mirror of https://github.com/mikefarah/yq.git
87 lines
2.9 KiB
Go
87 lines
2.9 KiB
Go
package treeops
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import (
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"errors"
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"gopkg.in/op/go-logging.v1"
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)
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type PathPostFixer interface {
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ConvertToPostfix([]*Token) ([]*Operation, error)
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}
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type pathPostFixer struct {
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}
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func NewPathPostFixer() PathPostFixer {
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return &pathPostFixer{}
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}
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func popOpToResult(opStack []*Token, result []*Operation) ([]*Token, []*Operation) {
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var newOp *Token
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opStack, newOp = opStack[0:len(opStack)-1], opStack[len(opStack)-1]
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return opStack, append(result, newOp.Operation)
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}
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func (p *pathPostFixer) ConvertToPostfix(infixTokens []*Token) ([]*Operation, error) {
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var result []*Operation
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// surround the whole thing with quotes
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var opStack = []*Token{&Token{TokenType: OpenBracket}}
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var tokens = append(infixTokens, &Token{TokenType: CloseBracket})
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for _, token := range tokens {
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log.Debugf("postfix processing token %v, %v", token.toString(), token.Operation)
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switch token.TokenType {
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case OpenBracket, OpenCollect, OpenCollectObject:
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opStack = append(opStack, token)
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case CloseCollect, CloseCollectObject:
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var opener TokenType = OpenCollect
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var collectOperator *OperationType = Collect
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if token.TokenType == CloseCollectObject {
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opener = OpenCollectObject
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collectOperator = CollectObject
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}
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for len(opStack) > 0 && opStack[len(opStack)-1].TokenType != opener {
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opStack, result = popOpToResult(opStack, result)
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}
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if len(opStack) == 0 {
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return nil, errors.New("Bad path expression, got close collect brackets without matching opening bracket")
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}
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// now we should have [] as the last element on the opStack, get rid of it
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opStack = opStack[0 : len(opStack)-1]
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//and append a collect to the opStack
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opStack = append(opStack, &Token{TokenType: OperationToken, Operation: &Operation{OperationType: Pipe}})
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opStack = append(opStack, &Token{TokenType: OperationToken, Operation: &Operation{OperationType: collectOperator}})
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case CloseBracket:
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for len(opStack) > 0 && opStack[len(opStack)-1].TokenType != OpenBracket {
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opStack, result = popOpToResult(opStack, result)
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}
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if len(opStack) == 0 {
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return nil, errors.New("Bad path expression, got close brackets without matching opening bracket")
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}
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// now we should have ( as the last element on the opStack, get rid of it
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opStack = opStack[0 : len(opStack)-1]
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default:
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var currentPrecedence = token.Operation.OperationType.Precedence
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// pop off higher precedent operators onto the result
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for len(opStack) > 0 &&
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opStack[len(opStack)-1].TokenType == OperationToken &&
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opStack[len(opStack)-1].Operation.OperationType.Precedence >= currentPrecedence {
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opStack, result = popOpToResult(opStack, result)
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}
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// add this operator to the opStack
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opStack = append(opStack, token)
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}
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}
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if log.IsEnabledFor(logging.DEBUG) {
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log.Debugf("PostFix Result:")
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for _, token := range result {
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log.Debugf("> %v", token.toString())
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}
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}
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return result, nil
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}
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