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| 1 // Copyright 2016 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 // This file contains structs used for constructing type descriptors for | |
| 6 // generated mojom types. A type descriptor for a mojom struct is a table | |
| 7 // describing the byte-offsets of all the pointers and handles in the struct, | |
| 8 // and has references to the type descriptorss that further describe the | |
| 9 // pointers. The table is used for doing all computations for the struct -- | |
| 10 // determining serialized size, encoding and decoding recursively, etc. A type | |
| 11 // descriptor is generated for each struct, union, array and map. Mojom maps are | |
| 12 // just mojom structs with two mojom arrays. We denote it as a separate type, | |
| 13 // but it is described the same way as a mojom struct. | |
| 14 // | |
| 15 // The user is not expected to construct type descriptors -- a bindings | |
| 16 // generator will do this when it generates bindings for a mojom file. | |
| 17 // | |
| 18 // A type descriptor for a mojom struct is a |MojomTypeDescriptorStruct| | |
| 19 // containing an array of entries of types of |MojomTypeDescriptorStructEntry|. | |
| 20 // Similarly, unions are described with |MojomTypeDescriptorUnion| with entries | |
| 21 // of |MojomTypeDescriptorUnionEntry|. Arrays are described with | |
| 22 // |MojomTypeDescriptorArray|. | |
| 23 | |
| 24 #ifndef MOJO_PUBLIC_C_BINDINGS_LIB_TYPE_DESCRIPTOR_H_ | |
| 25 #define MOJO_PUBLIC_C_BINDINGS_LIB_TYPE_DESCRIPTOR_H_ | |
| 26 | |
| 27 #include <mojo/macros.h> | |
| 28 #include <mojo/system/handle.h> | |
| 29 #include <stdbool.h> | |
| 30 #include <stddef.h> | |
| 31 #include <stdint.h> | |
| 32 | |
| 33 #include "mojo/public/c/bindings/buffer.h" | |
| 34 #include "mojo/public/c/bindings/lib/util.h" | |
| 35 #include "mojo/public/c/bindings/validation.h" | |
| 36 | |
| 37 MOJO_BEGIN_EXTERN_C | |
| 38 | |
| 39 // This enum is used in a type descriptor entry for the |elem_type| field, and | |
| 40 // indicates which type the accompanying |elem_descriptor| is describing (if it | |
| 41 // is describing a reference type), or to indicate that it's a handle type. | |
| 42 // Values that correspond to an |elem_descriptor|'s pointer type: | |
| 43 // - If MOJOM_TYPE_DESCRIPTOR_TYPE_STRUCT_PTR, then |elem_descriptor| points to | |
| 44 // a |MojomTypeDescriptorStruct|. | |
| 45 // - If MOJOM_TYPE_DESCRIPTOR_TYPE_MAP_PTR, then |elem_descriptor| points to | |
| 46 // a |MojomTypeDescriptorStruct|. | |
| 47 // - If MOJOM_TYPE_DESCRIPTOR_TYPE_UNION or | |
| 48 // MOJOM_TYPE_DESCRIPTOR_TYPE_UNION_PTR, then |elem_descriptor| points to a | |
| 49 // |MojomTypeDescriptorUnion|. | |
| 50 // - If MOJOM_TYPE_DESCRIPTOR_TYPE_ARRAY_PTR, then |elem_descriptor| points to a | |
| 51 // |MojomTypeDescriptorArray|. | |
| 52 // - For any other value, |elem_descriptor| is NULL. | |
| 53 enum MojomTypeDescriptorType { | |
| 54 // Note: A map is a mojom struct with 2 mojom arrays, so we don't have a | |
| 55 // separate descriptor type for it. | |
| 56 MOJOM_TYPE_DESCRIPTOR_TYPE_STRUCT_PTR = 0, | |
| 57 MOJOM_TYPE_DESCRIPTOR_TYPE_MAP_PTR = 1, | |
| 58 MOJOM_TYPE_DESCRIPTOR_TYPE_ARRAY_PTR = 2, | |
| 59 // A MOJOM_TYPE_DESCRIPTOR_TYPE_UNION_PTR only occurs inside a | |
| 60 // |MojomTypeDescriptorUnion|, since union fields inside unions are encoded as | |
| 61 // pointers to an out-of-line union. | |
| 62 MOJOM_TYPE_DESCRIPTOR_TYPE_UNION_PTR = 3, | |
| 63 // A union that is not inside a union is inlined, and described by | |
| 64 // MOJOM_TYPE_DESCRIPTOR_TYPE_UNION. | |
| 65 MOJOM_TYPE_DESCRIPTOR_TYPE_UNION = 4, | |
| 66 MOJOM_TYPE_DESCRIPTOR_TYPE_HANDLE = 5, | |
| 67 MOJOM_TYPE_DESCRIPTOR_TYPE_INTERFACE = 6, | |
