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attr.c: outline the future plans by heavily commenting

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Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano 2017-01-27 18:01:53 -08:00
parent faa4e8ceb5
commit 7d42ec547c
1 changed files with 39 additions and 1 deletions
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40
attr.c
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@ -30,6 +30,11 @@ static const char git_attr__unknown[] = "(builtin)unknown";
#define DEBUG_ATTR 0
#endif
/*
* NEEDSWORK: the global dictionary of the interned attributes
* must stay a singleton even after we become thread-ready.
* Access to these must be surrounded with mutex when it happens.
*/
struct git_attr {
struct git_attr *next;
unsigned h;
@ -39,10 +44,19 @@ struct git_attr {
char name[FLEX_ARRAY];
};
static int attr_nr;
static struct git_attr *(git_attr_hash[HASHSIZE]);
/*
* NEEDSWORK: maybe-real, maybe-macro are not property of
* an attribute, as it depends on what .gitattributes are
* read. Once we introduce per git_attr_check attr_stack
* and check_all_attr, the optimization based on them will
* become unnecessary and can go away. So is this variable.
*/
static int cannot_trust_maybe_real;
/* NEEDSWORK: This will become per git_attr_check */
static struct git_attr_check *check_all_attr;
static struct git_attr *(git_attr_hash[HASHSIZE]);
const char *git_attr_name(const struct git_attr *attr)
{
@ -102,6 +116,11 @@ static struct git_attr *git_attr_internal(const char *name, int len)
a->maybe_real = 0;
git_attr_hash[pos] = a;
/*
* NEEDSWORK: per git_attr_check check_all_attr
* will be initialized a lot more lazily, not
* like this, and not here.
*/
REALLOC_ARRAY(check_all_attr, attr_nr);
check_all_attr[a->attr_nr].attr = a;
check_all_attr[a->attr_nr].value = ATTR__UNKNOWN;
@ -318,6 +337,7 @@ fail_return:
* .gitignore file and info/excludes file as a fallback.
*/
/* NEEDSWORK: This will become per git_attr_check */
static struct attr_stack {
struct attr_stack *prev;
char *origin;
@ -382,6 +402,24 @@ static struct attr_stack *read_attr_from_array(const char **list)
return res;
}
/*
* NEEDSWORK: these two are tricky. The callers assume there is a
* single, system-wide global state "where we read attributes from?"
* and when the state is flipped by calling git_attr_set_direction(),
* attr_stack is discarded so that subsequent attr_check will lazily
* read from the right place. And they do not know or care who called
* by them uses the attribute subsystem, hence have no knowledge of
* existing git_attr_check instances or future ones that will be
* created).
*
* Probably we need a thread_local that holds these two variables,
* and a list of git_attr_check instances (which need to be maintained
* by hooking into git_attr_check_alloc(), git_attr_check_initl(), and
* git_attr_check_clear(). Then git_attr_set_direction() updates the
* fields in that thread_local for these two variables, iterate over
* all the active git_attr_check instances and discard the attr_stack
* they hold. Yuck, but it sounds doable.
*/
static enum git_attr_direction direction;
static struct index_state *use_index;