mirror of
https://github.com/matrix-construct/construct
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70 lines
2.4 KiB
C++
70 lines
2.4 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2023 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_JSON_STACK_CHECKPOINT_H
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/// Checkpoint captures the current state of the json::stack on construction
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/// and allows a restoration to that state in one of three ways:
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///
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/// - Calling rollback() will immediately rewind the json::stack buffer and
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/// allow continuing from the check point. This should be used with care, as
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/// other json::stack objects may still be pending on the stack and destruct
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/// after calling rollback(), leaving an incoherent attempt to close the JSON.
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///
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/// - Calling decommit() will defer the rollback() until destruction time. Take
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/// care again that the checkpoint was still placed on the stack to avoid the
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/// rollback() pitfall.
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///
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/// - Destruction under an exception is equivalent to a decommit() and will
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/// perform a rollback() if exception_rollback is set.
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///
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/// Flushes are avoided under the scope of a checkpoint, but they are still
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/// forced if the json::stack buffer fills up. In this case all active
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/// checkpoints are invalidated and cannot be rolled back.
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///
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struct ircd::json::stack::checkpoint
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{
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stack *s {nullptr};
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checkpoint *pc {nullptr};
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size_t point {0};
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size_t vc {0};
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bool committed {true};
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bool exception_rollback {true};
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public:
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bool committing() const noexcept; ///< When false, destructor will rollback()
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bool committing(const bool &) noexcept; ///< Sets committing() to value.
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bool rollback(); ///< Performs rollback of buffer.
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checkpoint(stack &s,
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const bool committed = true,
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const bool exception_rollback = true);
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checkpoint(checkpoint &&) = delete;
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checkpoint(const checkpoint &) = delete;
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~checkpoint() noexcept;
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};
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inline bool
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ircd::json::stack::checkpoint::committing(const bool &committed)
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noexcept
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{
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const bool ret(this->committed);
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this->committed = committed;
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return ret;
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}
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inline bool
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ircd::json::stack::checkpoint::committing()
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const noexcept
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{
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return committed;
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}
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