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reader.go
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reader.go
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package jsonio
import (
"bufio"
"fmt"
"io"
"github.com/brimdata/zed"
"github.com/brimdata/zed/pkg/byteconv"
"github.com/brimdata/zed/pkg/jsonlexer"
"golang.org/x/text/unicode/norm"
)
type Reader struct {
builder builder
lexer *jsonlexer.Lexer
buf []byte
}
func NewReader(zctx *zed.Context, r io.Reader) *Reader {
return &Reader{
builder: builder{zctx: zctx},
// 64 KB gave the best performance when this was written.
lexer: jsonlexer.New(bufio.NewReaderSize(r, 64*1024)),
// Ensure handleToken never passes a nil buf to
// builder.pushPrimitiveItem.
buf: make([]byte, 0, 64),
}
}
func (r *Reader) Read() (*zed.Value, error) {
t := r.lexer.Token()
if t == jsonlexer.TokenErr {
err := r.lexer.Err()
if err == io.EOF {
return nil, nil
}
return nil, err
}
r.builder.reset()
if err := r.handleToken("", t); err != nil {
return nil, err
}
return r.builder.value(), nil
}
func (r *Reader) handleToken(fieldName string, t jsonlexer.Token) error {
r.buf = r.buf[:0]
switch t {
case jsonlexer.TokenString:
b, ok := unquoteBytes(r.lexer.Buf())
if !ok {
return fmt.Errorf("invalid JSON string %q", r.lexer.Buf())
}
r.buf = norm.NFC.Append(r.buf, b...)
r.builder.pushPrimitiveItem(fieldName, zed.TypeString, r.buf)
case jsonlexer.TokenNumber:
if i, err := byteconv.ParseInt64(r.lexer.Buf()); err == nil {
r.buf = zed.AppendInt(r.buf, i)
r.builder.pushPrimitiveItem(fieldName, zed.TypeInt64, r.buf)
} else if f, err := byteconv.ParseFloat64(r.lexer.Buf()); err == nil {
r.buf = zed.AppendFloat64(r.buf, f)
r.builder.pushPrimitiveItem(fieldName, zed.TypeFloat64, r.buf)
} else {
return err
}
case jsonlexer.TokenBeginObject:
r.builder.beginContainer(fieldName)
if err := r.readRecord(); err != nil {
return err
}
r.builder.endRecord()
case jsonlexer.TokenBeginArray:
r.builder.beginContainer(fieldName)
if err := r.readArray(); err != nil {
return err
}
r.builder.endArray()
case jsonlexer.TokenNull:
r.builder.pushPrimitiveItem(fieldName, zed.TypeNull, nil)
case jsonlexer.TokenFalse, jsonlexer.TokenTrue:
r.buf = zed.AppendBool(r.buf, t == jsonlexer.TokenTrue)
r.builder.pushPrimitiveItem(fieldName, zed.TypeBool, r.buf)
default:
return r.error(t, "looking for beginning of value")
}
return nil
}
func (r *Reader) readArray() error {
switch t := r.lexer.Token(); t {
case jsonlexer.TokenEndArray:
return nil
default:
if err := r.handleToken("", t); err != nil {
return err
}
}
for {
switch t := r.lexer.Token(); t {
case jsonlexer.TokenEndArray:
return nil
case jsonlexer.TokenValueSeparator:
if err := r.handleToken("", r.lexer.Token()); err != nil {
return err
}
default:
return r.error(t, "after array value")
}
}
}
func (r *Reader) readRecord() error {
switch t := r.lexer.Token(); t {
case jsonlexer.TokenEndObject:
return nil
default:
if err := r.readNameValuePair(t); err != nil {
return err
}
}
for {
switch t := r.lexer.Token(); t {
case jsonlexer.TokenEndObject:
return nil
case jsonlexer.TokenValueSeparator:
if err := r.readNameValuePair(r.lexer.Token()); err != nil {
return err
}
default:
return r.error(t, "after object key")
}
}
}
func (r *Reader) readNameValuePair(t jsonlexer.Token) error {
if t != jsonlexer.TokenString {
return r.error(t, "looking for beginning of object key string")
}
fieldName, ok := unquote(r.lexer.Buf())
if !ok {
return fmt.Errorf("invalid string %q", r.lexer.Buf())
}
if t := r.lexer.Token(); t != jsonlexer.TokenNameSeparator {
return r.error(t, "after object key")
}
return r.handleToken(fieldName, r.lexer.Token())
}
func (r *Reader) error(t jsonlexer.Token, msg string) error {
if t == jsonlexer.TokenErr {
return r.lexer.Err()
}
return fmt.Errorf("invalid character %q %s", r.lexer.Buf()[0], msg)
}