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1 | = How to use the QAPI code generator = |
2 | ||
6fb55451 | 3 | Copyright IBM Corp. 2011 |
9ee86b85 | 4 | Copyright (C) 2012-2016 Red Hat, Inc. |
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5 | |
6 | This work is licensed under the terms of the GNU GPL, version 2 or | |
7 | later. See the COPYING file in the top-level directory. | |
8 | ||
9 | == Introduction == | |
10 | ||
b84da831 | 11 | QAPI is a native C API within QEMU which provides management-level |
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12 | functionality to internal and external users. For external |
13 | users/processes, this interface is made available by a JSON-based wire | |
14 | format for the QEMU Monitor Protocol (QMP) for controlling qemu, as | |
15 | well as the QEMU Guest Agent (QGA) for communicating with the guest. | |
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16 | The remainder of this document uses "Client JSON Protocol" when |
17 | referring to the wire contents of a QMP or QGA connection. | |
b84da831 | 18 | |
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19 | To map Client JSON Protocol interfaces to the native C QAPI |
20 | implementations, a JSON-based schema is used to define types and | |
21 | function signatures, and a set of scripts is used to generate types, | |
22 | signatures, and marshaling/dispatch code. This document will describe | |
23 | how the schemas, scripts, and resulting code are used. | |
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24 | |
25 | ||
26 | == QMP/Guest agent schema == | |
27 | ||
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28 | A QAPI schema file is designed to be loosely based on JSON |
29 | (http://www.ietf.org/rfc/rfc7159.txt) with changes for quoting style | |
30 | and the use of comments; a QAPI schema file is then parsed by a python | |
31 | code generation program. A valid QAPI schema consists of a series of | |
32 | top-level expressions, with no commas between them. Where | |
33 | dictionaries (JSON objects) are used, they are parsed as python | |
34 | OrderedDicts so that ordering is preserved (for predictable layout of | |
35 | generated C structs and parameter lists). Ordering doesn't matter | |
36 | between top-level expressions or the keys within an expression, but | |
37 | does matter within dictionary values for 'data' and 'returns' members | |
38 | of a single expression. QAPI schema input is written using 'single | |
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39 | quotes' instead of JSON's "double quotes" (in contrast, Client JSON |
40 | Protocol uses no comments, and while input accepts 'single quotes' as | |
41 | an extension, output is strict JSON using only "double quotes"). As | |
42 | in JSON, trailing commas are not permitted in arrays or dictionaries. | |
43 | Input must be ASCII (although QMP supports full Unicode strings, the | |
44 | QAPI parser does not). At present, there is no place where a QAPI | |
45 | schema requires the use of JSON numbers or null. | |
e790e666 | 46 | |
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47 | |
48 | === Comments === | |
49 | ||
e790e666 | 50 | Comments are allowed; anything between an unquoted # and the following |
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51 | newline is ignored. |
52 | ||
53 | A multi-line comment that starts and ends with a '##' line is a | |
54 | documentation comment. These are parsed by the documentation | |
55 | generator, which recognizes certain markup detailed below. | |
56 | ||
57 | ||
58 | ==== Documentation markup ==== | |
59 | ||
60 | Comment text starting with '=' is a section title: | |
61 | ||
62 | # = Section title | |
63 | ||
64 | Double the '=' for a subsection title: | |
65 | ||
66 | # == Subection title | |
67 | ||
68 | '|' denotes examples: | |
69 | ||
70 | # | Text of the example, may span | |
71 | # | multiple lines | |
72 | ||
73 | '*' starts an itemized list: | |
74 | ||
75 | # * First item, may span | |
76 | # multiple lines | |
77 | # * Second item | |
78 | ||
79 | You can also use '-' instead of '*'. | |
80 | ||
81 | A decimal number followed by '.' starts a numbered list: | |
82 | ||
83 | # 1. First item, may span | |
84 | # multiple lines | |
85 | # 2. Second item | |
86 | ||
87 | The actual number doesn't matter. You could even use '*' instead of | |
88 | '2.' for the second item. | |
89 | ||
90 | Lists can't be nested. Blank lines are currently not supported within | |
91 | lists. | |
92 | ||
93 | Additional whitespace between the initial '#' and the comment text is | |
94 | permitted. | |
95 | ||
96 | *foo* and _foo_ are for strong and emphasis styles respectively (they | |
97 | do not work over multiple lines). @foo is used to reference a name in | |
98 | the schema. | |
99 | ||
100 | Example: | |
101 | ||
102 | ## | |
103 | # = Section | |
104 | # == Subsection | |
105 | # | |
106 | # Some text foo with *strong* and _emphasis_ | |
107 | # 1. with a list | |
108 | # 2. like that | |
109 | # | |
110 | # And some code: | |
111 | # | $ echo foo | |
112 | # | -> do this | |
113 | # | <- get that | |
114 | # | |
115 | ## | |
116 | ||
117 | ||
118 | ==== Expression documentation ==== | |
119 | ||
120 | Each expression that isn't an include directive must be preceded by a | |
121 | documentation block. Such blocks are called expression documentation | |
122 | blocks. | |
123 | ||
124 | The documentation block consists of a first line naming the | |
125 | expression, an optional overview, a description of each argument (for | |
126 | commands and events) or member (for structs, unions and alternates), | |
127 | and optional tagged sections. | |
128 | ||
129 | FIXME: the parser accepts these things in almost any order. | |
130 | ||
131 | Optional arguments / members are tagged with the phrase '#optional', | |
132 | often with their default value; and extensions added after the | |
133 | expression was first released are also given a '(since x.y.z)' | |
134 | comment. | |
135 | ||
136 | A tagged section starts with one of the following words: | |
137 | "Note:"/"Notes:", "Since:", "Example"/"Examples", "Returns:", "TODO:". | |
138 | The section ends with the start of a new section. | |
139 | ||
140 | A 'Since: x.y.z' tagged section lists the release that introduced the | |
141 | expression. | |
142 | ||
143 | For example: | |
144 | ||
145 | ## | |
146 | # @BlockStats: | |
147 | # | |
148 | # Statistics of a virtual block device or a block backing device. | |
149 | # | |
150 | # @device: #optional If the stats are for a virtual block device, the name | |
151 | # corresponding to the virtual block device. | |
152 | # | |
153 | # @node-name: #optional The node name of the device. (since 2.3) | |
154 | # | |
155 | # ... more members ... | |
156 | # | |
157 | # Since: 0.14.0 | |
158 | ## | |
159 | { 'struct': 'BlockStats', | |
160 | 'data': {'*device': 'str', '*node-name': 'str', | |
161 | ... more members ... } } | |
162 | ||
163 | ## | |
164 | # @query-blockstats: | |
165 | # | |
166 | # Query the @BlockStats for all virtual block devices. | |
167 | # | |
168 | # @query-nodes: #optional If true, the command will query all the | |
169 | # block nodes ... explain, explain ... (since 2.3) | |
170 | # | |
171 | # Returns: A list of @BlockStats for each virtual block devices. | |
172 | # | |
173 | # Since: 0.14.0 | |
174 | # | |
175 | # Example: | |
176 | # | |
177 | # -> { "execute": "query-blockstats" } | |
178 | # <- { | |
179 | # ... lots of output ... | |
180 | # } | |
181 | # | |
182 | ## | |
183 | { 'command': 'query-blockstats', | |
184 | 'data': { '*query-nodes': 'bool' }, | |
185 | 'returns': ['BlockStats'] } | |
186 | ||
187 | ==== Free-form documentation ==== | |
188 | ||
189 | A documentation block that isn't an expression documentation block is | |
190 | a free-form documentation block. These may be used to provide | |
191 | additional text and structuring content. | |
192 | ||
193 | ||
194 | === Schema overview === | |
