thodg/libgit2/src/diff_file.c

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• Hash : a521f5b1
  Author :
  Date : 2017-12-15T10:47:01
  

  diff_file: properly refcount blobs when initializing file contents When initializing a `git_diff_file_content` from a source whose data is derived from a blob, we simply assign the blob's pointer to the resulting struct without incrementing its refcount. Thus, the structure can only be used as long as the blob is kept alive by the caller. Fix the issue by using `git_blob_dup` instead of a direct assignment. This function will increment the refcount of the blob without allocating new memory, so it does exactly what we want. As `git_diff_file_content__unload` already frees the blob when `GIT_DIFF_FLAG__FREE_BLOB` is set, we don't need to add new code handling the free but only have to set that flag correctly.

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• src/diff_file.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 "git2/blob.h"
  #include "git2/submodule.h"
  #include "diff.h"
  #include "diff_generate.h"
  #include "diff_file.h"
  #include "odb.h"
  #include "fileops.h"
  #include "filter.h"
  
  #define DIFF_MAX_FILESIZE 0x20000000
  
  static bool diff_file_content_binary_by_size(git_diff_file_content *fc)
  {
  	/* if we have diff opts, check max_size vs file size */
  	if ((fc->file->flags & DIFF_FLAGS_KNOWN_BINARY) == 0 &&
  		fc->opts_max_size > 0 &&
  		fc->file->size > fc->opts_max_size)
  		fc->file->flags |= GIT_DIFF_FLAG_BINARY;
  
  	return ((fc->file->flags & GIT_DIFF_FLAG_BINARY) != 0);
  }
  
  static void diff_file_content_binary_by_content(git_diff_file_content *fc)
  {
  	if ((fc->file->flags & DIFF_FLAGS_KNOWN_BINARY) != 0)
  		return;
  
  	switch (git_diff_driver_content_is_binary(
  		fc->driver, fc->map.data, fc->map.len)) {
  	case 0: fc->file->flags |= GIT_DIFF_FLAG_NOT_BINARY; break;
  	case 1: fc->file->flags |= GIT_DIFF_FLAG_BINARY; break;
  	default: break;
  	}
  }
  
  static int diff_file_content_init_common(
  	git_diff_file_content *fc, const git_diff_options *opts)
  {
  	fc->opts_flags = opts ? opts->flags : GIT_DIFF_NORMAL;
  
  	if (opts && opts->max_size >= 0)
  		fc->opts_max_size = opts->max_size ?
  			opts->max_size : DIFF_MAX_FILESIZE;
  
  	if (fc->src == GIT_ITERATOR_TYPE_EMPTY)
  		fc->src = GIT_ITERATOR_TYPE_TREE;
  
  	if (!fc->driver &&
  		git_diff_driver_lookup(&fc->driver, fc->repo, fc->file->path) < 0)
  		return -1;
  
  	/* give driver a chance to modify options */
  	git_diff_driver_update_options(&fc->opts_flags, fc->driver);
  
  	/* make sure file is conceivable mmap-able */
  	if ((git_off_t)((size_t)fc->file->size) != fc->file->size)
  		fc->file->flags |= GIT_DIFF_FLAG_BINARY;
  	/* check if user is forcing text diff the file */
  	else if (fc->opts_flags & GIT_DIFF_FORCE_TEXT) {
  		fc->file->flags &= ~GIT_DIFF_FLAG_BINARY;
  		fc->file->flags |= GIT_DIFF_FLAG_NOT_BINARY;
  	}
  	/* check if user is forcing binary diff the file */
  	else if (fc->opts_flags & GIT_DIFF_FORCE_BINARY) {
  		fc->file->flags &= ~GIT_DIFF_FLAG_NOT_BINARY;
  		fc->file->flags |= GIT_DIFF_FLAG_BINARY;
  	}
  
  	diff_file_content_binary_by_size(fc);
  
  	if ((fc->flags & GIT_DIFF_FLAG__NO_DATA) != 0) {
  		fc->flags |= GIT_DIFF_FLAG__LOADED;
  		fc->map.len  = 0;
  		fc->map.data = "";
  	}
  
  	if ((fc->flags & GIT_DIFF_FLAG__LOADED) != 0)
  		diff_file_content_binary_by_content(fc);
  
  	return 0;
  }
  
  int git_diff_file_content__init_from_diff(
  	git_diff_file_content *fc,
  	git_diff *diff,
  	git_diff_delta *delta,
  	bool use_old)
  {
  	bool has_data = true;
  
