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Reduce number of allocations during deserialize
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,224 @@ | ||
| package builder | ||
|
|
||
| import ( | ||
| gojson "encoding/json" | ||
| "fmt" | ||
| "io" | ||
| "reflect" | ||
| "runtime" | ||
| "unsafe" | ||
|
|
||
| "sigs.k8s.io/json" | ||
| ) | ||
|
|
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| type parserState int | ||
|
|
||
| const ( | ||
| stateLookingForObj parserState = iota | ||
| stateLookingForItem | ||
| stateLookingForKeyValueSep | ||
| stateLookingForItemSep | ||
| stateLookingForValue | ||
| stateEnd | ||
| ) | ||
|
|
||
| type FastObjParser struct { | ||
| input []byte | ||
| pos int | ||
|
|
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| state parserState | ||
| } | ||
|
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| func NewFastObjParser(input []byte) FastObjParser { | ||
| return FastObjParser{ | ||
| input: input, | ||
| state: stateLookingForObj, | ||
| } | ||
| } | ||
|
|
||
| var whitespace = [256]bool{ | ||
| ' ': true, | ||
| '\t': true, | ||
| '\n': true, | ||
| '\r': true, | ||
| } | ||
|
|
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| func isWhitespace(c byte) bool { | ||
| return whitespace[c] | ||
| } | ||
|
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| func (p *FastObjParser) getValue(startPos int) ([]byte, error) { | ||
| foundRootValue := false | ||
| isQuoted := false | ||
| isEscaped := false | ||
| level := 0 | ||
| i := startPos | ||
| Loop: | ||
| for ; i < len(p.input); i++ { | ||
| if isQuoted { | ||
| // Skip escaped character | ||
| if isEscaped { | ||
| isEscaped = false | ||
| continue | ||
| } | ||
|
|
||
| switch p.input[i] { | ||
| case '\\': | ||
| isEscaped = true | ||
| case '"': | ||
| isQuoted = false | ||
| } | ||
|
|
||
| continue | ||
| } | ||
|
|
||
| // Skip whitespace | ||
| if isWhitespace(p.input[i]) { | ||
| continue | ||
| } | ||
|
|
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| // If we are at the top level and find the next object, we are done | ||
| if level == 0 && foundRootValue { | ||
| switch p.input[i] { | ||
| case ',', '}', ']', ':', '{', '[': | ||
| break Loop | ||
| } | ||
| } | ||
|
|
||
| switch p.input[i] { | ||
| // Keep track of the nesting level | ||
| case '{': | ||
| level++ | ||
| case '}': | ||
| level-- | ||
| case '[': | ||
| level++ | ||
| case ']': | ||
| level-- | ||
|
|
||
| // Start of a string | ||
| case '"': | ||
| isQuoted = true | ||
| } | ||
|
|
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| foundRootValue = true | ||
| } | ||
|
|
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| if level != 0 { | ||
| return nil, fmt.Errorf("expected '}' or ']' but reached end of input") | ||
| } | ||
|
|
||
| if isQuoted { | ||
| return nil, fmt.Errorf("expected '\"' but reached end of input") | ||
| } | ||
|
|
||
| if !foundRootValue { | ||
| return nil, fmt.Errorf("expected value but reached end of input") | ||
| } | ||
|
|
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| return p.input[startPos:i], nil | ||
| } | ||
|
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| func (p *FastObjParser) Parse() ([]byte, error) { | ||
| for { | ||
| if p.pos >= len(p.input) { | ||
| return nil, io.EOF | ||
| } | ||
|
|
||
| // Skip whitespace | ||
| if isWhitespace(p.input[p.pos]) { | ||
| p.pos++ | ||
| continue | ||
| } | ||
|
|
||
| switch p.state { | ||
| case stateLookingForObj: | ||
| if p.input[p.pos] != '{' { | ||
| return nil, fmt.Errorf("expected '{' at position %d", p.pos) | ||
| } | ||
|
|
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| p.state = stateLookingForItem | ||
|
|
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| case stateLookingForItem: | ||
| if p.input[p.pos] == '}' { | ||
| p.state = stateEnd | ||
| return nil, io.EOF | ||
| } | ||
|
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| strSlice, err := p.getValue(p.pos) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| p.pos += len(strSlice) | ||
| p.state = stateLookingForKeyValueSep | ||
| return strSlice, nil | ||
|
|
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| case stateLookingForKeyValueSep: | ||
| if p.input[p.pos] != ':' { | ||
| return nil, fmt.Errorf("expected ':' at position %d", p.pos) | ||
| } | ||
|
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| p.state = stateLookingForValue | ||
|
|
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| case stateLookingForValue: | ||
| valueSlice, err := p.getValue(p.pos) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
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| p.pos += len(valueSlice) | ||
| p.state = stateLookingForItemSep | ||
| return valueSlice, nil | ||
|
|
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| case stateLookingForItemSep: | ||
| if p.input[p.pos] == ',' { | ||
| p.state = stateLookingForItem | ||
| } else if p.input[p.pos] == '}' { | ||
| p.state = stateEnd | ||
| } else { | ||
| return nil, fmt.Errorf("expected ',' or '}' at position %d", p.pos) | ||
| } | ||
|
|
||
| case stateEnd: | ||
| return nil, io.EOF | ||
| } | ||
|
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| p.pos++ | ||
| } | ||
| } | ||
|
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| func UnmarshalString(input []byte) (string, error) { | ||
| var v string | ||
| // No need to enable case sensitivity or int preservation here, as we are only unmarshalling strings. | ||
| if err := gojson.Unmarshal(input, (*string)(noescape(unsafe.Pointer(&v)))); err != nil { | ||
| return "", err | ||
| } | ||
|
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| runtime.KeepAlive(v) | ||
|
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| return v, nil | ||
| } | ||
|
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| func UnmarshalInterface(input []byte) (interface{}, error) { | ||
| var v interface{} | ||
| if err := json.UnmarshalCaseSensitivePreserveInts(input, (*interface{})(noescape(unsafe.Pointer(&v)))); err != nil { | ||
| return "", err | ||
| } | ||
|
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| runtime.KeepAlive(v) | ||
|
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| return v, nil | ||
| } | ||
|
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| // Create a read-only byte array from a string | ||
| func StringToReadOnlyByteSlice(s string) []byte { | ||
| // Get StringHeader from string | ||
| stringHeader := (*reflect.StringHeader)(unsafe.Pointer(&s)) | ||
|
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| // Construct SliceHeader with capacity equal to the length | ||
| sliceHeader := reflect.SliceHeader{Data: stringHeader.Data, Len: stringHeader.Len, Cap: stringHeader.Len} | ||
|
|
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| // Convert SliceHeader to a byte slice | ||
| return *(*[]byte)(unsafe.Pointer(&sliceHeader)) | ||
| } |
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