1 /* pb_encode.h: Functions to encode protocol buffers. Depends on pb_encode.c. 2 * The main function is pb_encode. You also need an output stream, and the 3 * field descriptions created by nanopb_generator.py. 4 */ 5 6 #ifndef PB_ENCODE_H_INCLUDED 7 #define PB_ENCODE_H_INCLUDED 8 9 #include "pb.h" 10 11 #ifdef __cplusplus 12 extern "C" { 13 #endif 14 15 /* Structure for defining custom output streams. You will need to provide 16 * a callback function to write the bytes to your storage, which can be 17 * for example a file or a network socket. 18 * 19 * The callback must conform to these rules: 20 * 21 * 1) Return false on IO errors. This will cause encoding to abort. 22 * 2) You can use state to store your own data (e.g. buffer pointer). 23 * 3) pb_write will update bytes_written after your callback runs. 24 * 4) Substreams will modify max_size and bytes_written. Don't use them 25 * to calculate any pointers. 26 */ 27 struct pb_ostream_s 28 { 29 #ifdef PB_BUFFER_ONLY 30 /* Callback pointer is not used in buffer-only configuration. 31 * Having an int pointer here allows binary compatibility but 32 * gives an error if someone tries to assign callback function. 33 * Also, NULL pointer marks a 'sizing stream' that does not 34 * write anything. 35 */ 36 const int *callback; 37 #else 38 bool (*callback)(pb_ostream_t *stream, const pb_byte_t *buf, size_t count); 39 #endif 40 41 /* state is a free field for use of the callback function defined above. 42 * Note that when pb_ostream_from_buffer() is used, it reserves this field 43 * for its own use. 44 */ 45 void *state; 46 47 /* Limit number of output bytes written. Can be set to SIZE_MAX. */ 48 size_t max_size; 49 50 /* Number of bytes written so far. */ 51 size_t bytes_written; 52 53 #ifndef PB_NO_ERRMSG 54 /* Pointer to constant (ROM) string when decoding function returns error */ 55 const char *errmsg; 56 #endif 57 }; 58 59 /*************************** 60 * Main encoding functions * 61 ***************************/ 62 63 /* Encode a single protocol buffers message from C structure into a stream. 64 * Returns true on success, false on any failure. 65 * The actual struct pointed to by src_struct must match the description in fields. 66 * All required fields in the struct are assumed to have been filled in. 67 * 68 * Example usage: 69 * MyMessage msg = {}; 70 * uint8_t buffer[64]; 71 * pb_ostream_t stream; 72 * 73 * msg.field1 = 42; 74 * stream = pb_ostream_from_buffer(buffer, sizeof(buffer)); 75 * pb_encode(&stream, MyMessage_fields, &msg); 76 */ 77 bool pb_encode(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct); 78 79 /* Extended version of pb_encode, with several options to control the 80 * encoding process: 81 * 82 * PB_ENCODE_DELIMITED: Prepend the length of message as a varint. 83 * Corresponds to writeDelimitedTo() in Google's 84 * protobuf API. 85 * 86 * PB_ENCODE_NULLTERMINATED: Append a null byte to the message for termination. 87 * NOTE: This behaviour is not supported in most other 88 * protobuf implementations, so PB_ENCODE_DELIMITED 89 * is a better option for compatibility. 90 */ 91 #define PB_ENCODE_DELIMITED 0x02U 92 #define PB_ENCODE_NULLTERMINATED 0x04U 93 bool pb_encode_ex(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct, unsigned int flags); 94 95 /* Defines for backwards compatibility with code written before nanopb-0.4.0 */ 96 #define pb_encode_delimited(s,f,d) pb_encode_ex(s,f,d, PB_ENCODE_DELIMITED) 97 #define pb_encode_nullterminated(s,f,d) pb_encode_ex(s,f,d, PB_ENCODE_NULLTERMINATED) 98 99 /* Encode the message to get the size of the encoded data, but do not store 100 * the data. */ 101 bool pb_get_encoded_size(size_t *size, const pb_msgdesc_t *fields, const void *src_struct); 102 103 /************************************** 104 * Functions for manipulating streams * 105 **************************************/ 106 107 /* Create an output stream for writing into a memory buffer. 108 * The number of bytes written can be found in stream.bytes_written after 109 * encoding the message. 110 * 111 * Alternatively, you can use a custom stream that writes directly to e.g. 112 * a file or a network socket. 113 */ 114 pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize); 115 116 /* Pseudo-stream for measuring the size of a message without actually storing 117 * the encoded data. 118 * 119 * Example usage: 120 * MyMessage msg = {}; 121 * pb_ostream_t stream = PB_OSTREAM_SIZING; 122 * pb_encode(&stream, MyMessage_fields, &msg); 123 * printf("Message size is %d\n", stream.bytes_written); 124 */ 125 #ifndef PB_NO_ERRMSG 126 #define PB_OSTREAM_SIZING {0,0,0,0,0} 127 #else 128 #define PB_OSTREAM_SIZING {0,0,0,0} 129 #endif 130 131 /* Function to write into a pb_ostream_t stream. You can use this if you need 132 * to append or prepend some custom headers to the message. 133 */ 134 bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count); 135 136 137 /************************************************ 138 * Helper functions for writing field callbacks * 139 ************************************************/ 140 141 /* Encode field header based on type and field number defined in the field 142 * structure. Call this from the callback before writing out field contents. */ 143 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_iter_t *field); 144 145 /* Encode field header by manually specifying wire type. You need to use this 146 * if you want to write out packed arrays from a callback field. */ 147 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number); 148 149 /* Encode an integer in the varint format. 150 * This works for bool, enum, int32, int64, uint32 and uint64 field types. */ 151 #ifndef PB_WITHOUT_64BIT 152 bool pb_encode_varint(pb_ostream_t *stream, uint64_t value); 153 #else 154 bool pb_encode_varint(pb_ostream_t *stream, uint32_t value); 155 #endif 156 157 /* Encode an integer in the zig-zagged svarint format. 158 * This works for sint32 and sint64. */ 159 #ifndef PB_WITHOUT_64BIT 160 bool pb_encode_svarint(pb_ostream_t *stream, int64_t value); 161 #else 162 bool pb_encode_svarint(pb_ostream_t *stream, int32_t value); 163 #endif 164 165 /* Encode a string or bytes type field. For strings, pass strlen(s) as size. */ 166 bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size); 167 168 /* Encode a fixed32, sfixed32 or float value. 169 * You need to pass a pointer to a 4-byte wide C variable. */ 170 bool pb_encode_fixed32(pb_ostream_t *stream, const void *value); 171 172 #ifndef PB_WITHOUT_64BIT 173 /* Encode a fixed64, sfixed64 or double value. 174 * You need to pass a pointer to a 8-byte wide C variable. */ 175 bool pb_encode_fixed64(pb_ostream_t *stream, const void *value); 176 #endif 177 178 #ifdef PB_CONVERT_DOUBLE_FLOAT 179 /* Encode a float value so that it appears like a double in the encoded 180 * message. */ 181 bool pb_encode_float_as_double(pb_ostream_t *stream, float value); 182 #endif 183 184 /* Encode a submessage field. 185 * You need to pass the pb_field_t array and pointer to struct, just like 186 * with pb_encode(). This internally encodes the submessage twice, first to 187 * calculate message size and then to actually write it out. 188 */ 189 bool pb_encode_submessage(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct); 190 191 #ifdef __cplusplus 192 } /* extern "C" */ 193 #endif 194 195 #endif 196
