github.com/vescale/zgraph@v0.0.0-20230410094002-959c02d50f95/parser/parser.go (about)

     1  // Copyright 2022 zGraph Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package parser
    16  
    17  import (
    18  	"github.com/pingcap/errors"
    19  	"github.com/vescale/zgraph/parser/ast"
    20  )
    21  
    22  type Parser struct {
    23  	src    string
    24  	lexer  *Lexer
    25  	result []ast.StmtNode
    26  
    27  	// the following fields are used by yyParse to reduce allocation.
    28  	cache  []yySymType
    29  	yylval yySymType
    30  	yyVAL  *yySymType
    31  }
    32  
    33  func yySetOffset(yyVAL *yySymType, offset int) {
    34  	if yyVAL.expr != nil {
    35  		yyVAL.expr.SetOriginTextPosition(offset)
    36  	}
    37  }
    38  
    39  func New() *Parser {
    40  	return &Parser{
    41  		lexer: NewLexer(""),
    42  		cache: make([]yySymType, 200),
    43  	}
    44  }
    45  
    46  func (p *Parser) Parse(sql string) (stmts []ast.StmtNode, warns []error, err error) {
    47  	p.lexer.reset(sql)
    48  	p.src = sql
    49  	p.result = p.result[:0]
    50  	yyParse(p.lexer, p)
    51  
    52  	warns, errs := p.lexer.Errors()
    53  	if len(warns) > 0 {
    54  		warns = append([]error(nil), warns...)
    55  	} else {
    56  		warns = nil
    57  	}
    58  	if len(errs) != 0 {
    59  		return nil, warns, errors.Trace(errs[0])
    60  	}
    61  	return p.result, warns, nil
    62  }
    63  
    64  // ParseOneStmt parses a query and returns an ast.StmtNode.
    65  // The query must have exactly one statement.
    66  func (p *Parser) ParseOneStmt(sql string) (ast.StmtNode, error) {
    67  	stmts, _, err := p.Parse(sql)
    68  	if err != nil {
    69  		return nil, errors.Trace(err)
    70  	}
    71  	if len(stmts) != 1 {
    72  		return nil, errors.New("query must have exactly one statement")
    73  	}
    74  	return stmts[0], nil
    75  }