  	memset(fc, 0, sizeof(*fc));
  	fc->repo = diff->repo;
  	fc->file = use_old ? &delta->old_file : &delta->new_file;
  	fc->src  = use_old ? diff->old_src : diff->new_src;
  
  	if (git_diff_driver_lookup(&fc->driver, fc->repo, fc->file->path) < 0)
  		return -1;
  
  	switch (delta->status) {
  	case GIT_DELTA_ADDED:
  		has_data = !use_old; break;
  	case GIT_DELTA_DELETED:
  		has_data = use_old; break;
  	case GIT_DELTA_UNTRACKED:
  		has_data = !use_old &&
  			(diff->opts.flags & GIT_DIFF_SHOW_UNTRACKED_CONTENT) != 0;
  		break;
  	case GIT_DELTA_UNREADABLE:
  	case GIT_DELTA_MODIFIED:
  	case GIT_DELTA_COPIED:
  	case GIT_DELTA_RENAMED:
  		break;
  	default:
  		has_data = false;
  		break;
  	}
  
  	if (!has_data)
  		fc->flags |= GIT_DIFF_FLAG__NO_DATA;
  
  	return diff_file_content_init_common(fc, &diff->opts);
  }
  
  int git_diff_file_content__init_from_src(
  	git_diff_file_content *fc,
  	git_repository *repo,
  	const git_diff_options *opts,
  	const git_diff_file_content_src *src,
  	git_diff_file *as_file)
  {
  	memset(fc, 0, sizeof(*fc));
  	fc->repo = repo;
  	fc->file = as_file;
  
  	if (!src->blob && !src->buf) {
  		fc->flags |= GIT_DIFF_FLAG__NO_DATA;
  	} else {
  		fc->flags |= GIT_DIFF_FLAG__LOADED;
  		fc->file->flags |= GIT_DIFF_FLAG_VALID_ID;
  		fc->file->mode = GIT_FILEMODE_BLOB;
  
  		if (src->blob) {
  			git_blob_dup((git_blob **)&fc->blob, (git_blob *) src->blob);
  			fc->file->size = git_blob_rawsize(src->blob);
  			git_oid_cpy(&fc->file->id, git_blob_id(src->blob));
  			fc->file->id_abbrev = GIT_OID_HEXSZ;
  
  			fc->map.len  = (size_t)fc->file->size;
  			fc->map.data = (char *)git_blob_rawcontent(src->blob);
  
  			fc->flags |= GIT_DIFF_FLAG__FREE_BLOB;
  		} else {
  			fc->file->size = src->buflen;
  			git_odb_hash(&fc->file->id, src->buf, src->buflen, GIT_OBJ_BLOB);
  			fc->file->id_abbrev = GIT_OID_HEXSZ;
  
  			fc->map.len  = src->buflen;
  			fc->map.data = (char *)src->buf;
  		}
  	}
  
  	return diff_file_content_init_common(fc, opts);
  }
  
  static int diff_file_content_commit_to_str(
  	git_diff_file_content *fc, bool check_status)
  {
  	char oid[GIT_OID_HEXSZ+1];
  	git_buf content = GIT_BUF_INIT;
  	const char *status = "";
  
  	if (check_status) {
  		int error = 0;
  		git_submodule *sm = NULL;
  		unsigned int sm_status = 0;
  		const git_oid *sm_head;
  
  		if ((error = git_submodule_lookup(&sm, fc->repo, fc->file->path)) < 0) {
  			/* GIT_EEXISTS means a "submodule" that has not been git added */
  			if (error == GIT_EEXISTS) {
  				giterr_clear();
  				error = 0;
  			}
  			return error;
  		}
  
  		if ((error = git_submodule_status(&sm_status, fc->repo, fc->file->path, GIT_SUBMODULE_IGNORE_UNSPECIFIED)) < 0) {
  			git_submodule_free(sm);
  			return error;
  		}
  
  		/* update OID if we didn't have it previously */
  		if ((fc->file->flags & GIT_DIFF_FLAG_VALID_ID) == 0 &&
  			((sm_head = git_submodule_wd_id(sm)) != NULL ||
  			 (sm_head = git_submodule_head_id(sm)) != NULL))
  		{
  			git_oid_cpy(&fc->file->id, sm_head);
  			fc->file->flags |= GIT_DIFF_FLAG_VALID_ID;
  		}
  
  		if (GIT_SUBMODULE_STATUS_IS_WD_DIRTY(sm_status))
  			status = "-dirty";
  
  		git_submodule_free(sm);
  	}
  
  	git_oid_tostr(oid, sizeof(oid), &fc->file->id);
  	if (git_buf_printf(&content, "Subproject commit %s%s\n", oid, status) < 0)
  		return -1;
  
