1 /*
2 * Copyright (c) 2013-2016 Dave Collins <dave@davec.name>
3 *
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16 17 package spew
18 19 import (
20 "bytes"
21 "fmt"
22 "reflect"
23 "strconv"
24 "strings"
25 )
26 27 // supportedFlags is a list of all the character flags supported by fmt package.
28 const supportedFlags = "0-+# "
29 30 // formatState implements the fmt.Formatter interface and contains information
31 // about the state of a formatting operation. The NewFormatter function can
32 // be used to get a new Formatter which can be used directly as arguments
33 // in standard fmt package printing calls.
34 type formatState struct {
35 value interface{}
36 fs fmt.State
37 depth int
38 pointers map[uintptr]int
39 ignoreNextType bool
40 cs *ConfigState
41 }
42 43 // buildDefaultFormat recreates the original format string without precision
44 // and width information to pass in to fmt.Sprintf in the case of an
45 // unrecognized type. Unless new types are added to the language, this
46 // function won't ever be called.
47 func (f *formatState) buildDefaultFormat() (format string) {
48 buf := bytes.NewBuffer(percentBytes)
49 50 for _, flag := range supportedFlags {
51 if f.fs.Flag(int(flag)) {
52 buf.WriteRune(flag)
53 }
54 }
55 56 buf.WriteRune('v')
57 58 format = buf.String()
59 return format
60 }
61 62 // constructOrigFormat recreates the original format string including precision
63 // and width information to pass along to the standard fmt package. This allows
64 // automatic deferral of all format strings this package doesn't support.
65 func (f *formatState) constructOrigFormat(verb rune) (format string) {
66 buf := bytes.NewBuffer(percentBytes)
67 68 for _, flag := range supportedFlags {
69 if f.fs.Flag(int(flag)) {
70 buf.WriteRune(flag)
71 }
72 }
73 74 if width, ok := f.fs.Width(); ok {
75 buf.WriteString(strconv.Itoa(width))
76 }
77 78 if precision, ok := f.fs.Precision(); ok {
79 buf.Write(precisionBytes)
80 buf.WriteString(strconv.Itoa(precision))
81 }
82 83 buf.WriteRune(verb)
84 85 format = buf.String()
86 return format
87 }
88 89 // unpackValue returns values inside of non-nil interfaces when possible and
90 // ensures that types for values which have been unpacked from an interface
91 // are displayed when the show types flag is also set.
92 // This is useful for data types like structs, arrays, slices, and maps which
93 // can contain varying types packed inside an interface.
94 func (f *formatState) unpackValue(v reflect.Value) reflect.Value {
95 if v.Kind() == reflect.Interface {
96 f.ignoreNextType = false
97 if !v.IsNil() {
98 v = v.Elem()
99 }
100 }
101 return v
102 }
103 104 // formatPtr handles formatting of pointers by indirecting them as necessary.
105 func (f *formatState) formatPtr(v reflect.Value) {
106 // Display nil if top level pointer is nil.
107 showTypes := f.fs.Flag('#')
108 if v.IsNil() && (!showTypes || f.ignoreNextType) {
109 f.fs.Write(nilAngleBytes)
110 return
111 }
112 113 // Remove pointers at or below the current depth from map used to detect
114 // circular refs.
115 for k, depth := range f.pointers {
116 if depth >= f.depth {
117 delete(f.pointers, k)
118 }
119 }
120 121 // Keep list of all dereferenced pointers to possibly show later.
122 pointerChain := make([]uintptr, 0)
123 124 // Figure out how many levels of indirection there are by derferencing
125 // pointers and unpacking interfaces down the chain while detecting circular
126 // references.
127 nilFound := false
128 cycleFound := false
129 indirects := 0
130 ve := v
131 for ve.Kind() == reflect.Ptr {
132 if ve.IsNil() {
133 nilFound = true
134 break
135 }
136 indirects++
137 addr := ve.Pointer()
138 pointerChain = append(pointerChain, addr)
139 if pd, ok := f.pointers[addr]; ok && pd < f.depth {
140 cycleFound = true
141 indirects--
142 break
143 }
144 f.pointers[addr] = f.depth
145 146 ve = ve.Elem()
147 if ve.Kind() == reflect.Interface {
148 if ve.IsNil() {
149 nilFound = true
150 break
151 }
152 ve = ve.Elem()
153 }
154 }
155 156 // Display type or indirection level depending on flags.
