On Wed, 6 Jan 2021 18:11:17 +0200
"Yordan Karadzhov (VMware)" <y.karadz@xxxxxxxxx> wrote:
> When we implement a KernelShark plugins, we often need a way to define
> a structure that can hold context data that is visible only inside the
> plugin and that has specific values for each data stream. The tricky
> part here is that the total number of data streams and the IDs of the
> active streams are dynamic quantities that can change as the user adds
> or removes data streams. The macro defines an interface of functions
> that will be useful for the plugin developer, helping to directly use
> context objects, without caring for the complications due to the dynamic
> configuration of active data streams.
> ---
> src/libkshark-plugin.h | 43 +++++++++++++++++++++++++++++++++++++++
> tests/libkshark-tests.cpp | 32 +++++++++++++++++++++++++++++
> 2 files changed, 75 insertions(+)
>
> diff --git a/src/libkshark-plugin.h b/src/libkshark-plugin.h
> index f3c724f..e58d658 100644
> --- a/src/libkshark-plugin.h
> +++ b/src/libkshark-plugin.h
> @@ -360,6 +360,49 @@ int kshark_handle_all_dpis(struct kshark_data_stream *stream,
> } \
> } \
>
> +/** General purpose macro defining methods for adding plugin context. */
> +#define KS_DEFINE_PLUGIN_CONTEXT(type) \
When macros like this are done in Linux, it is common to add a "prefix"
argument, and name all the variables and functions created by it with that
prefix.
#define KS_DEFINE_PLUGIN_CONTEXT(prefix, type) \
static type **prefix##_context_handler; \
[..]
static inline type *prefix##_init(int sd) \
[..]
This would allow this macro to be used more than once in a file.
It's up to you if you want to do it that way.
-- Steve
> +static type **__context_handler; \
> +static ssize_t __n_streams = -1; \
> +static bool ok; \
> +static inline type *__init(int sd) \
> +{ \
> + type *obj; \
> + if (__n_streams < 0 && sd < KS_DEFAULT_NUM_STREAMS) { \
> + __context_handler = \
> + (type **) calloc(KS_DEFAULT_NUM_STREAMS, \
> + sizeof(*__context_handler)); \
> + if (!__context_handler) \
> + return NULL; \
> + __n_streams = KS_DEFAULT_NUM_STREAMS; \
> + } else if (sd >= __n_streams) { \
> + KS_DOUBLE_SIZE(type *, __context_handler, \
> + &__n_streams, &ok) \
> + if (!ok) \
> + return NULL; \
> + } \
> + assert(__context_handler[sd] == NULL); \
> + obj = (type *) calloc(1, sizeof(*obj)); \
> + __context_handler[sd] = obj; \
> + return obj; \
> +} \
> +static inline void __close(int sd) \
> +{ \
> + if (sd < 0) { \
> + free(__context_handler); \
> + __n_streams = -1; \
> + return; \
> + } \
> + free(__context_handler[sd]); \
> + __context_handler[sd] = NULL; \
> +} \
> +static inline type *__get_context(int sd) \
> +{ \
> + if (sd < 0 || sd >= __n_streams) \
> + return NULL; \
> + return __context_handler[sd]; \
> +} \
> +
> #ifdef __cplusplus
> }
> #endif // __cplusplus
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