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195 | |
196 | The schema sets up a series of types, as well as commands and events | |
197 | that will use those types. Forward references are allowed: the parser | |
198 | scans in two passes, where the first pass learns all type names, and | |
199 | the second validates the schema and generates the code. This allows | |
200 | the definition of complex structs that can have mutually recursive | |
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201 | types, and allows for indefinite nesting of Client JSON Protocol that |
202 | satisfies the schema. A type name should not be defined more than | |
203 | once. It is permissible for the schema to contain additional types | |
204 | not used by any commands or events in the Client JSON Protocol, for | |
205 | the side effect of generated C code used internally. | |
e790e666 | 206 | |
7b1b98c4 | 207 | There are seven top-level expressions recognized by the parser: |
3b2a8b85 | 208 | 'include', 'command', 'struct', 'enum', 'union', 'alternate', and |
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209 | 'event'. There are several groups of types: simple types (a number of |
210 | built-in types, such as 'int' and 'str'; as well as enumerations), | |
211 | complex types (structs and two flavors of unions), and alternate types | |
212 | (a choice between other types). The 'command' and 'event' expressions | |
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213 | can refer to existing types by name, or list an anonymous type as a |
214 | dictionary. Listing a type name inside an array refers to a | |
215 | single-dimension array of that type; multi-dimension arrays are not | |
216 | directly supported (although an array of a complex struct that | |
217 | contains an array member is possible). | |
218 | ||
219 | Types, commands, and events share a common namespace. Therefore, | |
220 | generally speaking, type definitions should always use CamelCase for | |
221 | user-defined type names, while built-in types are lowercase. Type | |
222 | definitions should not end in 'Kind', as this namespace is used for | |
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223 | creating implicit C enums for visiting union types, or in 'List', as |
224 | this namespace is used for creating array types. Command names, | |
9ee86b85 | 225 | and member names within a type, should be all lower case with words |
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226 | separated by a hyphen. However, some existing older commands and |
227 | complex types use underscore; when extending such expressions, | |
228 | consistency is preferred over blindly avoiding underscore. Event | |
9ee86b85 | 229 | names should be ALL_CAPS with words separated by underscore. Member |
9fb081e0 | 230 | names cannot start with 'has-' or 'has_', as this is reserved for |
9ee86b85 | 231 | tracking optional members. |
e790e666 | 232 | |
9ee86b85 | 233 | Any name (command, event, type, member, or enum value) beginning with |
e790e666 | 234 | "x-" is marked experimental, and may be withdrawn or changed |
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235 | incompatibly in a future release. All names must begin with a letter, |
236 | and contain only ASCII letters, digits, dash, and underscore. There | |
237 | are two exceptions: enum values may start with a digit, and any | |
238 | extensions added by downstream vendors should start with a prefix | |
239 | matching "__RFQDN_" (for the reverse-fully-qualified-domain-name of | |
240 | the vendor), even if the rest of the name uses dash (example: | |
241 | __com.redhat_drive-mirror). Names beginning with 'q_' are reserved | |
242 | for the generator: QMP names that resemble C keywords or other | |
243 | problematic strings will be munged in C to use this prefix. For | |
9ee86b85 | 244 | example, a member named "default" in qapi becomes "q_default" in the |
59a92fee | 245 | generated C code. |
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246 | |
247 | In the rest of this document, usage lines are given for each | |
248 | expression type, with literal strings written in lower case and | |
249 | placeholders written in capitals. If a literal string includes a | |
250 | prefix of '*', that key/value pair can be omitted from the expression. | |
3b2a8b85 | 251 | For example, a usage statement that includes '*base':STRUCT-NAME |
e790e666 | 252 | means that an expression has an optional key 'base', which if present |
3b2a8b85 | 253 | must have a value that forms a struct name. |
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254 | |
255 | ||
256 | === Built-in Types === | |
257 | ||
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258 | The following types are predefined, and map to C as follows: |
259 | ||
260 | Schema C JSON | |
261 | str char * any JSON string, UTF-8 | |
262 | number double any JSON number | |
263 | int int64_t a JSON number without fractional part | |
264 | that fits into the C integer type | |
265 | int8 int8_t likewise | |
266 | int16 int16_t likewise | |
267 | int32 int32_t likewise | |
268 | int64 int64_t likewise | |
269 | uint8 uint8_t likewise | |
270 | uint16 uint16_t likewise | |
271 | uint32 uint32_t likewise | |
272 | uint64 uint64_t likewise | |
273 | size uint64_t like uint64_t, except StringInputVisitor | |
274 | accepts size suffixes | |
275 | bool bool JSON true or false | |
28770e05 | 276 | any QObject * any JSON value |
7264f5c5 | 277 | QType QType JSON string matching enum QType values |
51631493 | 278 | |
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279 | |
280 | === Includes === | |
281 | ||
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282 | Usage: { 'include': STRING } |
283 | ||
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284 | The QAPI schema definitions can be modularized using the 'include' directive: |
285 | ||
e790e666 | 286 | { 'include': 'path/to/file.json' } |
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287 | |
288 | The directive is evaluated recursively, and include paths are relative to the | |
e790e666 | 289 | file using the directive. Multiple includes of the same file are |
4247f839 | 290 | idempotent. No other keys should appear in the expression, and the include |
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291 | value should be a string. |
292 | ||
293 | As a matter of style, it is a good idea to have all files be | |
294 | self-contained, but at the moment, nothing prevents an included file | |
295 | from making a forward reference to a type that is only introduced by | |
296 | an outer file. The parser may be made stricter in the future to | |
297 | prevent incomplete include files. | |
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298 | |
299 | ||
3b2a8b85 | 300 | === Struct types === |
51631493 | 301 | |
3b2a8b85 | 302 | Usage: { 'struct': STRING, 'data': DICT, '*base': STRUCT-NAME } |
e790e666 | 303 | |
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304 | A struct is a dictionary containing a single 'data' key whose value is |
305 | a dictionary; the dictionary may be empty. This corresponds to a | |
306 | struct in C or an Object in JSON. Each value of the 'data' dictionary | |
307 | must be the name of a type, or a one-element array containing a type | |
308 | name. An example of a struct is: | |
b84da831 | 309 | |
3b2a8b85 | 310 | { 'struct': 'MyType', |
acf8394e | 311 | 'data': { 'member1': 'str', 'member2': 'int', '*member3': 'str' } } |
b84da831 | 312 | |
e790e666 | 313 | The use of '*' as a prefix to the name means the member is optional in |
363b4262 | 314 | the corresponding JSON protocol usage. |
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315 | |
316 | The default initialization value of an optional argument should not be changed | |
317 | between versions of QEMU unless the new default maintains backward | |
318 | compatibility to the user-visible behavior of the old default. | |
319 | ||
320 | With proper documentation, this policy still allows some flexibility; for | |