157 if showTypes && !f.ignoreNextType {
158 f.fs.Write(openParenBytes)
159 f.fs.Write(bytes.Repeat(asteriskBytes, indirects))
160 f.fs.Write([]byte(ve.Type().String()))
161 f.fs.Write(closeParenBytes)
162 } else {
163 if nilFound || cycleFound {
164 indirects += strings.Count(ve.Type().String(), "*")
165 }
166 f.fs.Write(openAngleBytes)
167 f.fs.Write([]byte(strings.Repeat("*", indirects)))
168 f.fs.Write(closeAngleBytes)
169 }
170 171 // Display pointer information depending on flags.
172 if f.fs.Flag('+') && (len(pointerChain) > 0) {
173 f.fs.Write(openParenBytes)
174 for i, addr := range pointerChain {
175 if i > 0 {
176 f.fs.Write(pointerChainBytes)
177 }
178 printHexPtr(f.fs, addr)
179 }
180 f.fs.Write(closeParenBytes)
181 }
182 183 // Display dereferenced value.
184 switch {
185 case nilFound:
186 f.fs.Write(nilAngleBytes)
187 188 case cycleFound:
189 f.fs.Write(circularShortBytes)
190 191 default:
192 f.ignoreNextType = true
193 f.format(ve)
194 }
195 }
196 197 // format is the main workhorse for providing the Formatter interface. It
198 // uses the passed reflect value to figure out what kind of object we are
199 // dealing with and formats it appropriately. It is a recursive function,
200 // however circular data structures are detected and handled properly.
201 func (f *formatState) format(v reflect.Value) {
202 // Handle invalid reflect values immediately.
203 kind := v.Kind()
204 if kind == reflect.Invalid {
205 f.fs.Write(invalidAngleBytes)
206 return
207 }
208 209 // Handle pointers specially.
210 if kind == reflect.Ptr {
211 f.formatPtr(v)
212 return
213 }
214 215 // Print type information unless already handled elsewhere.
216 if !f.ignoreNextType && f.fs.Flag('#') {
217 f.fs.Write(openParenBytes)
218 f.fs.Write([]byte(v.Type().String()))
219 f.fs.Write(closeParenBytes)
220 }
221 f.ignoreNextType = false
222 223 // Call Stringer/error interfaces if they exist and the handle methods
224 // flag is enabled.
225 if !f.cs.DisableMethods {
226 if (kind != reflect.Invalid) && (kind != reflect.Interface) {
227 if handled := handleMethods(f.cs, f.fs, v); handled {
228 return
229 }
230 }
231 }
232 233 switch kind {
234 case reflect.Invalid:
235 // Do nothing. We should never get here since invalid has already
236 // been handled above.
237 238 case reflect.Bool:
239 printBool(f.fs, v.Bool())
240 241 case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
242 printInt(f.fs, v.Int(), 10)
243 244 case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint:
245 printUint(f.fs, v.Uint(), 10)
246 247 case reflect.Float32:
248 printFloat(f.fs, v.Float(), 32)
249 250 case reflect.Float64:
251 printFloat(f.fs, v.Float(), 64)
252 253 case reflect.Complex64:
254 printComplex(f.fs, v.Complex(), 32)
255 256 case reflect.Complex128:
257 printComplex(f.fs, v.Complex(), 64)
258 259 case reflect.Slice:
260 if v.IsNil() {
261 f.fs.Write(nilAngleBytes)
262 break
263 }
264 fallthrough
265 266 case reflect.Array:
267 f.fs.Write(openBracketBytes)
268 f.depth++
269 if (f.cs.MaxDepth != 0) && (f.depth > f.cs.MaxDepth) {
270 f.fs.Write(maxShortBytes)
271 } else {
272 numEntries := v.Len()
273 for i := 0; i < numEntries; i++ {
274 if i > 0 {
275 f.fs.Write(spaceBytes)
276 }
277 f.ignoreNextType = true
278 f.format(f.unpackValue(v.Index(i)))
279 }
280 }
281 f.depth--
282 f.fs.Write(closeBracketBytes)
283 284 case reflect.String:
285 f.fs.Write([]byte(v.String()))
286 287 case reflect.Interface:
288 // The only time we should get here is for nil interfaces due to
289 // unpackValue calls.
290 if v.IsNil() {
291 f.fs.Write(nilAngleBytes)
292 }
293 294 case reflect.Ptr:
295 // Do nothing. We should never get here since pointers have already
296 // been handled above.
