[PATCH] ui-blob.c: Use a context structure in walk_tree()

[Lukas Fleischer]

On Sat, Mar 02, 2013 at 08:11:48PM +0100, Lukas Fleischer wrote:
> Do not misuse global variables to save the context. Instead, use the
> context pointer which was designed to share information between a
> read_tree_fn and the caller.
> 
> This also prevents from potential misuse of the global pointers
> match_path and matched_sha1 after the referenced values have been
> overwritten on the stack.
> 
> Signed-off-by: Lukas Fleischer <cgit at cryptocrack.de>
> ---
> Note that this is completely untested and I don't have time to test it
> now since my cgit development environment is down. I decided to submit
> nonetheless, so that someone else can have a look.
> 
>  ui-blob.c | 38 +++++++++++++++++++++++---------------
>  1 file changed, 23 insertions(+), 15 deletions(-)

I just noticed that we also use global variables in similar walk_tree()
functions in "ui-plain.c" and "ui-tree.c". I will submit a patch that
fixes several whitespace errors and, based on that, a reworked version
of this one that also fixes the other callback functions.

> 
> diff --git a/ui-blob.c b/ui-blob.c
> index 3de4473..b6f01cf 100644
> --- a/ui-blob.c
> +++ b/ui-blob.c
> @@ -11,17 +11,20 @@
>  #include "html.h"
>  #include "ui-shared.h"
>  
> -static char *match_path;
> -static unsigned char *matched_sha1;
> -static int found_path;
> +struct walk_tree_context {
> +	char *match_path;
> +	unsigned char *matched_sha1;
> +	int found_path;
> +};
>  
>  static int walk_tree(const unsigned char *sha1, const char *base,int baselen,
>  	const char *pathname, unsigned mode, int stage, void *cbdata) {
> -	if(strncmp(base,match_path,baselen)
> -		|| strcmp(match_path+baselen,pathname) )
> +	struct walk_tree_context *ctx = cbdata;
> +	if(strncmp(base,ctx->match_path,baselen)
> +		|| strcmp(ctx->match_path+baselen,pathname) )
>  		return READ_TREE_RECURSIVE;
> -	memmove(matched_sha1,sha1,20);
> -	found_path = 1;
> +	memmove(ctx->matched_sha1,sha1,20);
> +	ctx->found_path = 1;
>  	return 0;
>  }
>  
> @@ -40,16 +43,19 @@ int cgit_print_file(char *path, const char *head)
>  		.nr = 1,
>  		.items = &path_items
>  	};
> +	struct walk_tree_context walk_tree_ctx = {
> +		.match_path = path,
> +		.matched_sha1 = sha1,
> +		.found_path = 0
> +	};
> +
>  	if (get_sha1(head, sha1))
>  		return -1;
>  	type = sha1_object_info(sha1, &size);
>  	if(type == OBJ_COMMIT && path) {
>  		commit = lookup_commit_reference(sha1);
> -		match_path = path;
> -		matched_sha1 = sha1;
> -		found_path = 0;
> -		read_tree_recursive(commit->tree, "", 0, 0, &paths, walk_tree, NULL);
> -		if (!found_path)
> +		read_tree_recursive(commit->tree, "", 0, 0, &paths, walk_tree, &walk_tree_ctx);
> +		if (!walk_tree_ctx.found_path)
>  			return -1;
>  		type = sha1_object_info(sha1, &size);
>  	}
> @@ -78,6 +84,10 @@ void cgit_print_blob(const char *hex, char *path, const char *head)
>  		.nr = 1,
>  		.items = &path_items
>  	};
> +	struct walk_tree_context walk_tree_ctx = {
> +		.match_path = path,
> +		.matched_sha1 = sha1,
> +	};
>  
>  	if (hex) {
>  		if (get_sha1_hex(hex, sha1)){
> @@ -95,9 +105,7 @@ void cgit_print_blob(const char *hex, char *path, const char *head)
>  
>  	if((!hex) && type == OBJ_COMMIT && path) {
>  		commit = lookup_commit_reference(sha1);
> -		match_path = path;
> -		matched_sha1 = sha1;
> -		read_tree_recursive(commit->tree, "", 0, 0, &paths, walk_tree, NULL);
> +		read_tree_recursive(commit->tree, "", 0, 0, &paths, walk_tree, &walk_tree_ctx);
>  		type = sha1_object_info(sha1,&size);
>  	}
>  
> -- 
> 1.8.2.rc0.247.g811e0c0