From 632dd719b385016eb62273f12fe51512453624c1 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 9 Aug 2018 23:52:59 +0200 Subject: slirp: document mbuf pointers and sizes and fix confusing datasize name into gapsize in m_inc. Signed-off-by: Peter Maydell Signed-off-by: Samuel Thibault --- slirp/mbuf.c | 14 +++++++------- slirp/mbuf.h | 13 +++++++++++++ 2 files changed, 20 insertions(+), 7 deletions(-) (limited to 'slirp') 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 */ -- cgit v1.2.3