thodg/libgit2/src/filter.c

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• Hash : 2ed855a9
  Author :
  Date : 2016-02-07T13:16:30
  

  filter: avoid races during filter registration Previously we would set the global filter registry structure before adding filters to the structure, without a lock, which is quite racy. Now, register default filters during global registration and use an rwlock to read and write the filter registry (as appopriate).

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• src/filter.c

• /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  
  #include "common.h"
  #include "fileops.h"
  #include "hash.h"
  #include "filter.h"
  #include "repository.h"
  #include "global.h"
  #include "git2/sys/filter.h"
  #include "git2/config.h"
  #include "blob.h"
  #include "attr_file.h"
  #include "array.h"
  
  struct git_filter_source {
  	git_repository *repo;
  	const char     *path;
  	git_oid         oid;  /* zero if unknown (which is likely) */
  	uint16_t        filemode; /* zero if unknown */
  	git_filter_mode_t mode;
  	uint32_t        flags;
  };
  
  typedef struct {
  	const char *filter_name;
  	git_filter *filter;
  	void *payload;
  } git_filter_entry;
  
  struct git_filter_list {
  	git_array_t(git_filter_entry) filters;
  	git_filter_source source;
  	git_buf *temp_buf;
  	char path[GIT_FLEX_ARRAY];
  };
  
  typedef struct {
  	char *filter_name;
  	git_filter *filter;
  	int priority;
  	int initialized;
  	size_t nattrs, nmatches;
  	char *attrdata;
  	const char *attrs[GIT_FLEX_ARRAY];
  } git_filter_def;
  
  static int filter_def_priority_cmp(const void *a, const void *b)
  {
  	int pa = ((const git_filter_def *)a)->priority;
  	int pb = ((const git_filter_def *)b)->priority;
  	return (pa < pb) ? -1 : (pa > pb) ? 1 : 0;
  }
  
  struct git_filter_registry {
  	git_rwlock lock;
  	git_vector filters;
  };
  
  static struct git_filter_registry filter_registry;
  
  static void git_filter_global_shutdown(void);
  
  
  static int filter_def_scan_attrs(
  	git_buf *attrs, size_t *nattr, size_t *nmatch, const char *attr_str)
  {
  	const char *start, *scan = attr_str;
  	int has_eq;
  
  	*nattr = *nmatch = 0;
  
  	if (!scan)
  		return 0;
  
  	while (*scan) {
  		while (git__isspace(*scan)) scan++;
  
  		for (start = scan, has_eq = 0; *scan && !git__isspace(*scan); ++scan) {
  			if (*scan == '=')
  				has_eq = 1;
  		}
  
  		if (scan > start) {
  			(*nattr)++;
  			if (has_eq || *start == '-' || *start == '+' || *start == '!')
  				(*nmatch)++;
  
  			if (has_eq)
  				git_buf_putc(attrs, '=');
  			git_buf_put(attrs, start, scan - start);
  			git_buf_putc(attrs, '\0');
  		}
  	}
  
  	return 0;
  }
  
  static void filter_def_set_attrs(git_filter_def *fdef)
  {
  	char *scan = fdef->attrdata;
  	size_t i;
  
  	for (i = 0; i < fdef->nattrs; ++i) {
  		const char *name, *value;
  
  		switch (*scan) {
  		case '=':
  			name = scan + 1;
  			for (scan++; *scan != '='; scan++) /* find '=' */;
  			*scan++ = '\0';
  			value = scan;
  			break;
  		case '-':
  			name = scan + 1; value = git_attr__false; break;
  		case '+':
  			name = scan + 1; value = git_attr__true;  break;
  		case '!':
  			name = scan + 1; value = git_attr__unset; break;
  		default:
  			name = scan;     value = NULL; break;
  		}
  
  		fdef->attrs[i] = name;
  		fdef->attrs[i + fdef->nattrs] = value;
  
  		scan += strlen(scan) + 1;
  	}
  }
  
  static int filter_def_name_key_check(const void *key, const void *fdef)
  {
  	const char *name =
  		fdef ? ((const git_filter_def *)fdef)->filter_name : NULL;
  	return name ? git__strcmp(key, name) : -1;
  }
  
  static int filter_def_filter_key_check(const void *key, const void *fdef)
  {
  	const void *filter = fdef ? ((const git_filter_def *)fdef)->filter : NULL;
  	return (key == filter) ? 0 : -1;
  }
  
