mirror of
https://github.com/golang/go
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96da3e96c3
Fixes #309. R=rsc CC=golang-dev https://golang.org/cl/181044
962 lines
24 KiB
Go
962 lines
24 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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Data-driven templates for generating textual output such as
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HTML. See
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http://code.google.com/p/json-template/wiki/Reference
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for full documentation of the template language. A summary:
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Templates are executed by applying them to a data structure.
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Annotations in the template refer to elements of the data
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structure (typically a field of a struct or a key in a map)
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to control execution and derive values to be displayed.
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The template walks the structure as it executes and the
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"cursor" @ represents the value at the current location
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in the structure.
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Data items may be values or pointers; the interface hides the
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indirection.
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In the following, 'field' is one of several things, according to the data.
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- the name of a field of a struct (result = data.field)
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- the value stored in a map under that key (result = data[field])
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- the result of invoking a niladic single-valued method with that name
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(result = data.field())
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Major constructs ({} are metacharacters; [] marks optional elements):
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{# comment }
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A one-line comment.
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{.section field} XXX [ {.or} YYY ] {.end}
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Set @ to the value of the field. It may be an explicit @
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to stay at the same point in the data. If the field is nil
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or empty, execute YYY; otherwise execute XXX.
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{.repeated section field} XXX [ {.alternates with} ZZZ ] [ {.or} YYY ] {.end}
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Like .section, but field must be an array or slice. XXX
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is executed for each element. If the array is nil or empty,
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YYY is executed instead. If the {.alternates with} marker
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is present, ZZZ is executed between iterations of XXX.
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{field}
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{field|formatter}
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Insert the value of the field into the output. Field is
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first looked for in the cursor, as in .section and .repeated.
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If it is not found, the search continues in outer sections
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until the top level is reached.
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If a formatter is specified, it must be named in the formatter
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map passed to the template set up routines or in the default
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set ("html","str","") and is used to process the data for
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output. The formatter function has signature
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func(wr io.Write, data interface{}, formatter string)
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where wr is the destination for output, data is the field
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value, and formatter is its name at the invocation site.
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*/
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package template
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import (
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"container/vector"
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"fmt"
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"io"
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"os"
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"reflect"
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"runtime"
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"strings"
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)
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// Errors returned during parsing and execution. Users may extract the information and reformat
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// if they desire.
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type Error struct {
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Line int
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Msg string
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}
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func (e *Error) String() string { return fmt.Sprintf("line %d: %s", e.Line, e.Msg) }
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// Most of the literals are aces.
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var lbrace = []byte{'{'}
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var rbrace = []byte{'}'}
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var space = []byte{' '}
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var tab = []byte{'\t'}
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// The various types of "tokens", which are plain text or (usually) brace-delimited descriptors
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const (
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tokAlternates = iota
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tokComment
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tokEnd
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tokLiteral
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tokOr
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tokRepeated
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tokSection
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tokText
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tokVariable
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)
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// FormatterMap is the type describing the mapping from formatter
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// names to the functions that implement them.
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type FormatterMap map[string]func(io.Writer, interface{}, string)
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// Built-in formatters.
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var builtins = FormatterMap{
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"html": HTMLFormatter,
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"str": StringFormatter,
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"": StringFormatter,
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}
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// The parsed state of a template is a vector of xxxElement structs.
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// Sections have line numbers so errors can be reported better during execution.
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// Plain text.
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type textElement struct {
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text []byte
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}
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// A literal such as .meta-left or .meta-right
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type literalElement struct {
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text []byte
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}
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// A variable to be evaluated
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type variableElement struct {
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linenum int
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name string
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formatter string // TODO(r): implement pipelines
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}
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// A .section block, possibly with a .or
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type sectionElement struct {
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linenum int // of .section itself
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field string // cursor field for this block
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start int // first element
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or int // first element of .or block
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end int // one beyond last element
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}
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// A .repeated block, possibly with a .or and a .alternates
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type repeatedElement struct {
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sectionElement // It has the same structure...
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altstart int // ... except for alternates
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altend int
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}
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// Template is the type that represents a template definition.
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// It is unchanged after parsing.