321 | example, documenting that a default of 0 picks an optimal buffer size allows | |
322 | one release to declare the optimal size at 512 while another release declares | |
323 | the optimal size at 4096 - the user-visible behavior is not the bytes used by | |
324 | the buffer, but the fact that the buffer was optimal size. | |
325 | ||
326 | On input structures (only mentioned in the 'data' side of a command), changing | |
327 | from mandatory to optional is safe (older clients will supply the option, and | |
328 | newer clients can benefit from the default); changing from optional to | |
329 | mandatory is backwards incompatible (older clients may be omitting the option, | |
330 | and must continue to work). | |
331 | ||
332 | On output structures (only mentioned in the 'returns' side of a command), | |
333 | changing from mandatory to optional is in general unsafe (older clients may be | |
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334 | expecting the member, and could crash if it is missing), although it |
335 | can be done if the only way that the optional argument will be omitted | |
336 | is when it is triggered by the presence of a new input flag to the | |
337 | command that older clients don't know to send. Changing from optional | |
338 | to mandatory is safe. | |
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339 | |
340 | A structure that is used in both input and output of various commands | |
341 | must consider the backwards compatibility constraints of both directions | |
342 | of use. | |
622f557f | 343 | |
3b2a8b85 | 344 | A struct definition can specify another struct as its base. |
9ee86b85 | 345 | In this case, the members of the base type are included as top-level members |
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346 | of the new struct's dictionary in the Client JSON Protocol wire |
347 | format. An example definition is: | |
622f557f | 348 | |
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349 | { 'struct': 'BlockdevOptionsGenericFormat', 'data': { 'file': 'str' } } |
350 | { 'struct': 'BlockdevOptionsGenericCOWFormat', | |
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351 | 'base': 'BlockdevOptionsGenericFormat', |
352 | 'data': { '*backing': 'str' } } | |
353 | ||
354 | An example BlockdevOptionsGenericCOWFormat object on the wire could use | |
9ee86b85 | 355 | both members like this: |
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356 | |
357 | { "file": "/some/place/my-image", | |
358 | "backing": "/some/place/my-backing-file" } | |
359 | ||
e790e666 | 360 | |
51631493 KW |
361 | === Enumeration types === |
362 | ||
e790e666 | 363 | Usage: { 'enum': STRING, 'data': ARRAY-OF-STRING } |
351d36e4 | 364 | { 'enum': STRING, '*prefix': STRING, 'data': ARRAY-OF-STRING } |
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365 | |
366 | An enumeration type is a dictionary containing a single 'data' key | |
367 | whose value is a list of strings. An example enumeration is: | |
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368 | |
369 | { 'enum': 'MyEnum', 'data': [ 'value1', 'value2', 'value3' ] } | |
370 | ||
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371 | Nothing prevents an empty enumeration, although it is probably not |
372 | useful. The list of strings should be lower case; if an enum name | |
373 | represents multiple words, use '-' between words. The string 'max' is | |
374 | not allowed as an enum value, and values should not be repeated. | |
375 | ||
351d36e4 DB |
376 | The enum constants will be named by using a heuristic to turn the |
377 | type name into a set of underscore separated words. For the example | |
378 | above, 'MyEnum' will turn into 'MY_ENUM' giving a constant name | |
379 | of 'MY_ENUM_VALUE1' for the first value. If the default heuristic | |
9ee86b85 | 380 | does not result in a desirable name, the optional 'prefix' member |
351d36e4 DB |
381 | can be used when defining the enum. |
382 | ||
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383 | The enumeration values are passed as strings over the Client JSON |
384 | Protocol, but are encoded as C enum integral values in generated code. | |
385 | While the C code starts numbering at 0, it is better to use explicit | |
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386 | comparisons to enum values than implicit comparisons to 0; the C code |
387 | will also include a generated enum member ending in _MAX for tracking | |
388 | the size of the enum, useful when using common functions for | |
389 | converting between strings and enum values. Since the wire format | |
390 | always passes by name, it is acceptable to reorder or add new | |
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391 | enumeration members in any location without breaking clients of Client |
392 | JSON Protocol; however, removing enum values would break | |
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393 | compatibility. For any struct that has a member that will only contain |
394 | a finite set of string values, using an enum type for that member is | |
395 | better than open-coding the member to be type 'str'. | |
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396 | |
397 | ||
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398 | === Union types === |
399 | ||
e790e666 | 400 | Usage: { 'union': STRING, 'data': DICT } |
ac4338f8 | 401 | or: { 'union': STRING, 'data': DICT, 'base': STRUCT-NAME-OR-DICT, |
e790e666 | 402 | 'discriminator': ENUM-MEMBER-OF-BASE } |
51631493 | 403 | |
e790e666 | 404 | Union types are used to let the user choose between several different |
7b1b98c4 | 405 | variants for an object. There are two flavors: simple (no |
02a57ae3 | 406 | discriminator or base), and flat (both discriminator and base). A union |
7b1b98c4 | 407 | type is defined using a data dictionary as explained in the following |
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408 | paragraphs. The data dictionary for either type of union must not |
409 | be empty. | |
51631493 | 410 | |
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411 | A simple union type defines a mapping from automatic discriminator |
412 | values to data types like in this example: | |
51631493 | 413 | |
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414 | { 'struct': 'BlockdevOptionsFile', 'data': { 'filename': 'str' } } |
415 | { 'struct': 'BlockdevOptionsQcow2', | |
416 | 'data': { 'backing': 'str', '*lazy-refcounts': 'bool' } } | |
51631493 | 417 | |
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418 | { 'union': 'BlockdevOptionsSimple', |
419 | 'data': { 'file': 'BlockdevOptionsFile', | |
420 | 'qcow2': 'BlockdevOptionsQcow2' } } | |
51631493 | 421 | |
363b4262 | 422 | In the Client JSON Protocol, a simple union is represented by a |
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423 | dictionary that contains the 'type' member as a discriminator, and a |
424 | 'data' member that is of the specified data type corresponding to the | |
363b4262 | 425 | discriminator value, as in these examples: |
51631493 | 426 | |
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427 | { "type": "file", "data": { "filename": "/some/place/my-image" } } |
428 | { "type": "qcow2", "data": { "backing": "/some/place/my-image", | |
429 | "lazy-refcounts": true } } | |
51631493 | 430 | |
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431 | The generated C code uses a struct containing a union. Additionally, |
432 | an implicit C enum 'NameKind' is created, corresponding to the union | |
433 | 'Name', for accessing the various branches of the union. No branch of | |
434 | the union can be named 'max', as this would collide with the implicit | |
435 | enum. The value for each branch can be of any type. | |
51631493 | 436 | |
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437 | A flat union definition avoids nesting on the wire, and specifies a |
438 | set of common members that occur in all variants of the union. The | |
