Changelog for package data_tamer

Unreleased

• Fixed, deadlocks: unregister(), removeDataSink() or a LoggedValue destructor inside scopedWrite() while a snapshot waited; a const query inside scopedWrite() while another thread ran one of those, or startLogging(); startLogging() inside scopedWrite(). The snapshot path takes the write mutex before its epoch, and startLogging() before the control mutex.
• Behaviour change: a snapshot taken by a thread that holds the channel's transaction or a LoggedValue guard returns blocked (it hung).
• New: several threads may take snapshots of one channel; they take turns on the write mutex. blocked now takes precedence over pool_exhausted.
• Fixed: a consumer built with -fvisibility=hidden against a shared libdata_tamer hung in LoggedValue::set() inside scopedWrite(); ChannelSharedState has default visibility.
• Behaviour change: SinkWorker::stop(), start() and drain() throw std::logic_error from a callback of their own sink (they deadlocked, or stop() closed the worker silently). Concurrent stop() and start(), two stopAll() included, are serialized (they hung). A callback that releases the last reference to its own worker no longer calls std::terminate.
• Fixed: a sink attached during a failing startLogging() could miss the final schema, and a concurrent addDataSink() of one worker announced it twice.
• Real-time: no notify_all() per snapshot or refused push unless a thread waits; each one could be a futex call.
• Behaviour change: names must be non-empty and free of whitespace and control characters (only the space was refused); IsCanonicalName() agrees. A ninth default sink throws in addDefaultSink() (it made every later getChannel() throw).
• Behaviour change: custom type names, their field names, the typeName() of a registerCustomValue() serializer and channel names are checked too: a line break in any of them split the schema text, and a space in a type or field name broke its field line. Type and field names follow the value name rules, and the registration throws std::runtime_error. A channel name can contain spaces, but LogChannel::create() and getChannel() throw for an empty one or one with a control character.
• Fixed: a registration that throws leaves the channel unchanged (custom types, an allocation failure, createLoggedValue()). Two C++ types that return one custom type name in a channel make registerValue() throw (the second used the first one's serializer and read past its object). ToStr(Schema) rethrows allocation failures.
• Fixed: long long, unsigned long long, wchar_t, char16_t, char32_t and enums over them are recorded by size and signedness; they were recorded as other, which no decoder reads. long double is a compile error. A class template with two or more type parameters can have a TypeDefinition.
• Fixed: a vector of structs was sized with padding, so tryTakeSnapshot() could return oversize for a payload that fit. ValuePtr checks the room before writing a number and writes little-endian on any host; a custom type without a serializer throws std::invalid_argument.
• Fixed, wire: a std::string, registered or inside a custom type, is written as char[] (a uint32 count and the characters), as its schema says. It carried a 16-bit length that no decoder could read, and a string over 65535 bytes made the snapshot throw.
• Fixed: MCAPSink reset without rollover and restartRecording() of the file in use wrote the old footer into the new file; the old writer is now closed first, and a failed reopen of that file stops the sink. A rollover that cannot open its next file is counted once and retried after another reset time.
• Fixed: MCAPRingSink::flushPendingDump() and stop() on an untriggered request use the newest timestamp of the current run, so a simulation reset no longer dumps the previous run. dumps_written and dumps_failed count a dump before its callback.
• Fixed: MCAPRingSink starts a new run only when a channel's clock steps back by more than window. Snapshots of one channel taken by several threads can arrive slightly out of order, and each step back started a run, so a flush right after ended its dump before the newest snapshot.
• Behaviour change: MCAP sinks reject a negative snapshot timestamp (counted in errors(), not written), and mcap_encoding::WriteMessage() throws for one.
• Parser and Python decoder: the work of a decode is bounded by the payload (a zero-size element type looped for minutes); a bool is true for any non-zero byte; empty schema text is rejected; ### key:value headers are read; version and hash are strict unsigned decimals; a separator is a whole line of at least 30 =; ENCODING: sections are opaque types and must follow MSG:; upper-case legacy names are read only without a ### version: line. New SplitMcapMessage() and split_mcap_message(), used by mcap_reader.
• Breaking, parser: ParseSnapshot() loses its unused callback_custom parameter; SizeOf, kMaxSchemaDepth and ParseSnapshotRecursive move to DataTamerParser::detail and NullCustomCallback is removed; the header needs a little endian host and no longer includes <iostream>.
• SerializeMe: bounds checks for byte vectors and 1-byte arrays, exact BufferSize() for arrays and padded structs, bool decoding, a container of 2\^32 elements or more throws, an ADL TypeDefinition() may return const char* or std::string, Span<const T> from std::array, and the big endian path compiles for enums and std::byte.
• API: [[nodiscard]] on trySetEnabled(),

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