  /* Note: callers must lock the registry before calling this function */
  static int filter_registry_insert(
  	const char *name, git_filter *filter, int priority)
  {
  	git_filter_def *fdef;
  	size_t nattr = 0, nmatch = 0, alloc_len;
  	git_buf attrs = GIT_BUF_INIT;
  
  	if (filter_def_scan_attrs(&attrs, &nattr, &nmatch, filter->attributes) < 0)
  		return -1;
  
  	GITERR_CHECK_ALLOC_MULTIPLY(&alloc_len, nattr, 2);
  	GITERR_CHECK_ALLOC_MULTIPLY(&alloc_len, alloc_len, sizeof(char *));
  	GITERR_CHECK_ALLOC_ADD(&alloc_len, alloc_len, sizeof(git_filter_def));
  
  	fdef = git__calloc(1, alloc_len);
  	GITERR_CHECK_ALLOC(fdef);
  
  	fdef->filter_name = git__strdup(name);
  	GITERR_CHECK_ALLOC(fdef->filter_name);
  
  	fdef->filter      = filter;
  	fdef->priority    = priority;
  	fdef->nattrs      = nattr;
  	fdef->nmatches    = nmatch;
  	fdef->attrdata    = git_buf_detach(&attrs);
  
  	filter_def_set_attrs(fdef);
  
  	if (git_vector_insert(&filter_registry.filters, fdef) < 0) {
  		git__free(fdef->filter_name);
  		git__free(fdef->attrdata);
  		git__free(fdef);
  		return -1;
  	}
  
  	git_vector_sort(&filter_registry.filters);
  	return 0;
  }
  
  int git_filter_global_init(void)
  {
  	git_filter *crlf = NULL, *ident = NULL;
  	int error = 0;
  
  	if (git_rwlock_init(&filter_registry.lock) < 0)
  		return -1;
  
  	if ((error = git_vector_init(&filter_registry.filters, 2,
  		filter_def_priority_cmp)) < 0)
  		goto done;
  
  	if ((crlf = git_crlf_filter_new()) == NULL ||
  		filter_registry_insert(
  			GIT_FILTER_CRLF, crlf, GIT_FILTER_CRLF_PRIORITY) < 0 ||
  		(ident = git_ident_filter_new()) == NULL ||
  		filter_registry_insert(
  			GIT_FILTER_IDENT, ident, GIT_FILTER_IDENT_PRIORITY) < 0)
  		error = -1;
  
  	git__on_shutdown(git_filter_global_shutdown);
  
  done:
  	if (error) {
  		git_filter_free(crlf);
  		git_filter_free(ident);
  	}
  
  	return error;
  }
  
  static void git_filter_global_shutdown(void)
  {
  	size_t pos;
  	git_filter_def *fdef;
  
  	if (git_rwlock_wrlock(&filter_registry.lock) < 0)
  		return;
  
  	git_vector_foreach(&filter_registry.filters, pos, fdef) {
  		if (fdef->filter && fdef->filter->shutdown) {
  			fdef->filter->shutdown(fdef->filter);
  			fdef->initialized = false;
  		}
  
  		git__free(fdef->filter_name);
  		git__free(fdef->attrdata);
  		git__free(fdef);
  	}
  
  	git_vector_free(&filter_registry.filters);
  
  	git_rwlock_wrunlock(&filter_registry.lock);
  	git_rwlock_free(&filter_registry.lock);
  }
  
  /* Note: callers must lock the registry before calling this function */
  static int filter_registry_find(size_t *pos, const char *name)
  {
  	return git_vector_search2(
  		pos, &filter_registry.filters, filter_def_name_key_check, name);
  }
  
  /* Note: callers must lock the registry before calling this function */
  static git_filter_def *filter_registry_lookup(size_t *pos, const char *name)
  {
  	git_filter_def *fdef = NULL;
  
  	if (!filter_registry_find(pos, name))
  		fdef = git_vector_get(&filter_registry.filters, *pos);
  
  	return fdef;
  }
  
  
  int git_filter_register(
  	const char *name, git_filter *filter, int priority)
  {
  	int error;
  
  	assert(name && filter);
  
  	if (git_rwlock_wrlock(&filter_registry.lock) < 0) {
  		giterr_set(GITERR_OS, "failed to lock filter registry");
  		return -1;
  	}
  
  	if (!filter_registry_find(NULL, name)) {
  		giterr_set(
  			GITERR_FILTER, "attempt to reregister existing filter '%s'", name);
  		error = GIT_EEXISTS;
  		goto done;
  	}
  
  	error = filter_registry_insert(name, filter, priority);
  
  done:
  	git_rwlock_wrunlock(&filter_registry.lock);
  	return error;
  }
  
  int git_filter_unregister(const char *name)
  {
  	size_t pos;
  	git_filter_def *fdef;
  	int error = 0;
  
  	assert(name);
  