d33c8a7d | 439 | 'base' key must specify either a type name (the type must be a |
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440 | struct, not a union), or a dictionary representing an anonymous type. |
441 | All branches of the union must be complex types, and the top-level | |
442 | members of the union dictionary on the wire will be combination of | |
443 | members from both the base type and the appropriate branch type (when | |
444 | merging two dictionaries, there must be no keys in common). The | |
445 | 'discriminator' member must be the name of a non-optional enum-typed | |
446 | member of the base struct. | |
51631493 | 447 | |
e790e666 | 448 | The following example enhances the above simple union example by |
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449 | adding an optional common member 'read-only', renaming the |
450 | discriminator to something more applicable than the simple union's | |
451 | default of 'type', and reducing the number of {} required on the wire: | |
50f2bdc7 | 452 | |
94a3f0af | 453 | { 'enum': 'BlockdevDriver', 'data': [ 'file', 'qcow2' ] } |
50f2bdc7 | 454 | { 'union': 'BlockdevOptions', |
ac4338f8 | 455 | 'base': { 'driver': 'BlockdevDriver', '*read-only': 'bool' }, |
50f2bdc7 | 456 | 'discriminator': 'driver', |
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457 | 'data': { 'file': 'BlockdevOptionsFile', |
458 | 'qcow2': 'BlockdevOptionsQcow2' } } | |
50f2bdc7 | 459 | |
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460 | Resulting in these JSON objects: |
461 | ||
bd59adce | 462 | { "driver": "file", "read-only": true, |
e790e666 | 463 | "filename": "/some/place/my-image" } |
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464 | { "driver": "qcow2", "read-only": false, |
465 | "backing": "/some/place/my-image", "lazy-refcounts": true } | |
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466 | |
467 | Notice that in a flat union, the discriminator name is controlled by | |
468 | the user, but because it must map to a base member with enum type, the | |
469 | code generator can ensure that branches exist for all values of the | |
470 | enum (although the order of the keys need not match the declaration of | |
471 | the enum). In the resulting generated C data types, a flat union is | |
9ee86b85 EB |
472 | represented as a struct with the base members included directly, and |
473 | then a union of structures for each branch of the struct. | |
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474 | |
475 | A simple union can always be re-written as a flat union where the base | |
476 | class has a single member named 'type', and where each branch of the | |
3b2a8b85 | 477 | union has a struct with a single member named 'data'. That is, |
50f2bdc7 | 478 | |
e790e666 | 479 | { 'union': 'Simple', 'data': { 'one': 'str', 'two': 'int' } } |
50f2bdc7 | 480 | |
e790e666 | 481 | is identical on the wire to: |
50f2bdc7 | 482 | |
e790e666 | 483 | { 'enum': 'Enum', 'data': ['one', 'two'] } |
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484 | { 'struct': 'Branch1', 'data': { 'data': 'str' } } |
485 | { 'struct': 'Branch2', 'data': { 'data': 'int' } } | |
ac4338f8 | 486 | { 'union': 'Flat': 'base': { 'type': 'Enum' }, 'discriminator': 'type', |
e790e666 | 487 | 'data': { 'one': 'Branch1', 'two': 'Branch2' } } |
69dd62df | 488 | |
e790e666 | 489 | |
7b1b98c4 | 490 | === Alternate types === |
69dd62df | 491 | |
7b1b98c4 EB |
492 | Usage: { 'alternate': STRING, 'data': DICT } |
493 | ||
494 | An alternate type is one that allows a choice between two or more JSON | |
495 | data types (string, integer, number, or object, but currently not | |
496 | array) on the wire. The definition is similar to a simple union type, | |
497 | where each branch of the union names a QAPI type. For example: | |
498 | ||
bd59adce | 499 | { 'alternate': 'BlockdevRef', |
69dd62df KW |
500 | 'data': { 'definition': 'BlockdevOptions', |
501 | 'reference': 'str' } } | |
502 | ||
7b1b98c4 | 503 | Unlike a union, the discriminator string is never passed on the wire |
363b4262 EB |
504 | for the Client JSON Protocol. Instead, the value's JSON type serves |
505 | as an implicit discriminator, which in turn means that an alternate | |
506 | can only express a choice between types represented differently in | |
507 | JSON. If a branch is typed as the 'bool' built-in, the alternate | |
508 | accepts true and false; if it is typed as any of the various numeric | |
509 | built-ins, it accepts a JSON number; if it is typed as a 'str' | |
510 | built-in or named enum type, it accepts a JSON string; and if it is | |
511 | typed as a complex type (struct or union), it accepts a JSON object. | |
512 | Two different complex types, for instance, aren't permitted, because | |
513 | both are represented as a JSON object. | |
7b1b98c4 EB |
514 | |
515 | The example alternate declaration above allows using both of the | |
516 | following example objects: | |
69dd62df KW |
517 | |
518 | { "file": "my_existing_block_device_id" } | |
519 | { "file": { "driver": "file", | |
bd59adce | 520 | "read-only": false, |
63922c64 | 521 | "filename": "/tmp/mydisk.qcow2" } } |
69dd62df KW |
522 | |
523 | ||
51631493 | 524 | === Commands === |
b84da831 | 525 | |
e790e666 | 526 | Usage: { 'command': STRING, '*data': COMPLEX-TYPE-NAME-OR-DICT, |
c818408e | 527 | '*returns': TYPE-NAME, '*boxed': true, |
e790e666 EB |
528 | '*gen': false, '*success-response': false } |
529 | ||
530 | Commands are defined by using a dictionary containing several members, | |
531 | where three members are most common. The 'command' member is a | |
363b4262 EB |
532 | mandatory string, and determines the "execute" value passed in a |
533 | Client JSON Protocol command exchange. | |
e790e666 EB |
534 | |
535 | The 'data' argument maps to the "arguments" dictionary passed in as | |
363b4262 EB |
536 | part of a Client JSON Protocol command. The 'data' member is optional |
537 | and defaults to {} (an empty dictionary). If present, it must be the | |
315932b5 MA |
538 | string name of a complex type, or a dictionary that declares an |
539 | anonymous type with the same semantics as a 'struct' expression, with | |
540 | one exception noted below when 'gen' is used. | |
e790e666 | 541 | |
9ee86b85 | 542 | The 'returns' member describes what will appear in the "return" member |
363b4262 EB |
543 | of a Client JSON Protocol reply on successful completion of a command. |
544 | The member is optional from the command declaration; if absent, the | |
9ee86b85 | 545 | "return" member will be an empty dictionary. If 'returns' is present, |
363b4262 EB |
546 | it must be the string name of a complex or built-in type, a |
547 | one-element array containing the name of a complex or built-in type, | |
9b090d42 MA |
548 | with one exception noted below when 'gen' is used. Although it is |
549 | permitted to have the 'returns' member name a built-in type or an | |
550 | array of built-in types, any command that does this cannot be extended | |
551 | to return additional information in the future; thus, new commands | |
552 | should strongly consider returning a dictionary-based type or an array | |
9ee86b85 | 553 | of dictionaries, even if the dictionary only contains one member at the |
9b090d42 | 554 | present. |
363b4262 EB |
555 | |
556 | All commands in Client JSON Protocol use a dictionary to report | |
557 | failure, with no way to specify that in QAPI. Where the error return | |
558 | is different than the usual GenericError class in order to help the | |
559 | client react differently to certain error conditions, it is worth | |
560 | documenting this in the comments before the command declaration. | |
e790e666 EB |
561 | |
562 | Some example commands: | |
563 | ||
564 | { 'command': 'my-first-command', | |
565 | 'data': { 'arg1': 'str', '*arg2': 'str' } } | |
3b2a8b85 | 566 | { 'struct': 'MyType', 'data': { '*value': 'str' } } |
e790e666 EB |
567 | { 'command': 'my-second-command', |
568 | 'returns': [ 'MyType' ] } | |
569 | ||
