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60 lines
2.4 KiB
Go
60 lines
2.4 KiB
Go
/*
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Maddy Mail Server - Composable all-in-one email server.
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Copyright © 2019-2020 Max Mazurov <fox.cpp@disroot.org>, Maddy Mail Server contributors
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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// The buffer package provides utilities for temporary storage (buffering)
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// of large blobs.
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package buffer
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import (
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"io"
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)
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// Buffer interface represents abstract temporary storage for blobs.
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//
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// The Buffer storage is assumed to be immutable. If any modifications
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// are made - new storage location should be used for them.
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// This is important to ensure goroutine-safety.
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//
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// Since Buffer objects require a careful management of lifetimes, here
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// is the convention: Its always creator responsibility to call Remove after
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// Buffer is no longer used. If Buffer object is passed to a function - it is not
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// guaranteed to be valid after this function returns. If function needs to preserve
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// the storage contents, it should "re-buffer" it either by reading entire blob
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// and storing it somewhere or applying implementation-specific methods (for example,
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// the FileBuffer storage may be "re-buffered" by hard-linking the underlying file).
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type Buffer interface {
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// Open creates new Reader reading from the underlying storage.
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Open() (io.ReadCloser, error)
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// Len reports the length of the stored blob.
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//
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// Notably, it indicates the amount of bytes that can be read from the
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// newly created Reader without hiting io.EOF.
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Len() int
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// Remove discards buffered body and releases all associated resources.
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//
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// Multiple Buffer objects may refer to the same underlying storage.
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// In this case, care should be taken to ensure that Remove is called
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// only once since it will discard the shared storage and invalidate
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// all Buffer objects using it.
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//
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// Readers previously created using Open can still be used, but
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// new ones can't be created.
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Remove() error
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}
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