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type Template struct {
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fmap FormatterMap // formatters for variables
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// Used during parsing:
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ldelim, rdelim []byte // delimiters; default {}
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buf []byte // input text to process
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p int // position in buf
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linenum int // position in input
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error os.Error // error during parsing (only)
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// Parsed results:
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elems *vector.Vector
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}
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// Internal state for executing a Template. As we evaluate the struct,
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// the data item descends into the fields associated with sections, etc.
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// Parent is used to walk upwards to find variables higher in the tree.
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type state struct {
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parent *state // parent in hierarchy
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data reflect.Value // the driver data for this section etc.
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wr io.Writer // where to send output
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errors chan os.Error // for reporting errors during execute
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}
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func (parent *state) clone(data reflect.Value) *state {
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return &state{parent, data, parent.wr, parent.errors}
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}
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// New creates a new template with the specified formatter map (which
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// may be nil) to define auxiliary functions for formatting variables.
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func New(fmap FormatterMap) *Template {
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t := new(Template)
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t.fmap = fmap
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t.ldelim = lbrace
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t.rdelim = rbrace
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t.elems = new(vector.Vector)
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return t
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}
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// Report error and stop executing. The line number must be provided explicitly.
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func (t *Template) execError(st *state, line int, err string, args ...) {
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st.errors <- &Error{line, fmt.Sprintf(err, args)}
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runtime.Goexit()
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}
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// Report error, save in Template to terminate parsing.
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// The line number comes from the template state.
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func (t *Template) parseError(err string, args ...) {
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t.error = &Error{t.linenum, fmt.Sprintf(err, args)}
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}
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// -- Lexical analysis
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// Is c a white space character?
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func white(c uint8) bool { return c == ' ' || c == '\t' || c == '\r' || c == '\n' }
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// Safely, does s[n:n+len(t)] == t?
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func equal(s []byte, n int, t []byte) bool {
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b := s[n:]
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if len(t) > len(b) { // not enough space left for a match.
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return false
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}
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for i, c := range t {
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if c != b[i] {
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return false
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}
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}
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return true
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}
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// nextItem returns the next item from the input buffer. If the returned
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// item is empty, we are at EOF. The item will be either a
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// delimited string or a non-empty string between delimited
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// strings. Tokens stop at (but include, if plain text) a newline.
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// Action tokens on a line by themselves drop the white space on
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// either side, up to and including the newline.
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func (t *Template) nextItem() []byte {
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sawLeft := false // are we waiting for an opening delimiter?
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special := false // is this a {.foo} directive, which means trim white space?
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// Delete surrounding white space if this {.foo} is the only thing on the line.
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trim_white := t.p == 0 || t.buf[t.p-1] == '\n'
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only_white := true // we have seen only white space so far
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var i int
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start := t.p
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Loop:
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for i = t.p; i < len(t.buf); i++ {
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switch {
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case t.buf[i] == '\n':
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t.linenum++
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i++
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break Loop
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case white(t.buf[i]):
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// white space, do nothing
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case !sawLeft && equal(t.buf, i, t.ldelim): // sawLeft checked because delims may be equal
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// anything interesting already on the line?
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if !only_white {
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break Loop
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}
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// is it a directive or comment?
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j := i + len(t.ldelim) // position after delimiter
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if j+1 < len(t.buf) && (t.buf[j] == '.' || t.buf[j] == '#') {
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special = true
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if trim_white && only_white {
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start = i
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}
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} else if i > t.p { // have some text accumulated so stop before delimiter
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break Loop
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}
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sawLeft = true
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i = j - 1
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case equal(t.buf, i, t.rdelim):
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if !sawLeft {
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t.parseError("unmatched closing delimiter")
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return nil
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}
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sawLeft = false
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i += len(t.rdelim)
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break Loop
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default:
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only_white = false
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}
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}
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if sawLeft {
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t.parseError("unmatched opening delimiter")
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return nil
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}
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item := t.buf[start:i]
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if special && trim_white {
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// consume trailing white space
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for ; i < len(t.buf) && white(t.buf[i]); i++ {
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if t.buf[i] == '\n' {
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t.linenum++
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i++
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break // stop after newline
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}
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}
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}
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t.p = i
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return item
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}
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// Turn a byte array into a white-space-split array of strings.
