RFC2045 第 6.8 節規定 Base64 輸出的最大編碼行長度應為 76 個字符或更少。Golang 流編寫器base64.NewEncoder沒有任何行分割選項，如此處所示。package mainimport ( "encoding/base64" "io" "os" "strings")// See https://www.ietf.org/rfc/rfc2045.txt, section 6.8 for notes on maximum line length of 76 charactersfunc main() { data := "It is only the hairs on a gooseberry that prevent it from being a grape! This is long enough to need a line split" rdr := strings.NewReader(data) wrt := base64.NewEncoder(base64.StdEncoding, os.Stdout) io.Copy(wrt, rdr)}輸出是SXQgaXMgb25seSB0aGUgaGFpcnMgb24gYSBnb29zZWJlcnJ5IHRoYXQgcHJldmVudCBpdCBmcm9tIGJlaW5nIGEgZ3JhcGUhIEl0IGlzIG9ubHkgdGhlIGhhaXJzIG9uIGEgZ29vc2ViZXJyeSB0aGF0IHByZXZlbnQgaXQgZnJvbSBiZWluZyBhIGdyYXBl是否有基于流的分割線解決方案？MIME庫僅提供基于字符串的編碼選項。
1 回答
夢里花落0921
TA貢獻1772條經驗 獲得超6個贊
這是我嘗試創建一個簡單的Writer. 它考慮到不同數量的輸入數據，具有可配置的塊長度和分隔符序列。它使用字節片寫入塊，這有望提高效率。
package main
import (
"encoding/base64"
"io"
"os"
"strings"
)
func min(a, b int) int {
if a < b {
return a
}
return b
}
type linesplitter struct {
len int
count int
sep []byte
w io.Writer
}
// NewWriter that splits input every len bytes with a sep byte sequence, outputting to writer w
func (ls *linesplitter) NewWriter(len int, sep []byte, w io.Writer) io.WriteCloser {
return &linesplitter{len: len, count: 0, sep: sep, w: w}
}
// Split a line in to ls.len chunks with separator
func (ls *linesplitter) Write(in []byte) (n int, err error) {
writtenThisCall := 0
readPos := 0
// Leading chunk size is limited by: how much input there is; defined split length; and
// any residual from last time
chunkSize := min(len(in), ls.len-ls.count)
// Pass on chunk(s)
for {
ls.w.Write(in[readPos:(readPos + chunkSize)])
readPos += chunkSize // Skip forward ready for next chunk
ls.count += chunkSize
writtenThisCall += chunkSize
// if we have completed a chunk, emit a separator
if ls.count >= ls.len {
ls.w.Write(ls.sep)
writtenThisCall += len(ls.sep)
ls.count = 0
}
inToGo := len(in) - readPos
if inToGo <= 0 {
break // reached end of input data
}
// Determine size of the NEXT chunk
chunkSize = min(inToGo, ls.len)
}
return writtenThisCall, nil
}
func (ls *linesplitter) Close() (err error) {
return nil
}
// See https://www.ietf.org/rfc/rfc2045.txt, section 6.8 for notes on maximum line length of 76 characters
func main() {
data := "It is only the hairs on a gooseberry that prevent it from being a grape! This is long enough to need a line split"
shortData := "hello there"
var ls linesplitter
lsWriter := ls.NewWriter(76, []byte("\r\n"), os.Stdout)
wrt := base64.NewEncoder(base64.StdEncoding, lsWriter)
for i := 0; i < 10; i++ {
io.Copy(wrt, strings.NewReader(shortData))
io.Copy(wrt, strings.NewReader(data))
io.Copy(wrt, strings.NewReader(shortData))
}
}
...歡迎提出意見/改進。
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