Code: // An artificial input source. If max <= cap(buf), Scan will use this buffer only and do no allocation. Learn more First 25 Users Free
Use a Scanner to implement a simple word-count utility by scanning the input as a sequence of space-delimited tokens. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information.
ScanRunes is a split function for a Scanner that returns each UTF-8-encoded rune as a token. My CountingReader could (correctly) say that 11 bytes had been read from it, even though only, say, 4 bytes of data ("foo ") had been yielded from the Scanner.
bufio.Scanner is basically a convenience tool for parsing a stream of data. And text() creates a string from the current line. scanner.Split(bufio…
package main import ( "bufio" "fmt" "os" "strings" ) func main() { // 人为输入源。 const input = "Now is the winter of our discontent,\nMade glorious summer by this sun of York.\n" scanner := bufio.NewScanner(strings.NewReader(input)) // 设置扫描操作的分割功能。 scanner.Split(bufio.ScanWords) // 计算单词。 Bytes は，Scan 呼び出しで最後に生成されたトークンを返します。 内部の配列は，次回の Scan 呼び出しで上書きされるかもしれないデータを指しており， メモリ割り当ては行なっていないことに注意してください。
buf:= make ([] byte, 2) scanner. 262 func (s *Scanner) Buffer(buf []byte, max int) { 263 if s.scanCalled { 264 panic("Buffer called after Scan") 265 } 266 s.buf = buf[0:cap(buf)] 267 …
func (*Buffer) Grow ¶ 1.1 func (b *Buffer) Grow(n int) Grow grows the buffer's capacity, if necessary, to guarantee space for another n bytes.
func (*Scanner) Bytes ¶ 1.1 func (s *Scanner) Bytes() []byte. buf:= make ([] byte, 2) scanner. 260 // 261 // Buffer panics if it is called after scanning has started. Buffer (buf, bufio. MaxScanTokenSize) 在第一次调用 split 方法后，Scanner 会将缓冲区的大小加倍，读取更多的数据并第二次调用分割函数。第二次次场景将完全相同。
The maximum token size is the larger of max and cap(buf).
For example, if you want to use ScanLines on a []byte, you can instead use bytes.Split(s, []byte("\n")) and iterate over the resulting slice..
const input = "Now is the winter of our discontent,\nMade glorious summer by this sun of York.\n" scanner := bufio.NewScanner(strings.NewReader(input)) // Set the split function for the scanning operation. Buffer 必须在第一次 Scan 之前设置，否则会引发 panic。 // 默认情况下，Scanner 会使用一个 4096 - bufio.MaxScanTokenSize 大小的内部缓存。 func (s *Scanner) Buffer(buf []byte, max int) // Split 用于设置“匹配函数”，这个函数必须在调用 Scan 前执行。
If max <= cap(buf), 256 // Scan will use this buffer only and do no allocation.
func (s *Scanner) Buffer(buf []byte, max int) Buffer sets the initial buffer to use when scanning and the maximum size of buffer that may be allocated during scanning. When you have all the data in memory anyhow, there are usually simpler techniques. The reason for this behavior, as I found out, is that bufio.Scanner maintains an internal buffer which it reads to in large chunks.
Golang program that uses bufio, reads text file package main import ( "bufio" "fmt" "os" ) func main() { // Open the file. 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". Scan: This advances to the next part of the file and returns true if there is more data. Buffer (buf, bufio. scanner.Split(bufio.ScanBytes) // Use For-loop.
257 // 258 // By default, Scan uses an internal buffer and sets the 259 // maximum token size to MaxScanTokenSize. If on the other hand buffer has less than n bytes then bufio.Reader will read required amount of data making sure no less than n bytes will be discarded (source code):
Cap returns the capacity of the buffer's underlying byte slice, that is, the total space allocated for the buffer's data.
... 32 } 33 34 // Return the most recent call to Scan as a []byte. Go is an open source programming language that makes it easy to build simple, reliable, and efficient software. And text() creates a string from the current line. MaxScanTokenSize) 在第一次调用 split 方法后，Scanner 会将缓冲区的大小加倍，读取更多的数据并第二次调用分割函数。第二次次场景将完全相同。 Golang program that uses bufio.NewScanner, Split, ScanBytes package main import ( "bufio" "fmt" "os" ) func BytesInFile (fileName string) { f, _ := os.Open(fileName) scanner := bufio.NewScanner(f) // Call Split to specify that we want to Scan each individual byte. Scan方法获取当前位置的token（该token可以通过Bytes或Text方法获得），并让Scanner的扫描位置移动到下一个token。 当扫描因为抵达输入流结尾或者遇到错误而停止时，本方法会返回false。