297 298 case reflect.Map:
299 // nil maps should be indicated as different than empty maps
300 if v.IsNil() {
301 f.fs.Write(nilAngleBytes)
302 break
303 }
304 305 f.fs.Write(openMapBytes)
306 f.depth++
307 if (f.cs.MaxDepth != 0) && (f.depth > f.cs.MaxDepth) {
308 f.fs.Write(maxShortBytes)
309 } else {
310 keys := v.MapKeys()
311 if f.cs.SortKeys {
312 sortValues(keys, f.cs)
313 }
314 for i, key := range keys {
315 if i > 0 {
316 f.fs.Write(spaceBytes)
317 }
318 f.ignoreNextType = true
319 f.format(f.unpackValue(key))
320 f.fs.Write(colonBytes)
321 f.ignoreNextType = true
322 f.format(f.unpackValue(v.MapIndex(key)))
323 }
324 }
325 f.depth--
326 f.fs.Write(closeMapBytes)
327 328 case reflect.Struct:
329 numFields := v.NumField()
330 f.fs.Write(openBraceBytes)
331 f.depth++
332 if (f.cs.MaxDepth != 0) && (f.depth > f.cs.MaxDepth) {
333 f.fs.Write(maxShortBytes)
334 } else {
335 vt := v.Type()
336 for i := 0; i < numFields; i++ {
337 if i > 0 {
338 f.fs.Write(spaceBytes)
339 }
340 vtf := vt.Field(i)
341 if f.fs.Flag('+') || f.fs.Flag('#') {
342 f.fs.Write([]byte(vtf.Name))
343 f.fs.Write(colonBytes)
344 }
345 f.format(f.unpackValue(v.Field(i)))
346 }
347 }
348 f.depth--
349 f.fs.Write(closeBraceBytes)
350 351 case reflect.Uintptr:
352 printHexPtr(f.fs, uintptr(v.Uint()))
353 354 case reflect.UnsafePointer, reflect.Chan, reflect.Func:
355 printHexPtr(f.fs, v.Pointer())
356 357 // There were not any other types at the time this code was written, but
358 // fall back to letting the default fmt package handle it if any get added.
359 default:
360 format := f.buildDefaultFormat()
361 if v.CanInterface() {
362 fmt.Fprintf(f.fs, format, v.Interface())
363 } else {
364 fmt.Fprintf(f.fs, format, v.String())
365 }
366 }
367 }
368 369 // Format satisfies the fmt.Formatter interface. See NewFormatter for usage
370 // details.
371 func (f *formatState) Format(fs fmt.State, verb rune) {
372 f.fs = fs
373 374 // Use standard formatting for verbs that are not v.
375 if verb != 'v' {
376 format := f.constructOrigFormat(verb)
377 fmt.Fprintf(fs, format, f.value)
378 return
379 }
380 381 if f.value == nil {
382 if fs.Flag('#') {
383 fs.Write(interfaceBytes)
384 }
385 fs.Write(nilAngleBytes)
386 return
387 }
388 389 f.format(reflect.ValueOf(f.value))
390 }
391 392 // newFormatter is a helper function to consolidate the logic from the various
393 // public methods which take varying config states.
394 func newFormatter(cs *ConfigState, v interface{}) fmt.Formatter {
395 fs := &formatState{value: v, cs: cs}
396 fs.pointers = make(map[uintptr]int)
397 return fs
398 }
399 400 /*
401 NewFormatter returns a custom formatter that satisfies the fmt.Formatter
402 interface. As a result, it integrates cleanly with standard fmt package
403 printing functions. The formatter is useful for inline printing of smaller data
404 types similar to the standard %v format specifier.
405 406 The custom formatter only responds to the %v (most compact), %+v (adds pointer
407 addresses), %#v (adds types), or %#+v (adds types and pointer addresses) verb
408 combinations. Any other verbs such as %x and %q will be sent to the the
409 standard fmt package for formatting. In addition, the custom formatter ignores
410 the width and precision arguments (however they will still work on the format
411 specifiers not handled by the custom formatter).
412 413 Typically this function shouldn't be called directly. It is much easier to make
414 use of the custom formatter by calling one of the convenience functions such as
415 Printf, Println, or Fprintf.
416 */
417 func NewFormatter(v interface{}) fmt.Formatter {
418 return newFormatter(&Config, v)
419 }
420