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// Copyright 2019+ Klaus Post. All rights reserved.
// License information can be found in the LICENSE file.
// Based on work by Yann Collet, released under BSD License.
package zstd
import (
"errors"
"runtime"
)
// DOption is an option for creating a decoder.
type DOption func(*decoderOptions) error
// options retains accumulated state of multiple options.
type decoderOptions struct {
lowMem bool
concurrent int
maxDecodedSize uint64
dicts []dict
}
func (o *decoderOptions) setDefault() {
*o = decoderOptions{
// use less ram: true for now, but may change.
lowMem: true,
concurrent: runtime.GOMAXPROCS(0),
}
o.maxDecodedSize = 1 << 63
}
// WithDecoderLowmem will set whether to use a lower amount of memory,
// but possibly have to allocate more while running.
func WithDecoderLowmem(b bool) DOption {
return func(o *decoderOptions) error { o.lowMem = b; return nil }
}
// WithDecoderConcurrency will set the concurrency,
// meaning the maximum number of decoders to run concurrently.
// The value supplied must be at least 1.
// By default this will be set to GOMAXPROCS.
func WithDecoderConcurrency(n int) DOption {
return func(o *decoderOptions) error {
if n <= 0 {
return errors.New("concurrency must be at least 1")
}
o.concurrent = n
return nil
}
}
// WithDecoderMaxMemory allows to set a maximum decoded size for in-memory
// non-streaming operations or maximum window size for streaming operations.
// This can be used to control memory usage of potentially hostile content.
// For streaming operations, the maximum window size is capped at 1<<30 bytes.
// Maximum and default is 1 << 63 bytes.
func WithDecoderMaxMemory(n uint64) DOption {
return func(o *decoderOptions) error {
if n == 0 {
return errors.New("WithDecoderMaxMemory must be at least 1")
}
if n > 1<<63 {
return errors.New("WithDecoderMaxmemory must be less than 1 << 63")
}
o.maxDecodedSize = n
return nil
}
}
// WithDecoderDicts allows to register one or more dictionaries for the decoder.
// If several dictionaries with the same ID is provided the last one will be used.
func WithDecoderDicts(dicts ...[]byte) DOption {
return func(o *decoderOptions) error {
for _, b := range dicts {
d, err := loadDict(b)
if err != nil {
return err
}
o.dicts = append(o.dicts, *d)
}
return nil
}
}
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