iter_skip.go

package jsoniter

import "fmt"

func (iter *Iterator) skipNumber() error {
	for i := iter.head; i < len(iter.buf); i++ {
		c := iter.buf[i]
		switch c {
		case ' ', '\n', '\r', '\t', ',', '}', ']':
			iter.head = i
			return nil
		}
	}
	iter.head = len(iter.buf)
	return nil
}

func (iter *Iterator) skipArray() error {
	level := 1
	for i := iter.head; i < len(iter.buf); i++ {
		switch iter.buf[i] {
		case '"': // If inside string, skip it
			iter.head = i + 1
			iter.skipString()
			i = iter.head - 1 // it will be i++ soon
		case '[': // If open symbol, increase level
			level++
		case ']': // If close symbol, increase level
			level--
			// If we have returned to the original level, we're done
			if level == 0 {
				iter.head = i + 1
				return nil
			}
		}
	}
	return iter.ReportError("skipArray", "balanced bracket")
}

func (iter *Iterator) skipObject() error {
	level := 1
	for i := iter.head; i < len(iter.buf); i++ {
		switch iter.buf[i] {
		case '"': // If inside string, skip it
			iter.head = i + 1
			iter.skipString()
			i = iter.head - 1 // it will be i++ soon
		case '{': // If open symbol, increase level
			level++
		case '}': // If close symbol, increase level
			level--
			// If we have returned to the original level, we're done
			if level == 0 {
				iter.head = i + 1
				return nil
			}
		}
	}
	return iter.ReportError("skipObject", "balanced brace")
}

// adapted from: https://github.com/buger/jsonparser/blob/master/parser.go
func (iter *Iterator) skipString() error {
	escaped := false
	for i := iter.head; i < len(iter.buf); i++ {
		c := iter.buf[i]
		if c == '"' {
			if !escaped {
				iter.head = i + 1
				return nil
			}
			j := i - 1
			for {
				if j < iter.head || iter.buf[j] != '\\' {
					// even number of backslashes
					// either end of buffer, or " found
					iter.head = i + 1
					return nil
				}
				j--
				if j < iter.head || iter.buf[j] != '\\' {
					// odd number of backslashes
					// it is \" or \\\"
					break
				}
				j--
			}
		} else if c == '\\' {
			escaped = true
		}
	}
	iter.head = len(iter.buf)
	return iter.ReportError("skipString", "incomplete string")
}

func (iter *Iterator) ReadRawMessage(out *RawMessage) (ret error) {
	before := iter.head
	ret = iter.Skip()
	if ret == nil {
		after := iter.head
		*out = iter.buf[before:after]
	}
	return
}

// Skip skips a json object and positions to relatively the next json object
func (iter *Iterator) Skip() error {
	return iter.skip(iter.nextToken())
}

func (iter *Iterator) skip(c byte) error {
	switch c {
	case '"':
		return iter.skipString()
	case 'n':
		return iter.skipThreeBytes('u', 'l', 'l') // null
	case 't':
		return iter.skipThreeBytes('r', 'u', 'e') // true
	case 'f':
		return iter.skipFourBytes('a', 'l', 's', 'e') // false
	case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
		return iter.skipNumber()
	case '[':
		return iter.skipArray()
	case '{':
		return iter.skipObject()
	default:
		return iter.ReportError("Skip", fmt.Sprintf("do not know how to skip: %v", c))
	}
}

func (iter *Iterator) skipFourBytes(b1, b2, b3, b4 byte) error {
	if iter.readByte() != b1 {
		return iter.ReportError("skipFourBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3, b4})))
	}
	if iter.readByte() != b2 {
		return iter.ReportError("skipFourBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3, b4})))
	}
	if iter.readByte() != b3 {
		return iter.ReportError("skipFourBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3, b4})))
	}
	if iter.readByte() != b4 {
		return iter.ReportError("skipFourBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3, b4})))
	}
	return nil
}

func (iter *Iterator) skipThreeBytes(b1, b2, b3 byte) error {
	if iter.readByte() != b1 {
		return iter.ReportError("skipThreeBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3})))
	}
	if iter.readByte() != b2 {
		return iter.ReportError("skipThreeBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3})))
	}
	if iter.readByte() != b3 {
		return iter.ReportError("skipThreeBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3})))
	}
	return nil
}