--- /dev/null
+// 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"
+ "github.com/valyala/bytebufferpool"
+ "io"
+)
+
+// 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)
+ 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) })
+}
+
+// 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 {
+ tagsCount := bytes.Count(unsafeString2Bytes(template), unsafeString2Bytes(startTag))
+ if tagsCount == 0 {
+ return template
+ }
+
+ bb := byteBufferPool.Get()
+ if _, err := ExecuteFunc(template, startTag, endTag, bb, f); err != nil {
+ panic(fmt.Sprintf("unexpected error: %s", err))
+ }
+ s := string(bb.B)
+ bb.Reset()
+ byteBufferPool.Put(bb)
+ return s
+}
+
+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) })
+}
+
+// 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) })
+}
+
+// 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 {
+ bb := t.byteBufferPool.Get()
+ if _, err := t.ExecuteFunc(bb, f); err != nil {
+ panic(fmt.Sprintf("unexpected error: %s", err))
+ }
+ s := string(bb.Bytes())
+ bb.Reset()
+ t.byteBufferPool.Put(bb)
+ return s
+}
+
+// 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) })
+}
+
+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))
+ }
+}
Code Review / barometer.git / blobdiff