  	fc->map.len  = git_buf_len(&content);
  	fc->map.data = git_buf_detach(&content);
  	fc->flags |= GIT_DIFF_FLAG__FREE_DATA;
  
  	return 0;
  }
  
  static int diff_file_content_load_blob(
  	git_diff_file_content *fc,
  	git_diff_options *opts)
  {
  	int error = 0;
  	git_odb_object *odb_obj = NULL;
  
  	if (git_oid_iszero(&fc->file->id))
  		return 0;
  
  	if (fc->file->mode == GIT_FILEMODE_COMMIT)
  		return diff_file_content_commit_to_str(fc, false);
  
  	/* if we don't know size, try to peek at object header first */
  	if (!fc->file->size) {
  		if ((error = git_diff_file__resolve_zero_size(
  				fc->file, &odb_obj, fc->repo)) < 0)
  			return error;
  	}
  
  	if ((opts->flags & GIT_DIFF_SHOW_BINARY) == 0 &&
  		diff_file_content_binary_by_size(fc))
  		return 0;
  
  	if (odb_obj != NULL) {
  		error = git_object__from_odb_object(
  			(git_object **)&fc->blob, fc->repo, odb_obj, GIT_OBJ_BLOB);
  		git_odb_object_free(odb_obj);
  	} else {
  		error = git_blob_lookup(
  			(git_blob **)&fc->blob, fc->repo, &fc->file->id);
  	}
  
  	if (!error) {
  		fc->flags |= GIT_DIFF_FLAG__FREE_BLOB;
  		fc->map.data = (void *)git_blob_rawcontent(fc->blob);
  		fc->map.len  = (size_t)git_blob_rawsize(fc->blob);
  	}
  
  	return error;
  }
  
  static int diff_file_content_load_workdir_symlink_fake(
  	git_diff_file_content *fc, git_buf *path)
  {
  	git_buf target = GIT_BUF_INIT;
  	int error;
  
  	if ((error = git_futils_readbuffer(&target, path->ptr)) < 0)
  		return error;
  
  	fc->map.len = git_buf_len(&target);
  	fc->map.data = git_buf_detach(&target);
  	fc->flags |= GIT_DIFF_FLAG__FREE_DATA;
  
  	git_buf_free(&target);
  	return error;
  }
  
  static int diff_file_content_load_workdir_symlink(
  	git_diff_file_content *fc, git_buf *path)
  {
  	ssize_t alloc_len, read_len;
  	int symlink_supported, error;
  
  	if ((error = git_repository__cvar(
  		&symlink_supported, fc->repo, GIT_CVAR_SYMLINKS)) < 0)
  		return -1;
  
  	if (!symlink_supported)
  		return diff_file_content_load_workdir_symlink_fake(fc, path);
  
  	/* link path on disk could be UTF-16, so prepare a buffer that is
  	 * big enough to handle some UTF-8 data expansion
  	 */
  	alloc_len = (ssize_t)(fc->file->size * 2) + 1;
  
  	fc->map.data = git__calloc(alloc_len, sizeof(char));
  	GITERR_CHECK_ALLOC(fc->map.data);
  
  	fc->flags |= GIT_DIFF_FLAG__FREE_DATA;
  
  	read_len = p_readlink(git_buf_cstr(path), fc->map.data, alloc_len);
  	if (read_len < 0) {
  		giterr_set(GITERR_OS, "failed to read symlink '%s'", fc->file->path);
  		return -1;
  	}
  
  	fc->map.len = read_len;
  	return 0;
  }
  
  static int diff_file_content_load_workdir_file(
  	git_diff_file_content *fc,
  	git_buf *path,
  	git_diff_options *diff_opts)
  {
  	int error = 0;
  	git_filter_list *fl = NULL;
  	git_file fd = git_futils_open_ro(git_buf_cstr(path));
  	git_buf raw = GIT_BUF_INIT;
  
  	if (fd < 0)
  		return fd;
  
  	if (!fc->file->size &&
  		!(fc->file->size = git_futils_filesize(fd)))
  		goto cleanup;
  
  	if ((diff_opts->flags & GIT_DIFF_SHOW_BINARY) == 0 &&
  		diff_file_content_binary_by_size(fc))
  		goto cleanup;
  
  	if ((error = git_filter_list_load(
  			&fl, fc->repo, NULL, fc->file->path,
  			GIT_FILTER_TO_ODB, GIT_FILTER_ALLOW_UNSAFE)) < 0)
  		goto cleanup;
  
