wehub-resource-sync
60 lines
1.8 KiB
Go
60 lines
1.8 KiB
Go
// Copyright 2024 Dolthub, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package dataloader
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import "io"
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// stringPrefixReader is an io.ReadCloser that reads from a string prefix before reading from
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// another io.Reader. This is used for reassembling partial records across multi-message
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// exchanges, since the end of a wire message does not typically line up with the end of a record.
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type stringPrefixReader struct {
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prefix string
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prefixPosition uint
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reader io.Reader
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}
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var _ io.ReadCloser = (*stringPrefixReader)(nil)
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// NewStringPrefixReader creates a new stringPrefixReader that first returns the data in |prefix| and
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// then returns data from |reader|.
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func NewStringPrefixReader(prefix string, reader io.Reader) *stringPrefixReader {
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return &stringPrefixReader{
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prefix: prefix,
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reader: reader,
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}
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}
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// Read implements the io.Reader interface
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func (spr *stringPrefixReader) Read(p []byte) (n int, err error) {
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if spr.prefixPosition < uint(len(spr.prefix)) {
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n = copy(p, spr.prefix[spr.prefixPosition:])
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spr.prefixPosition += uint(n)
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if n == len(p) {
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return n, nil
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}
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}
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read, err := spr.reader.Read(p[n:])
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return n + read, err
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}
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// Close implements the io.Closer interface
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func (spr *stringPrefixReader) Close() error {
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if closer, ok := spr.reader.(io.Closer); ok {
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return closer.Close()
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}
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return nil
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}
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