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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package lowmemjson
import (
"bytes"
"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
)
type reEncodeCompactWSIfUnder struct {
out reEncoderModule
// CompactWSIfUnder runs uses reEncodeCompactWScauses for
// individual elements if doing so would cause that element to
// be under this number of bytes.
//
// This has O(2^min(CompactWSIfUnder, depth)) time overhead,
// so set with caution.
CompactWSIfUnder int
// state
compactor reEncodeWrite
compacted bytes.Buffer
full []handleRuneCall
endWhenStackSize int
}
var _ reEncoderModule = (*reEncodeCompactWSIfUnder)(nil)
type handleRuneCall struct {
c rune
t jsonparse.RuneType
escape BackslashEscapeMode
stackSize int
}
func (enc *reEncodeCompactWSIfUnder) reset() {
enc.compactor = reEncodeWrite{}
enc.compacted.Reset()
enc.full = enc.full[:0]
enc.endWhenStackSize = 0
}
func (enc *reEncodeCompactWSIfUnder) PopWriteBarrier() {
enc.out.PopWriteBarrier()
}
func (enc *reEncodeCompactWSIfUnder) HandleRune(c rune, t jsonparse.RuneType, escape BackslashEscapeMode, stackSize int) error {
if enc.compactor.out == nil { // not speculating
switch t {
case jsonparse.RuneTypeObjectBeg, jsonparse.RuneTypeArrayBeg: // start speculating
enc.endWhenStackSize = stackSize - 1
enc.compactor = reEncodeWrite{
out: &enc.compacted,
}
enc.full = append(enc.full, handleRuneCall{
c: c,
t: t,
escape: escape,
stackSize: stackSize,
})
return enc.compactor.HandleRune(c, t, escape, stackSize)
default:
return enc.out.HandleRune(c, t, escape, stackSize)
}
} else { // speculating
enc.full = append(enc.full, handleRuneCall{
c: c,
t: t,
escape: escape,
stackSize: stackSize,
})
if t != jsonparse.RuneTypeSpace {
if err := enc.compactor.HandleRune(c, t, escape, stackSize); err != nil {
return err
}
}
switch {
case enc.compacted.Len() >= enc.CompactWSIfUnder: // stop speculating; use indent
buf := append([]handleRuneCall(nil), enc.full...)
enc.reset()
if err := enc.out.HandleRune(buf[0].c, buf[0].t, buf[0].escape, buf[0].stackSize); err != nil {
return err
}
for _, tuple := range buf[1:] {
if err := enc.HandleRune(tuple.c, tuple.t, tuple.escape, tuple.stackSize); err != nil {
return err
}
}
case stackSize == enc.endWhenStackSize: // stop speculating; use compact
for _, tuple := range enc.full {
if tuple.t == jsonparse.RuneTypeSpace {
continue
}
if err := enc.out.HandleRune(tuple.c, tuple.t, tuple.escape, tuple.stackSize); err != nil {
return err
}
}
enc.reset()
}
return nil
}
}
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