363b4262 | 570 | which would validate this Client JSON Protocol transaction: |
e790e666 EB |
571 | |
572 | => { "execute": "my-first-command", | |
573 | "arguments": { "arg1": "hello" } } | |
574 | <= { "return": { } } | |
575 | => { "execute": "my-second-command" } | |
576 | <= { "return": [ { "value": "one" }, { } ] } | |
577 | ||
c818408e EB |
578 | The generator emits a prototype for the user's function implementing |
579 | the command. Normally, 'data' is a dictionary for an anonymous type, | |
580 | or names a struct type (possibly empty, but not a union), and its | |
581 | members are passed as separate arguments to this function. If the | |
582 | command definition includes a key 'boxed' with the boolean value true, | |
583 | then 'data' is instead the name of any non-empty complex type | |
584 | (struct, union, or alternate), and a pointer to that QAPI type is | |
585 | passed as a single argument. | |
586 | ||
587 | The generator also emits a marshalling function that extracts | |
588 | arguments for the user's function out of an input QDict, calls the | |
589 | user's function, and if it succeeded, builds an output QObject from | |
590 | its return value. | |
591 | ||
e790e666 | 592 | In rare cases, QAPI cannot express a type-safe representation of a |
2d21291a MA |
593 | corresponding Client JSON Protocol command. You then have to suppress |
594 | generation of a marshalling function by including a key 'gen' with | |
595 | boolean value false, and instead write your own function. Please try | |
596 | to avoid adding new commands that rely on this, and instead use | |
597 | type-safe unions. For an example of this usage: | |
e790e666 EB |
598 | |
599 | { 'command': 'netdev_add', | |
b8a98326 | 600 | 'data': {'type': 'str', 'id': 'str'}, |
e790e666 EB |
601 | 'gen': false } |
602 | ||
603 | Normally, the QAPI schema is used to describe synchronous exchanges, | |
604 | where a response is expected. But in some cases, the action of a | |
605 | command is expected to change state in a way that a successful | |
606 | response is not possible (although the command will still return a | |
607 | normal dictionary error on failure). When a successful reply is not | |
608 | possible, the command expression should include the optional key | |
609 | 'success-response' with boolean value false. So far, only QGA makes | |
9ee86b85 | 610 | use of this member. |
b84da831 | 611 | |
b84da831 | 612 | |
21cd70df WX |
613 | === Events === |
614 | ||
c818408e EB |
615 | Usage: { 'event': STRING, '*data': COMPLEX-TYPE-NAME-OR-DICT, |
616 | '*boxed': true } | |
e790e666 EB |
617 | |
618 | Events are defined with the keyword 'event'. It is not allowed to | |
619 | name an event 'MAX', since the generator also produces a C enumeration | |
620 | of all event names with a generated _MAX value at the end. When | |
621 | 'data' is also specified, additional info will be included in the | |
3b2a8b85 | 622 | event, with similar semantics to a 'struct' expression. Finally there |
e790e666 EB |
623 | will be C API generated in qapi-event.h; when called by QEMU code, a |
624 | message with timestamp will be emitted on the wire. | |
21cd70df WX |
625 | |
626 | An example event is: | |
627 | ||
628 | { 'event': 'EVENT_C', | |
629 | 'data': { '*a': 'int', 'b': 'str' } } | |
630 | ||
631 | Resulting in this JSON object: | |
632 | ||
633 | { "event": "EVENT_C", | |
634 | "data": { "b": "test string" }, | |
635 | "timestamp": { "seconds": 1267020223, "microseconds": 435656 } } | |
b84da831 | 636 | |
c818408e EB |
637 | The generator emits a function to send the event. Normally, 'data' is |
638 | a dictionary for an anonymous type, or names a struct type (possibly | |
639 | empty, but not a union), and its members are passed as separate | |
640 | arguments to this function. If the event definition includes a key | |
641 | 'boxed' with the boolean value true, then 'data' is instead the name of | |
642 | any non-empty complex type (struct, union, or alternate), and a | |
643 | pointer to that QAPI type is passed as a single argument. | |
644 | ||
59a2c4ce | 645 | |
39a18158 MA |
646 | == Client JSON Protocol introspection == |
647 | ||
648 | Clients of a Client JSON Protocol commonly need to figure out what | |
649 | exactly the server (QEMU) supports. | |
650 | ||
651 | For this purpose, QMP provides introspection via command | |
652 | query-qmp-schema. QGA currently doesn't support introspection. | |
653 | ||
39a65e2c EB |
654 | While Client JSON Protocol wire compatibility should be maintained |
655 | between qemu versions, we cannot make the same guarantees for | |
656 | introspection stability. For example, one version of qemu may provide | |
657 | a non-variant optional member of a struct, and a later version rework | |
658 | the member to instead be non-optional and associated with a variant. | |
659 | Likewise, one version of qemu may list a member with open-ended type | |
660 | 'str', and a later version could convert it to a finite set of strings | |
661 | via an enum type; or a member may be converted from a specific type to | |
662 | an alternate that represents a choice between the original type and | |
663 | something else. | |
664 | ||
39a18158 MA |
665 | query-qmp-schema returns a JSON array of SchemaInfo objects. These |
666 | objects together describe the wire ABI, as defined in the QAPI schema. | |
f5455044 EB |
667 | There is no specified order to the SchemaInfo objects returned; a |
668 | client must search for a particular name throughout the entire array | |
669 | to learn more about that name, but is at least guaranteed that there | |
670 | will be no collisions between type, command, and event names. | |
39a18158 MA |
671 | |
672 | However, the SchemaInfo can't reflect all the rules and restrictions | |
673 | that apply to QMP. It's interface introspection (figuring out what's | |
674 | there), not interface specification. The specification is in the QAPI | |
675 | schema. To understand how QMP is to be used, you need to study the | |
676 | QAPI schema. | |
677 | ||
678 | Like any other command, query-qmp-schema is itself defined in the QAPI | |
679 | schema, along with the SchemaInfo type. This text attempts to give an | |
680 | overview how things work. For details you need to consult the QAPI | |
681 | schema. | |
682 | ||
683 | SchemaInfo objects have common members "name" and "meta-type", and | |
684 | additional variant members depending on the value of meta-type. | |
685 | ||
686 | Each SchemaInfo object describes a wire ABI entity of a certain | |
687 | meta-type: a command, event or one of several kinds of type. | |
688 | ||
1a9a507b MA |
689 | SchemaInfo for commands and events have the same name as in the QAPI |
690 | schema. | |
39a18158 MA |
691 | |
692 | Command and event names are part of the wire ABI, but type names are | |
1a9a507b MA |
693 | not. Therefore, the SchemaInfo for types have auto-generated |
694 | meaningless names. For readability, the examples in this section use | |
695 | meaningful type names instead. | |
696 | ||
697 | To examine a type, start with a command or event using it, then follow | |
698 | references by name. | |
39a18158 MA |
699 | |
700 | QAPI schema definitions not reachable that way are omitted. | |
701 | ||
702 | The SchemaInfo for a command has meta-type "command", and variant | |
703 | members "arg-type" and "ret-type". On the wire, the "arguments" | |
704 | member of a client's "execute" command must conform to the object type | |
705 | named by "arg-type". The "return" member that the server passes in a | |
706 | success response conforms to the type named by "ret-type". | |
707 | ||
708 | If the command takes no arguments, "arg-type" names an object type | |
709 | without members. Likewise, if the command returns nothing, "ret-type" | |
710 | names an object type without members. | |
711 | ||
712 | Example: the SchemaInfo for command query-qmp-schema | |
713 | ||
714 | { "name": "query-qmp-schema", "meta-type": "command", | |
7599697c | 715 | "arg-type": "q_empty", "ret-type": "SchemaInfoList" } |
