diff: unify external diff and funcname parsing code

Both sets of code assume that one specifies a diff profile
as a gitattribute via the "diff=foo" attribute. They then
pull information about that profile from the config as
diff.foo.*.

The code for each is currently completely separate from the
other, which has several disadvantages:

  - there is duplication as we maintain code to create and
    search the separate lists of external drivers and
    funcname patterns

  - it is difficult to add new profile options, since it is
    unclear where they should go

  - the code is difficult to follow, as we rely on the
    "check if this file is binary" code to find the funcname
    pattern as a side effect. This is the first step in
    refactoring the binary-checking code.

This patch factors out these diff profiles into "userdiff"
drivers. A file with "diff=foo" uses the "foo" driver, which
is specified by a single struct.

Note that one major difference between the two pieces of
code is that the funcname patterns are always loaded,
whereas external drivers are loaded only for the "git diff"
porcelain; the new code takes care to retain that situation.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 160 insertions, 0 deletions

diff --git a/userdiff.c b/userdiff.c
new file mode 100644
index 0000000000..80e2857abb
--- /dev/null
+++ b/userdiff.c
@@ -0,0 +1,160 @@
+#include "userdiff.h"
+#include "cache.h"
+#include "attr.h"
+
+static struct userdiff_driver *drivers;
+static int ndrivers;
+static int drivers_alloc;
+
+#define FUNCNAME(name, pattern) \
+	{ name, NULL, { pattern, REG_EXTENDED } }
+static struct userdiff_driver builtin_drivers[] = {
+FUNCNAME("html", "^[ \t]*(<[Hh][1-6][ \t].*>.*)$"),
+FUNCNAME("java",
+	 "!^[ \t]*(catch|do|for|if|instanceof|new|return|switch|throw|while)\n"
+	 "^[ \t]*(([ \t]*[A-Za-z_][A-Za-z_0-9]*){2,}[ \t]*\\([^;]*)$"),
+FUNCNAME("objc",
+	 /* Negate C statements that can look like functions */
+	 "!^[ \t]*(do|for|if|else|return|switch|while)\n"
+	 /* Objective-C methods */
+	 "^[ \t]*([-+][ \t]*\\([ \t]*[A-Za-z_][A-Za-z_0-9* \t]*\\)[ \t]*[A-Za-z_].*)$\n"
+	 /* C functions */
+	 "^[ \t]*(([ \t]*[A-Za-z_][A-Za-z_0-9]*){2,}[ \t]*\\([^;]*)$\n"
+	 /* Objective-C class/protocol definitions */
+	 "^(@(implementation|interface|protocol)[ \t].*)$"),
+FUNCNAME("pascal",
+	 "^((procedure|function|constructor|destructor|interface|"
+		"implementation|initialization|finalization)[ \t]*.*)$"
+	 "\n"
+	 "^(.*=[ \t]*(class|record).*)$"),
+FUNCNAME("php", "^[\t ]*((function|class).*)"),
+FUNCNAME("python", "^[ \t]*((class|def)[ \t].*)$"),
+FUNCNAME("ruby", "^[ \t]*((class|module|def)[ \t].*)$"),
+FUNCNAME("bibtex", "(@[a-zA-Z]{1,}[ \t]*\\{{0,1}[ \t]*[^ \t\"@',\\#}{~%]*).*$"),
+FUNCNAME("tex", "^(\\\\((sub)*section|chapter|part)\\*{0,1}\\{.*)$"),
+};
+#undef FUNCNAME
+
+static struct userdiff_driver driver_true = {
+	"diff=true",
+	NULL,
+	{ NULL, 0 }
+};
+struct userdiff_driver *USERDIFF_ATTR_TRUE = &driver_true;
+
+static struct userdiff_driver driver_false = {
+	"!diff",
+	NULL,
+	{ NULL, 0 }
+};
+struct userdiff_driver *USERDIFF_ATTR_FALSE = &driver_false;
+
+static struct userdiff_driver *userdiff_find_by_namelen(const char *k, int len)
+{
+	int i;
+	for (i = 0; i < ndrivers; i++) {
+		struct userdiff_driver *drv = drivers + i;
+		if (!strncmp(drv->name, k, len) && !drv->name[len])
+			return drv;
+	}
+	for (i = 0; i < ARRAY_SIZE(builtin_drivers); i++) {
+		struct userdiff_driver *drv = builtin_drivers + i;
+		if (!strncmp(drv->name, k, len) && !drv->name[len])
+			return drv;
+	}
+	return NULL;
+}
+
+static struct userdiff_driver *parse_driver(const char *var,
+		const char *value, const char *type)
+{
+	struct userdiff_driver *drv;
+	const char *dot;
+	const char *name;
+	int namelen;
+
+	if (prefixcmp(var, "diff."))
+		return NULL;
+	dot = strrchr(var, '.');
+	if (dot == var + 4)
+		return NULL;
+	if (strcmp(type, dot+1))
+		return NULL;
+
+	name = var + 5;
+	namelen = dot - name;
+	drv = userdiff_find_by_namelen(name, namelen);
+	if (!drv) {
+		ALLOC_GROW(drivers, ndrivers+1, drivers_alloc);
+		drv = &drivers[ndrivers++];
+		memset(drv, 0, sizeof(*drv));
+		drv->name = xmemdupz(name, namelen);
+	}
+	return drv;
+}
+
+static int parse_funcname(struct userdiff_funcname *f, const char *k,
+		const char *v, int cflags)
+{
+	if (git_config_string(&f->pattern, k, v) < 0)
+		return -1;
+	f->cflags = cflags;
+	return 1;
+}
+
+static int parse_string(const char **d, const char *k, const char *v)
+{
+	if (git_config_string(d, k, v) < 0)
+		return -1;
+	return 1;
+}
+
+int userdiff_config_basic(const char *k, const char *v)
+{
+	struct userdiff_driver *drv;
+
+	if ((drv = parse_driver(k, v, "funcname")))
+		return parse_funcname(&drv->funcname, k, v, 0);
+	if ((drv = parse_driver(k, v, "xfuncname")))
+		return parse_funcname(&drv->funcname, k, v, REG_EXTENDED);
+
+	return 0;
+}
+
+int userdiff_config_porcelain(const char *k, const char *v)
+{
+	struct userdiff_driver *drv;
+
+	if ((drv = parse_driver(k, v, "command")))
+		return parse_string(&drv->external, k, v);
+
+	return 0;
+}
+
+struct userdiff_driver *userdiff_find_by_name(const char *name) {
+	int len = strlen(name);
+	return userdiff_find_by_namelen(name, len);
+}
+
+struct userdiff_driver *userdiff_find_by_path(const char *path)
+{
+	static struct git_attr *attr;
+	struct git_attr_check check;
+
+	if (!attr)
+		attr = git_attr("diff", 4);
+	check.attr = attr;
+
+	if (!path)
+		return NULL;
+	if (git_checkattr(path, 1, &check))
+		return NULL;
+
+	if (ATTR_TRUE(check.value))
+		return &driver_true;
+	if (ATTR_FALSE(check.value))
+		return &driver_false;
+	if (ATTR_UNSET(check.value))
+		return NULL;
+	return userdiff_find_by_name(check.value);
+}