VictoriaMetrics/vendor/github.com/valyala/fasttemplate/template.go
2022-11-10 13:55:47 +02:00

436 lines
13 KiB
Go

// Package fasttemplate implements simple and fast template library.
//
// Fasttemplate is faster than text/template, strings.Replace
// and strings.Replacer.
//
// Fasttemplate ideally fits for fast and simple placeholders' substitutions.
package fasttemplate
import (
"bytes"
"fmt"
"io"
"github.com/valyala/bytebufferpool"
)
// ExecuteFunc calls f on each template tag (placeholder) occurrence.
//
// Returns the number of bytes written to w.
//
// This function is optimized for constantly changing templates.
// Use Template.ExecuteFunc for frozen templates.
func ExecuteFunc(template, startTag, endTag string, w io.Writer, f TagFunc) (int64, error) {
s := unsafeString2Bytes(template)
a := unsafeString2Bytes(startTag)
b := unsafeString2Bytes(endTag)
var nn int64
var ni int
var err error
for {
n := bytes.Index(s, a)
if n < 0 {
break
}
ni, err = w.Write(s[:n])
nn += int64(ni)
if err != nil {
return nn, err
}
s = s[n+len(a):]
n = bytes.Index(s, b)
if n < 0 {
// cannot find end tag - just write it to the output.
ni, _ = w.Write(a)
nn += int64(ni)
break
}
ni, err = f(w, unsafeBytes2String(s[:n]))
nn += int64(ni)
if err != nil {
return nn, err
}
s = s[n+len(b):]
}
ni, err = w.Write(s)
nn += int64(ni)
return nn, err
}
// Execute substitutes template tags (placeholders) with the corresponding
// values from the map m and writes the result to the given writer w.
//
// Substitution map m may contain values with the following types:
// * []byte - the fastest value type
// * string - convenient value type
// * TagFunc - flexible value type
//
// Returns the number of bytes written to w.
//
// This function is optimized for constantly changing templates.
// Use Template.Execute for frozen templates.
func Execute(template, startTag, endTag string, w io.Writer, m map[string]interface{}) (int64, error) {
return ExecuteFunc(template, startTag, endTag, w, func(w io.Writer, tag string) (int, error) { return stdTagFunc(w, tag, m) })
}
// ExecuteStd works the same way as Execute, but keeps the unknown placeholders.
// This can be used as a drop-in replacement for strings.Replacer
//
// Substitution map m may contain values with the following types:
// * []byte - the fastest value type
// * string - convenient value type
// * TagFunc - flexible value type
//
// Returns the number of bytes written to w.
//
// This function is optimized for constantly changing templates.
// Use Template.ExecuteStd for frozen templates.
func ExecuteStd(template, startTag, endTag string, w io.Writer, m map[string]interface{}) (int64, error) {
return ExecuteFunc(template, startTag, endTag, w, func(w io.Writer, tag string) (int, error) { return keepUnknownTagFunc(w, startTag, endTag, tag, m) })
}
// ExecuteFuncString calls f on each template tag (placeholder) occurrence
// and substitutes it with the data written to TagFunc's w.
//
// Returns the resulting string.
//
// This function is optimized for constantly changing templates.
// Use Template.ExecuteFuncString for frozen templates.
func ExecuteFuncString(template, startTag, endTag string, f TagFunc) string {
s, err := ExecuteFuncStringWithErr(template, startTag, endTag, f)
if err != nil {
panic(fmt.Sprintf("unexpected error: %s", err))
}
return s
}
// ExecuteFuncStringWithErr is nearly the same as ExecuteFuncString
// but when f returns an error, ExecuteFuncStringWithErr won't panic like ExecuteFuncString
// it just returns an empty string and the error f returned
func ExecuteFuncStringWithErr(template, startTag, endTag string, f TagFunc) (string, error) {
if n := bytes.Index(unsafeString2Bytes(template), unsafeString2Bytes(startTag)); n < 0 {
return template, nil
}
bb := byteBufferPool.Get()
if _, err := ExecuteFunc(template, startTag, endTag, bb, f); err != nil {
bb.Reset()
byteBufferPool.Put(bb)
return "", err
}
s := string(bb.B)
bb.Reset()
byteBufferPool.Put(bb)
return s, nil
}
var byteBufferPool bytebufferpool.Pool
// ExecuteString substitutes template tags (placeholders) with the corresponding
// values from the map m and returns the result.
//
// Substitution map m may contain values with the following types:
// * []byte - the fastest value type
// * string - convenient value type
// * TagFunc - flexible value type
//
// This function is optimized for constantly changing templates.
