diff options
Diffstat (limited to 'src/pkg/bufio/scan.go')
| -rw-r--r-- | src/pkg/bufio/scan.go | 34 |
1 files changed, 21 insertions, 13 deletions
diff --git a/src/pkg/bufio/scan.go b/src/pkg/bufio/scan.go index 268ce6d1d..2e1a2e999 100644 --- a/src/pkg/bufio/scan.go +++ b/src/pkg/bufio/scan.go @@ -16,7 +16,7 @@ import ( // the Scan method will step through the 'tokens' of a file, skipping // the bytes between the tokens. The specification of a token is // defined by a split function of type SplitFunc; the default split -// function breaks the input into lines with newlines stripped. Split +// function breaks the input into lines with line termination stripped. Split // functions are defined in this package for scanning a file into // lines, bytes, UTF-8-encoded runes, and space-delimited words. The // client may instead provide a custom split function. @@ -27,8 +27,6 @@ import ( // control over error handling or large tokens, or must run sequential scans // on a reader, should use bufio.Reader instead. // -// TODO(r): Provide executable examples. -// type Scanner struct { r io.Reader // The reader provided by the client. split SplitFunc // The function to split the tokens. @@ -72,6 +70,7 @@ const ( ) // NewScanner returns a new Scanner to read from r. +// The split function defaults to ScanLines. func NewScanner(r io.Reader) *Scanner { return &Scanner{ r: r, @@ -159,17 +158,26 @@ func (s *Scanner) Scan() bool { s.start = 0 continue } - // Finally we can read some input. - n, err := s.r.Read(s.buf[s.end:len(s.buf)]) - if err != nil { - s.setErr(err) - } - if n == 0 { // Don't loop forever if Reader doesn't deliver EOF. - s.err = io.EOF + // Finally we can read some input. Make sure we don't get stuck with + // a misbehaving Reader. Officially we don't need to do this, but let's + // be extra careful: Scanner is for safe, simple jobs. + for loop := 0; ; { + n, err := s.r.Read(s.buf[s.end:len(s.buf)]) + s.end += n + if err != nil { + s.setErr(err) + break + } + if n > 0 { + break + } + loop++ + if loop > 100 { + s.setErr(io.ErrNoProgress) + break + } } - s.end += n } - panic("not reached") } // advance consumes n bytes of the buffer. It reports whether the advance was legal. @@ -260,7 +268,7 @@ func dropCR(data []byte) []byte { // ScanLines is a split function for a Scanner that returns each line of // text, stripped of any trailing end-of-line marker. The returned line may // be empty. The end-of-line marker is one optional carriage return followed -// by one mandatory newline. In regular expression notation, it is `\r?\n'. +// by one mandatory newline. In regular expression notation, it is `\r?\n`. // The last non-empty line of input will be returned even if it has no // newline. func ScanLines(data []byte, atEOF bool) (advance int, token []byte, err error) { |