39a18158 | 716 | |
7599697c | 717 | Type "q_empty" is an automatic object type without members, and type |
39a18158 MA |
718 | "SchemaInfoList" is the array of SchemaInfo type. |
719 | ||
720 | The SchemaInfo for an event has meta-type "event", and variant member | |
721 | "arg-type". On the wire, a "data" member that the server passes in an | |
722 | event conforms to the object type named by "arg-type". | |
723 | ||
724 | If the event carries no additional information, "arg-type" names an | |
725 | object type without members. The event may not have a data member on | |
726 | the wire then. | |
727 | ||
728 | Each command or event defined with dictionary-valued 'data' in the | |
1a9a507b | 729 | QAPI schema implicitly defines an object type. |
39a18158 MA |
730 | |
731 | Example: the SchemaInfo for EVENT_C from section Events | |
732 | ||
733 | { "name": "EVENT_C", "meta-type": "event", | |
7599697c | 734 | "arg-type": "q_obj-EVENT_C-arg" } |
39a18158 | 735 | |
7599697c | 736 | Type "q_obj-EVENT_C-arg" is an implicitly defined object type with |
39a18158 MA |
737 | the two members from the event's definition. |
738 | ||
739 | The SchemaInfo for struct and union types has meta-type "object". | |
740 | ||
741 | The SchemaInfo for a struct type has variant member "members". | |
742 | ||
743 | The SchemaInfo for a union type additionally has variant members "tag" | |
744 | and "variants". | |
745 | ||
746 | "members" is a JSON array describing the object's common members, if | |
747 | any. Each element is a JSON object with members "name" (the member's | |
748 | name), "type" (the name of its type), and optionally "default". The | |
749 | member is optional if "default" is present. Currently, "default" can | |
750 | only have value null. Other values are reserved for future | |
f5455044 EB |
751 | extensions. The "members" array is in no particular order; clients |
752 | must search the entire object when learning whether a particular | |
753 | member is supported. | |
39a18158 MA |
754 | |
755 | Example: the SchemaInfo for MyType from section Struct types | |
756 | ||
757 | { "name": "MyType", "meta-type": "object", | |
758 | "members": [ | |
759 | { "name": "member1", "type": "str" }, | |
760 | { "name": "member2", "type": "int" }, | |
761 | { "name": "member3", "type": "str", "default": null } ] } | |
762 | ||
763 | "tag" is the name of the common member serving as type tag. | |
764 | "variants" is a JSON array describing the object's variant members. | |
765 | Each element is a JSON object with members "case" (the value of type | |
766 | tag this element applies to) and "type" (the name of an object type | |
f5455044 EB |
767 | that provides the variant members for this type tag value). The |
768 | "variants" array is in no particular order, and is not guaranteed to | |
769 | list cases in the same order as the corresponding "tag" enum type. | |
39a18158 MA |
770 | |
771 | Example: the SchemaInfo for flat union BlockdevOptions from section | |
772 | Union types | |
773 | ||
774 | { "name": "BlockdevOptions", "meta-type": "object", | |
775 | "members": [ | |
776 | { "name": "driver", "type": "BlockdevDriver" }, | |
bd59adce | 777 | { "name": "read-only", "type": "bool", "default": null } ], |
39a18158 MA |
778 | "tag": "driver", |
779 | "variants": [ | |
bd59adce EB |
780 | { "case": "file", "type": "BlockdevOptionsFile" }, |
781 | { "case": "qcow2", "type": "BlockdevOptionsQcow2" } ] } | |
39a18158 MA |
782 | |
783 | Note that base types are "flattened": its members are included in the | |
784 | "members" array. | |
785 | ||
786 | A simple union implicitly defines an enumeration type for its implicit | |
787 | discriminator (called "type" on the wire, see section Union types). | |
39a18158 MA |
788 | |
789 | A simple union implicitly defines an object type for each of its | |
1a9a507b | 790 | variants. |
39a18158 | 791 | |
bd59adce | 792 | Example: the SchemaInfo for simple union BlockdevOptionsSimple from section |
39a18158 MA |
793 | Union types |
794 | ||
bd59adce | 795 | { "name": "BlockdevOptionsSimple", "meta-type": "object", |
39a18158 | 796 | "members": [ |
bd59adce | 797 | { "name": "type", "type": "BlockdevOptionsSimpleKind" } ], |
39a18158 MA |
798 | "tag": "type", |
799 | "variants": [ | |
bd59adce EB |
800 | { "case": "file", "type": "q_obj-BlockdevOptionsFile-wrapper" }, |
801 | { "case": "qcow2", "type": "q_obj-BlockdevOptionsQcow2-wrapper" } ] } | |
39a18158 | 802 | |
bd59adce EB |
803 | Enumeration type "BlockdevOptionsSimpleKind" and the object types |
804 | "q_obj-BlockdevOptionsFile-wrapper", "q_obj-BlockdevOptionsQcow2-wrapper" | |
805 | are implicitly defined. | |
39a18158 MA |
806 | |
807 | The SchemaInfo for an alternate type has meta-type "alternate", and | |
808 | variant member "members". "members" is a JSON array. Each element is | |
809 | a JSON object with member "type", which names a type. Values of the | |
f5455044 EB |
810 | alternate type conform to exactly one of its member types. There is |
811 | no guarantee on the order in which "members" will be listed. | |
39a18158 | 812 | |
bd59adce | 813 | Example: the SchemaInfo for BlockdevRef from section Alternate types |
39a18158 | 814 | |
bd59adce | 815 | { "name": "BlockdevRef", "meta-type": "alternate", |
39a18158 MA |
816 | "members": [ |
817 | { "type": "BlockdevOptions" }, | |
818 | { "type": "str" } ] } | |
819 | ||
820 | The SchemaInfo for an array type has meta-type "array", and variant | |
821 | member "element-type", which names the array's element type. Array | |
ce5fcb47 EB |
822 | types are implicitly defined. For convenience, the array's name may |
823 | resemble the element type; however, clients should examine member | |
824 | "element-type" instead of making assumptions based on parsing member | |
825 | "name". | |
39a18158 MA |
826 | |
827 | Example: the SchemaInfo for ['str'] | |
828 | ||
ce5fcb47 | 829 | { "name": "[str]", "meta-type": "array", |
39a18158 MA |
830 | "element-type": "str" } |
831 | ||
832 | The SchemaInfo for an enumeration type has meta-type "enum" and | |
f5455044 EB |
833 | variant member "values". The values are listed in no particular |
834 | order; clients must search the entire enum when learning whether a | |
835 | particular value is supported. | |
39a18158 MA |
836 | |
837 | Example: the SchemaInfo for MyEnum from section Enumeration types | |
838 | ||
839 | { "name": "MyEnum", "meta-type": "enum", | |
840 | "values": [ "value1", "value2", "value3" ] } | |
841 | ||
842 | The SchemaInfo for a built-in type has the same name as the type in | |
843 | the QAPI schema (see section Built-in Types), with one exception | |
844 | detailed below. It has variant member "json-type" that shows how | |
845 | values of this type are encoded on the wire. | |
846 | ||
847 | Example: the SchemaInfo for str | |
848 | ||
849 | { "name": "str", "meta-type": "builtin", "json-type": "string" } | |
850 | ||
851 | The QAPI schema supports a number of integer types that only differ in | |
852 | how they map to C. They are identical as far as SchemaInfo is | |
853 | concerned. Therefore, they get all mapped to a single type "int" in | |
854 | SchemaInfo. | |
855 | ||
856 | As explained above, type names are not part of the wire ABI. Not even | |
857 | the names of built-in types. Clients should examine member | |
858 | "json-type" instead of hard-coding names of built-in types. | |
859 | ||
860 | ||
b84da831 MR |
861 | == Code generation == |
862 | ||
9ee86b85 | 863 | Schemas are fed into five scripts to generate all the code/files that, |
39a18158 MA |
864 | paired with the core QAPI libraries, comprise everything required to |
865 | take JSON commands read in by a Client JSON Protocol server, unmarshal | |
866 | the arguments into the underlying C types, call into the corresponding | |
9ee86b85 EB |
867 | C function, map the response back to a Client JSON Protocol response |
868 | to be returned to the user, and introspect the commands. | |
b84da831 | 869 | |
9ee86b85 EB |
