From 510fae5b0a78f9ba6b8b342ea8620d8eda951ca8 Mon Sep 17 00:00:00 2001
From: CismonX <admin@cismon.net>
Date: Thu, 10 Dec 2020 17:27:34 +0800
Subject: [PATCH] Implement `ctlseqs_purge()`.

---
 man/Makefile.am     | 11 +++++++++--
 man/ctlseqs_purge.3 | 40 ++++++++++++++++++++++++++++++++++++++++
 src/ctlseqs.c       | 17 +++++++++++++++++
 src/ctlseqs.h       |  3 +++
 4 files changed, 69 insertions(+), 2 deletions(-)
 create mode 100644 man/ctlseqs_purge.3

diff --git a/man/Makefile.am b/man/Makefile.am
index d9382d7..3162f91 100644
--- a/man/Makefile.am
+++ b/man/Makefile.am
@@ -6,7 +6,14 @@
 # this notice are preserved. This file is offered as-is, without any warranty.
 # 
 
-dist_man3_MANS = ctlseqs_matcher_init.3 ctlseqs_matcher_setopt.3 ctlseqs_matcher_free.3 \
-    ctlseqs_reader_init.3 ctlseqs_reader_setopt.3 ctlseqs_read.3 ctlseqs_reader_free.3
+dist_man3_MANS = \
+    ctlseqs_matcher_init.3 \
+    ctlseqs_matcher_setopt.3 \
+    ctlseqs_matcher_free.3 \
+    ctlseqs_reader_init.3 \
+    ctlseqs_reader_setopt.3 \
+    ctlseqs_read.3 \
+    ctlseqs_purge.3 \
+    ctlseqs_reader_free.3
 
 dist_man7_MANS = ctlseqs.7
diff --git a/man/ctlseqs_purge.3 b/man/ctlseqs_purge.3
new file mode 100644
index 0000000..f147a43
--- /dev/null
+++ b/man/ctlseqs_purge.3
@@ -0,0 +1,40 @@
+.TH CTLSEQS_PURGE 3 "Sep 01, 2020" 0.1.0 "Ctlseqs Library Manual"
+.
+.SH NAME
+ctlseqs_purge - purge read buffer
+.
+.SH SYNOPSYS
+.nf
+.B #include <ctlseqs.h>
+.PP
+.BI "void ctlseqs_purge(struct ctlseqs_reader *" reader ", size_t " nbytes );
+.fi
+.
+.SH DESCRIPTION
+Removes up to
+.I nbytes
+number of leading bytes from the internal read buffer of given
+.IR reader ,
+and resets the current state of the reader.
+.PP
+If
+.I nbytes
+is zero, this function has no effect.
+.
+.SH RETURN VALUE
+This function has no return values.
+.
+.SH NOTES
+This function is useful when dealing with partial sequences returned by
+.BR ctlseqs_read ()
+whose future completion is not desired.
+.
+.SH SEE ALSO
+.BR ctlseqs_read (3),
+.BR ctlseqs (7)
+.
+.SH COPYRIGHT
+Copyright (c)  2020  CismonX <admin@cismon.net>
+.PP
+Copying and distribution of this file, with or without modification, are permitted in any medium without royalty, provided the copyright notice and this notice are preserved.
+This file is offered as-is, without any warranty.
diff --git a/src/ctlseqs.c b/src/ctlseqs.c
index 517e2f0..a167637 100644
--- a/src/ctlseqs.c
+++ b/src/ctlseqs.c
@@ -518,6 +518,23 @@ ctlseqs_read(struct ctlseqs_reader *reader, struct ctlseqs_matcher const *matche
     return ctlseqs_match(reader, matcher);
 }
 
+void
+ctlseqs_purge(struct ctlseqs_reader *reader, size_t nbytes)
+{
+    size_t bufsize = reader->buf_end - reader->buf_start;
+    nbytes = nbytes > bufsize ? bufsize : nbytes;
+    if (nbytes == 0) {
+        return;
+    }
+    reader->buf_start += nbytes;
+    if (reader->buf_start == reader->buf_end) {
+        reader->buf_start = 0;
+        reader->buf_end = 0;
+    }
+    reader->last_idx = 0;
+    reader->state = ctlseqs_state_none;
+}
+
 CTLSEQS_COLD void
 ctlseqs_reader_free(struct ctlseqs_reader *reader)
 {
diff --git a/src/ctlseqs.h b/src/ctlseqs.h
index cb5b97b..6da1625 100644
--- a/src/ctlseqs.h
+++ b/src/ctlseqs.h
@@ -408,6 +408,9 @@ ctlseqs_reader_setopt(struct ctlseqs_reader *reader, struct ctlseqs_reader_opts
 ssize_t
 ctlseqs_read(struct ctlseqs_reader *reader, struct ctlseqs_matcher const *matcher, int timeout);
 
+void
+ctlseqs_purge(struct ctlseqs_reader *reader, size_t nbytes);
+
 void
 ctlseqs_reader_free(struct ctlseqs_reader *reader);