// Use Template.ExecuteString for frozen templates.
func ExecuteString(template, startTag, endTag string, m map[string]interface{}) string {
return ExecuteFuncString(template, startTag, endTag, func(w io.Writer, tag string) (int, error) { return stdTagFunc(w, tag, m) })
}
// ExecuteStringStd works the same way as ExecuteString, but keeps the unknown placeholders.
// This can be used as a drop-in replacement for strings.Replacer
//
// Substitution map m may contain values with the following types:
// * []byte - the fastest value type
// * string - convenient value type
// * TagFunc - flexible value type
//
// This function is optimized for constantly changing templates.
// Use Template.ExecuteStringStd for frozen templates.
func ExecuteStringStd(template, startTag, endTag string, m map[string]interface{}) string {
return ExecuteFuncString(template, startTag, endTag, func(w io.Writer, tag string) (int, error) { return keepUnknownTagFunc(w, startTag, endTag, tag, m) })
}
// Template implements simple template engine, which can be used for fast
// tags' (aka placeholders) substitution.
type Template struct {
template string
startTag string
endTag string
texts [][]byte
tags []string
byteBufferPool bytebufferpool.Pool
}
// New parses the given template using the given startTag and endTag
// as tag start and tag end.
//
// The returned template can be executed by concurrently running goroutines
// using Execute* methods.
//
// New panics if the given template cannot be parsed. Use NewTemplate instead
// if template may contain errors.
func New(template, startTag, endTag string) *Template {
t, err := NewTemplate(template, startTag, endTag)
if err != nil {
panic(err)
}
return t
}
// NewTemplate parses the given template using the given startTag and endTag
// as tag start and tag end.
//
// The returned template can be executed by concurrently running goroutines
// using Execute* methods.
func NewTemplate(template, startTag, endTag string) (*Template, error) {
var t Template
err := t.Reset(template, startTag, endTag)
if err != nil {
return nil, err
}
return &t, nil
}
// TagFunc can be used as a substitution value in the map passed to Execute*.
// Execute* functions pass tag (placeholder) name in 'tag' argument.
//
// TagFunc must be safe to call from concurrently running goroutines.
//
// TagFunc must write contents to w and return the number of bytes written.
type TagFunc func(w io.Writer, tag string) (int, error)
// Reset resets the template t to new one defined by
// template, startTag and endTag.
//
// Reset allows Template object re-use.
//
// Reset may be called only if no other goroutines call t methods at the moment.
func (t *Template) Reset(template, startTag, endTag string) error {
// Keep these vars in t, so GC won't collect them and won't break
// vars derived via unsafe*
t.template = template
t.startTag = startTag
t.endTag = endTag
t.texts = t.texts[:0]
t.tags = t.tags[:0]
if len(startTag) == 0 {
panic("startTag cannot be empty")
}
if len(endTag) == 0 {
panic("endTag cannot be empty")
}
s := unsafeString2Bytes(template)
a := unsafeString2Bytes(startTag)
b := unsafeString2Bytes(endTag)
tagsCount := bytes.Count(s, a)
if tagsCount == 0 {
return nil
}
if tagsCount+1 > cap(t.texts) {
t.texts = make([][]byte, 0, tagsCount+1)
}
if tagsCount > cap(t.tags) {
t.tags = make([]string, 0, tagsCount)
}
for {
n := bytes.Index(s, a)
if n < 0 {
t.texts = append(t.texts, s)
break
}
t.texts = append(t.texts, s[:n])
s = s[n+len(a):]
n = bytes.Index(s, b)
if n < 0 {
return fmt.Errorf("Cannot find end tag=%q in the template=%q starting from %q", endTag, template, s)
}
t.tags = append(t.tags, unsafeBytes2String(s[:n]))
s = s[n+len(b):]
}
return nil
}
// ExecuteFunc calls f on each template tag (placeholder) occurrence.
//
// Returns the number of bytes written to w.
//
// This function is optimized for frozen templates.
// Use ExecuteFunc for constantly changing templates.
func (t *Template) ExecuteFunc(w io.Writer, f TagFunc) (int64, error) {
var nn int64
n := len(t.texts) - 1
if n == -1 {
ni, err := w.Write(unsafeString2Bytes(t.template))
return int64(ni), err
}
for i := 0; i < n; i++ {
ni, err := w.Write(t.texts[i])
nn += int64(ni)
if err != nil {
return nn, err
}
ni, err = f(w, t.tags[i])
nn += int64(ni)
if err != nil {
return nn, err
}
}
ni, err := w.Write(t.texts[n])
nn += int64(ni)
return nn, err
}
// Execute substitutes template tags (placeholders) with the corresponding
// values from the map m and writes the result to the given writer w.