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func words(buf []byte) []string {
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s := make([]string, 0, 5)
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p := 0 // position in buf
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// one word per loop
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for i := 0; ; i++ {
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// skip white space
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for ; p < len(buf) && white(buf[p]); p++ {
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}
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// grab word
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start := p
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for ; p < len(buf) && !white(buf[p]); p++ {
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}
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if start == p { // no text left
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break
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}
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if i == cap(s) {
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ns := make([]string, 2*cap(s))
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for j := range s {
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ns[j] = s[j]
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}
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s = ns
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}
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s = s[0 : i+1]
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s[i] = string(buf[start:p])
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}
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return s
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}
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// Analyze an item and return its token type and, if it's an action item, an array of
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// its constituent words.
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func (t *Template) analyze(item []byte) (tok int, w []string) {
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// item is known to be non-empty
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if !equal(item, 0, t.ldelim) { // doesn't start with left delimiter
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tok = tokText
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return
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}
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if !equal(item, len(item)-len(t.rdelim), t.rdelim) { // doesn't end with right delimiter
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t.parseError("internal error: unmatched opening delimiter") // lexing should prevent this
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return
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}
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if len(item) <= len(t.ldelim)+len(t.rdelim) { // no contents
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t.parseError("empty directive")
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return
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}
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// Comment
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if item[len(t.ldelim)] == '#' {
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tok = tokComment
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return
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}
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// Split into words
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w = words(item[len(t.ldelim) : len(item)-len(t.rdelim)]) // drop final delimiter
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if len(w) == 0 {
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t.parseError("empty directive")
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return
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}
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if len(w) == 1 && w[0][0] != '.' {
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tok = tokVariable
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return
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}
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switch w[0] {
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case ".meta-left", ".meta-right", ".space", ".tab":
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tok = tokLiteral
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return
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case ".or":
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tok = tokOr
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return
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case ".end":
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tok = tokEnd
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return
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case ".section":
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if len(w) != 2 {
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t.parseError("incorrect fields for .section: %s", item)
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return
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}
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tok = tokSection
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return
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case ".repeated":
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if len(w) != 3 || w[1] != "section" {
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t.parseError("incorrect fields for .repeated: %s", item)
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return
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}
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tok = tokRepeated
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return
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case ".alternates":
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if len(w) != 2 || w[1] != "with" {
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t.parseError("incorrect fields for .alternates: %s", item)
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return
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}
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tok = tokAlternates
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return
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}
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t.parseError("bad directive: %s", item)
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return
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}
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// -- Parsing
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// Allocate a new variable-evaluation element.
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func (t *Template) newVariable(name_formatter string) (v *variableElement) {
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name := name_formatter
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formatter := ""
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bar := strings.Index(name_formatter, "|")
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if bar >= 0 {
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name = name_formatter[0:bar]
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formatter = name_formatter[bar+1:]
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}
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// Probably ok, so let's build it.
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v = &variableElement{t.linenum, name, formatter}
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// We could remember the function address here and avoid the lookup later,
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// but it's more dynamic to let the user change the map contents underfoot.
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// We do require the name to be present, though.
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// Is it in user-supplied map?
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if t.fmap != nil {
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if _, ok := t.fmap[formatter]; ok {
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return
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}
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}
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// Is it in builtin map?
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if _, ok := builtins[formatter]; ok {
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return
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}
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t.parseError("unknown formatter: %s", formatter)
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return
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}
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// Grab the next item. If it's simple, just append it to the template.
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// Otherwise return its details.
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func (t *Template) parseSimple(item []byte) (done bool, tok int, w []string) {
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tok, w = t.analyze(item)
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if t.error != nil {
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return
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}
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done = true // assume for simplicity
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switch tok {
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case tokComment:
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return
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case tokText:
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t.elems.Push(&textElement{item})
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return
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case tokLiteral:
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switch w[0] {
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case ".meta-left":
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t.elems.Push(&literalElement{t.ldelim})
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case ".meta-right":
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t.elems.Push(&literalElement{t.rdelim})
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case ".space":
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t.elems.Push(&literalElement{space})
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case ".tab":
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t.elems.Push(&literalElement{tab})
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default:
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t.parseError("internal error: unknown literal: %s", w[0])
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return
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}
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return
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case tokVariable:
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t.elems.Push(t.newVariable(w[0]))
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return
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}
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return false, tok, w
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}
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// parseRepeated and parseSection are mutually recursive
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func (t *Template) parseRepeated(words []string) *repeatedElement {
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r := new(repeatedElement)
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t.elems.Push(r)
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r.linenum = t.linenum
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r.field = words[2]
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// Scan section, collecting true and false (.or) blocks.
