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_ 7 #define _PB_ENCODE_H_ 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_t 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 int *callback; 37 #else 38 bool (*callback)(pb_ostream_t *stream, const uint8_t *buf, size_t count); 39 #endif 40 void *state; /* Free field for use by callback implementation. */ 41 size_t max_size; /* Limit number of output bytes written (or use SIZE_MAX). */ 42 size_t bytes_written; /* Number of bytes written so far. */ 43 44 #ifndef PB_NO_ERRMSG 45 const char *errmsg; 46 #endif 47 }; 48 49 /*************************** 50 * Main encoding functions * 51 ***************************/ 52 53 /* Encode a single protocol buffers message from C structure into a stream. 54 * Returns true on success, false on any failure. 55 * The actual struct pointed to by src_struct must match the description in fields. 56 * All required fields in the struct are assumed to have been filled in. 57 * 58 * Example usage: 59 * MyMessage msg = {}; 60 * uint8_t buffer[64]; 61 * pb_ostream_t stream; 62 * 63 * msg.field1 = 42; 64 * stream = pb_ostream_from_buffer(buffer, sizeof(buffer)); 65 * pb_encode(&stream, MyMessage_fields, &msg); 66 */ 67 bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], 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[], const void *src_struct); 73 74 /* Encode the message to get the size of the encoded data, but do not store 75 * the data. */ 76 bool pb_get_encoded_size(size_t *size, const pb_field_t fields[], const void *src_struct); 77 78 /************************************** 79 * Functions for manipulating streams * 80 **************************************/ 81 82 /* Create an output stream for writing into a memory buffer. 83 * The number of bytes written can be found in stream.bytes_written after 84 * encoding the message. 85 * 86 * Alternatively, you can use a custom stream that writes directly to e.g. 87 * a file or a network socket. 88 */ 89 pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize); 90 91 /* Pseudo-stream for measuring the size of a message without actually storing 92 * the encoded data. 93 * 94 * Example usage: 95 * MyMessage msg = {}; 96 * pb_ostream_t stream = PB_OSTREAM_SIZING; 97 * pb_encode(&stream, MyMessage_fields, &msg); 98 * printf("Message size is %d\n", stream.bytes_written); 99 */ 100 #ifndef PB_NO_ERRMSG 101 #define PB_OSTREAM_SIZING {0,0,0,0,0} 102 #else 103 #define PB_OSTREAM_SIZING {0,0,0,0} 104 #endif 105 106 /* Function to write into a pb_ostream_t stream. You can use this if you need 107 * to append or prepend some custom headers to the message. 108 */ 109 bool pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count); 110 111 112 /************************************************ 113 * Helper functions for writing field callbacks * 114 ************************************************/ 115 116 /* Encode field header based on type and field number defined in the field 117 * structure. Call this from the callback before writing out field contents. */ 118 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field); 119 120 /* Encode field header by manually specifing wire type. You need to use this 121 * if you want to write out packed arrays from a callback field. */ 122 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number); 123 124 /* Encode an integer in the varint format. 125 * This works for bool, enum, int32, int64, uint32 and uint64 field types. */ 126 bool pb_encode_varint(pb_ostream_t *stream, uint64_t value); 127 128 /* Encode an integer in the zig-zagged svarint format. 129 * This works for sint32 and sint64. */ 130 bool pb_encode_svarint(pb_ostream_t *stream, int64_t value); 131 132 /* Encode a string or bytes type field. For strings, pass strlen(s) as size. */ 133 bool pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size); 134 135 /* Encode a fixed32, sfixed32 or float value. 136 * You need to pass a pointer to a 4-byte wide C variable. */ 137 bool pb_encode_fixed32(pb_ostream_t *stream, const void *value); 138 139 /* Encode a fixed64, sfixed64 or double value. 140 * You need to pass a pointer to a 8-byte wide C variable. */ 141 bool pb_encode_fixed64(pb_ostream_t *stream, const void *value); 142 143 /* Encode a submessage field. 144 * You need to pass the pb_field_t array and pointer to struct, just like 145 * with pb_encode(). This internally encodes the submessage twice, first to 146 * calculate message size and then to actually write it out. 147 */ 148 bool pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct); 149 150 #ifdef __cplusplus 151 } /* extern "C" */ 152 #endif 153 154 #endif 155