  	/* cannot unregister default filters */
  	if (!strcmp(GIT_FILTER_CRLF, name) || !strcmp(GIT_FILTER_IDENT, name)) {
  		giterr_set(GITERR_FILTER, "Cannot unregister filter '%s'", name);
  		return -1;
  	}
  
  	if (git_rwlock_wrlock(&filter_registry.lock) < 0) {
  		giterr_set(GITERR_OS, "failed to lock filter registry");
  		return -1;
  	}
  
  	if ((fdef = filter_registry_lookup(&pos, name)) == NULL) {
  		giterr_set(GITERR_FILTER, "Cannot find filter '%s' to unregister", name);
  		error = GIT_ENOTFOUND;
  		goto done;
  	}
  
  	git_vector_remove(&filter_registry.filters, pos);
  
  	if (fdef->initialized && fdef->filter && fdef->filter->shutdown) {
  		fdef->filter->shutdown(fdef->filter);
  		fdef->initialized = false;
  	}
  
  	git__free(fdef->filter_name);
  	git__free(fdef->attrdata);
  	git__free(fdef);
  
  done:
  	git_rwlock_wrunlock(&filter_registry.lock);
  	return error;
  }
  
  static int filter_initialize(git_filter_def *fdef)
  {
  	int error = 0;
  
  	if (!fdef->initialized && fdef->filter && fdef->filter->initialize) {
  		if ((error = fdef->filter->initialize(fdef->filter)) < 0)
  			return error;
  	}
  
  	fdef->initialized = true;
  	return 0;
  }
  
  git_filter *git_filter_lookup(const char *name)
  {
  	size_t pos;
  	git_filter_def *fdef;
  	git_filter *filter = NULL;
  
  	if (git_rwlock_rdlock(&filter_registry.lock) < 0) {
  		giterr_set(GITERR_OS, "failed to lock filter registry");
  		return NULL;
  	}
  
  	if ((fdef = filter_registry_lookup(&pos, name)) == NULL ||
  		(!fdef->initialized && filter_initialize(fdef) < 0))
  		goto done;
  
  	filter = fdef->filter;
  
  done:
  	git_rwlock_rdunlock(&filter_registry.lock);
  	return filter;
  }
  
  void git_filter_free(git_filter *filter)
  {
  	git__free(filter);
  }
  
  git_repository *git_filter_source_repo(const git_filter_source *src)
  {
  	return src->repo;
  }
  
  const char *git_filter_source_path(const git_filter_source *src)
  {
  	return src->path;
  }
  
  uint16_t git_filter_source_filemode(const git_filter_source *src)
  {
  	return src->filemode;
  }
  
  const git_oid *git_filter_source_id(const git_filter_source *src)
  {
  	return git_oid_iszero(&src->oid) ? NULL : &src->oid;
  }
  
  git_filter_mode_t git_filter_source_mode(const git_filter_source *src)
  {
  	return src->mode;
  }
  
  uint32_t git_filter_source_flags(const git_filter_source *src)
  {
  	return src->flags;
  }
  
  static int filter_list_new(
  	git_filter_list **out, const git_filter_source *src)
  {
  	git_filter_list *fl = NULL;
  	size_t pathlen = src->path ? strlen(src->path) : 0, alloclen;
  
  	GITERR_CHECK_ALLOC_ADD(&alloclen, sizeof(git_filter_list), pathlen);
  	GITERR_CHECK_ALLOC_ADD(&alloclen, alloclen, 1);
  
  	fl = git__calloc(1, alloclen);
  	GITERR_CHECK_ALLOC(fl);
  
  	if (src->path)
  		memcpy(fl->path, src->path, pathlen);
  	fl->source.repo = src->repo;
  	fl->source.path = fl->path;
  	fl->source.mode = src->mode;
  	fl->source.flags = src->flags;
  
  	*out = fl;
  	return 0;
  }
  
  static int filter_list_check_attributes(
  	const char ***out,
  	git_repository *repo,
  	git_attr_session *attr_session,
  	git_filter_def *fdef,
  	const git_filter_source *src)
  {
  	int error;
  	size_t i;
  	const char **strs = git__calloc(fdef->nattrs, sizeof(const char *));
  	GITERR_CHECK_ALLOC(strs);
  
  	error = git_attr_get_many_with_session(
  		strs, repo, attr_session, 0, src->path, fdef->nattrs, fdef->attrs);
  