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r.start = t.elems.Len()
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r.or = -1
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r.altstart = -1
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r.altend = -1
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Loop:
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for t.error == nil {
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item := t.nextItem()
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if t.error != nil {
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break
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}
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if len(item) == 0 {
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t.parseError("missing .end for .repeated section")
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break
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}
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done, tok, w := t.parseSimple(item)
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if t.error != nil {
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break
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}
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if done {
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continue
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}
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switch tok {
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case tokEnd:
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break Loop
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case tokOr:
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if r.or >= 0 {
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t.parseError("extra .or in .repeated section")
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break Loop
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}
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r.altend = t.elems.Len()
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r.or = t.elems.Len()
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case tokSection:
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t.parseSection(w)
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case tokRepeated:
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t.parseRepeated(w)
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case tokAlternates:
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if r.altstart >= 0 {
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t.parseError("extra .alternates in .repeated section")
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break Loop
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}
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if r.or >= 0 {
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t.parseError(".alternates inside .or block in .repeated section")
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break Loop
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}
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r.altstart = t.elems.Len()
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default:
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t.parseError("internal error: unknown repeated section item: %s", item)
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break Loop
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}
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}
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if t.error != nil {
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return nil
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}
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if r.altend < 0 {
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r.altend = t.elems.Len()
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}
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r.end = t.elems.Len()
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return r
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}
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func (t *Template) parseSection(words []string) *sectionElement {
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s := new(sectionElement)
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t.elems.Push(s)
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s.linenum = t.linenum
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s.field = words[1]
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// Scan section, collecting true and false (.or) blocks.
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s.start = t.elems.Len()
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s.or = -1
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Loop:
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for t.error == nil {
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item := t.nextItem()
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if t.error != nil {
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break
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}
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if len(item) == 0 {
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t.parseError("missing .end for .section")
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break
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}
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done, tok, w := t.parseSimple(item)
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if t.error != nil {
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break
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}
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if done {
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continue
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}
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switch tok {
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case tokEnd:
|
|
break Loop
|
|
case tokOr:
|
|
if s.or >= 0 {
|
|
t.parseError("extra .or in .section")
|
|
break Loop
|
|
}
|
|
s.or = t.elems.Len()
|
|
case tokSection:
|
|
t.parseSection(w)
|
|
case tokRepeated:
|
|
t.parseRepeated(w)
|
|
case tokAlternates:
|
|
t.parseError(".alternates not in .repeated")
|
|
default:
|
|
t.parseError("internal error: unknown section item: %s", item)
|
|
}
|
|
}
|
|
if t.error != nil {
|
|
return nil
|
|
}
|
|
s.end = t.elems.Len()
|
|
return s
|
|
}
|
|
|
|
func (t *Template) parse() {
|
|
for t.error == nil {
|
|
item := t.nextItem()
|
|
if t.error != nil {
|
|
break
|
|
}
|
|
if len(item) == 0 {
|
|
break
|
|
}
|
|
done, tok, w := t.parseSimple(item)
|
|
if done {
|
|
continue
|
|
}
|
|
switch tok {
|
|
case tokOr, tokEnd, tokAlternates:
|
|
t.parseError("unexpected %s", w[0])
|
|
case tokSection:
|
|
t.parseSection(w)
|
|
case tokRepeated:
|
|
t.parseRepeated(w)
|
|
default:
|
|
t.parseError("internal error: bad directive in parse: %s", item)
|
|
}
|
|
}
|
|
}
|
|
|
|
// -- Execution
|
|
|
|
// If the data for this template is a struct, find the named variable.
|
|
// Names of the form a.b.c are walked down the data tree.
|
|
// The special name "@" (the "cursor") denotes the current data.
|
|
// The value coming in (st.data) might need indirecting to reach
|
|
// a struct while the return value is not indirected - that is,
|
|
// it represents the actual named field.
|
|
func (st *state) findVar(s string) reflect.Value {
|
|
if s == "@" {
|
|
return st.data
|
|
}
|
|
data := st.data
|
|
for _, elem := range strings.Split(s, ".", 0) {
|
|
origData := data // for method lookup need value before indirection.
