55 lines
1.9 KiB
Go
55 lines
1.9 KiB
Go
package parsekit
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import (
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"strings"
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)
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// Parser is the top-level struct that holds the configuration for a parser.
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// The Parser can be instantiated using the parsekit.NewParser() method.
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type Parser struct {
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startHandler ParseHandler // the function that handles the very first state
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}
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// ParseHandler defines the type of function that must be implemented to handle
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// a parsing state in a Parser state machine.
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//
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// A ParseHandler function gets a ParseAPI struct as its input. This struct holds
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// all the internal state for the parsing state machine and provides the
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// interface that the ParseHandler uses to interact with the parser.
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type ParseHandler func(*ParseAPI)
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// NewParser instantiates a new Parser.
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//
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// The Parser is a state machine-style recursive descent parser, in which
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// ParseHandler functions are used to move the state machine forward during
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// parsing. This style of parser is typically used for parsing programming
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// languages and structured data formats (like json, xml, toml, etc.)
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//
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// To parse input data, use the method Parser.Execute().
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func NewParser(startHandler ParseHandler) *Parser {
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if startHandler == nil {
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callerPanic(1, "parsekit.NewParser(): NewParser() called with nil input at {caller}")
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}
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return &Parser{startHandler: startHandler}
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}
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// Execute starts the parser for the provided input.
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// When an error occurs during parsing, then this error is returned. Nil otherwise.
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func (p *Parser) Execute(input string) *Error {
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api := &ParseAPI{
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tokenAPI: NewTokenAPI(strings.NewReader(input)),
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loopCheck: map[string]bool{},
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}
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if api.Handle(p.startHandler) {
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// Handle returned true, indicating that parsing could still continue.
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// There was no error and that the parsing has not actively been Stop()-ed.
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// Let's try to make the best of it.
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if api.expecting != "" {
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api.UnexpectedInput()
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} else {
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api.ExpectEndOfFile()
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}
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}
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return api.err
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}
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