BUG/MEDIUM: lua: segfault with buffer_replace2
The function buffer_contig_space() returns the contiguous space avalaible
to add data (at the end of the input side) while the function
hlua_channel_send_yield() needs to insert data starting at p. Here we
introduce a new function bi_space_for_replace() which returns the amount
of space that can be inserted at the head of the input side with one of
the buffer_replace* functions.
This patch proposes a function that returns the space avalaible after buf->p.
diff --git a/include/common/buffer.h b/include/common/buffer.h
index 446bd1a..ca90fbe 100644
--- a/include/common/buffer.h
+++ b/include/common/buffer.h
@@ -233,6 +233,32 @@
return right - left;
}
+/* Returns the amount of byte that can be written starting from <p> into the
+ * input buffer at once, including reserved space which may be overwritten.
+ * This is used by Lua to insert data in the input side just before the other
+ * data using buffer_replace(). The goal is to transfer these new data in the
+ * output buffer.
+ */
+static inline int bi_space_for_replace(const struct buffer *buf)
+{
+ const char *end;
+
+ /* If the input side data overflows, we cannot insert data contiguously. */
+ if (buf->p + buf->i >= buf->data + buf->size)
+ return 0;
+
+ /* Check the last byte used in the buffer, it may be a byte of the output
+ * side if the buffer wraps, or its the end of the buffer.
+ */
+ end = buffer_wrap_sub(buf, buf->p - buf->o);
+ if (end <= buf->p)
+ end = buf->data + buf->size;
+
+ /* Compute the amount of bytes which can be written. */
+ return end - (buf->p + buf->i);
+}
+
+
/* Normalizes a pointer which is supposed to be relative to the beginning of a
* buffer, so that wrapping is correctly handled. The intent is to use this
* when increasing a pointer. Note that the wrapping test is only performed
diff --git a/src/hlua.c b/src/hlua.c
index 75dd077..3f9b909 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -2281,7 +2281,7 @@
/* The buffer avalaible size may be not contiguous. This test
* detects a non contiguous buffer and realign it.
*/
- if (buffer_contig_space(chn->chn->buf) < max)
+ if (bi_space_for_replace(chn->chn->buf) < max)
buffer_slow_realign(chn->chn->buf);
/* Copy input data in the buffer. */