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|
// Package streamquote implements a streaming version of strconv.Quote.
//go:build !go1.19
package streamquote
import (
"io"
"strconv"
"unicode/utf8"
)
// Converter converts data by escaping control characters and
// non-printable characters using Go escape sequences.
type Converter interface {
// Convert converts the data in "in", writing it to "out".
// It uses Go escape sequences (\t, \n, \xFF, \u0100) for control characters
// and non-printable characters as defined by strconv.IsPrint.
// It is not safe for concurrent use.
Convert(in io.Reader, out io.Writer) (int, error)
}
const bufSize = 100 * 1024
const lowerhex = "0123456789abcdef"
type converter struct {
readBuffer [bufSize]byte
writeBuffer [10]byte
}
// New returns a new Converter.
func New() Converter {
return &converter{}
}
// Convert converts the data in "in", writing it to "out".
// It uses Go escape sequences (\t, \n, \xFF, \u0100) for control characters
// and non-printable characters as defined by strconv.IsPrint.
// It is not safe for concurrent use.
func (c *converter) Convert(in io.Reader, out io.Writer) (int, error) {
var err error
bufSize := len(c.readBuffer)
n := 0
var processed = bufSize
var dataLen = 0
for {
if processed+utf8.UTFMax > bufSize {
// need to read more
leftover := bufSize - processed
if leftover > 0 {
copy(c.readBuffer[:leftover], c.readBuffer[processed:])
}
read, peekErr := in.Read(c.readBuffer[leftover:])
if peekErr != nil && peekErr != io.EOF {
err = peekErr
break
}
dataLen = leftover + read
processed = 0
}
if dataLen-processed == 0 {
break
}
maxRune := processed + utf8.UTFMax
if maxRune > dataLen {
maxRune = dataLen
}
data := c.readBuffer[processed:maxRune]
var discard, n2 int
r, width := utf8.DecodeRune(data)
if width == 1 && r == utf8.RuneError {
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'x'
c.writeBuffer[2] = lowerhex[data[0]>>4]
c.writeBuffer[3] = lowerhex[data[0]&0xF]
out.Write(c.writeBuffer[0:4])
n2 = 4
discard = 1
} else {
discard = width
if r == rune('"') || r == '\\' { // always backslashed
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = byte(r)
out.Write(c.writeBuffer[0:2])
n2 = 2
} else if strconv.IsPrint(r) {
out.Write(data[:width])
n2 = width
} else {
switch r {
case '\a':
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'a'
out.Write(c.writeBuffer[0:2])
n2 = 2
case '\b':
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'b'
out.Write(c.writeBuffer[0:2])
n2 = 2
case '\f':
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'f'
out.Write(c.writeBuffer[0:2])
n2 = 2
case '\n':
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'n'
out.Write(c.writeBuffer[0:2])
n2 = 2
case '\r':
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'r'
out.Write(c.writeBuffer[0:2])
n2 = 2
case '\t':
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 't'
out.Write(c.writeBuffer[0:2])
n2 = 2
case '\v':
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'v'
out.Write(c.writeBuffer[0:2])
n2 = 2
default:
switch {
case r < ' ':
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'x'
c.writeBuffer[2] = lowerhex[data[0]>>4]
c.writeBuffer[3] = lowerhex[data[0]&0xF]
out.Write(c.writeBuffer[0:4])
n2 = 4
case r > utf8.MaxRune:
r = 0xFFFD
fallthrough
case r < 0x10000:
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'u'
n2 = 2
i := 2
for s := 12; s >= 0; s -= 4 {
c.writeBuffer[i] = lowerhex[r>>uint(s)&0xF]
i++
n2++
}
out.Write(c.writeBuffer[0:i])
default:
c.writeBuffer[0] = '\\'
c.writeBuffer[1] = 'U'
n2 = 2
i := 2
for s := 28; s >= 0; s -= 4 {
c.writeBuffer[i] = lowerhex[r>>uint(s)&0xF]
i++
n2++
}
out.Write(c.writeBuffer[0:i])
}
}
}
}
processed += discard
n += n2
}
return n, err
}
|
