1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package gen
6
7import (
8	"bytes"
9	"encoding/gob"
10	"fmt"
11	"hash"
12	"hash/fnv"
13	"io"
14	"log"
15	"os"
16	"reflect"
17	"strings"
18	"unicode"
19	"unicode/utf8"
20)
21
22// This file contains utilities for generating code.
23
24// TODO: other write methods like:
25// - slices, maps, types, etc.
26
27// CodeWriter is a utility for writing structured code. It computes the content
28// hash and size of written content. It ensures there are newlines between
29// written code blocks.
30type CodeWriter struct {
31	buf  bytes.Buffer
32	Size int
33	Hash hash.Hash32 // content hash
34	gob  *gob.Encoder
35	// For comments we skip the usual one-line separator if they are followed by
36	// a code block.
37	skipSep bool
38}
39
40func (w *CodeWriter) Write(p []byte) (n int, err error) {
41	return w.buf.Write(p)
42}
43
44// NewCodeWriter returns a new CodeWriter.
45func NewCodeWriter() *CodeWriter {
46	h := fnv.New32()
47	return &CodeWriter{Hash: h, gob: gob.NewEncoder(h)}
48}
49
50// WriteGoFile appends the buffer with the total size of all created structures
51// and writes it as a Go file to the the given file with the given package name.
52func (w *CodeWriter) WriteGoFile(filename, pkg string) {
53	f, err := os.Create(filename)
54	if err != nil {
55		log.Fatalf("Could not create file %s: %v", filename, err)
56	}
57	defer f.Close()
58	if _, err = w.WriteGo(f, pkg, ""); err != nil {
59		log.Fatalf("Error writing file %s: %v", filename, err)
60	}
61}
62
63// WriteVersionedGoFile appends the buffer with the total size of all created
64// structures and writes it as a Go file to the the given file with the given
65// package name and build tags for the current Unicode version,
66func (w *CodeWriter) WriteVersionedGoFile(filename, pkg string) {
67	tags := buildTags()
68	if tags != "" {
69		filename = insertVersion(filename, UnicodeVersion())
70	}
71	f, err := os.Create(filename)
72	if err != nil {
73		log.Fatalf("Could not create file %s: %v", filename, err)
74	}
75	defer f.Close()
76	if _, err = w.WriteGo(f, pkg, tags); err != nil {
77		log.Fatalf("Error writing file %s: %v", filename, err)
78	}
79}
80
81// WriteGo appends the buffer with the total size of all created structures and
82// writes it as a Go file to the the given writer with the given package name.
83func (w *CodeWriter) WriteGo(out io.Writer, pkg, tags string) (n int, err error) {
84	sz := w.Size
85	w.WriteComment("Total table size %d bytes (%dKiB); checksum: %X\n", sz, sz/1024, w.Hash.Sum32())
86	defer w.buf.Reset()
87	return WriteGo(out, pkg, tags, w.buf.Bytes())
88}
89
90func (w *CodeWriter) printf(f string, x ...interface{}) {
91	fmt.Fprintf(w, f, x...)
92}
93
94func (w *CodeWriter) insertSep() {
95	if w.skipSep {
96		w.skipSep = false
97		return
98	}
99	// Use at least two newlines to ensure a blank space between the previous
100	// block. WriteGoFile will remove extraneous newlines.
101	w.printf("\n\n")
102}
103
104// WriteComment writes a comment block. All line starts are prefixed with "//".
105// Initial empty lines are gobbled. The indentation for the first line is
106// stripped from consecutive lines.
107func (w *CodeWriter) WriteComment(comment string, args ...interface{}) {
108	s := fmt.Sprintf(comment, args...)
109	s = strings.Trim(s, "\n")
110
111	// Use at least two newlines to ensure a blank space between the previous
112	// block. WriteGoFile will remove extraneous newlines.
113	w.printf("\n\n// ")
114	w.skipSep = true
115
116	// strip first indent level.
117	sep := "\n"
118	for ; len(s) > 0 && (s[0] == '\t' || s[0] == ' '); s = s[1:] {
119		sep += s[:1]
120	}
121
122	strings.NewReplacer(sep, "\n// ", "\n", "\n// ").WriteString(w, s)
123
124	w.printf("\n")
125}
126
127func (w *CodeWriter) writeSizeInfo(size int) {
128	w.printf("// Size: %d bytes\n", size)
129}
130
131// WriteConst writes a constant of the given name and value.
