Add ident filter

This adds the ident filter (that knows how to replace $Id$) and
tweaks the filter APIs and code so that git_filter_source objects
actually have the updated OID of the object being filtered when
it is a known value.

1 files changed, 128 insertions, 0 deletions

diff --git a/src/ident.c b/src/ident.c
new file mode 100644
index 000000000..aedb973f9
--- /dev/null
+++ b/src/ident.c
@@ -0,0 +1,128 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "git2/sys/filter.h"
+#include "filter.h"
+#include "buffer.h"
+
+int ident_find_id(
+	const char **id_start, const char **id_end, const char *start, size_t len)
+{
+	const char *found;
+
+	while (len > 0 && (found = memchr(start, '$', len)) != NULL) {
+		size_t remaining = len - (size_t)(found - start);
+		if (remaining < 3)
+			return GIT_ENOTFOUND;
+		if (found[1] == 'I' && found[2] == 'd')
+			break;
+		start = found + 1;
+		len = remaining - 1;
+	}
+
+	if (len < 3)
+		return GIT_ENOTFOUND;
+	*id_start = found;
+
+	if ((found = memchr(found + 3, '$', len - 3)) == NULL)
+		return GIT_ENOTFOUND;
+
+	*id_end = found + 1;
+	return 0;
+}
+
+static int ident_insert_id(
+	git_buffer *to, const git_buffer *from, const git_filter_source *src)
+{
+	char oid[GIT_OID_HEXSZ+1];
+	const char *id_start, *id_end, *from_end = from->ptr + from->size;
+	size_t need_size;
+	git_buf to_buf = GIT_BUF_FROM_BUFFER(to);
+
+	/* replace $Id$ with blob id */
+
+	if (!git_filter_source_id(src))
+		return GIT_ENOTFOUND;
+
+	git_oid_tostr(oid, sizeof(oid), git_filter_source_id(src));
+
+	if (ident_find_id(&id_start, &id_end, from->ptr, from->size) < 0)
+		return GIT_ENOTFOUND;
+
+	need_size = (size_t)(id_start - from->ptr) +
+		5 /* "$Id: " */ + GIT_OID_HEXSZ + 1 /* "$" */ +
+		(size_t)(from_end - id_end);
+
+	if (git_buf_grow(&to_buf, need_size) < 0)
+		return -1;
+
+	git_buf_set(&to_buf, from->ptr, (size_t)(id_start - from->ptr));
+	git_buf_put(&to_buf, "$Id: ", 5);
+	git_buf_put(&to_buf, oid, GIT_OID_HEXSZ);
+	git_buf_putc(&to_buf, '$');
+	git_buf_put(&to_buf, id_end, (size_t)(from_end - id_end));
+
+	if (git_buf_oom(&to_buf))
+		return -1;
+
+	git_buffer_from_buf(to, &to_buf);
+	return 0;
+}
+
+static int ident_remove_id(
+	git_buffer *to, const git_buffer *from)
+{
+	const char *id_start, *id_end, *from_end = from->ptr + from->size;
+	size_t need_size;
+	git_buf to_buf = GIT_BUF_FROM_BUFFER(to);
+
+	if (ident_find_id(&id_start, &id_end, from->ptr, from->size) < 0)
+		return GIT_ENOTFOUND;
+
+	need_size = (size_t)(id_start - from->ptr) +
+		4 /* "$Id$" */ + (size_t)(from_end - id_end);
+
+	if (git_buf_grow(&to_buf, need_size) < 0)
+		return -1;
+
+	git_buf_set(&to_buf, from->ptr, (size_t)(id_start - from->ptr));
+	git_buf_put(&to_buf, "$Id$", 4);
+	git_buf_put(&to_buf, id_end, (size_t)(from_end - id_end));
+
+	if (git_buf_oom(&to_buf))
+		return -1;
+
+	git_buffer_from_buf(to, &to_buf);
+	return 0;
+}
+
+static int ident_apply(
+	git_filter        *self,
+	void              **payload,
+	git_buffer        *to,
+	const git_buffer  *from,
+	const git_filter_source *src)
+{
+	GIT_UNUSED(self); GIT_UNUSED(payload);
+
+	if (git_filter_source_mode(src) == GIT_FILTER_SMUDGE)
+		return ident_insert_id(to, from, src);
+	else
+		return ident_remove_id(to, from);
+}
+
+git_filter *git_ident_filter_new(void)
+{
+	git_filter *f = git__calloc(1, sizeof(git_filter));
+
+	f->version = GIT_FILTER_VERSION;
+	f->attributes = "+ident"; /* apply to files with ident attribute set */
+	f->shutdown = git_filter_free;
+	f->apply    = ident_apply;
+
+	return f;
+}