1 files changed, 120 insertions, 0 deletions
diff --git a/src/pkg/mime/mediatype.go b/src/pkg/mime/mediatype.go
new file mode 100644
index 000000000..eb629aa6f
--- /dev/null
+++ b/src/pkg/mime/mediatype.go
@@ -0,0 +1,120 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package mime
+
+import (
+	"bytes"
+	"strings"
+	"unicode"
+)
+
+// ParseMediaType parses a media type value and any optional
+// parameters, per RFC 1531.  Media types are the values in
+// Content-Type and Content-Disposition headers (RFC 2183).  On
+// success, ParseMediaType returns the media type converted to
+// lowercase and trimmed of white space and a non-nil params.  On
+// error, it returns an empty string and a nil params.
+func ParseMediaType(v string) (mediatype string, params map[string]string) {
+	i := strings.Index(v, ";")
+	if i == -1 {
+		i = len(v)
+	}
+	mediatype = strings.TrimSpace(strings.ToLower(v[0:i]))
+	params = make(map[string]string)
+
+	v = v[i:]
+	for len(v) > 0 {
+		v = strings.TrimLeftFunc(v, unicode.IsSpace)
+		if len(v) == 0 {
+			return
+		}
+		key, value, rest := consumeMediaParam(v)
+		if key == "" {
+			// Parse error.
+			return "", nil
+		}
+		params[key] = value
+		v = rest
+	}
+	return
+}
+
+func isNotTokenChar(rune int) bool {
+	return !IsTokenChar(rune)
+}
+
+// consumeToken consumes a token from the beginning of provided
+// string, per RFC 2045 section 5.1 (referenced from 2183), and return
+// the token consumed and the rest of the string.  Returns ("", v) on
+// failure to consume at least one character.
+func consumeToken(v string) (token, rest string) {
+	notPos := strings.IndexFunc(v, isNotTokenChar)
+	if notPos == -1 {
+		return v, ""
+	}
+	if notPos == 0 {
+		return "", v
+	}
+	return v[0:notPos], v[notPos:]
+}
+
+// consumeValue consumes a "value" per RFC 2045, where a value is
+// either a 'token' or a 'quoted-string'.  On success, consumeValue
+// returns the value consumed (and de-quoted/escaped, if a
+// quoted-string) and the rest of the string.  On failure, returns
+// ("", v).
+func consumeValue(v string) (value, rest string) {
+	if !strings.HasPrefix(v, `"`) {
+		return consumeToken(v)
+	}
+
+	// parse a quoted-string
+	rest = v[1:] // consume the leading quote
+	buffer := new(bytes.Buffer)
+	var idx, rune int
+	var nextIsLiteral bool
+	for idx, rune = range rest {
+		switch {
+		case nextIsLiteral:
+			if rune >= 0x80 {
+				return "", v
+			}
+			buffer.WriteRune(rune)
+			nextIsLiteral = false
+		case rune == '"':
+			return buffer.String(), rest[idx+1:]
+		case IsQText(rune):
+			buffer.WriteRune(rune)
+		case rune == '\\':
+			nextIsLiteral = true
+		default:
+			return "", v
+		}
+	}
+	return "", v
+}
+
+func consumeMediaParam(v string) (param, value, rest string) {
+	rest = strings.TrimLeftFunc(v, unicode.IsSpace)
+	if !strings.HasPrefix(rest, ";") {
+		return "", "", v
+	}
+
+	rest = rest[1:] // consume semicolon
+	rest = strings.TrimLeftFunc(rest, unicode.IsSpace)
+	param, rest = consumeToken(rest)
+	if param == "" {
+		return "", "", v
+	}
+	if !strings.HasPrefix(rest, "=") {
+		return "", "", v
+	}
+	rest = rest[1:] // consume equals sign
+	value, rest = consumeValue(rest)
+	if value == "" {
+		return "", "", v
+	}
+	return param, value, rest
+}