155 lines
5.7 KiB
C
155 lines
5.7 KiB
C
/* pb_encode.h: Functions to encode protocol buffers. Depends on pb_encode.c.
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* The main function is pb_encode. You also need an output stream, and the
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* field descriptions created by nanopb_generator.py.
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*/
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#ifndef PB_ENCODE_H_INCLUDED
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#define PB_ENCODE_H_INCLUDED
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#include "pb.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Structure for defining custom output streams. You will need to provide
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* a callback function to write the bytes to your storage, which can be
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* for example a file or a network socket.
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*
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* The callback must conform to these rules:
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*
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* 1) Return false on IO errors. This will cause encoding to abort.
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* 2) You can use state to store your own data (e.g. buffer pointer).
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* 3) pb_write will update bytes_written after your callback runs.
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* 4) Substreams will modify max_size and bytes_written. Don't use them
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* to calculate any pointers.
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*/
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struct pb_ostream_s
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{
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#ifdef PB_BUFFER_ONLY
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/* Callback pointer is not used in buffer-only configuration.
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* Having an int pointer here allows binary compatibility but
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* gives an error if someone tries to assign callback function.
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* Also, NULL pointer marks a 'sizing stream' that does not
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* write anything.
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*/
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int *callback;
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#else
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bool (*callback)(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
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#endif
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void *state; /* Free field for use by callback implementation. */
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size_t max_size; /* Limit number of output bytes written (or use SIZE_MAX). */
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size_t bytes_written; /* Number of bytes written so far. */
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#ifndef PB_NO_ERRMSG
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const char *errmsg;
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#endif
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};
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/***************************
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* Main encoding functions *
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***************************/
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/* Encode a single protocol buffers message from C structure into a stream.
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* Returns true on success, false on any failure.
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* The actual struct pointed to by src_struct must match the description in fields.
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* All required fields in the struct are assumed to have been filled in.
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*
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* Example usage:
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* MyMessage msg = {};
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* uint8_t buffer[64];
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* pb_ostream_t stream;
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*
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* msg.field1 = 42;
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* stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
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* pb_encode(&stream, MyMessage_fields, &msg);
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*/
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bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
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/* Same as pb_encode, but prepends the length of the message as a varint.
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* Corresponds to writeDelimitedTo() in Google's protobuf API.
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*/
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bool pb_encode_delimited(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
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/* Encode the message to get the size of the encoded data, but do not store
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* the data. */
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bool pb_get_encoded_size(size_t *size, const pb_field_t fields[], const void *src_struct);
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/**************************************
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* Functions for manipulating streams *
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**************************************/
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/* Create an output stream for writing into a memory buffer.
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* The number of bytes written can be found in stream.bytes_written after
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* encoding the message.
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*
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* Alternatively, you can use a custom stream that writes directly to e.g.
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* a file or a network socket.
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*/
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pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize);
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/* Pseudo-stream for measuring the size of a message without actually storing
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* the encoded data.
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*
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* Example usage:
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* MyMessage msg = {};
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* pb_ostream_t stream = PB_OSTREAM_SIZING;
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* pb_encode(&stream, MyMessage_fields, &msg);
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* printf("Message size is %d\n", stream.bytes_written);
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*/
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#ifndef PB_NO_ERRMSG
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#define PB_OSTREAM_SIZING {0,0,0,0,0}
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#else
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#define PB_OSTREAM_SIZING {0,0,0,0}
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#endif
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/* Function to write into a pb_ostream_t stream. You can use this if you need
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* to append or prepend some custom headers to the message.
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*/
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bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
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/************************************************
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* Helper functions for writing field callbacks *
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************************************************/
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/* Encode field header based on type and field number defined in the field
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* structure. Call this from the callback before writing out field contents. */
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bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field);
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/* Encode field header by manually specifing wire type. You need to use this
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* if you want to write out packed arrays from a callback field. */
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bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
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/* Encode an integer in the varint format.
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* This works for bool, enum, int32, int64, uint32 and uint64 field types. */
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bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
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/* Encode an integer in the zig-zagged svarint format.
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* This works for sint32 and sint64. */
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bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
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/* Encode a string or bytes type field. For strings, pass strlen(s) as size. */
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bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size);
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/* Encode a fixed32, sfixed32 or float value.
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* You need to pass a pointer to a 4-byte wide C variable. */
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bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
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/* Encode a fixed64, sfixed64 or double value.
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* You need to pass a pointer to a 8-byte wide C variable. */
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bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
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/* Encode a submessage field.
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* You need to pass the pb_field_t array and pointer to struct, just like
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* with pb_encode(). This internally encodes the submessage twice, first to
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* calculate message size and then to actually write it out.
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*/
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bool pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
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#ifdef __cplusplus
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} /* extern "C" */
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#endif
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#endif
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