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|
package rfc822
import (
"fmt"
"io"
)
type headerParser struct {
header []byte
offset int
}
func newHeaderParser(header []byte) headerParser {
return headerParser{header: header}
}
// next will keep parsing until it collects a new entry. io.EOF is returned when there is nothing left to parse.
func (hp *headerParser) next() (parsedHeaderEntry, error) {
headerLen := len(hp.header)
if hp.offset >= headerLen {
return parsedHeaderEntry{}, io.EOF
}
result := parsedHeaderEntry{
keyStart: hp.offset,
keyEnd: -1,
valueStart: -1,
valueEnd: -1,
}
// Detect key, have to handle prelude case where there is no header information or last empty new line.
{
for hp.offset < headerLen {
if hp.header[hp.offset] == ':' {
prevOffset := hp.offset
hp.offset++
if hp.offset < headerLen {
result.keyEnd = prevOffset
validateHeaderField := func(h parsedHeaderEntry) error {
for i := h.keyStart; i < h.keyEnd; i++ {
if v := hp.header[i]; v < 33 || v > 126 {
return ErrNonASCIIHeaderKey
}
}
return nil
}
switch {
case hp.header[hp.offset] == ' ':
if err := validateHeaderField(result); err != nil {
return parsedHeaderEntry{}, err
}
case hp.header[hp.offset] == '\r':
// ensure next char is '\n'
hp.offset++
if hp.offset < headerLen && hp.header[hp.offset] != '\n' {
return parsedHeaderEntry{}, fmt.Errorf("expected \\n after \\r: %w", ErrParseHeader)
}
fallthrough
case hp.header[hp.offset] == '\n':
hp.offset++
if err := validateHeaderField(result); err != nil {
return parsedHeaderEntry{}, err
}
// If the next char it's not a space, it's an empty header field.
if hp.offset < headerLen && !isWSP(hp.header[hp.offset]) {
result.valueStart = result.keyEnd
result.valueEnd = result.keyEnd
return result, nil
}
case hp.header[hp.offset] == ':':
return parsedHeaderEntry{}, fmt.Errorf("unexpected char '%v', for header field value: %w", string(hp.header[hp.offset]), ErrParseHeader)
default:
if err := validateHeaderField(result); err != nil {
return parsedHeaderEntry{}, err
}
}
break
}
} else if hp.header[hp.offset] == '\n' {
hp.offset++
result.keyEnd = result.keyStart
result.valueStart = result.keyStart
result.valueEnd = hp.offset
return result, nil
} else {
hp.offset++
}
}
if result.keyEnd == -1 {
return parsedHeaderEntry{}, ErrKeyNotFound
}
}
// collect value.
searchOffset := hp.offset
for searchOffset < headerLen && isWSP(hp.header[searchOffset]) {
searchOffset++
}
if searchOffset < headerLen {
result.valueStart = searchOffset
} else {
result.valueStart = headerLen
}
for searchOffset < headerLen {
b := hp.header[searchOffset]
if b == '\r' {
searchOffset++
if searchOffset >= headerLen {
return parsedHeaderEntry{}, io.ErrUnexpectedEOF
}
if hp.header[searchOffset] != '\n' {
return parsedHeaderEntry{}, fmt.Errorf(`expected \n after \n`)
}
searchOffset++
// If the next character after new line is a space, it's a fold
if searchOffset < headerLen && isWSP(hp.header[searchOffset]) {
continue
}
result.valueEnd = searchOffset
break
} else if b == '\n' {
searchOffset++
// If the next character after new line is a space, it's a fold
if searchOffset < headerLen && isWSP(hp.header[searchOffset]) {
continue
}
result.valueEnd = searchOffset
break
} else {
searchOffset++
}
}
hp.offset = searchOffset
// handle case where we may have reached EOF without concluding any previous processing.
if result.valueEnd == -1 && searchOffset >= headerLen {
result.valueEnd = headerLen
}
return result, nil
}
func isWSP(b byte) bool {
return b == ' ' || b == '\t'
}
type parsedHeaderEntry struct {
keyStart int
keyEnd int
valueStart int
valueEnd int
}
func (p parsedHeaderEntry) hasKey() bool {
return p.keyStart != p.keyEnd
}
func (p parsedHeaderEntry) getKey(header []byte) []byte {
return header[p.keyStart:p.keyEnd]
}
func (p parsedHeaderEntry) getValue(header []byte) []byte {
return header[p.valueStart:p.valueEnd]
}
func (p parsedHeaderEntry) getAll(header []byte) []byte {
return header[p.keyStart:p.valueEnd]
}
func (p *parsedHeaderEntry) applyOffset(offset int) {
p.keyStart += offset
p.keyEnd += offset
p.valueStart += offset
p.valueEnd += offset
}
|