| 68 // This is only used in an array descriptor, and serves as a way to terminate | |
| 69 // a chain of array descriptors; the last entry in the chain always contains a | |
| 70 // plain-old-data type. | |
| 71 MOJOM_TYPE_DESCRIPTOR_TYPE_POD = 7, | |
| 72 }; | |
| 73 | |
| 74 struct MojomTypeDescriptorStructVersion { | |
| 75 uint32_t version; | |
| 76 uint32_t num_bytes; | |
| 77 }; | |
| 78 | |
| 79 // Mojom structs are described using this struct. | |
| 80 struct MojomTypeDescriptorStruct { | |
| 81 uint32_t num_versions; | |
| 82 // Increasing ordered by version. | |
| 83 struct MojomTypeDescriptorStructVersion* versions; | |
| 84 // |entries| is an array of |num_entries|, each describing a field of | |
| 85 // reference or handle type. | |
| 86 uint32_t num_entries; | |
| 87 const struct MojomTypeDescriptorStructEntry* entries; | |
| 88 }; | |
| 89 | |
| 90 // This struct is used to describe each entry in a mojom struct. Each entry | |
| 91 // indicates whether it is describing a reference type, or a handle type through | |
| 92 // the field |elem_type|. |elem_descriptor| points to the type descriptor | |
| 93 // describing the field, if the type has one (handles don't have type | |
| 94 // descriptors). |offset| indicates the starting byte offset of the element | |
| 95 // within the struct. | |
| 96 struct MojomTypeDescriptorStructEntry { | |
| 97 // See comments for |MojomTypeDescriptorType| on possible values and | |
| 98 // corresponding behaviour with |elem_descriptor|. | |
| 99 enum MojomTypeDescriptorType elem_type; | |
| 100 // Use |elem_type| to decide which type |elem_descriptor| should be casted to. | |
| 101 const void* elem_descriptor; | |
| 102 // |offset| does not account for the struct header. Offset 0 always refers to | |
| 103 // the first element. | |
| 104 uint32_t offset; | |
| 105 // Corresponds to the '[MinVersion]' attribute in mojom IDL. This determines | |
| 106 // if this field should be ignored if its min_version < version of the struct | |
| 107 // we are dealing with. | |
| 108 uint32_t min_version; | |
| 109 // Is this field nullable? | |
| 110 bool nullable; | |
| 111 }; | |
| 112 | |
| 113 // Mojom unions are described using this struct. | |
| 114 struct MojomTypeDescriptorUnion { | |
| 115 // Number of fields in the union. | |
| 116 uint32_t num_fields; | |
| 117 // Number of elements in the |entries| array below. | |
| 118 uint32_t num_entries; | |
| 119 // |entries| only includes entries for pointer and handle types. | |
| 120 const struct MojomTypeDescriptorUnionEntry* entries; | |
| 121 }; | |
| 122 | |
| 123 // Like |MojomTypeDescriptorStructEntry|, this variant is used to construct a | |
| 124 // type descriptor for a union. Instead of an offset, it describes a union field | |
| 125 // by its |tag|. | |
| 126 struct MojomTypeDescriptorUnionEntry { | |
| 127 // See comments for |MojomTypeDescriptorType| on possible values and | |
| 128 // corresponding behaviour with |elem_descriptor|. | |
| 129 enum MojomTypeDescriptorType elem_type; | |
| 130 const void* elem_descriptor; | |
| 131 // The tag of the union field. | |
| 132 uint32_t tag; | |
| 133 bool nullable; | |
| 134 }; | |
| 135 | |
| 136 // Describes a mojom array. To describe an array, we don't need a table of | |
| 137 // entries, since arrays can only describe 1 type. However, that one type can | |
| 138 // recursively be an array (e.g, array<array<int>>), in which case a chain of | |
| 139 // array entries are constructed. | |
| 140 struct MojomTypeDescriptorArray { | |
| 141 enum MojomTypeDescriptorType elem_type; | |
| 142 const void* elem_descriptor; | |
| 143 // How many elements is this array expected to hold? | |
| 144 // 0 means unspecified. | |
