diff options
Diffstat (limited to 'pb_encode.h')
| -rw-r--r-- | pb_encode.h | 130 |
1 files changed, 82 insertions, 48 deletions
diff --git a/pb_encode.h b/pb_encode.h index 773b7178..d9e0336a 100644 --- a/pb_encode.h +++ b/pb_encode.h @@ -1,33 +1,82 @@ -#ifndef _PB_ENCODE_H_ -#define _PB_ENCODE_H_ - /* 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, structures - * and their field descriptions (just like with pb_decode). + * 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_ +#define _PB_ENCODE_H_ + #include "pb.h" #ifdef __cplusplus extern "C" { #endif -/* Lightweight output stream. - * You can provide callback for writing or use pb_ostream_from_buffer. +/*************************** + * 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); + + +/************************************** + * 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. * - * Alternatively, callback can be NULL in which case the stream will just - * count the number of bytes that would have been written. In this case - * max_size is not checked. + * 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); + +/* 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: * - * Rules for callback: * 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. + * 4) Substreams will modify max_size and bytes_written. Don't use them + * to calculate any pointers. */ struct _pb_ostream_t { @@ -42,42 +91,26 @@ struct _pb_ostream_t #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; + 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 }; -pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize); -bool pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count); - -/* Stream type for use in computing message sizes */ -#ifndef PB_NO_ERRMSG -#define PB_OSTREAM_SIZING {0,0,0,0,0} -#else -#define PB_OSTREAM_SIZING {0,0,0,0} -#endif - -/* Encode struct to given output 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. - */ -bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct); -/* --- Helper functions --- - * You may want to use these from your caller or callbacks. - */ +/************************************************ + * Helper functions for writing field callbacks * + ************************************************/ -/* Encode field header based on LTYPE and field number defined in the field structure. - * Call this from the callback before writing out field contents. */ +/* 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. */ +/* 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. @@ -100,15 +133,16 @@ bool pb_encode_fixed32(pb_ostream_t *stream, const void *value); 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. + * 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); -/* --- Internal functions --- - * These functions are not terribly useful for the average library user, but - * are exported to make the unit testing and extending nanopb easier. - */ + +/******************************* + * Internal / legacy functions * + *******************************/ #ifdef NANOPB_INTERNALS bool pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src); |