102 lines
2.6 KiB
Go
102 lines
2.6 KiB
Go
// Package prnt provides common functionality for code generators.
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package prnt
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import (
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"bytes"
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"fmt"
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"go/build/constraint"
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"io"
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"strings"
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)
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// Generator provides convenience methods for code generators. In particular it
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// provides fmt-like methods which print to an internal buffer. It also allows
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// any errors to be stored so they can be checked at the end, rather than having
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// error checks obscuring the code generation.
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type Generator struct {
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buf bytes.Buffer
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level int // current indentation level
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indent string // indentation string
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pending bool // if there's a pending indentation
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err error // saved error from printing
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}
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// Raw provides direct access to the underlying output stream.
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func (g *Generator) Raw() io.Writer {
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return &g.buf
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}
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// SetIndentString sets the string used for one level of indentation. Use
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// Indent() and Dedent() to control indent level.
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func (g *Generator) SetIndentString(indent string) {
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g.indent = indent
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}
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// Indent increments the indent level.
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func (g *Generator) Indent() {
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g.level++
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}
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// Dedent decrements the indent level.
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func (g *Generator) Dedent() {
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g.level--
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}
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// Linef prints formatted output terminated with a new line.
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func (g *Generator) Linef(format string, args ...any) {
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g.Printf(format, args...)
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g.NL()
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}
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// Printf prints to the internal buffer.
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func (g *Generator) Printf(format string, args ...any) {
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if g.err != nil {
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return
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}
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if g.pending {
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indent := strings.Repeat(g.indent, g.level)
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format = indent + format
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g.pending = false
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}
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_, err := fmt.Fprintf(&g.buf, format, args...)
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g.AddError(err)
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}
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// NL prints a new line.
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func (g *Generator) NL() {
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g.Printf("\n")
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g.pending = true
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}
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// Comment writes comment lines prefixed with "// ".
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func (g *Generator) Comment(lines ...string) {
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for _, line := range lines {
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line = strings.TrimSpace("// " + line)
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g.Printf("%s\n", line)
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}
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}
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// BuildConstraint outputs a build constraint.
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func (g *Generator) BuildConstraint(expr string) {
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line := fmt.Sprintf("//go:build %s", expr)
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if _, err := constraint.Parse(line); err != nil {
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g.AddError(err)
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}
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g.Linef(line)
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}
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// AddError records an error in code generation. The first non-nil error will
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// prevent printing operations from writing anything else, and the error will be
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// returned from Result().
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func (g *Generator) AddError(err error) {
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if err != nil && g.err == nil {
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g.err = err
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}
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}
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// Result returns the printed bytes. If any error was recorded with AddError
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// during code generation, the first such error will be returned here.
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func (g *Generator) Result() ([]byte, error) {
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return g.buf.Bytes(), g.err
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}
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