870 | As an example, we'll use the following schema, which describes a |
871 | single complex user-defined type, along with command which takes a | |
872 | list of that type as a parameter, and returns a single element of that | |
873 | type. The user is responsible for writing the implementation of | |
874 | qmp_my_command(); everything else is produced by the generator. | |
b84da831 | 875 | |
87a560c4 | 876 | $ cat example-schema.json |
3b2a8b85 | 877 | { 'struct': 'UserDefOne', |
9ee86b85 | 878 | 'data': { 'integer': 'int', '*string': 'str' } } |
b84da831 MR |
879 | |
880 | { 'command': 'my-command', | |
9ee86b85 | 881 | 'data': { 'arg1': ['UserDefOne'] }, |
b84da831 | 882 | 'returns': 'UserDefOne' } |
b84da831 | 883 | |
59a2c4ce EB |
884 | { 'event': 'MY_EVENT' } |
885 | ||
9ee86b85 EB |
886 | For a more thorough look at generated code, the testsuite includes |
887 | tests/qapi-schema/qapi-schema-tests.json that covers more examples of | |
888 | what the generator will accept, and compiles the resulting C code as | |
889 | part of 'make check-unit'. | |
890 | ||
b84da831 MR |
891 | === scripts/qapi-types.py === |
892 | ||
9ee86b85 EB |
893 | Used to generate the C types defined by a schema, along with |
894 | supporting code. The following files are created: | |
b84da831 MR |
895 | |
896 | $(prefix)qapi-types.h - C types corresponding to types defined in | |
897 | the schema you pass in | |
898 | $(prefix)qapi-types.c - Cleanup functions for the above C types | |
899 | ||
900 | The $(prefix) is an optional parameter used as a namespace to keep the | |
901 | generated code from one schema/code-generation separated from others so code | |
902 | can be generated/used from multiple schemas without clobbering previously | |
903 | created code. | |
904 | ||
905 | Example: | |
906 | ||
87a560c4 | 907 | $ python scripts/qapi-types.py --output-dir="qapi-generated" \ |
16d80f61 | 908 | --prefix="example-" example-schema.json |
9ee86b85 EB |
909 | $ cat qapi-generated/example-qapi-types.h |
910 | [Uninteresting stuff omitted...] | |
911 | ||
912 | #ifndef EXAMPLE_QAPI_TYPES_H | |
913 | #define EXAMPLE_QAPI_TYPES_H | |
914 | ||
915 | [Built-in types omitted...] | |
916 | ||
917 | typedef struct UserDefOne UserDefOne; | |
918 | ||
919 | typedef struct UserDefOneList UserDefOneList; | |
920 | ||
921 | struct UserDefOne { | |
922 | int64_t integer; | |
923 | bool has_string; | |
924 | char *string; | |
925 | }; | |
926 | ||
927 | void qapi_free_UserDefOne(UserDefOne *obj); | |
928 | ||
929 | struct UserDefOneList { | |
930 | UserDefOneList *next; | |
931 | UserDefOne *value; | |
932 | }; | |
933 | ||
934 | void qapi_free_UserDefOneList(UserDefOneList *obj); | |
935 | ||
936 | #endif | |
87a560c4 | 937 | $ cat qapi-generated/example-qapi-types.c |
6e2bb3ec MA |
938 | [Uninteresting stuff omitted...] |
939 | ||
2b162ccb | 940 | void qapi_free_UserDefOne(UserDefOne *obj) |
6e2bb3ec | 941 | { |
6e2bb3ec MA |
942 | Visitor *v; |
943 | ||
944 | if (!obj) { | |
945 | return; | |
946 | } | |
947 | ||
2c0ef9f4 | 948 | v = qapi_dealloc_visitor_new(); |
9ee86b85 | 949 | visit_type_UserDefOne(v, NULL, &obj, NULL); |
2c0ef9f4 | 950 | visit_free(v); |
6e2bb3ec | 951 | } |
b84da831 | 952 | |
2b162ccb | 953 | void qapi_free_UserDefOneList(UserDefOneList *obj) |
b84da831 | 954 | { |
b84da831 MR |
955 | Visitor *v; |
956 | ||
957 | if (!obj) { | |
958 | return; | |
959 | } | |
960 | ||
2c0ef9f4 | 961 | v = qapi_dealloc_visitor_new(); |
9ee86b85 | 962 | visit_type_UserDefOneList(v, NULL, &obj, NULL); |
2c0ef9f4 | 963 | visit_free(v); |
b84da831 | 964 | } |
b84da831 | 965 | |
b84da831 MR |
966 | === scripts/qapi-visit.py === |
967 | ||
9ee86b85 EB |
968 | Used to generate the visitor functions used to walk through and |
969 | convert between a native QAPI C data structure and some other format | |
970 | (such as QObject); the generated functions are named visit_type_FOO() | |
971 | and visit_type_FOO_members(). | |
b84da831 MR |
972 | |
973 | The following files are generated: | |
974 | ||
975 | $(prefix)qapi-visit.c: visitor function for a particular C type, used | |
976 | to automagically convert QObjects into the | |
977 | corresponding C type and vice-versa, as well | |
978 | as for deallocating memory for an existing C | |
979 | type | |
980 | ||
981 | $(prefix)qapi-visit.h: declarations for previously mentioned visitor | |
982 | functions | |
983 | ||
984 | Example: | |
985 | ||
87a560c4 | 986 | $ python scripts/qapi-visit.py --output-dir="qapi-generated" |
16d80f61 | 987 | --prefix="example-" example-schema.json |
9ee86b85 EB |
988 | $ cat qapi-generated/example-qapi-visit.h |
989 | [Uninteresting stuff omitted...] | |
990 | ||
991 | #ifndef EXAMPLE_QAPI_VISIT_H | |
992 | #define EXAMPLE_QAPI_VISIT_H | |
993 | ||
994 | [Visitors for built-in types omitted...] | |
995 | ||
996 | void visit_type_UserDefOne_members(Visitor *v, UserDefOne *obj, Error **errp); | |
997 | void visit_type_UserDefOne(Visitor *v, const char *name, UserDefOne **obj, Error **errp); | |
998 | void visit_type_UserDefOneList(Visitor *v, const char *name, UserDefOneList **obj, Error **errp); | |
999 | ||
1000 | #endif | |
87a560c4 | 1001 | $ cat qapi-generated/example-qapi-visit.c |
6e2bb3ec | 1002 | [Uninteresting stuff omitted...] |
b84da831 | 1003 | |
9ee86b85 | 1004 | void visit_type_UserDefOne_members(Visitor *v, UserDefOne *obj, Error **errp) |
6e2bb3ec MA |
1005 | { |
1006 | Error *err = NULL; | |
3a864e7c | 1007 | |
9ee86b85 | 1008 | visit_type_int(v, "integer", &obj->integer, &err); |
297a3646 MA |
1009 | if (err) { |
1010 | goto out; | |
1011 | } | |
9ee86b85 EB |
1012 | if (visit_optional(v, "string", &obj->has_string)) { |
1013 | visit_type_str(v, "string", &obj->string, &err); | |
1014 | if (err) { | |
1015 | goto out; | |
1016 | } | |
297a3646 | 1017 | } |
6e2bb3ec | 1018 | |
297a3646 | 1019 | out: |
6e2bb3ec MA |
1020 | error_propagate(errp, err); |
1021 | } | |
b84da831 | 1022 | |
9ee86b85 | 1023 | void visit_type_UserDefOne(Visitor *v, const char *name, UserDefOne **obj, Error **errp) |
b84da831 | 1024 | { |
297a3646 MA |
1025 | Error *err = NULL; |
1026 | ||
9ee86b85 EB |
1027 | visit_start_struct(v, name, (void **)obj, sizeof(UserDefOne), &err); |
1028 | if (err) { | |
1029 | goto out; | |
1030 | } | |
1031 | if (!*obj) { | |
1032 | goto out_obj; | |
6e2bb3ec | 1033 | } |
9ee86b85 | 1034 | visit_type_UserDefOne_members(v, *obj, &err); |
15c2f669 EB |
1035 | if (err) { |
1036 | goto out_obj; | |
1037 | } | |
1038 | visit_check_struct(v, &err); | |
9ee86b85 | 1039 | out_obj: |
1158bb2a | 1040 | visit_end_struct(v, (void **)obj); |
68ab47e4 EB |
1041 | if (err && visit_is_input(v)) { |
1042 | qapi_free_UserDefOne(*obj); | |
1043 | *obj = NULL; | |
1044 | } | |
9ee86b85 | 1045 | out: |
297a3646 | 1046 | error_propagate(errp, err); |
b84da831 MR |
1047 | } |
1048 | ||
9ee86b85 | 1049 | void visit_type_UserDefOneList(Visitor *v, const char *name, UserDefOneList **obj, Error **errp) |
b84da831 | 1050 | { |
6e2bb3ec | 1051 | Error *err = NULL; |
d9f62dde EB |
1052 | UserDefOneList *tail; |
1053 | size_t size = sizeof(**obj); | |
6e2bb3ec | 1054 | |
d9f62dde | 1055 | visit_start_list(v, name, (GenericList **)obj, size, &err); |
297a3646 MA |
1056 | if (err) { |
1057 | goto out; | |
1058 | } | |
1059 | ||
d9f62dde EB |
1060 | for (tail = *obj; tail; |
1061 | tail = (UserDefOneList *)visit_next_list(v, (GenericList *)tail, size)) { | |
1062 | visit_type_UserDefOne(v, NULL, &tail->value, &err); | |
1063 | if (err) { | |
1064 | break; | |
1065 | } | |
b84da831 | 1066 | } |
297a3646 | 1067 | |
1158bb2a | 1068 | visit_end_list(v, (void **)obj); |
68ab47e4 EB |
1069 | if (err && visit_is_input(v)) { |
1070 | qapi_free_UserDefOneList(*obj); | |
1071 | *obj = NULL; | |
1072 | } | |
297a3646 MA |
1073 | out: |
1074 | error_propagate(errp, err); | |
b84da831 | 1075 | } |
b84da831 | 1076 | |
b84da831 MR |
1077 | === scripts/qapi-commands.py === |
1078 | ||
9ee86b85 EB |
1079 | Used to generate the marshaling/dispatch functions for the commands |
