package brace import ( "io" "sourcecode.social/reiver/go-erorr" ) // Parse parses a brace-string literal from a io.RuneScanner. // // Parse will call ‘fn’ for each logical character it receives. // So — if this is the brace-literal it parses: // // `{a b \{ c \} d}` // // Then ‘fn’ would be called 11 times, and given these runes: // // 'a' // ' ' // 'b' // ' ' // '{' // ' ' // 'c' // ' ' // '}' // ' ' // 'd' // // Note that the beginning '{' and ending '}' of the brace-string literal are not part of this. // Also note that the '\' (black-slash) before the '{' and the '}' was not included either. func Parse(fn func(rune)error, runescanner io.RuneScanner) error { if nil == runescanner { return errNilRuneScanner } var nextRead uint64 = 1 { r, _, err := runescanner.ReadRune() if io.EOF == err { return errProblemReadingCharacterNumber(nextRead, errEmptyString) } if nil != err { return errProblemReadingCharacterNumber(nextRead, err) } nextRead++ { const expected = leftbrace actual := r if expected != actual { err := runescanner.UnreadRune() if nil != err { characterNumber := nextRead - 1 return errProblemUnreadingCharacterNumber(characterNumber, err, r) } return erorr.Errorf("brace: expected first character of brace-string literal to be a %q (%U), but actually was %q (%U)", expected, expected, actual, actual) } } } var depth int64 = 1 loop: for { r, _, err := runescanner.ReadRune() if io.EOF == err { return errProblemReadingCharacterNumber(nextRead, errFileEndedBeforeBraceStringLiteralClosed(depth)) } if nil != err { return errProblemReadingCharacterNumber(nextRead, err) } nextRead++ switch r { case leftbrace: depth++ case rightbrace: depth-- case '\\': r, _, err = runescanner.ReadRune() if io.EOF == err { return errProblemReadingCharacterNumber(nextRead, errFileEndedBeforeBraceStringLiteralClosed(depth)) } if nil != err { return erorr.Errorf("brace: problem reading character №%d (which would have followed a black-slash %q (%U) that was just read) of what should have been a brace-string literal: %w", nextRead, r, r, err) } nextRead++ } switch { case 0 == depth: ////////////// BREAK break loop case depth < 0: return errInternalError(errParserDepthNegative(depth)) } { err := fn(r) if nil != err { return err } } } return nil }