| 145 uint32_t num_elements; | |
| 146 // Size of each element, in bits (since bools are 1-bit in size). This is | |
| 147 // needed to validate the size of an array. | |
| 148 uint32_t elem_num_bits; | |
| 149 bool nullable; | |
| 150 }; | |
| 151 | |
| 152 // This describes a mojom string. | |
| 153 // A mojom string is a mojom array of chars without a fixed-sized. | |
| 154 extern const struct MojomTypeDescriptorArray g_mojom_string_type_description; | |
| 155 | |
| 156 // Returns true if |type| is a "pointer" type: an array or a struct, whose data | |
| 157 // is referenced by a pointer (or an offset, if serialized). | |
| 158 // Since unions being pointer types depends on their container, we don't include | |
| 159 // them here. | |
| 160 bool MojomType_IsPointer(enum MojomTypeDescriptorType type); | |
| 161 | |
| 162 // This helper function, depending on |type|, calls the appropriate | |
| 163 // *_ComputeSerializedSize(|type_desc|, |data|). | |
| 164 size_t MojomType_DispatchComputeSerializedSize( | |
| 165 enum MojomTypeDescriptorType type, | |
| 166 const void* type_desc, | |
| 167 bool nullable, | |
| 168 const void* data); | |
| 169 | |
| 170 // This helper function, depending on |in_elem_type|, calls the appropriate | |
| 171 // *_EncodePointersAndHandles(...). If |in_elem_type| describes a pointer, it | |
| 172 // first encodes the pointer before calling the associated | |
| 173 // *_EncodePointersAndHandles(...). If |in_elem_type| describes a handle, it | |
| 174 // encodes the handle into |inout_handles|. | |
| 175 void MojomType_DispatchEncodePointersAndHandles( | |
| 176 enum MojomTypeDescriptorType in_elem_type, | |
| 177 const void* in_type_desc, | |
| 178 bool in_nullable, | |
| 179 void* inout_buf, | |
| 180 uint32_t in_buf_size, | |
| 181 struct MojomHandleBuffer* inout_handles_buffer); | |
| 182 | |
| 183 // This helper function, depending on |in_elem_type|, calls the appropriate | |
| 184 // *_DecodePointersAndHandles(...). If |in_elem_type| describes a pointer, it | |
| 185 // first decodes the offset into a pointer before calling the associated | |
| 186 // *_DecodePointersAndHandles(...). If |in_elem_type| describes a handle, it | |
| 187 // decodes the handle by looking up it up in |inout_handles|. | |
| 188 void MojomType_DispatchDecodePointersAndHandles( | |
| 189 enum MojomTypeDescriptorType in_elem_type, | |
| 190 const void* in_type_desc, | |
| 191 bool in_nullable, | |
| 192 void* inout_buf, | |
| 193 uint32_t in_buf_size, | |
| 194 MojoHandle* inout_handles, | |
| 195 uint32_t in_num_handles); | |
| 196 | |
| 197 MojomValidationResult MojomType_DispatchValidate( | |
| 198 enum MojomTypeDescriptorType in_elem_type, | |
| 199 const void* in_type_desc, | |
| 200 bool in_nullable, | |
| 201 const void* in_buf, | |
| 202 uint32_t in_buf_size, | |
| 203 uint32_t in_num_handles, | |
| 204 struct MojomValidationContext* inout_context); | |
| 205 | |
| 206 // This helper function, depending on |in_elem_type|, calls the appropriate | |
| 207 // *_DeepCopy(...). The result of that call is then assigned to |out_data|. If | |
| 208 // |in_type_type| describes a pointer to a union, it allocates space for the | |
| 209 // new union before dispatching a call to MojomUnion_DeepCopy. Returns false if | |
| 210 // the copy failed due to insufficient space in the buffer. | |
| 211 bool MojomType_DispatchDeepCopy(struct MojomBuffer* buffer, | |
| 212 enum MojomTypeDescriptorType in_elem_type, | |
| 213 const void* in_type_desc, | |
| 214 const void* in_data, | |
| 215 void* out_data); | |
| 216 | |
| 217 MOJO_END_EXTERN_C | |
| 218 | |
| 219 #endif // MOJO_PUBLIC_C_BINDINGS_LIB_TYPE_DESCRIPTOR_H_ | |
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