  	/* if there are no filters, try to mmap the file */
  	if (fl == NULL) {
  		if (!(error = git_futils_mmap_ro(
  				&fc->map, fd, 0, (size_t)fc->file->size))) {
  			fc->flags |= GIT_DIFF_FLAG__UNMAP_DATA;
  			goto cleanup;
  		}
  
  		/* if mmap failed, fall through to try readbuffer below */
  		giterr_clear();
  	}
  
  	if (!(error = git_futils_readbuffer_fd(&raw, fd, (size_t)fc->file->size))) {
  		git_buf out = GIT_BUF_INIT;
  
  		error = git_filter_list_apply_to_data(&out, fl, &raw);
  
  		if (out.ptr != raw.ptr)
  			git_buf_free(&raw);
  
  		if (!error) {
  			fc->map.len  = out.size;
  			fc->map.data = out.ptr;
  			fc->flags |= GIT_DIFF_FLAG__FREE_DATA;
  		}
  	}
  
  cleanup:
  	git_filter_list_free(fl);
  	p_close(fd);
  
  	return error;
  }
  
  static int diff_file_content_load_workdir(
  	git_diff_file_content *fc,
  	git_diff_options *diff_opts)
  {
  	int error = 0;
  	git_buf path = GIT_BUF_INIT;
  
  	if (fc->file->mode == GIT_FILEMODE_COMMIT)
  		return diff_file_content_commit_to_str(fc, true);
  
  	if (fc->file->mode == GIT_FILEMODE_TREE)
  		return 0;
  
  	if (git_buf_joinpath(
  			&path, git_repository_workdir(fc->repo), fc->file->path) < 0)
  		return -1;
  
  	if (S_ISLNK(fc->file->mode))
  		error = diff_file_content_load_workdir_symlink(fc, &path);
  	else
  		error = diff_file_content_load_workdir_file(fc, &path, diff_opts);
  
  	/* once data is loaded, update OID if we didn't have it previously */
  	if (!error && (fc->file->flags & GIT_DIFF_FLAG_VALID_ID) == 0) {
  		error = git_odb_hash(
  			&fc->file->id, fc->map.data, fc->map.len, GIT_OBJ_BLOB);
  		fc->file->flags |= GIT_DIFF_FLAG_VALID_ID;
  	}
  
  	git_buf_free(&path);
  	return error;
  }
  
  int git_diff_file_content__load(
  	git_diff_file_content *fc,
  	git_diff_options *diff_opts)
  {
  	int error = 0;
  
  	if ((fc->flags & GIT_DIFF_FLAG__LOADED) != 0)
  		return 0;
  
  	if ((fc->file->flags & GIT_DIFF_FLAG_BINARY) != 0 &&
  		(diff_opts->flags & GIT_DIFF_SHOW_BINARY) == 0)
  		return 0;
  
  	if (fc->src == GIT_ITERATOR_TYPE_WORKDIR)
  		error = diff_file_content_load_workdir(fc, diff_opts);
  	else
  		error = diff_file_content_load_blob(fc, diff_opts);
  	if (error)
  		return error;
  
  	fc->flags |= GIT_DIFF_FLAG__LOADED;
  
  	diff_file_content_binary_by_content(fc);
  
  	return 0;
  }
  
  void git_diff_file_content__unload(git_diff_file_content *fc)
  {
  	if ((fc->flags & GIT_DIFF_FLAG__LOADED) == 0)
  		return;
  
  	if (fc->flags & GIT_DIFF_FLAG__FREE_DATA) {
  		git__free(fc->map.data);
  		fc->map.data = "";
  		fc->map.len  = 0;
  		fc->flags &= ~GIT_DIFF_FLAG__FREE_DATA;
  	}
  	else if (fc->flags & GIT_DIFF_FLAG__UNMAP_DATA) {
  		git_futils_mmap_free(&fc->map);
  		fc->map.data = "";
  		fc->map.len  = 0;
  		fc->flags &= ~GIT_DIFF_FLAG__UNMAP_DATA;
  	}
  
  	if (fc->flags & GIT_DIFF_FLAG__FREE_BLOB) {
  		git_blob_free((git_blob *)fc->blob);
  		fc->blob = NULL;
  		fc->flags &= ~GIT_DIFF_FLAG__FREE_BLOB;
  	}
  
  	fc->flags &= ~GIT_DIFF_FLAG__LOADED;
  }
  
  void git_diff_file_content__clear(git_diff_file_content *fc)
  {
  	git_diff_file_content__unload(fc);
  
  	/* for now, nothing else to do */
  }
  

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