Scanner provides a convenient interface for reading data such as
a file of newline-delimited lines of text. Successive calls to
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 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.
Scanning stops unrecoverably at EOF, the first I/O error, or a token too
large to fit in the buffer. When a scan stops, the reader may have
advanced arbitrarily far past the last token. Programs that need more
control over error handling or large tokens, or must run sequential scans
on a reader, should use bufio.Reader instead.
(*T) Buffer(buf byte, max int)
(*T) Bytes() byte
(*T) Err() error
(*T) Scan() bool
(*T) Split(split SplitFunc)
(*T) Text() string
func NewScanner(r io.Reader) *Scanner
SplitFunc is the signature of the split function used to tokenize the
input. The arguments are an initial substring of the remaining unprocessed
data and a flag, atEOF, that reports whether the Reader has no more data
to give. The return values are the number of bytes to advance the input
and the next token to return to the user, if any, plus an error, if any.
Scanning stops if the function returns an error, in which case some of
the input may be discarded.
Otherwise, the Scanner advances the input. If the token is not nil,
the Scanner returns it to the user. If the token is nil, the
Scanner reads more data and continues scanning; if there is no more
data--if atEOF was true--the Scanner returns. If the data does not
yet hold a complete token, for instance if it has no newline while
scanning lines, a SplitFunc can return (0, nil, nil) to signal the
Scanner to read more data into the slice and try again with a
longer slice starting at the same point in the input.
The function is never called with an empty data slice unless atEOF
is true. If atEOF is true, however, data may be non-empty and,
as always, holds unprocessed text.
func (*Scanner).Split(split SplitFunc)
ErrFinalToken is a special sentinel error value. It is intended to be
returned by a Split function to indicate that the token being delivered
with the error is the last token and scanning should stop after this one.
After ErrFinalToken is received by Scan, scanning stops with no error.
The value is useful to stop processing early or when it is necessary to
deliver a final empty token. One could achieve the same behavior
with a custom error value but providing one here is tidier.
See the emptyFinalToken example for a use of this value.
const MaxScanTokenSize = 65536
MaxScanTokenSize is the maximum size used to buffer a token
unless the user provides an explicit buffer with Scanner.Buffer.
The actual maximum token size may be smaller as the buffer
may need to include, for instance, a newline.
func NewReaderSize(rd io.Reader, size int) *Reader
NewReaderSize returns a new Reader whose buffer has at least the specified
size. If the argument io.Reader is already a Reader with large enough
size, it returns the underlying Reader.
func NewWriterSize(w io.Writer, size int) *Writer
NewWriterSize returns a new Writer whose buffer has at least the specified
size. If the argument io.Writer is already a Writer with large enough
size, it returns the underlying Writer.
func ScanBytes(data byte, atEOF bool) (advance int, token byte, err error)
ScanBytes is a split function for a Scanner that returns each byte as a token.
func ScanLines(data byte, atEOF bool) (advance int, token byte, err error)
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`.
The last non-empty line of input will be returned even if it has no
func ScanRunes(data byte, atEOF bool) (advance int, token byte, err error)
ScanRunes is a split function for a Scanner that returns each
UTF-8-encoded rune as a token. The sequence of runes returned is
equivalent to that from a range loop over the input as a string, which
means that erroneous UTF-8 encodings translate to U+FFFD = "\xef\xbf\xbd".
Because of the Scan interface, this makes it impossible for the client to
distinguish correctly encoded replacement runes from encoding errors.
func ScanWords(data byte, atEOF bool) (advance int, token byte, err error)
ScanWords is a split function for a Scanner that returns each
space-separated word of text, with surrounding spaces deleted. It will
never return an empty string. The definition of space is set by
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