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[Qemu-devel] [PULL 1/3] slirp: document mbuf pointers and sizes
From: |
Samuel Thibault |
Subject: |
[Qemu-devel] [PULL 1/3] slirp: document mbuf pointers and sizes |
Date: |
Sun, 7 Oct 2018 20:05:16 +0200 |
From: Peter Maydell <address@hidden>
and fix confusing datasize name into gapsize in m_inc.
Signed-off-by: Peter Maydell <address@hidden>
Signed-off-by: Samuel Thibault <address@hidden>
---
slirp/mbuf.c | 14 +++++++-------
slirp/mbuf.h | 13 +++++++++++++
2 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/slirp/mbuf.c b/slirp/mbuf.c
index 1b7868355a..aa1f28afb1 100644
--- a/slirp/mbuf.c
+++ b/slirp/mbuf.c
@@ -151,7 +151,7 @@ m_cat(struct mbuf *m, struct mbuf *n)
void
m_inc(struct mbuf *m, int size)
{
- int datasize;
+ int gapsize;
/* some compilers throw up on gotos. This one we can fake. */
if (M_ROOM(m) > size) {
@@ -159,17 +159,17 @@ m_inc(struct mbuf *m, int size)
}
if (m->m_flags & M_EXT) {
- datasize = m->m_data - m->m_ext;
- m->m_ext = g_realloc(m->m_ext, size + datasize);
+ gapsize = m->m_data - m->m_ext;
+ m->m_ext = g_realloc(m->m_ext, size + gapsize);
} else {
- datasize = m->m_data - m->m_dat;
- m->m_ext = g_malloc(size + datasize);
+ gapsize = m->m_data - m->m_dat;
+ m->m_ext = g_malloc(size + gapsize);
memcpy(m->m_ext, m->m_dat, m->m_size);
m->m_flags |= M_EXT;
}
- m->m_data = m->m_ext + datasize;
- m->m_size = size + datasize;
+ m->m_data = m->m_ext + gapsize;
+ m->m_size = size + gapsize;
}
diff --git a/slirp/mbuf.h b/slirp/mbuf.h
index 33b84485d6..bfdf8c4577 100644
--- a/slirp/mbuf.h
+++ b/slirp/mbuf.h
@@ -47,6 +47,19 @@
* free the m_ext. This is inefficient memory-wise, but who cares.
*/
+/*
+ * mbufs allow to have a gap between the start of the allocated buffer (m_ext
if
+ * M_EXT is set, m_dat otherwise) and the in-use data:
+ *
+ * |--gapsize----->|---m_len------->
+ * |----------m_size------------------------------>
+ * |----M_ROOM-------------------->
+ * |-M_FREEROOM-->
+ *
+ * ^ ^ ^
+ * m_dat/m_ext m_data end of buffer
+ */
+
/*
* How much room is in the mbuf, from m_data to the end of the mbuf
*/
--
2.19.0