|
|
// Look up field; data must be a struct or map.
|
|
data = reflect.Indirect(data)
|
|
if data == nil {
|
|
return nil
|
|
}
|
|
|
|
switch typ := data.Type().(type) {
|
|
case *reflect.StructType:
|
|
if field, ok := typ.FieldByName(elem); ok {
|
|
data = data.(*reflect.StructValue).FieldByIndex(field.Index)
|
|
continue
|
|
}
|
|
case *reflect.MapType:
|
|
data = data.(*reflect.MapValue).Elem(reflect.NewValue(elem))
|
|
continue
|
|
}
|
|
|
|
// No luck with that name; is it a method?
|
|
if result, found := callMethod(origData, elem); found {
|
|
data = result
|
|
continue
|
|
}
|
|
return nil
|
|
}
|
|
return data
|
|
}
|
|
|
|
// See if name is a method of the value at some level of indirection.
|
|
// The return values are the result of the call (which may be nil if
|
|
// there's trouble) and whether a method of the right name exists with
|
|
// any signature.
|
|
func callMethod(data reflect.Value, name string) (result reflect.Value, found bool) {
|
|
found = false
|
|
// Method set depends on pointerness, and the value may be arbitrarily
|
|
// indirect. Simplest approach is to walk down the pointer chain and
|
|
// see if we can find the method at each step.
|
|
// Most steps will see NumMethod() == 0.
|
|
for {
|
|
typ := data.Type()
|
|
if nMethod := data.Type().NumMethod(); nMethod > 0 {
|
|
for i := 0; i < nMethod; i++ {
|
|
method := typ.Method(i)
|
|
if method.Name == name {
|
|
found = true // we found the name regardless
|
|
// does receiver type match? (pointerness might be off)
|
|
if typ == method.Type.In(0) {
|
|
return call(data, method), found
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if nd, ok := data.(*reflect.PtrValue); ok {
|
|
data = nd.Elem()
|
|
} else {
|
|
break
|
|
}
|
|
}
|
|
return
|
|
}
|
|
|
|
// Invoke the method. If its signature is wrong, return nil.
|
|
func call(v reflect.Value, method reflect.Method) reflect.Value {
|
|
funcType := method.Type
|
|
// Method must take no arguments, meaning as a func it has one argument (the receiver)
|
|
if funcType.NumIn() != 1 {
|
|
return nil
|
|
}
|
|
// Method must return a single value.
|
|
if funcType.NumOut() != 1 {
|
|
return nil
|
|
}
|
|
// Result will be the zeroth element of the returned slice.
|
|
return method.Func.Call([]reflect.Value{v})[0]
|
|
}
|
|
|
|
// Is there no data to look at?
|
|
func empty(v reflect.Value) bool {
|
|
v = reflect.Indirect(v)
|
|
if v == nil {
|
|
return true
|
|
}
|
|
switch v := v.(type) {
|
|
case *reflect.BoolValue:
|
|
return v.Get() == false
|
|
case *reflect.StringValue:
|
|
return v.Get() == ""
|
|
case *reflect.StructValue:
|
|
return false
|
|
case *reflect.ArrayValue:
|
|
return v.Len() == 0
|
|
case *reflect.SliceValue:
|
|
return v.Len() == 0
|
|
}
|
|
return true
|
|
}
|
|
|
|
// Look up a variable or method, up through the parent if necessary.
|
|
func (t *Template) varValue(name string, st *state) reflect.Value {
|
|
field := st.findVar(name)
|
|
if field == nil {
|
|
if st.parent == nil {
|
|
t.execError(st, t.linenum, "name not found: %s", name)
|
|
}
|
|
return t.varValue(name, st.parent)
|
|
}
|
|
return field
|
|
}
|
|
|
|
// Evaluate a variable, looking up through the parent if necessary.
|
|
// If it has a formatter attached ({var|formatter}) run that too.
|
|
func (t *Template) writeVariable(v *variableElement, st *state) {
|
|
formatter := v.formatter
|
|
val := t.varValue(v.name, st).Interface()
|
|
// is it in user-supplied map?