132func (w *CodeWriter) WriteConst(name string, x interface{}) {
133	w.insertSep()
134	v := reflect.ValueOf(x)
135
136	switch v.Type().Kind() {
137	case reflect.String:
138		w.printf("const %s %s = ", name, typeName(x))
139		w.WriteString(v.String())
140		w.printf("\n")
141	default:
142		w.printf("const %s = %#v\n", name, x)
143	}
144}
145
146// WriteVar writes a variable of the given name and value.
147func (w *CodeWriter) WriteVar(name string, x interface{}) {
148	w.insertSep()
149	v := reflect.ValueOf(x)
150	oldSize := w.Size
151	sz := int(v.Type().Size())
152	w.Size += sz
153
154	switch v.Type().Kind() {
155	case reflect.String:
156		w.printf("var %s %s = ", name, typeName(x))
157		w.WriteString(v.String())
158	case reflect.Struct:
159		w.gob.Encode(x)
160		fallthrough
161	case reflect.Slice, reflect.Array:
162		w.printf("var %s = ", name)
163		w.writeValue(v)
164		w.writeSizeInfo(w.Size - oldSize)
165	default:
166		w.printf("var %s %s = ", name, typeName(x))
167		w.gob.Encode(x)
168		w.writeValue(v)
169		w.writeSizeInfo(w.Size - oldSize)
170	}
171	w.printf("\n")
172}
173
174func (w *CodeWriter) writeValue(v reflect.Value) {
175	x := v.Interface()
176	switch v.Kind() {
177	case reflect.String:
178		w.WriteString(v.String())
179	case reflect.Array:
180		// Don't double count: callers of WriteArray count on the size being
181		// added, so we need to discount it here.
182		w.Size -= int(v.Type().Size())
183		w.writeSlice(x, true)
184	case reflect.Slice:
185		w.writeSlice(x, false)
186	case reflect.Struct:
187		w.printf("%s{\n", typeName(v.Interface()))
188		t := v.Type()
189		for i := 0; i < v.NumField(); i++ {
190			w.printf("%s: ", t.Field(i).Name)
191			w.writeValue(v.Field(i))
192			w.printf(",\n")
193		}
194		w.printf("}")
195	default:
196		w.printf("%#v", x)
197	}
198}
199
200// WriteString writes a string literal.
201func (w *CodeWriter) WriteString(s string) {
202	s = strings.Replace(s, `\`, `\\`, -1)
203	io.WriteString(w.Hash, s) // content hash
204	w.Size += len(s)
205
206	const maxInline = 40
207	if len(s) <= maxInline {
208		w.printf("%q", s)
209		return
210	}
211
212	// We will render the string as a multi-line string.
213	const maxWidth = 80 - 4 - len(`"`) - len(`" +`)
214
215	// When starting on its own line, go fmt indents line 2+ an extra level.
216	n, max := maxWidth, maxWidth-4
217
218	// As per https://golang.org/issue/18078, the compiler has trouble
219	// compiling the concatenation of many strings, s0 + s1 + s2 + ... + sN,
220	// for large N. We insert redundant, explicit parentheses to work around
221	// that, lowering the N at any given step: (s0 + s1 + ... + s63) + (s64 +
222	// ... + s127) + etc + (etc + ... + sN).
223	explicitParens, extraComment := len(s) > 128*1024, ""
224	if explicitParens {
225		w.printf(`(`)
226		extraComment = "; the redundant, explicit parens are for https://golang.org/issue/18078"
227	}
228
229	// Print "" +\n, if a string does not start on its own line.
