111 lines
2.4 KiB
Go
111 lines
2.4 KiB
Go
package brace
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import (
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"io"
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"sourcecode.social/reiver/go-erorr"
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)
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// Parse parses a brace-string literal from a io.RuneScanner.
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//
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// Parse will call ‘fn’ for each logical character it receives.
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// So — if this is the brace-literal it parses:
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//
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// `{a b \{ c \} d}`
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//
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// Then ‘fn’ would be called 11 times, and given these runes:
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//
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// 'a'
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// ' '
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// 'b'
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// ' '
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// '{'
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// ' '
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// 'c'
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// ' '
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// '}'
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// ' '
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// 'd'
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//
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// Note that the beginning '{' and ending '}' of the brace-string literal are not part of this.
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// Also note that the '\' (black-slash) before the '{' and the '}' was not included either.
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func Parse(fn func(rune)error, runescanner io.RuneScanner) error {
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if nil == runescanner {
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return errNilRuneScanner
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}
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var nextRead uint64 = 1
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{
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r, _, err := runescanner.ReadRune()
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if io.EOF == err {
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return errProblemReadingCharacterNumber(nextRead, errEmptyString)
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}
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if nil != err {
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return errProblemReadingCharacterNumber(nextRead, err)
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}
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nextRead++
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{
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const expected = leftbrace
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actual := r
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if expected != actual {
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err := runescanner.UnreadRune()
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if nil != err {
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characterNumber := nextRead - 1
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return errProblemUnreadingCharacterNumber(characterNumber, err, r)
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}
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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)
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}
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}
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}
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var depth int64 = 1
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loop: for {
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r, _, err := runescanner.ReadRune()
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if io.EOF == err {
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return errProblemReadingCharacterNumber(nextRead, errFileEndedBeforeBraceStringLiteralClosed(depth))
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}
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if nil != err {
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return errProblemReadingCharacterNumber(nextRead, err)
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}
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nextRead++
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switch r {
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case leftbrace:
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depth++
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case rightbrace:
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depth--
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case '\\':
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r, _, err = runescanner.ReadRune()
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if io.EOF == err {
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return errProblemReadingCharacterNumber(nextRead, errFileEndedBeforeBraceStringLiteralClosed(depth))
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}
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if nil != err {
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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)
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}
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nextRead++
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}
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switch {
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case 0 == depth:
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////////////// BREAK
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break loop
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case depth < 0:
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return errInternalError(errParserDepthNegative(depth))
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}
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{
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err := fn(r)
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if nil != err {
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return err
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}
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}
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}
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return nil
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}
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