	proxy_stream->output = temp_buf ? temp_buf : &proxy_stream->temp_buf;
+
+	*out = (git_writestream *)proxy_stream;
+	return 0;
+}
+
+static int stream_list_init(
+	git_writestream **out,
+	git_vector *streams,
+	git_filter_list *filters,
+	git_writestream *target)
+{
+	git_writestream *last_stream = target;
+	size_t i;
+	int error = 0;
+
+	*out = NULL;
+
+	if (!filters) {
+		*out = target;
+		return 0;
+	}
+
+	/* Create filters last to first to get the chaining direction */
+	for (i = 0; i < git_array_size(filters->filters); ++i) {
+		size_t filter_idx = (filters->source.mode == GIT_FILTER_TO_WORKTREE) ?
+			git_array_size(filters->filters) - 1 - i : i;
+		git_filter_entry *fe = git_array_get(filters->filters, filter_idx);
+		git_writestream *filter_stream;
+		
+		assert(fe->filter->stream || fe->filter->apply);
+
+		/* If necessary, create a stream that proxies the traditional
+		 * application.
+		 */
+		if (fe->filter->stream)
+			error = fe->filter->stream(&filter_stream, fe->filter,
+				&fe->payload, &filters->source, last_stream);
+		else
+			/* Create a stream that proxies the one-shot apply */
+			error = proxy_stream_init(&filter_stream, fe->filter,
+				filters->temp_buf, &fe->payload, &filters->source,
+				last_stream);
+
+		if (error < 0)
+			return error;
+
+		git_vector_insert(streams, filter_stream);
+		last_stream = filter_stream;
+	}
+
+	*out = last_stream;
+	return 0;
+}
+
+void stream_list_free(git_vector *streams)
+{
+	git_writestream *stream;
+	size_t i;
+
+	git_vector_foreach(streams, i, stream)
+		stream->free(stream);
+	git_vector_free(streams);
+}
+
+#define STREAM_BUFSIZE 10240
+
+/* TODO: maybe not use filter_stream as a target but create one */
+int git_filter_list_stream_file(
+	git_filter_list *filters,
+	git_repository *repo,
+	const char *path,
+	git_writestream *target)
+{
+	char buf[STREAM_BUFSIZE];
+	git_buf abspath = GIT_BUF_INIT;
+	const char *base = repo ? git_repository_workdir(repo) : NULL;
+	git_vector filter_streams = GIT_VECTOR_INIT;
+	git_writestream *stream_start;
+	ssize_t readlen;
+	int fd, error;
+
+	if ((error = stream_list_init(
+			&stream_start, &filter_streams, filters, target)) < 0 ||
+		(error = git_path_join_unrooted(&abspath, path, base, NULL)) < 0)
+		goto done;
+
+	if ((fd = git_futils_open_ro(path)) < 0) {
+		error = fd;
+		goto done;
+	}
+
+	while ((readlen = p_read(fd, buf, STREAM_BUFSIZE)) > 0) {
+		if ((error = stream_start->write(stream_start, buf, readlen)) < 0)
+			goto done;
+	}
+
+	if (!readlen)
+		error = stream_start->close(stream_start);
+	else if (readlen < 0)
+		error = readlen;
+
+	p_close(fd);
+
+done:
+	stream_list_free(&filter_streams);
+	git_buf_free(&abspath);
+	return error;
+}
+
+int git_filter_list_stream_data(
+	git_filter_list *filters,
+	git_buf *data,
+	git_writestream *target)
+{
+	git_vector filter_streams = GIT_VECTOR_INIT;
+	git_writestream *stream_start;
+	int error = 0;
+
+	git_buf_sanitize(data);
+
+	if ((error = stream_list_init(
+			&stream_start, &filter_streams, filters, target)) == 0 &&
+		(error =
+			stream_start->write(stream_start, data->ptr, data->size)) == 0)
+		error = stream_start->close(stream_start);
+
+	stream_list_free(&filter_streams);
+	return error;
+}
+
+int git_filter_list_stream_blob(
+	git_filter_list *filters,
+	git_blob *blob,
+	git_writestream *target)
+{
+	git_buf in = GIT_BUF_INIT;
+
+	if (buf_from_blob(&in, blob) < 0)
+		return -1;
 
 	if (filters)
 		git_oid_cpy(&filters->source.oid, git_blob_id(blob));
 
-	return git_filter_list_apply_to_data(out, filters, &in);
+	return git_filter_list_stream_data(filters, &in, target);
 }
diff --git a/src/filter.h b/src/filter.h
index 390ffeb..5062afb 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -24,16 +24,23 @@ typedef enum {
 	GIT_CRLF_AUTO,
 } git_crlf_t;
 
