Re: [PATCH 1/4] index-pack: Refactor base arguments of resolve_delta into a struct

[Nicolas Pitre <nico@cam.org>]

On Sun, 13 Jul 2008, Shawn O. Pearce wrote:

> We need to discard base objects which are not recently used if our
> memory gets low, such as when we are unpacking a long delta chain
> of a very large object.
> 
> To support tracking the available base objects we combine the
> pointer and size into a struct.  Future changes would allow the
> data pointer to be free'd and marked NULL if memory gets low.
> 
> Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

ACK


> ---
>  index-pack.c |   60 +++++++++++++++++++++++++++++++--------------------------
>  1 files changed, 33 insertions(+), 27 deletions(-)
> 
> diff --git a/index-pack.c b/index-pack.c
> index 25db5db..db03478 100644
> --- a/index-pack.c
> +++ b/index-pack.c
> @@ -26,6 +26,11 @@ union delta_base {
>  	off_t offset;
>  };
>  
> +struct base_data {
> +	void *data;
> +	unsigned long size;
> +};
> +
>  /*
>   * Even if sizeof(union delta_base) == 24 on 64-bit archs, we really want
>   * to memcmp() only the first 20 bytes.
> @@ -426,25 +431,25 @@ static void sha1_object(const void *data, unsigned long size,
>  	}
>  }
>  
> -static void resolve_delta(struct object_entry *delta_obj, void *base_data,
> -			  unsigned long base_size, enum object_type type)
> +static void resolve_delta(struct object_entry *delta_obj,
> +			  struct base_data *base_obj, enum object_type type)
>  {
>  	void *delta_data;
>  	unsigned long delta_size;
> -	void *result;
> -	unsigned long result_size;
>  	union delta_base delta_base;
>  	int j, first, last;
> +	struct base_data result;
>  
>  	delta_obj->real_type = type;
>  	delta_data = get_data_from_pack(delta_obj);
>  	delta_size = delta_obj->size;
> -	result = patch_delta(base_data, base_size, delta_data, delta_size,
> -			     &result_size);
> +	result.data = patch_delta(base_obj->data, base_obj->size,
> +			     delta_data, delta_size,
> +			     &result.size);
>  	free(delta_data);
> -	if (!result)
> +	if (!result.data)
>  		bad_object(delta_obj->idx.offset, "failed to apply delta");
> -	sha1_object(result, result_size, type, delta_obj->idx.sha1);
> +	sha1_object(result.data, result.size, type, delta_obj->idx.sha1);
>  	nr_resolved_deltas++;
>  
>  	hashcpy(delta_base.sha1, delta_obj->idx.sha1);
> @@ -452,7 +457,7 @@ static void resolve_delta(struct object_entry *delta_obj, void *base_data,
>  		for (j = first; j <= last; j++) {
>  			struct object_entry *child = objects + deltas[j].obj_no;
>  			if (child->real_type == OBJ_REF_DELTA)
> -				resolve_delta(child, result, result_size, type);
> +				resolve_delta(child, &result, type);
>  		}
>  	}
>  
> @@ -462,11 +467,11 @@ static void resolve_delta(struct object_entry *delta_obj, void *base_data,
>  		for (j = first; j <= last; j++) {
>  			struct object_entry *child = objects + deltas[j].obj_no;
>  			if (child->real_type == OBJ_OFS_DELTA)
> -				resolve_delta(child, result, result_size, type);
> +				resolve_delta(child, &result, type);
>  		}
>  	}
>  
> -	free(result);
> +	free(result.data);
>  }
>  
>  static int compare_delta_entry(const void *a, const void *b)
> @@ -481,7 +486,6 @@ static void parse_pack_objects(unsigned char *sha1)
>  {
>  	int i;
>  	struct delta_entry *delta = deltas;
> -	void *data;
>  	struct stat st;
>  
>  	/*
> @@ -496,7 +500,7 @@ static void parse_pack_objects(unsigned char *sha1)
>  				nr_objects);
>  	for (i = 0; i < nr_objects; i++) {
>  		struct object_entry *obj = &objects[i];
> -		data = unpack_raw_entry(obj, &delta->base);
> +		void *data = unpack_raw_entry(obj, &delta->base);
>  		obj->real_type = obj->type;
>  		if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA) {
>  			nr_deltas++;
> @@ -545,6 +549,7 @@ static void parse_pack_objects(unsigned char *sha1)
>  		struct object_entry *obj = &objects[i];
>  		union delta_base base;
>  		int j, ref, ref_first, ref_last, ofs, ofs_first, ofs_last;
> +		struct base_data base_obj;
>  
>  		if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA)
>  			continue;
> @@ -555,22 +560,22 @@ static void parse_pack_objects(unsigned char *sha1)
>  		ofs = !find_delta_children(&base, &ofs_first, &ofs_last);
>  		if (!ref && !ofs)
>  			continue;
> -		data = get_data_from_pack(obj);
> +		base_obj.data = get_data_from_pack(obj);
> +		base_obj.size = obj->size;
> +
>  		if (ref)
>  			for (j = ref_first; j <= ref_last; j++) {
>  				struct object_entry *child = objects + deltas[j].obj_no;
>  				if (child->real_type == OBJ_REF_DELTA)
> -					resolve_delta(child, data,
> -						      obj->size, obj->type);
> +					resolve_delta(child, &base_obj, obj->type);
>  			}
>  		if (ofs)
>  			for (j = ofs_first; j <= ofs_last; j++) {
>  				struct object_entry *child = objects + deltas[j].obj_no;
>  				if (child->real_type == OBJ_OFS_DELTA)
> -					resolve_delta(child, data,
> -						      obj->size, obj->type);
> +					resolve_delta(child, &base_obj, obj->type);
>  			}
> -		free(data);
> +		free(base_obj.data);
>  		display_progress(progress, nr_resolved_deltas);
>  	}
>  }
> @@ -656,28 +661,29 @@ static void fix_unresolved_deltas(int nr_unresolved)
>  
>  	for (i = 0; i < n; i++) {
>  		struct delta_entry *d = sorted_by_pos[i];
> -		void *data;
> -		unsigned long size;
>  		enum object_type type;
>  		int j, first, last;
> +		struct base_data base_obj;
>  
>  		if (objects[d->obj_no].real_type != OBJ_REF_DELTA)
>  			continue;
> -		data = read_sha1_file(d->base.sha1, &type, &size);
> -		if (!data)
> +		base_obj.data = read_sha1_file(d->base.sha1, &type, &base_obj.size);
> +		if (!base_obj.data)
>  			continue;
>  
>  		find_delta_children(&d->base, &first, &last);
>  		for (j = first; j <= last; j++) {
>  			struct object_entry *child = objects + deltas[j].obj_no;
>  			if (child->real_type == OBJ_REF_DELTA)
> -				resolve_delta(child, data, size, type);
> +				resolve_delta(child, &base_obj, type);
>  		}
>  
> -		if (check_sha1_signature(d->base.sha1, data, size, typename(type)))
> +		if (check_sha1_signature(d->base.sha1, base_obj.data,
> +				base_obj.size, typename(type)))
>  			die("local object %s is corrupt", sha1_to_hex(d->base.sha1));
> -		append_obj_to_pack(d->base.sha1, data, size, type);
> -		free(data);
> +		append_obj_to_pack(d->base.sha1, base_obj.data,
> +			base_obj.size, type);
> +		free(base_obj.data);
>  		display_progress(progress, nr_resolved_deltas);
>  	}
>  	free(sorted_by_pos);
> -- 
> 1.5.6.2.393.g45096
> 


Nicolas