Maximum evbuffer read configuration

Before this patch evbuffer always reads 4K at a time, while this is fine
most of time you can find an example when this will decrease throughput.

So add an API to change default limit:
- evbuffer_set_max_read()
- evbuffer_get_max_read()

And a notice that most of time default is sane.

1 files changed, 24 insertions, 0 deletions

diff --git a/include/event2/buffer.h b/include/event2/buffer.h
index 468588b9..56f620af 100644
--- a/include/event2/buffer.h
+++ b/include/event2/buffer.h
@@ -158,6 +158,30 @@ struct evbuffer *evbuffer_new(void);
 EVENT2_EXPORT_SYMBOL
 void evbuffer_free(struct evbuffer *buf);
 
+
+/**
+  Set maximum read buffer size
+
+  Default is 4096 and it works fine most of time, so before increasing the
+  default check carefully, since this has some negative effects (like memory
+  fragmentation and unfair resource distribution, i.e. some events will make
+  less progress than others).
+
+  @param buf pointer to the evbuffer
+  @param max buffer size
+  @return 0 on success, -1 on failure (if @max > INT_MAX).
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_set_max_read(struct evbuffer *buf, size_t max);
+/**
+  Get maximum read buffer size
+
+  @param buf pointer to the evbuffer
+  @return current maximum buffer read
+ */
+EVENT2_EXPORT_SYMBOL
+size_t evbuffer_get_max_read(struct evbuffer *buf);
+
 /**
    Enable locking on an evbuffer so that it can safely be used by multiple
    threads at the same time.