1080 | defined in the schema. The generated code implements | |
bd6092e4 MAL |
1081 | qmp_marshal_COMMAND() (registered automatically), and declares |
1082 | qmp_COMMAND() that the user must implement. The following files are | |
1083 | generated: | |
b84da831 MR |
1084 | |
1085 | $(prefix)qmp-marshal.c: command marshal/dispatch functions for each | |
1086 | QMP command defined in the schema. Functions | |
1087 | generated by qapi-visit.py are used to | |
2542bfd5 | 1088 | convert QObjects received from the wire into |
b84da831 MR |
1089 | function parameters, and uses the same |
1090 | visitor functions to convert native C return | |
1091 | values to QObjects from transmission back | |
1092 | over the wire. | |
1093 | ||
1094 | $(prefix)qmp-commands.h: Function prototypes for the QMP commands | |
1095 | specified in the schema. | |
1096 | ||
1097 | Example: | |
1098 | ||
59a2c4ce | 1099 | $ python scripts/qapi-commands.py --output-dir="qapi-generated" |
16d80f61 | 1100 | --prefix="example-" example-schema.json |
9ee86b85 EB |
1101 | $ cat qapi-generated/example-qmp-commands.h |
1102 | [Uninteresting stuff omitted...] | |
1103 | ||
1104 | #ifndef EXAMPLE_QMP_COMMANDS_H | |
1105 | #define EXAMPLE_QMP_COMMANDS_H | |
1106 | ||
1107 | #include "example-qapi-types.h" | |
1108 | #include "qapi/qmp/qdict.h" | |
1109 | #include "qapi/error.h" | |
1110 | ||
1111 | UserDefOne *qmp_my_command(UserDefOneList *arg1, Error **errp); | |
1112 | ||
1113 | #endif | |
87a560c4 | 1114 | $ cat qapi-generated/example-qmp-marshal.c |
6e2bb3ec | 1115 | [Uninteresting stuff omitted...] |
b84da831 | 1116 | |
56d92b00 | 1117 | static void qmp_marshal_output_UserDefOne(UserDefOne *ret_in, QObject **ret_out, Error **errp) |
b84da831 | 1118 | { |
2a0f50e8 | 1119 | Error *err = NULL; |
b84da831 MR |
1120 | Visitor *v; |
1121 | ||
7d5e199a | 1122 | v = qobject_output_visitor_new(ret_out); |
9ee86b85 | 1123 | visit_type_UserDefOne(v, "unused", &ret_in, &err); |
3b098d56 EB |
1124 | if (!err) { |
1125 | visit_complete(v, ret_out); | |
6e2bb3ec | 1126 | } |
2a0f50e8 | 1127 | error_propagate(errp, err); |
2c0ef9f4 EB |
1128 | visit_free(v); |
1129 | v = qapi_dealloc_visitor_new(); | |
9ee86b85 | 1130 | visit_type_UserDefOne(v, "unused", &ret_in, NULL); |
2c0ef9f4 | 1131 | visit_free(v); |
b84da831 MR |
1132 | } |
1133 | ||
7fad30f0 | 1134 | static void qmp_marshal_my_command(QDict *args, QObject **ret, Error **errp) |
b84da831 | 1135 | { |
2a0f50e8 | 1136 | Error *err = NULL; |
3f99144c | 1137 | UserDefOne *retval; |
b84da831 | 1138 | Visitor *v; |
9ee86b85 | 1139 | UserDefOneList *arg1 = NULL; |
b84da831 | 1140 | |
09e68369 | 1141 | v = qobject_input_visitor_new(QOBJECT(args), true); |
ed841535 EB |
1142 | visit_start_struct(v, NULL, NULL, 0, &err); |
1143 | if (err) { | |
1144 | goto out; | |
1145 | } | |
9ee86b85 | 1146 | visit_type_UserDefOneList(v, "arg1", &arg1, &err); |
15c2f669 EB |
1147 | if (!err) { |
1148 | visit_check_struct(v, &err); | |
1149 | } | |
1158bb2a | 1150 | visit_end_struct(v, NULL); |
2a0f50e8 | 1151 | if (err) { |
b84da831 MR |
1152 | goto out; |
1153 | } | |
297a3646 | 1154 | |
2a0f50e8 EB |
1155 | retval = qmp_my_command(arg1, &err); |
1156 | if (err) { | |
297a3646 | 1157 | goto out; |
6e2bb3ec | 1158 | } |
b84da831 | 1159 | |
2a0f50e8 | 1160 | qmp_marshal_output_UserDefOne(retval, ret, &err); |
297a3646 | 1161 | |
b84da831 | 1162 | out: |
2a0f50e8 | 1163 | error_propagate(errp, err); |
2c0ef9f4 EB |
1164 | visit_free(v); |
1165 | v = qapi_dealloc_visitor_new(); | |
ed841535 | 1166 | visit_start_struct(v, NULL, NULL, 0, NULL); |
9ee86b85 | 1167 | visit_type_UserDefOneList(v, "arg1", &arg1, NULL); |
1158bb2a | 1168 | visit_end_struct(v, NULL); |
2c0ef9f4 | 1169 | visit_free(v); |
b84da831 MR |
1170 | } |
1171 | ||
1172 | static void qmp_init_marshal(void) | |
1173 | { | |
7fad30f0 | 1174 | qmp_register_command("my-command", qmp_marshal_my_command, QCO_NO_OPTIONS); |
b84da831 MR |
1175 | } |
1176 | ||
1177 | qapi_init(qmp_init_marshal); | |
59a2c4ce EB |
1178 | |
1179 | === scripts/qapi-event.py === | |
1180 | ||
9ee86b85 EB |
1181 | Used to generate the event-related C code defined by a schema, with |
1182 | implementations for qapi_event_send_FOO(). The following files are | |
1183 | created: | |
59a2c4ce EB |
1184 | |
1185 | $(prefix)qapi-event.h - Function prototypes for each event type, plus an | |
1186 | enumeration of all event names | |
1187 | $(prefix)qapi-event.c - Implementation of functions to send an event | |
1188 | ||
1189 | Example: | |
1190 | ||
1191 | $ python scripts/qapi-event.py --output-dir="qapi-generated" | |
16d80f61 | 1192 | --prefix="example-" example-schema.json |
9ee86b85 EB |
1193 | $ cat qapi-generated/example-qapi-event.h |
1194 | [Uninteresting stuff omitted...] | |
1195 | ||
1196 | #ifndef EXAMPLE_QAPI_EVENT_H | |
1197 | #define EXAMPLE_QAPI_EVENT_H | |
1198 | ||
1199 | #include "qapi/error.h" | |
1200 | #include "qapi/qmp/qdict.h" | |
1201 | #include "example-qapi-types.h" | |
1202 | ||
1203 | ||
1204 | void qapi_event_send_my_event(Error **errp); | |
1205 | ||
1206 | typedef enum example_QAPIEvent { | |
1207 | EXAMPLE_QAPI_EVENT_MY_EVENT = 0, | |
1208 | EXAMPLE_QAPI_EVENT__MAX = 1, | |
1209 | } example_QAPIEvent; | |
1210 | ||
1211 | extern const char *const example_QAPIEvent_lookup[]; | |
1212 | ||
1213 | #endif | |
59a2c4ce EB |
1214 | $ cat qapi-generated/example-qapi-event.c |
1215 | [Uninteresting stuff omitted...] | |
1216 | ||
1217 | void qapi_event_send_my_event(Error **errp) | |
1218 | { | |
1219 | QDict *qmp; | |
2a0f50e8 | 1220 | Error *err = NULL; |
59a2c4ce EB |
1221 | QMPEventFuncEmit emit; |
1222 | emit = qmp_event_get_func_emit(); | |
1223 | if (!emit) { | |
1224 | return; | |
1225 | } | |
1226 | ||
1227 | qmp = qmp_event_build_dict("MY_EVENT"); | |
1228 | ||
2a0f50e8 | 1229 | emit(EXAMPLE_QAPI_EVENT_MY_EVENT, qmp, &err); |
59a2c4ce | 1230 | |
2a0f50e8 | 1231 | error_propagate(errp, err); |
59a2c4ce EB |
1232 | QDECREF(qmp); |
1233 | } | |
1234 | ||
efd2eaa6 MA |
1235 | const char *const example_QAPIEvent_lookup[] = { |
1236 | [EXAMPLE_QAPI_EVENT_MY_EVENT] = "MY_EVENT", | |
7fb1cf16 | 1237 | [EXAMPLE_QAPI_EVENT__MAX] = NULL, |
59a2c4ce | 1238 | }; |
39a18158 MA |
1239 | |
1240 | === scripts/qapi-introspect.py === | |
1241 | ||
1242 | Used to generate the introspection C code for a schema. The following | |
1243 | files are created: | |
1244 | ||
1245 | $(prefix)qmp-introspect.c - Defines a string holding a JSON | |
1246 | description of the schema. | |
1247 | $(prefix)qmp-introspect.h - Declares the above string. | |
1248 | ||
1249 | Example: | |
1250 | ||
1251 | $ python scripts/qapi-introspect.py --output-dir="qapi-generated" | |
1252 | --prefix="example-" example-schema.json | |
39a18158 MA |
1253 | $ cat qapi-generated/example-qmp-introspect.h |
1254 | [Uninteresting stuff omitted...] | |
1255 | ||
1256 | #ifndef EXAMPLE_QMP_INTROSPECT_H | |
1257 | #define EXAMPLE_QMP_INTROSPECT_H | |
1258 | ||
1259 | extern const char example_qmp_schema_json[]; | |
1260 | ||
1261 | #endif | |
9ee86b85 EB |
1262 | $ cat qapi-generated/example-qmp-introspect.c |
1263 | [Uninteresting stuff omitted...] | |
1264 | ||
1265 | const char example_qmp_schema_json[] = "[" | |
1266 | "{\"arg-type\": \"0\", \"meta-type\": \"event\", \"name\": \"MY_EVENT\"}, " | |
1267 | "{\"arg-type\": \"1\", \"meta-type\": \"command\", \"name\": \"my-command\", \"ret-type\": \"2\"}, " | |
1268 | "{\"members\": [], \"meta-type\": \"object\", \"name\": \"0\"}, " | |
1269 | "{\"members\": [{\"name\": \"arg1\", \"type\": \"[2]\"}], \"meta-type\": \"object\", \"name\": \"1\"}, " | |
1270 | "{\"members\": [{\"name\": \"integer\", \"type\": \"int\"}, {\"default\": null, \"name\": \"string\", \"type\": \"str\"}], \"meta-type\": \"object\", \"name\": \"2\"}, " | |
1271 | "{\"element-type\": \"2\", \"meta-type\": \"array\", \"name\": \"[2]\"}, " | |
1272 | "{\"json-type\": \"int\", \"meta-type\": \"builtin\", \"name\": \"int\"}, " | |
1273 | "{\"json-type\": \"string\", \"meta-type\": \"builtin\", \"name\": \"str\"}]"; |