+typedef struct {
+	git_attr_session *attr_session;
+	git_buf *temp_buf;
+	uint32_t flags;
+} git_filter_options;
+
+#define GIT_FILTER_OPTIONS_INIT {0}
+
 extern void git_filter_free(git_filter *filter);
 
-extern int git_filter_list__load_with_attr_session(
+extern int git_filter_list__load_ext(
 	git_filter_list **filters,
 	git_repository *repo,
-	git_attr_session *attr_session,
 	git_blob *blob, /* can be NULL */
 	const char *path,
 	git_filter_mode_t mode,
-	uint32_t options);
+	git_filter_options *filter_opts);
 
 /*
  * Available filters
diff --git a/src/repository.c b/src/repository.c
index c927507..23c99b0 100644
--- a/src/repository.c
+++ b/src/repository.c
@@ -1849,7 +1849,7 @@ int git_repository_hashfile(
 	if (strlen(as_path) > 0) {
 		error = git_filter_list_load(
 			&fl, repo, NULL, as_path,
-			GIT_FILTER_TO_ODB, GIT_FILTER_OPT_DEFAULT);
+			GIT_FILTER_TO_ODB, GIT_FILTER_DEFAULT);
 		if (error < 0)
 			return error;
 	} else {
diff --git a/tests/filter/crlf.c b/tests/filter/crlf.c
index a31dac9..406d3b6 100644
--- a/tests/filter/crlf.c
+++ b/tests/filter/crlf.c
@@ -123,7 +123,7 @@ void test_filter_crlf__with_safecrlf_and_unsafe_allowed(void)
 	cl_repo_set_bool(g_repo, "core.safecrlf", true);
 
 	cl_git_pass(git_filter_list_new(
-		&fl, g_repo, GIT_FILTER_TO_ODB, GIT_FILTER_OPT_ALLOW_UNSAFE));
+		&fl, g_repo, GIT_FILTER_TO_ODB, GIT_FILTER_ALLOW_UNSAFE));
 
