1 files changed, 113 insertions, 0 deletions
diff --git a/src/lib/seq-set-builder.c b/src/lib/seq-set-builder.c
new file mode 100644
index 0000000..b5649b7
--- /dev/null
+++ b/src/lib/seq-set-builder.c
@@ -0,0 +1,113 @@
+/* Copyright (c) 2021 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "seq-set-builder.h"
+
+struct seqset_builder {
+	string_t *str;
+	uint32_t last_seq;
+	size_t last_seq_pos;
+	size_t prefix_length;
+};
+
+struct seqset_builder *seqset_builder_init(string_t *str)
+{
+	struct seqset_builder *builder;
+	builder = i_new(struct seqset_builder, 1);
+	builder->str = str;
+	builder->last_seq = 0;
+	builder->prefix_length = str_len(str);
+	builder->last_seq_pos = 0;
+	return builder;
+}
+
+static void
+seqset_builder_append_one(struct seqset_builder *builder, uint32_t seq)
+{
+	builder->last_seq_pos = str_len(builder->str)+1;
+	str_printfa(builder->str, "%u,", seq);
+}
+
+static void
+seqset_builder_create_or_merge_range(struct seqset_builder *builder,
+				     uint32_t seq)
+{
+	char delimiter = '\0';
+
+	i_assert(builder->last_seq_pos > builder->prefix_length);
+
+	str_truncate(builder->str, builder->last_seq_pos-1);
+
+	/* Get the delimiter from the builder string */
+	if (str_len(builder->str) > 0 &&
+	    str_len(builder->str) - 1 > builder->prefix_length)
+		delimiter = str_data(builder->str)[str_len(builder->str) - 1];
+
+	if (delimiter == ':') {
+		seqset_builder_append_one(builder, seq);
+	} else if (delimiter == ',' || delimiter == '\0') {
+		str_printfa(builder->str, "%u:", builder->last_seq);
+		builder->last_seq_pos = str_len(builder->str) + 1;
+		str_printfa(builder->str, "%u,", seq);
+	} else
+		i_unreached();
+	return;
+}
+
+void seqset_builder_add(struct seqset_builder *builder, uint32_t seq)
+{
+	if (builder->last_seq == 0) {
+		/* No seq was yet appened so just append this one */
+		seqset_builder_append_one(builder, seq);
+	} else if (builder->last_seq + 1 == seq) {
+		/* This seq is following directly on the previous one
+		   try to create a range of seqs */
+		seqset_builder_create_or_merge_range(builder, seq);
+	} else {
+		/* Append this seq without creating a range */
+		seqset_builder_append_one(builder, seq);
+	}
+	builder->last_seq = seq;
+}
+
+bool seqset_builder_try_add(struct seqset_builder *builder, size_t max_len,
+			    uint32_t seq)
+{
+	/* Length of this sequence to be appended */
+	unsigned int seq_len = 0;
+	/* Buffer to use when calculating seq length as string */
+	char seq_str[MAX_INT_STRLEN];
+	/* Current length of the seq string */
+	unsigned int builder_str_len = str_len(builder->str);
+
+	if (builder->last_seq + 1 == seq && builder_str_len + 1 <= max_len) {
+		/* Following sequence: This seq can't grow the overall length
+		   by more than one. */
+		seqset_builder_add(builder, seq);
+		return TRUE;
+	}
+
+	if (builder_str_len + MAX_INT_STRLEN + 1 <= max_len) {
+		/* Appending the maximum length of a sequence number and ','
+		   still fits into max_len. There is no need to check the
+		   actual length. */
+		seqset_builder_add(builder, seq);
+		return TRUE;
+	}
+
+	seq_len = strlen(dec2str_buf(seq_str, seq)) + 1;
+	if (seq_len + builder_str_len > max_len)
+		return FALSE;
+
+	seqset_builder_add(builder, seq);
+	return TRUE;
+}
+
+void seqset_builder_deinit(struct seqset_builder **builder)
+{
+	/* If anything was appened to the string remove the trailing ',' */
+	if ((*builder)->last_seq != 0)
+		str_truncate((*builder)->str, str_len((*builder)->str) - 1);
+	i_free(*builder);
+}