//
// Substitution map m may contain values with the following types:
// * []byte - the fastest value type
// * string - convenient value type
// * TagFunc - flexible value type
//
// Returns the number of bytes written to w.
func (t *Template) Execute(w io.Writer, m map[string]interface{}) (int64, error) {
return t.ExecuteFunc(w, func(w io.Writer, tag string) (int, error) { return stdTagFunc(w, tag, m) })
}
// ExecuteStd works the same way as Execute, but keeps the unknown placeholders.
// This can be used as a drop-in replacement for strings.Replacer
//
// Substitution map m may contain values with the following types:
// * []byte - the fastest value type
// * string - convenient value type
// * TagFunc - flexible value type
//
// Returns the number of bytes written to w.
func (t *Template) ExecuteStd(w io.Writer, m map[string]interface{}) (int64, error) {
return t.ExecuteFunc(w, func(w io.Writer, tag string) (int, error) { return keepUnknownTagFunc(w, t.startTag, t.endTag, tag, m) })
}
// ExecuteFuncString calls f on each template tag (placeholder) occurrence
// and substitutes it with the data written to TagFunc's w.
//
// Returns the resulting string.
//
// This function is optimized for frozen templates.
// Use ExecuteFuncString for constantly changing templates.
func (t *Template) ExecuteFuncString(f TagFunc) string {
s, err := t.ExecuteFuncStringWithErr(f)
if err != nil {
panic(fmt.Sprintf("unexpected error: %s", err))
}
return s
}
// ExecuteFuncStringWithErr calls f on each template tag (placeholder) occurrence
// and substitutes it with the data written to TagFunc's w.
//
// Returns the resulting string.
//
// This function is optimized for frozen templates.
// Use ExecuteFuncString for constantly changing templates.
func (t *Template) ExecuteFuncStringWithErr(f TagFunc) (string, error) {
bb := t.byteBufferPool.Get()
if _, err := t.ExecuteFunc(bb, f); err != nil {
bb.Reset()
t.byteBufferPool.Put(bb)
return "", err
}
s := string(bb.Bytes())
bb.Reset()
t.byteBufferPool.Put(bb)
return s, nil
}
// ExecuteString substitutes template tags (placeholders) with the corresponding
// values from the map m and returns the result.
//
// Substitution map m may contain values with the following types:
// * []byte - the fastest value type
// * string - convenient value type
// * TagFunc - flexible value type
//
// This function is optimized for frozen templates.
// Use ExecuteString for constantly changing templates.
func (t *Template) ExecuteString(m map[string]interface{}) string {
return t.ExecuteFuncString(func(w io.Writer, tag string) (int, error) { return stdTagFunc(w, tag, m) })
}
// ExecuteStringStd works the same way as ExecuteString, but keeps the unknown placeholders.
// This can be used as a drop-in replacement for strings.Replacer
//
// Substitution map m may contain values with the following types:
// * []byte - the fastest value type
// * string - convenient value type
// * TagFunc - flexible value type
//
// This function is optimized for frozen templates.
// Use ExecuteStringStd for constantly changing templates.
func (t *Template) ExecuteStringStd(m map[string]interface{}) string {
return t.ExecuteFuncString(func(w io.Writer, tag string) (int, error) { return keepUnknownTagFunc(w, t.startTag, t.endTag, tag, m) })
}
func stdTagFunc(w io.Writer, tag string, m map[string]interface{}) (int, error) {
v := m[tag]
if v == nil {
return 0, nil
}
switch value := v.(type) {
case []byte:
return w.Write(value)
case string:
return w.Write([]byte(value))
case TagFunc:
return value(w, tag)
default:
panic(fmt.Sprintf("tag=%q contains unexpected value type=%#v. Expected []byte, string or TagFunc", tag, v))
}
}
func keepUnknownTagFunc(w io.Writer, startTag, endTag, tag string, m map[string]interface{}) (int, error) {
v, ok := m[tag]
if !ok {
if _, err := w.Write(unsafeString2Bytes(startTag)); err != nil {
return 0, err
}
if _, err := w.Write(unsafeString2Bytes(tag)); err != nil {
return 0, err
}
if _, err := w.Write(unsafeString2Bytes(endTag)); err != nil {
return 0, err
}
return len(startTag) + len(tag) + len(endTag), nil
}
if v == nil {
return 0, nil
}
switch value := v.(type) {
case []byte:
return w.Write(value)
case string:
return w.Write([]byte(value))
case TagFunc:
return value(w, tag)
default:
panic(fmt.Sprintf("tag=%q contains unexpected value type=%#v. Expected []byte, string or TagFunc", tag, v))
}
}