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