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