230	b := w.buf.Bytes()
231	if p := len(bytes.TrimRight(b, " \t")); p > 0 && b[p-1] != '\n' {
232		w.printf("\"\" + // Size: %d bytes%s\n", len(s), extraComment)
233		n, max = maxWidth, maxWidth
234	}
235
236	w.printf(`"`)
237
238	for sz, p, nLines := 0, 0, 0; p < len(s); {
239		var r rune
240		r, sz = utf8.DecodeRuneInString(s[p:])
241		out := s[p : p+sz]
242		chars := 1
243		if !unicode.IsPrint(r) || r == utf8.RuneError || r == '"' {
244			switch sz {
245			case 1:
246				out = fmt.Sprintf("\\x%02x", s[p])
247			case 2, 3:
248				out = fmt.Sprintf("\\u%04x", r)
249			case 4:
250				out = fmt.Sprintf("\\U%08x", r)
251			}
252			chars = len(out)
253		}
254		if n -= chars; n < 0 {
255			nLines++
256			if explicitParens && nLines&63 == 63 {
257				w.printf("\") + (\"")
258			}
259			w.printf("\" +\n\"")
260			n = max - len(out)
261		}
262		w.printf("%s", out)
263		p += sz
264	}
265	w.printf(`"`)
266	if explicitParens {
267		w.printf(`)`)
268	}
269}
270
271// WriteSlice writes a slice value.
272func (w *CodeWriter) WriteSlice(x interface{}) {
273	w.writeSlice(x, false)
274}
275
276// WriteArray writes an array value.
277func (w *CodeWriter) WriteArray(x interface{}) {
278	w.writeSlice(x, true)
279}
280
281func (w *CodeWriter) writeSlice(x interface{}, isArray bool) {
282	v := reflect.ValueOf(x)
283	w.gob.Encode(v.Len())
284	w.Size += v.Len() * int(v.Type().Elem().Size())
285	name := typeName(x)
286	if isArray {
287		name = fmt.Sprintf("[%d]%s", v.Len(), name[strings.Index(name, "]")+1:])
288	}
289	if isArray {
290		w.printf("%s{\n", name)
291	} else {
292		w.printf("%s{ // %d elements\n", name, v.Len())
293	}
294
295	switch kind := v.Type().Elem().Kind(); kind {
296	case reflect.String:
297		for _, s := range x.([]string) {
298			w.WriteString(s)
299			w.printf(",\n")
300		}
301	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
302		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
303		// nLine and nBlock are the number of elements per line and block.
304		nLine, nBlock, format := 8, 64, "%d,"
305		switch kind {
306		case reflect.Uint8:
307			format = "%#02x,"
308		case reflect.Uint16:
309			format = "%#04x,"
310		case reflect.Uint32:
311			nLine, nBlock, format = 4, 32, "%#08x,"
312		case reflect.Uint, reflect.Uint64:
313			nLine, nBlock, format = 4, 32, "%#016x,"
314		case reflect.Int8:
315			nLine = 16
316		}
317		n := nLine
318		for i := 0; i < v.Len(); i++ {
319			if i%nBlock == 0 && v.Len() > nBlock {
320				w.printf("// Entry %X - %X\n", i, i+nBlock-1)
321			}
322			x := v.Index(i).Interface()
323			w.gob.Encode(x)
324			w.printf(format, x)
325			if n--; n == 0 {
326				n = nLine
327				w.printf("\n")
328			}
329		}
330		w.printf("\n")
331	case reflect.Struct:
332		zero := reflect.Zero(v.Type().Elem()).Interface()
333		for i := 0; i < v.Len(); i++ {
334			x := v.Index(i).Interface()
335			w.gob.EncodeValue(v)
336			if !reflect.DeepEqual(zero, x) {
337				line := fmt.Sprintf("%#v,\n", x)
338				line = line[strings.IndexByte(line, '{'):]
339				w.printf("%d: ", i)
340				w.printf(line)
341			}
342		}
343	case reflect.Array:
344		for i := 0; i < v.Len(); i++ {
345			w.printf("%d: %#v,\n", i, v.Index(i).Interface())
346		}
347	default:
348		panic("gen: slice elem type not supported")
349	}
350	w.printf("}")
351}
352
353// WriteType writes a definition of the type of the given value and returns the
354// type name.
355func (w *CodeWriter) WriteType(x interface{}) string {
356	t := reflect.TypeOf(x)
357	w.printf("type %s struct {\n", t.Name())
358	for i := 0; i < t.NumField(); i++ {
359		w.printf("\t%s %s\n", t.Field(i).Name, t.Field(i).Type)
360	}
361	w.printf("}\n")
362	return t.Name()
363}
364
365// typeName returns the name of the go type of x.
366func typeName(x interface{}) string {
367	t := reflect.ValueOf(x).Type()
368	return strings.Replace(fmt.Sprint(t), "main.", "", 1)
369}
370