[OpenWrt-Devel] [PATCH 1/3] ustream: add function ustream_read().

[Yousong Zhou]

It can be used to fill caller specified buffer area with data already in
ustream read buffer.  Useful in the following use pattern.

	int available = ustream_pending_data(s, false);
	if (available >= sizeof(struct msghdr)) {
		struct msghdr h;
		ustream_read(s, &h, sizeof(h));
	}

Signed-off-by: Yousong Zhou <yszhou4tech at gmail.com>
---
 ustream.c |   24 ++++++++++++++++++++++++
 ustream.h |    5 +++++
 2 files changed, 29 insertions(+)

diff --git a/ustream.c b/ustream.c
index 828a025..f1db809 100644
--- a/ustream.c
+++ b/ustream.c
@@ -333,6 +333,30 @@ char *ustream_get_read_buf(struct ustream *s, int *buflen)
 	return data;
 }
 
+int ustream_read(struct ustream *s, char *buf, int buflen)
+{
+	int len = 0;
+	int chunk_len;
+	struct ustream_buf *sbuf;
+
+	if (!s->r.head) {
+		return 0;
+	}
+
+	sbuf = s->r.head;
+	do {
+		chunk_len = sbuf->tail - sbuf->data;
+		if (chunk_len > buflen)
+			chunk_len = buflen;
+		memcpy(&buf[len], sbuf->data, chunk_len);
+		buflen -= chunk_len;
+		len += chunk_len;
+		sbuf = sbuf->next;
+	} while (buflen && sbuf);
+
+	return len;
+}
+
 static void ustream_write_error(struct ustream *s)
 {
 	if (!s->write_error)
diff --git a/ustream.h b/ustream.h
index 6431744..fadff3d 100644
--- a/ustream.h
+++ b/ustream.h
@@ -143,6 +143,11 @@ void ustream_free(struct ustream *s);
 /* ustream_consume: remove data from the head of the read buffer */
 void ustream_consume(struct ustream *s, int len);
 
+/*
+ * ustream_read: fill buf with data in internal read buffer.
+ * return size of filled data.
+ :*/
+int ustream_read(struct ustream *s, char *buf, int buflen);
 /* ustream_write: add data to the write buffer */
 int ustream_write(struct ustream *s, const char *buf, int len, bool more);
 int ustream_printf(struct ustream *s, const char *format, ...);
-- 
1.7.10.4
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