Add ASCII-only option, to mimic default RE2 behavior

.travis.yml

@@ -1,15 +1,20 @@
+dist: trusty
 language: go
+go:
+  - '1.11.x'
+  - '1.12.x'
+
 env:
   global:
     - LD_LIBRARY_PATH="/usr/local/lib":${LD_LIBRARY_PATH}
     - GO111MODULE=on
-addons:
-  apt:
-    packages:
-      - libonig-dev
+    - ONIGURUMA_VERSION='6.9.1'
 
-jobs:
-  include:
-    - go: 1.11.x
-      script:
-        - go test -v --cover -race
+before_install: # install oniguruma manually as trusty has only ancient 5.x
+  - sudo apt-get install -y dpkg # dpkg >= 1.17.5ubuntu5.8 fixes https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/1730627
+  - wget "http://archive.ubuntu.com/ubuntu/pool/universe/libo/libonig/libonig5_${ONIGURUMA_VERSION}-1_amd64.deb"
+  - sudo dpkg -i "libonig5_${ONIGURUMA_VERSION}-1_amd64.deb"
+  - wget "http://archive.ubuntu.com/ubuntu/pool/universe/libo/libonig/libonig-dev_${ONIGURUMA_VERSION}-1_amd64.deb"
+  - sudo dpkg -i "libonig-dev_${ONIGURUMA_VERSION}-1_amd64.deb"
+script:
+  - go test -v --cover -race

chelper.c

@@ -17,7 +17,7 @@ int NewOnigRegex( char *pattern, int pattern_length, int option,
     *error_info = (OnigErrorInfo *) malloc(sizeof(OnigErrorInfo));
     memset(*error_info, 0, sizeof(OnigErrorInfo));
 
-    *encoding = (void*)ONIG_ENCODING_UTF8;
+    onig_initialize_encoding(*encoding);
 
     *error_buffer = (char*) malloc(ONIG_MAX_ERROR_MESSAGE_LEN * sizeof(char));
 

regex.go

@@ -47,15 +47,24 @@ type Regexp struct {
 	namedGroupInfo NamedGroupInfo
 }
 
+// NewRegexp creates and initializes a new Regexp with the given pattern and option.
 func NewRegexp(pattern string, option int) (re *Regexp, err error) {
-	re = &Regexp{pattern: pattern}
-	patternCharPtr := C.CString(pattern)
-	defer C.free(unsafe.Pointer(patternCharPtr))
+	return initRegexp(&Regexp{pattern: pattern, encoding: C.ONIG_ENCODING_UTF8}, option)
+}
+
+// NewRegexpASCII is equivalent to NewRegexp, but with the encoding restricted to ASCII.
+func NewRegexpASCII(pattern string, option int) (re *Regexp, err error) {
+	return initRegexp(&Regexp{pattern: pattern, encoding: C.ONIG_ENCODING_ASCII}, option)
+}
 
+func initRegexp(re *Regexp, option int) (*Regexp, error) {
+	var err error
+	patternCharPtr := C.CString(re.pattern)
+	defer C.free(unsafe.Pointer(patternCharPtr))
 	mutex.Lock()
 	defer mutex.Unlock()
-	error_code := C.NewOnigRegex(patternCharPtr, C.int(len(pattern)), C.int(option), &re.regex, &re.region, &re.encoding, &re.errorInfo, &re.errorBuf)
-	if error_code != C.ONIG_NORMAL {
+	errorCode := C.NewOnigRegex(patternCharPtr, C.int(len(re.pattern)), C.int(option), &re.regex, &re.region, &re.encoding, &re.errorInfo, &re.errorBuf)
+	if errorCode != C.ONIG_NORMAL {
 		err = errors.New(C.GoString(re.errorBuf))
 	} else {
 		err = nil
@@ -95,6 +104,15 @@ func MustCompileWithOption(str string, option int) *Regexp {
 	return regexp
 }
 
+// MustCompileASCII is equivalent to MustCompile, but with the encoding restricted to ASCII.
+func MustCompileASCII(str string) *Regexp {
+	regexp, error := NewRegexpASCII(str, ONIG_OPTION_DEFAULT)
+	if error != nil {
+		panic("regexp: compiling " + str + ": " + error.Error())
+	}
+	return regexp
+}
+
 func (re *Regexp) Free() {
 	mutex.Lock()
 	if re.regex != nil {