|
|
if t.fmap != nil {
|
|
if fn, ok := t.fmap[formatter]; ok {
|
|
fn(st.wr, val, formatter)
|
|
return
|
|
}
|
|
}
|
|
// is it in builtin map?
|
|
if fn, ok := builtins[formatter]; ok {
|
|
fn(st.wr, val, formatter)
|
|
return
|
|
}
|
|
t.execError(st, v.linenum, "missing formatter %s for variable %s", formatter, v.name)
|
|
}
|
|
|
|
// Execute element i. Return next index to execute.
|
|
func (t *Template) executeElement(i int, st *state) int {
|
|
switch elem := t.elems.At(i).(type) {
|
|
case *textElement:
|
|
st.wr.Write(elem.text)
|
|
return i + 1
|
|
case *literalElement:
|
|
st.wr.Write(elem.text)
|
|
return i + 1
|
|
case *variableElement:
|
|
t.writeVariable(elem, st)
|
|
return i + 1
|
|
case *sectionElement:
|
|
t.executeSection(elem, st)
|
|
return elem.end
|
|
case *repeatedElement:
|
|
t.executeRepeated(elem, st)
|
|
return elem.end
|
|
}
|
|
e := t.elems.At(i)
|
|
t.execError(st, 0, "internal error: bad directive in execute: %v %T\n", reflect.NewValue(e).Interface(), e)
|
|
return 0
|
|
}
|
|
|
|
// Execute the template.
|
|
func (t *Template) execute(start, end int, st *state) {
|
|
for i := start; i < end; {
|
|
i = t.executeElement(i, st)
|
|
}
|
|
}
|
|
|
|
// Execute a .section
|
|
func (t *Template) executeSection(s *sectionElement, st *state) {
|
|
// Find driver data for this section. It must be in the current struct.
|
|
field := t.varValue(s.field, st)
|
|
if field == nil {
|
|
t.execError(st, s.linenum, ".section: cannot find field %s in %s", s.field, reflect.Indirect(st.data).Type())
|
|
}
|
|
st = st.clone(field)
|
|
start, end := s.start, s.or
|
|
if !empty(field) {
|
|
// Execute the normal block.
|
|
if end < 0 {
|
|
end = s.end
|
|
}
|
|
} else {
|
|
// Execute the .or block. If it's missing, do nothing.
|
|
start, end = s.or, s.end
|
|
if start < 0 {
|
|
return
|
|
}
|
|
}
|
|
for i := start; i < end; {
|
|
i = t.executeElement(i, st)
|
|
}
|
|
}
|
|
|
|
// Return the result of calling the Iter method on v, or nil.
|
|
func iter(v reflect.Value) *reflect.ChanValue {
|
|
for j := 0; j < v.Type().NumMethod(); j++ {
|
|
mth := v.Type().Method(j)
|
|
fv := v.Method(j)
|
|
ft := fv.Type().(*reflect.FuncType)
|
|
// TODO(rsc): NumIn() should return 0 here, because ft is from a curried FuncValue.
|
|
if mth.Name != "Iter" || ft.NumIn() != 1 || ft.NumOut() != 1 {
|
|
continue
|
|
}
|
|
ct, ok := ft.Out(0).(*reflect.ChanType)
|
|
if !ok || ct.Dir()&reflect.RecvDir == 0 {
|
|
continue
|
|
}
|
|
return fv.Call(nil)[0].(*reflect.ChanValue)
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// Execute a .repeated section
|
|
func (t *Template) executeRepeated(r *repeatedElement, st *state) {
|
|
// Find driver data for this section. It must be in the current struct.
|
|
field := t.varValue(r.field, st)
|
|
if field == nil {
|
|
t.execError(st, r.linenum, ".repeated: cannot find field %s in %s", r.field, reflect.Indirect(st.data).Type())
|
|
}
|
|
|
|
start, end := r.start, r.or
|
|
if end < 0 {
|
|
end = r.end
|
|
}
|
|
if r.altstart >= 0 {
|
|
end = r.altstart
|
|
}
|
|
first := true
|
|
|
|
// Code common to all the loops.
