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 #ifdef PB_BUFFER_ONLY 29 /* Callback pointer is not used in buffer-only configuration. 30 * Having an int pointer here allows binary compatibility but 31 * gives an error if someone tries to assign callback function. 32 * Also, NULL pointer marks a 'sizing stream' that does not 33 * write anything. 34 */ 35 int *callback; 36 #else 37 bool (*callback)(pb_ostream_t *stream, const pb_byte_t *buf, size_t count); 38 #endif 39 void *state; /* Free field for use by callback implementation. */ 40 size_t max_size; /* Limit number of output bytes written (or use SIZE_MAX). */ 41 size_t bytes_written; /* Number of bytes written so far. */ 42 43 #ifndef PB_NO_ERRMSG 44 const char *errmsg; 45 #endif 46 }; 47 48 /*************************** 49 * Main encoding functions * 50 ***************************/ 51 52 /* Encode a single protocol buffers message from C structure into a stream. 53 * Returns true on success, false on any failure. 54 * The actual struct pointed to by src_struct must match the description in 55 * fields. All required fields in the struct are assumed to have been filled in. 56 * 57 * Example usage: 58 * MyMessage msg = {}; 59 * uint8_t buffer[64]; 60 * pb_ostream_t stream; 61 * 62 * msg.field1 = 42; 63 * stream = pb_ostream_from_buffer(buffer, sizeof(buffer)); 64 * pb_encode(&stream, MyMessage_fields, &msg); 65 */ 66 bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], 67 const void *src_struct); 68 69 /* Same as pb_encode, but prepends the length of the message as a varint. 70 * Corresponds to writeDelimitedTo() in Google's protobuf API. 71 */ 72 bool pb_encode_delimited(pb_ostream_t *stream, const pb_field_t fields[], 73 const void *src_struct); 74 75 /* Same as pb_encode, but appends a null byte to the message for termination. 76 * NOTE: This behaviour is not supported in most other protobuf implementations, 77 * so pb_encode_delimited() is a better option for compatibility. 78 */ 79 bool pb_encode_nullterminated(pb_ostream_t *stream, const pb_field_t fields[], 80 const void *src_struct); 81 82 /* Encode the message to get the size of the encoded data, but do not store 83 * the data. */ 84 bool pb_get_encoded_size(size_t *size, const pb_field_t fields[], 85 const void *src_struct); 86 87 /************************************** 88 * Functions for manipulating streams * 89 **************************************/ 90 91 /* Create an output stream for writing into a memory buffer. 92 * The number of bytes written can be found in stream.bytes_written after 93 * encoding the message. 94 * 95 * Alternatively, you can use a custom stream that writes directly to e.g. 96 * a file or a network socket. 97 */ 98 pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize); 99 100 /* Pseudo-stream for measuring the size of a message without actually storing 101 * the encoded data. 102 * 103 * Example usage: 104 * MyMessage msg = {}; 105 * pb_ostream_t stream = PB_OSTREAM_SIZING; 106 * pb_encode(&stream, MyMessage_fields, &msg); 107 * printf("Message size is %d\n", stream.bytes_written); 108 */ 109 #ifndef PB_NO_ERRMSG 110 #define PB_OSTREAM_SIZING {0, 0, 0, 0, 0} 111 #else 112 #define PB_OSTREAM_SIZING {0, 0, 0, 0} 113 #endif 114 115 /* Function to write into a pb_ostream_t stream. You can use this if you need 116 * to append or prepend some custom headers to the message. 117 */ 118 bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count); 119 120 /************************************************ 121 * Helper functions for writing field callbacks * 122 ************************************************/ 123 124 /* Encode field header based on type and field number defined in the field 125 * structure. Call this from the callback before writing out field contents. */ 126 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field); 127 128 /* Encode field header by manually specifying wire type. You need to use this 129 * if you want to write out packed arrays from a callback field. */ 130 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, 131 uint32_t field_number); 132 133 /* Encode an integer in the varint format. 134 * This works for bool, enum, int32, int64, uint32 and uint64 field types. */ 135 #ifndef PB_WITHOUT_64BIT 136 bool pb_encode_varint(pb_ostream_t *stream, uint64_t value); 137 #else 138 bool pb_encode_varint(pb_ostream_t *stream, uint32_t value); 139 #endif 140 141 /* Encode an integer in the zig-zagged svarint format. 142 * This works for sint32 and sint64. */ 143 #ifndef PB_WITHOUT_64BIT 144 bool pb_encode_svarint(pb_ostream_t *stream, int64_t value); 145 #else 146 bool pb_encode_svarint(pb_ostream_t *stream, int32_t value); 147 #endif 148 149 /* Encode a string or bytes type field. For strings, pass strlen(s) as size. */ 150 bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, 151 size_t size); 152 153 /* Encode a fixed32, sfixed32 or float value. 154 * You need to pass a pointer to a 4-byte wide C variable. */ 155 bool pb_encode_fixed32(pb_ostream_t *stream, const void *value); 156 157 #ifndef PB_WITHOUT_64BIT 158 /* Encode a fixed64, sfixed64 or double value. 159 * You need to pass a pointer to a 8-byte wide C variable. */ 160 bool pb_encode_fixed64(pb_ostream_t *stream, const void *value); 161 #endif 162 163 /* Encode a submessage field. 164 * You need to pass the pb_field_t array and pointer to struct, just like 165 * with pb_encode(). This internally encodes the submessage twice, first to 166 * calculate message size and then to actually write it out. 167 */ 168 bool pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], 169 const void *src_struct); 170 171 #ifdef __cplusplus 172 } /* extern "C" */ 173 #endif 174 175 #endif 176