 	crlf = git_filter_lookup(GIT_FILTER_CRLF);
 	cl_assert(crlf != NULL);
diff --git a/tests/filter/stream.c b/tests/filter/stream.c
new file mode 100644
index 0000000..603f194
--- /dev/null
+++ b/tests/filter/stream.c
@@ -0,0 +1,221 @@
+#include "clar_libgit2.h"
+#include "posix.h"
+#include "blob.h"
+#include "filter.h"
+#include "buf_text.h"
+#include "git2/sys/filter.h"
+#include "git2/sys/repository.h"
+
+static git_repository *g_repo = NULL;
+
+static git_filter *create_compress_filter(void);
+static git_filter *compress_filter;
+
+void test_filter_stream__initialize(void)
+{
+	compress_filter = create_compress_filter();
+
+	cl_git_pass(git_filter_register("compress", compress_filter, 50));
+	g_repo = cl_git_sandbox_init("empty_standard_repo");
+}
+
+void test_filter_stream__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+	g_repo = NULL;
+
+	git_filter_unregister("compress");
+}
+
+#define CHUNKSIZE 10240
+
+struct compress_stream {
+	git_writestream parent;
+	git_writestream *next;
+	git_filter_mode_t mode;
+	char current;
+	size_t current_chunk;
+};
+
+static int compress_stream_write__deflated(struct compress_stream *stream, const char *buffer, size_t len)
+{
+	size_t idx = 0;
+
+	while (len > 0) {
+		size_t chunkremain, chunksize;
+
+		if (stream->current_chunk == 0)
+			stream->current = buffer[idx];
+
+		chunkremain = CHUNKSIZE - stream->current_chunk;
+		chunksize = min(chunkremain, len);
+
+		stream->current_chunk += chunksize;
+		len -= chunksize;
+		idx += chunksize;
+
+		if (stream->current_chunk == CHUNKSIZE) {
+			cl_git_pass(stream->next->write(stream->next, &stream->current, 1));
+			stream->current_chunk = 0;
+		}
+	}
+
+	return 0;
+}
+
+static int compress_stream_write__inflated(struct compress_stream *stream, const char *buffer, size_t len)
+{
+	char inflated[CHUNKSIZE];
+	size_t i, j;
+
+	for (i = 0; i < len; i++) {
+		for (j = 0; j < CHUNKSIZE; j++)
+			inflated[j] = buffer[i];
+
+		cl_git_pass(stream->next->write(stream->next, inflated, CHUNKSIZE));
+	}
+
+	return 0;
+}
+
+static int compress_stream_write(git_writestream *s, const char *buffer, size_t len)
+{
+	struct compress_stream *stream = (struct compress_stream *)s;
+
+	return (stream->mode == GIT_FILTER_TO_ODB) ?
+		compress_stream_write__deflated(stream, buffer, len) :
+		compress_stream_write__inflated(stream, buffer, len);
+}
+
+static int compress_stream_close(git_writestream *s)
+{
+	struct compress_stream *stream = (struct compress_stream *)s;
+	cl_assert_equal_i(0, stream->current_chunk);
+	stream->next->close(stream->next);
+	return 0;
+}
+
+static void compress_stream_free(git_writestream *stream)
+{
+	git__free(stream);
+}
+
+static int compress_filter_stream_init(
+	git_writestream **out,
+	git_filter *self,
+	void **payload,
+	const git_filter_source *src,
+	git_writestream *next)
+{
+	struct compress_stream *stream = git__calloc(1, sizeof(struct compress_stream));
+	cl_assert(stream);
+
+	GIT_UNUSED(self);
+	GIT_UNUSED(payload);
+
+	stream->parent.write = compress_stream_write;
+	stream->parent.close = compress_stream_close;
+	stream->parent.free = compress_stream_free;
+	stream->next = next;
+	stream->mode = git_filter_source_mode(src);
+
+	*out = (git_writestream *)stream;
+	return 0;
+}
+
+static void compress_filter_free(git_filter *f)
+{
+	git__free(f);
+}
+
+git_filter *create_compress_filter(void)
+{
+	git_filter *filter = git__calloc(1, sizeof(git_filter));
+	cl_assert(filter);
+
+	filter->version = GIT_FILTER_VERSION;
+	filter->attributes = "+compress";
+	filter->stream = compress_filter_stream_init;
+	filter->shutdown = compress_filter_free;
+
+	return filter;
+}
+
+static void writefile(const char *filename, size_t numchunks)
+{
+	git_buf path = GIT_BUF_INIT;
+	char buf[CHUNKSIZE];
+	size_t i = 0, j = 0;
+	int fd;
+
+	cl_git_pass(git_buf_joinpath(&path, "empty_standard_repo", filename));
+
+	fd = p_open(path.ptr, O_RDWR|O_CREAT, 0666);
+	cl_assert(fd >= 0);
+
+	for (i = 0; i < numchunks; i++) {
+		for (j = 0; j < CHUNKSIZE; j++) {
+			buf[j] = i % 256;
+		}
+
+		cl_git_pass(p_write(fd, buf, CHUNKSIZE));
+	}
+	p_close(fd);
+
+	git_buf_free(&path);
+}
+
+static void test_stream(size_t numchunks)
+{
+	git_index *index;
+	const git_index_entry *entry;
+	git_blob *blob;
+	struct stat st;
+	git_checkout_options checkout_opts = GIT_CHECKOUT_OPTIONS_INIT;
+
+	checkout_opts.checkout_strategy = GIT_CHECKOUT_FORCE;
+
+	cl_git_mkfile(
+		"empty_standard_repo/.gitattributes",
+		"* compress\n");
+
+	/* write a file to disk */
+	writefile("streamed_file", numchunks);
+
+	/* place it in the index */
+	cl_git_pass(git_repository_index(&index, g_repo));
+	cl_git_pass(git_index_add_bypath(index, "streamed_file"));
+	cl_git_pass(git_index_write(index));
+
+	/* ensure it was appropriately compressed */
+	cl_assert(entry = git_index_get_bypath(index, "streamed_file", 0));
+
+	cl_git_pass(git_blob_lookup(&blob, g_repo, &entry->id));
+	cl_assert_equal_i(numchunks, git_blob_rawsize(blob));
+
+	/* check the file back out */
+	cl_must_pass(p_unlink("empty_standard_repo/streamed_file"));
+	cl_git_pass(git_checkout_index(g_repo, index, &checkout_opts));
+
+	/* ensure it was decompressed */
+	cl_must_pass(p_stat("empty_standard_repo/streamed_file", &st));
+	cl_assert_equal_sz((numchunks * CHUNKSIZE), st.st_size);
+
+	git_index_free(index);
+	git_blob_free(blob);
+}
+
+/* write a 50KB file through the "compression" stream */
+void test_filter_stream__smallfile(void)
+{
+	test_stream(5);
+}
+
+/* optionally write a 500 MB file through the compression stream */
+void test_filter_stream__bigfile(void)
+{
+	if (!cl_getenv("GITTEST_INVASIVE_FS_SIZE"))
+		cl_skip();
+
+	test_stream(51200);
+}
diff --git a/tests/repo/init.c b/tests/repo/init.c
index 91747c9..0761568 100644
--- a/tests/repo/init.c
+++ b/tests/repo/init.c
@@ -722,7 +722,7 @@ void test_repo_init__at_filesystem_root(void)
 	git_buf root = GIT_BUF_INIT;
 	int root_len;
 
-	if (!cl_getenv("GITTEST_INVASIVE_FILESYSTEM"))
+	if (!cl_getenv("GITTEST_INVASIVE_FS_STRUCTURE"))
 		cl_skip();
 
 	root_len = git_path_root(sandbox);