x/stringutil

stringutil/build.go

@@ -0,0 +1,48 @@
+/*
+ Copyright 2024 Qiniu Limited (qiniu.com)
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package stringutil
+
+// -----------------------------------------------------------------------------
+
+// Builder concatenates parts of a string together.
+type Builder struct {
+	b []byte
+}
+
+// NewBuilder creates a new Builder object.
+func NewBuilder(ncap int) *Builder {
+	return &Builder{b: make([]byte, 0, ncap)}
+}
+
+// Add appends a string part.
+func (p *Builder) Add(s string) *Builder {
+	p.b = append(p.b, s...)
+	return p
+}
+
+// AddByte appends a bytes string part.
+func (p *Builder) AddByte(s ...byte) *Builder {
+	p.b = append(p.b, s...)
+	return p
+}
+
+// Build concatenates parts of a string together and returns it.
+func (p *Builder) Build() string {
+	return String(p.b)
+}
+
+// -----------------------------------------------------------------------------

stringutil/concat.go

@@ -0,0 +1,30 @@
+/*
+ Copyright 2024 Qiniu Limited (qiniu.com)
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package stringutil
+
+// Concat concatenates parts of a string together.
+func Concat(parts ...string) string {
+	n := 0
+	for _, part := range parts {
+		n += len(part)
+	}
+	b := make([]byte, 0, n)
+	for _, part := range parts {
+		b = append(b, part...)
+	}
+	return String(b)
+}

stringutil/diff.go

@@ -0,0 +1,40 @@
+/*
+Copyright 2024 Qiniu Limited (qiniu.com)
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package stringutil
+
+// Diff calculates difference of two sorted string (in ASC order).
+func Diff(new, old []string) (add, del []string) {
+	i, j := 0, 0
+	for i != len(new) && j != len(old) {
+		if new[i] < old[j] {
+			add = append(add, new[i])
+			i++
+		} else if old[j] < new[i] {
+			del = append(del, old[j])
+			j++
+		} else {
+			i++
+			j++
+		}
+	}
+	if i < len(new) {
+		add = append(add, new[i:]...)
+	} else {
+		del = append(del, old[j:]...)
+	}
+	return
+}

stringutil/string_go121.go

@@ -0,0 +1,34 @@
+//go:build go1.21
+// +build go1.21
+
+/*
+ Copyright 2024 Qiniu Limited (qiniu.com)
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package stringutil
+
+import (
+	"unsafe"
+)
+
+// String returns a string value whose underlying bytes is b.
+//
+// Since Go strings are immutable, the bytes passed to String
+// must not be modified afterwards.
+func String(b []byte) string {
+	// Although unsafe.SliceData/String was introduced in go1.20, but
+	// the go version in go.mod is 1.18 so we cannot use them.
+	return unsafe.String(unsafe.SliceData(b), len(b))
+}

stringutil/string_mock.go

@@ -0,0 +1,24 @@
+//go:build !go1.21
+// +build !go1.21
+
+/*
+ Copyright 2024 Qiniu Limited (qiniu.com)
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package stringutil
+
+func String(b []byte) string {
+	return string(b)
+}

stringutil/string_test.go

@@ -0,0 +1,62 @@
+/*
+ Copyright 2024 Qiniu Limited (qiniu.com)
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package stringutil
+
+import (
+	"reflect"
+	"sort"
+	"testing"
+)
+
+func TestConcat(t *testing.T) {
+	if ret := Concat("1", "23", "!"); ret != "123!" {
+		t.Fatal("Concat:", ret)
+	}
+}
+
+func TestBuild(t *testing.T) {
+	if ret := NewBuilder(0).Build(); ret != "" {
+		t.Fatal("NewBuilder(0):", ret)
+	}
+	if ret := NewBuilder(16).Add("1").AddByte('2', '3').AddByte('!').Build(); ret != "123!" {
+		t.Fatal("TestBuild:", ret)
+	}
+}
+
+func TestDiff(t *testing.T) {
+	type testCase struct {
+		new, old []string
+		add, del []string
+	}
+	cases := []testCase{
+		{[]string{"1", "3", "2", "4"}, []string{"2"}, []string{"1", "3", "4"}, nil},
+		{[]string{"1", "3", "2", "4"}, []string{"5", "2"}, []string{"1", "3", "4"}, []string{"5"}},
+		{[]string{"1", "3", "2", "4"}, []string{"0", "5", "2"}, []string{"1", "3", "4"}, []string{"0", "5"}},
+	}
+	for _, c := range cases {
+		add, del := uDiff(c.new, c.old)
+		if !reflect.DeepEqual(add, c.add) || !reflect.DeepEqual(del, c.del) {
+			t.Fatal("diff:", c, "=>", add, del)
+		}
+	}
+}
+
+func uDiff(new, old []string) (add, del []string) {
+	sort.Strings(new)
+	sort.Strings(old)
+	return Diff(new, old)
+}