  	/* if no values were found but no matches are needed, it's okay! */
  	if (error == GIT_ENOTFOUND && !fdef->nmatches) {
  		giterr_clear();
  		git__free((void *)strs);
  		return 0;
  	}
  
  	for (i = 0; !error && i < fdef->nattrs; ++i) {
  		const char *want = fdef->attrs[fdef->nattrs + i];
  		git_attr_t want_type, found_type;
  
  		if (!want)
  			continue;
  
  		want_type  = git_attr_value(want);
  		found_type = git_attr_value(strs[i]);
  
  		if (want_type != found_type)
  			error = GIT_ENOTFOUND;
  		else if (want_type == GIT_ATTR_VALUE_T &&
  				strcmp(want, strs[i]) &&
  				strcmp(want, "*"))
  			error = GIT_ENOTFOUND;
  	}
  
  	if (error)
  		git__free((void *)strs);
  	else
  		*out = strs;
  
  	return error;
  }
  
  int git_filter_list_new(
  	git_filter_list **out,
  	git_repository *repo,
  	git_filter_mode_t mode,
  	uint32_t flags)
  {
  	git_filter_source src = { 0 };
  	src.repo = repo;
  	src.path = NULL;
  	src.mode = mode;
  	src.flags = flags;
  	return filter_list_new(out, &src);
  }
  
  int git_filter_list__load_ext(
  	git_filter_list **filters,
  	git_repository *repo,
  	git_blob *blob, /* can be NULL */
  	const char *path,
  	git_filter_mode_t mode,
  	git_filter_options *filter_opts)
  {
  	int error = 0;
  	git_filter_list *fl = NULL;
  	git_filter_source src = { 0 };
  	git_filter_entry *fe;
  	size_t idx;
  	git_filter_def *fdef;
  
  	if (git_rwlock_rdlock(&filter_registry.lock) < 0) {
  		giterr_set(GITERR_OS, "failed to lock filter registry");
  		return -1;
  	}
  
  	src.repo = repo;
  	src.path = path;
  	src.mode = mode;
  	src.flags = filter_opts->flags;
  
  	if (blob)
  		git_oid_cpy(&src.oid, git_blob_id(blob));
  
  	git_vector_foreach(&filter_registry.filters, idx, fdef) {
  		const char **values = NULL;
  		void *payload = NULL;
  
  		if (!fdef || !fdef->filter)
  			continue;
  
  		if (fdef->nattrs > 0) {
  			error = filter_list_check_attributes(
  				&values, repo, filter_opts->attr_session, fdef, &src);
  
  			if (error == GIT_ENOTFOUND) {
  				error = 0;
  				continue;
  			} else if (error < 0)
  				break;
  		}
  
  		if (!fdef->initialized && (error = filter_initialize(fdef)) < 0)
  			break;
  
  		if (fdef->filter->check)
  			error = fdef->filter->check(
  				fdef->filter, &payload, &src, values);
  
  		git__free((void *)values);
  
  		if (error == GIT_PASSTHROUGH)
  			error = 0;
  		else if (error < 0)
  			break;
  		else {
  			if (!fl) {
  				if ((error = filter_list_new(&fl, &src)) < 0)
  					break;
  
  				fl->temp_buf = filter_opts->temp_buf;
  			}
  
  			fe = git_array_alloc(fl->filters);
  			GITERR_CHECK_ALLOC(fe);
  
  			fe->filter = fdef->filter;
  			fe->filter_name = fdef->filter_name;
  			fe->payload = payload;
  		}
  	}
  
  	git_rwlock_rdunlock(&filter_registry.lock);
  
  	if (error && fl != NULL) {
  		git_array_clear(fl->filters);
  		git__free(fl);
  		fl = NULL;
  	}
  
  	*filters = fl;
  	return error;
  }
  
  int git_filter_list_load(
  	git_filter_list **filters,
  	git_repository *repo,
  	git_blob *blob, /* can be NULL */
  	const char *path,
  	git_filter_mode_t mode,
  	uint32_t flags)
  {
  	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)
  {
  	uint32_t i;
  
  	if (!fl)
  		return;
  
  	for (i = 0; i < git_array_size(fl->filters); ++i) {
  		git_filter_entry *fe = git_array_get(fl->filters, i);
  		if (fe->filter->cleanup)
  			fe->filter->cleanup(fe->filter, fe->payload);
  	}
  
  	git_array_clear(fl->filters);
  	git__free(fl);
  }
  
  int git_filter_list_contains(
  	git_filter_list *fl,
  	const char *name)
  {
  	size_t i;
  
  	assert(name);
  
  	if (!fl)
  		return 0;
  
