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71c6d40942
We should drop the HISTORY file because it's confusing and the same information is covered by the release notes for .0 releases (or at least they should be). Remove references to the HISTORY file, update the README to tell people go look somewhere else.
56 lines
1.7 KiB
Text
56 lines
1.7 KiB
Text
Result Codes
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The use of global variables or a GetLastError() function to return results
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doesn't work well in a multithreaded application. The global variable has
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obvious problems, as does a global GetLastError(). A per-object GetLastError()
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seems more promising, e.g.
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sometype_t s;
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sometype_dosomething(s, buffer);
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if (sometype_error(s)) {
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/* ... */
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}
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If 's' is shared however this approach doesn't work unless the locking is
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done by the caller, e.g.
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sometype_lock();
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sometype_dosomething(s, buffer);
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if (sometype_error(s)) {
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/* ... */
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}
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sometype_unlock();
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Those ISC and DNS libraries which have locks almost universally put the
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locking inside of the called routines, since it's more convenient for
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the calling programmer, makes for a cleaner API, and puts the burden
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of locking on the library programmer, who should know best what the
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locking needs of the routine are.
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Because of this locking style the ISC and DNS libraries typically provide
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result information as the return value of the function. E.g.
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isc_result_t result;
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result = isc_task_send(task, &event);
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Note that an explicit result type is used, instead of mixing the error result
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type with the normal result type. E.g. the C library routine getc() can
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return a character or EOF, but the BIND 9 style keeps the types of the
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function's return values separate.
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char c;
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result = isc_io_getc(stream, &c);
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if (result == ISC_R_SUCCESS) {
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/* Do something with 'c'. */
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} else if (result == ISC_R_EOF) {
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/* EOF. */
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} else {
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/* Some other error. */
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}
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Functions which cannot fail (assuming the caller has provided valid
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arguments) need not return a result type. For example, dns_name_issubdomain()
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returns an bool, because it cannot fail.
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