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59 lines
2.6 KiB
Text
59 lines
2.6 KiB
Text
Some notes on the error handling introduced after 0.7.3
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- there are four domains for errors:
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- CORE: core GStreamer errors
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- LIBRARY: supporting library errors
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- RESOURCE: errors accessing resources (files, network, memory, ...)
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- STREAM: errors in the data stream
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- Each error in GStreamer or plug-ins can be put under one of these four.
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- the enum is called Gst(Domain)Error and has GST_(DOMAIN)_ERROR_(CODE) members
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(see GError API docs for rationale)
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- each of the enums starts with _FAILED at 1 (with FAILED being the generic
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error if none of the others applies)
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- second in the enum is TOO_LAZY, which allows us to keep track of those errors
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that we haven't categorized yet. This means they really should either move
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to another one, or a new one ought to be created.
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- each enum ends with NUM_ERRORS
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- elements call gst_element_error to signal an error:
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gst_element_error (element, domain, code, message, debug);
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With :
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- element being the one signalling the error
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- domain one of CORE, LIBRARY, RESOURCE, STREAM
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- code one of the suffixes in the Gst(Domain)Error enum
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- message is either NULL (to signal the standard error message for the
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given domain and code), or a printf-like set with the format being
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marked for translation.
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The string should start with a capital and end in a period so it forms
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a complete sentence.
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The string can/should be shown to the user of an application.
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- debug is either NULL or a non-translated debug string, which can be used
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to diagnose errors after they've happened.
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The string can be shown to the user when he asks for additional debug info.
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A useful macro is GST_ERROR_SYSTEM, which prints out the system error
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that explains the failure by using g_strerror.
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- Some example calls:
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gst_element_error (src, RESOURCE, OPEN_READ,
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(_("Could not open file \"%s\" for reading"), src->filename),
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GST_ERROR_SYSTEM);
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The message is specified since we have more information:
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- the resource is a file
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- we know the file name
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gst_element_error (element, CORE, NEGOTIATION, NULL, NULL);
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This is a simple negotiation error. The default message will be
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signaled, telling the user that GStreamer had an internal error.
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gst_element_error (ebml, RESOURCE, READ, NULL,
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("Read error at position %llu (0x%llx)",
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pos, pos));
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The plugin asked to read on the underlying resource (using bytestream),
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but failed. The user will get a generic read error. The debug info
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will contain the exact position in the stream at which the read error
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occurred.
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