|
|
loopBody := func(newst *state) {
|
|
// .alternates between elements
|
|
if !first && r.altstart >= 0 {
|
|
for i := r.altstart; i < r.altend; {
|
|
i = t.executeElement(i, newst)
|
|
}
|
|
}
|
|
first = false
|
|
for i := start; i < end; {
|
|
i = t.executeElement(i, newst)
|
|
}
|
|
}
|
|
|
|
if array, ok := field.(reflect.ArrayOrSliceValue); ok {
|
|
for j := 0; j < array.Len(); j++ {
|
|
loopBody(st.clone(array.Elem(j)))
|
|
}
|
|
} else if m, ok := field.(*reflect.MapValue); ok {
|
|
for _, key := range m.Keys() {
|
|
loopBody(st.clone(m.Elem(key)))
|
|
}
|
|
} else if ch := iter(field); ch != nil {
|
|
for {
|
|
e := ch.Recv()
|
|
if ch.Closed() {
|
|
break
|
|
}
|
|
loopBody(st.clone(e))
|
|
}
|
|
} else {
|
|
t.execError(st, r.linenum, ".repeated: cannot repeat %s (type %s)",
|
|
r.field, field.Type())
|
|
}
|
|
|
|
if first {
|
|
// Empty. Execute the .or block, once. If it's missing, do nothing.
|
|
start, end := r.or, r.end
|
|
if start >= 0 {
|
|
newst := st.clone(field)
|
|
for i := start; i < end; {
|
|
i = t.executeElement(i, newst)
|
|
}
|
|
}
|
|
return
|
|
}
|
|
}
|
|
|
|
// A valid delimiter must contain no white space and be non-empty.
|
|
func validDelim(d []byte) bool {
|
|
if len(d) == 0 {
|
|
return false
|
|
}
|
|
for _, c := range d {
|
|
if white(c) {
|
|
return false
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
// -- Public interface
|
|
|
|
// Parse initializes a Template by parsing its definition. The string
|
|
// s contains the template text. If any errors occur, Parse returns
|
|
// the error.
|
|
func (t *Template) Parse(s string) os.Error {
|
|
if t.elems == nil {
|
|
return &Error{1, "template not allocated with New"}
|
|
}
|
|
if !validDelim(t.ldelim) || !validDelim(t.rdelim) {
|
|
return &Error{1, fmt.Sprintf("bad delimiter strings %q %q", t.ldelim, t.rdelim)}
|
|
}
|
|
t.buf = strings.Bytes(s)
|
|
t.p = 0
|
|
t.linenum = 1
|
|
t.parse()
|
|
return t.error
|
|
}
|
|
|
|
// Execute applies a parsed template to the specified data object,
|
|
// generating output to wr.
|
|
func (t *Template) Execute(data interface{}, wr io.Writer) os.Error {
|
|
// Extract the driver data.
|
|
val := reflect.NewValue(data)
|
|
errors := make(chan os.Error)
|
|
go func() {
|
|
t.p = 0
|
|
t.execute(0, t.elems.Len(), &state{nil, val, wr, errors})
|
|
errors <- nil // clean return;
|
|
}()
|
|
return <-errors
|
|
}
|
|
|
|
// SetDelims sets the left and right delimiters for operations in the
|
|
// template. They are validated during parsing. They could be
|
|
// validated here but it's better to keep the routine simple. The
|
|
// delimiters are very rarely invalid and Parse has the necessary
|
|
// error-handling interface already.
|
|
func (t *Template) SetDelims(left, right string) {
|
|
t.ldelim = strings.Bytes(left)
|
|
t.rdelim = strings.Bytes(right)
|
|
}
|
|
|
|
// Parse creates a Template with default parameters (such as {} for
|
|
// metacharacters). The string s contains the template text while
|
|
// the formatter map fmap, which may be nil, defines auxiliary functions
|
|
// for formatting variables. The template is returned. If any errors
|
|
// occur, err will be non-nil.
|
|
func Parse(s string, fmap FormatterMap) (t *Template, err os.Error) {
|
|
t = New(fmap)
|
|
err = t.Parse(s)
|
|
if err != nil {
|
|
t = nil
|
|
}
|
|
return
|
|
}
|
|
|
|
// MustParse is like Parse but panics if the template cannot be parsed.
|
|
func MustParse(s string, fmap FormatterMap) *Template {
|
|
t, err := Parse(s, fmap)
|
|
if err != nil {
|
|
panic("template parse error: ", err.String())
|
|
}
|
|
return t
|
|
}
|