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https://issues.apache.org/jira/browse/HDFS-10339?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Clampffer updated HDFS-10339:
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Parent Issue: HDFS-14032 (was: HDFS-8707)
> libhdfs++: Expose async operations through the C API
> ----------------------------------------------------
>
> Key: HDFS-10339
> URL: https://issues.apache.org/jira/browse/HDFS-10339
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Reporter: James Clampffer
> Priority: Major
>
> I propose an API that looks like the following for doing async operations in
> C.
> (might be some typeos, going off memory of what I tried, will clean up)
> {code}
> typedef struct {
> int status;
> ssize_t count;
> ... whatever else ...
> } async_context;
> typedef void* caller_context;
> typedef void (*)(const async_context*, caller_context*) capi_callback;
> void hdfsAsyncPread(hdfsFS fs, hdfsFile file, off_t offset, void *buf, size_t
> count, capi_callback, caller_context);
> {code}
> When invoked we take a copy of the caller context that gets forwarded to the
> callback when the async op completes; this is where a user can keep a pointer
> to some state associated with the operation. The callback is invoked by a
> const async_contex* analogous to the Status object in the C++ API so the
> callback code can check status, bytes read, and other stuff.
> Internally this can be implemented by a callable struct/lambda that captures
> the caller_context and invokes the capi_callback with the caller_context and
> result async_context.
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