[tor-commits] [tor/master] Add a zero-copy buffer move implementation.

[nickm@xxxxxxxxxxxxxx]

commit 095e15f8ac8216cd945b85c159b461d8cd0697a3
Author: Nick Mathewson <nickm@xxxxxxxxxxxxxx>
Date:   Wed Sep 6 09:30:50 2017 -0400

    Add a zero-copy buffer move implementation.
---
 src/common/buffers.c | 22 ++++++++++++++++++++++
 src/common/buffers.h |  1 +
 2 files changed, 23 insertions(+)

diff --git a/src/common/buffers.c b/src/common/buffers.c
index d7c4e4d8c..d1725cf1a 100644
--- a/src/common/buffers.c
+++ b/src/common/buffers.c
@@ -838,6 +838,28 @@ buf_move_to_buf(buf_t *buf_out, buf_t *buf_in, size_t *buf_flushlen)
   return (int)cp;
 }
 
+/** Moves all data from <b>buf_in</b> to <b>buf_out</b>, without copying.
+ */
+void
+buf_move_all(buf_t *buf_out, buf_t *buf_in)
+{
+  tor_assert(buf_out);
+  if (!buf_in)
+    return;
+
+  if (buf_out->head == NULL) {
+    buf_out->head = buf_in->head;
+    buf_out->tail = buf_in->tail;
+  } else {
+    buf_out->tail->next = buf_in->head;
+    buf_out->tail = buf_in->tail;
+  }
+
+  buf_out->datalen += buf_in->datalen;
+  buf_in->head = buf_in->tail = NULL;
+  buf_in->datalen = 0;
+}
+
 /** Internal structure: represents a position in a buffer. */
 typedef struct buf_pos_t {
   const chunk_t *chunk; /**< Which chunk are we pointing to? */
diff --git a/src/common/buffers.h b/src/common/buffers.h
index b05c5b13d..56ba7c77b 100644
--- a/src/common/buffers.h
+++ b/src/common/buffers.h
@@ -51,6 +51,7 @@ void buf_add_vprintf(buf_t *buf, const char *format, va_list args)
 int buf_add_compress(buf_t *buf, struct tor_compress_state_t *state,
                           const char *data, size_t data_len, int done);
 int buf_move_to_buf(buf_t *buf_out, buf_t *buf_in, size_t *buf_flushlen);
+void buf_move_all(buf_t *buf_out, buf_t *buf_in);
 void buf_peek(const buf_t *buf, char *string, size_t string_len);
 void buf_drain(buf_t *buf, size_t n);
 int buf_get_bytes(buf_t *buf, char *string, size_t string_len);



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