  	for (i = 0; i < fl->filters.size; i++) {
  		if (strcmp(fl->filters.ptr[i].filter_name, name) == 0)
  			return 1;
  	}
  
  	return 0;
  }
  
  int git_filter_list_push(
  	git_filter_list *fl, git_filter *filter, void *payload)
  {
  	int error = 0;
  	size_t pos;
  	git_filter_def *fdef = NULL;
  	git_filter_entry *fe;
  
  	assert(fl && filter);
  
  	if (git_rwlock_rdlock(&filter_registry.lock) < 0) {
  		giterr_set(GITERR_OS, "failed to lock filter registry");
  		return -1;
  	}
  
  	if (git_vector_search2(
  			&pos, &filter_registry.filters,
  			filter_def_filter_key_check, filter) == 0)
  		fdef = git_vector_get(&filter_registry.filters, pos);
  
  	git_rwlock_rdunlock(&filter_registry.lock);
  
  	if (fdef == NULL) {
  		giterr_set(GITERR_FILTER, "Cannot use an unregistered filter");
  		return -1;
  	}
  
  	if (!fdef->initialized && (error = filter_initialize(fdef)) < 0)
  		return error;
  
  	fe = git_array_alloc(fl->filters);
  	GITERR_CHECK_ALLOC(fe);
  	fe->filter  = filter;
  	fe->payload = payload;
  
  	return 0;
  }
  
  size_t git_filter_list_length(const git_filter_list *fl)
  {
  	return fl ? git_array_size(fl->filters) : 0;
  }
  
  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)
  {
  	struct buf_stream *buf_stream = (struct buf_stream *)s;
  	assert(buf_stream);
  
  	assert(buf_stream->complete == 0);
  
  	return git_buf_put(buf_stream->target, buffer, len);
  }
  
  static int buf_stream_close(git_writestream *s)
  {
  	struct buf_stream *buf_stream = (struct buf_stream *)s;
  	assert(buf_stream);
  
  	assert(buf_stream->complete == 0);
  	buf_stream->complete = 1;
  
  	return 0;
  }
  
  static void buf_stream_free(git_writestream *s)
  {
  	GIT_UNUSED(s);
  }
  
  static void buf_stream_init(struct buf_stream *writer, git_buf *target)
  {
  	memset(writer, 0, sizeof(struct buf_stream));
  
  	writer->parent.write = buf_stream_write;
  	writer->parent.close = buf_stream_close;
  	writer->parent.free = buf_stream_free;
  	writer->target = target;
  
  	git_buf_clear(target);
  }
  
  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;
  	}
  
  	buf_stream_init(&writer, tgt);
  
  	if ((error = git_filter_list_stream_data(filters, src,
  		&writer.parent)) < 0)
  			return error;
  
  	assert(writer.complete);
  	return error;
  }
  
  int git_filter_list_apply_to_file(
  	git_buf *out,
  	git_filter_list *filters,
  	git_repository *repo,
  	const char *path)
  {
  	struct buf_stream writer;
  	int error;
  
  	buf_stream_init(&writer, out);
  
  	if ((error = git_filter_list_stream_file(
  		filters, repo, path, &writer.parent)) < 0)
  			return error;
  
  	assert(writer.complete);
  	return error;
  }
  
  static int buf_from_blob(git_buf *out, git_blob *blob)
  {
  	git_off_t rawsize = git_blob_rawsize(blob);
  
  	if (!git__is_sizet(rawsize)) {
  		giterr_set(GITERR_OS, "Blob is too large to filter");
  		return -1;
  	}
  
  	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, &writer.parent)) < 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;
  
  	if (temp_buf)
  		git_buf_clear(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);
  }
  
  int git_filter_list_stream_file(
  	git_filter_list *filters,
  	git_repository *repo,
  	const char *path,
  	git_writestream *target)
  {
  	char buf[FILTERIO_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 = -1, 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(abspath.ptr)) < 0) {
  		error = fd;
  		goto done;
  	}
  
  	while ((readlen = p_read(fd, buf, sizeof(buf))) > 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;
  
  
  done:
  	if (fd >= 0)
  		p_close(fd);
  	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, close_error;
  
  	git_buf_sanitize(data);
  
  	if ((error = stream_list_init(&stream_start, &filter_streams, filters, target)) < 0)
  		goto out;
  
  	error = stream_start->write(stream_start, data->ptr, data->size);
  
  out:
  	close_error = stream_start->close(stream_start);
  	stream_list_free(&filter_streams);
  	/* propagate the stream init or write error */
  	return error < 0 ? error : close_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_stream_data(filters, &in, target);
  }
  

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