attr.c: outline the future plans by heavily commenting
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>
Junio C Hamano committed
Jan 27, 2017 at 18:01 UTC
7d42ec547cb8edea8cb1c527a646cfd21aa1c295
1 file changed
+39
-1
attr.c
+39
-1
@@ -30,6 +30,11 @@ static const char git_attr__unknown[] = "(builtin)unknown";
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#define DEBUG_ATTR 0
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#endif
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+/*
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+ * NEEDSWORK: the global dictionary of the interned attributes
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+ * must stay a singleton even after we become thread-ready.
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+ * Access to these must be surrounded with mutex when it happens.
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+ */
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struct git_attr {
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struct git_attr *next;
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unsigned h;
@@ -39,10 +44,19 @@ struct git_attr {
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char name[FLEX_ARRAY];
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};
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static int attr_nr;
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+static struct git_attr *(git_attr_hash[HASHSIZE]);
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+
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+/*
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+ * NEEDSWORK: maybe-real, maybe-macro are not property of
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+ * an attribute, as it depends on what .gitattributes are
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+ * read. Once we introduce per git_attr_check attr_stack
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+ * and check_all_attr, the optimization based on them will
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+ * become unnecessary and can go away. So is this variable.
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+ */
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static int cannot_trust_maybe_real;
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+/* NEEDSWORK: This will become per git_attr_check */
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static struct git_attr_check *check_all_attr;
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-static struct git_attr *(git_attr_hash[HASHSIZE]);
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const char *git_attr_name(const struct git_attr *attr)
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{
@@ -102,6 +116,11 @@ static struct git_attr *git_attr_internal(const char *name, int len)
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a->maybe_real = 0;
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git_attr_hash[pos] = a;
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+ /*
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+ * NEEDSWORK: per git_attr_check check_all_attr
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+ * will be initialized a lot more lazily, not
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+ * like this, and not here.
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+ */
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REALLOC_ARRAY(check_all_attr, attr_nr);
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check_all_attr[a->attr_nr].attr = a;
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check_all_attr[a->attr_nr].value = ATTR__UNKNOWN;
@@ -318,6 +337,7 @@ fail_return:
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* .gitignore file and info/excludes file as a fallback.
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*/
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+/* NEEDSWORK: This will become per git_attr_check */
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static struct attr_stack {
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struct attr_stack *prev;
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char *origin;
@@ -382,6 +402,24 @@ static struct attr_stack *read_attr_from_array(const char **list)
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return res;
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}
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+/*
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+ * NEEDSWORK: these two are tricky. The callers assume there is a
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+ * single, system-wide global state "where we read attributes from?"
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+ * and when the state is flipped by calling git_attr_set_direction(),
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+ * attr_stack is discarded so that subsequent attr_check will lazily
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+ * read from the right place. And they do not know or care who called
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+ * by them uses the attribute subsystem, hence have no knowledge of
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+ * existing git_attr_check instances or future ones that will be
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+ * created).
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+ *
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+ * Probably we need a thread_local that holds these two variables,
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+ * and a list of git_attr_check instances (which need to be maintained
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+ * by hooking into git_attr_check_alloc(), git_attr_check_initl(), and
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+ * git_attr_check_clear(). Then git_attr_set_direction() updates the
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+ * fields in that thread_local for these two variables, iterate over
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+ * all the active git_attr_check instances and discard the attr_stack
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+ * they hold. Yuck, but it sounds doable.
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+ */
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static enum git_attr_direction direction;
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static struct index_state *use_index;
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