pb_decode.h

#ifndef _PB_DECODE_H_
#define _PB_DECODE_H_

/* pb_decode.h: Functions to decode protocol buffers. Depends on pb_decode.c.
 * The main function is pb_decode. You will also need to create an input
 * stream, which is easiest to do with pb_istream_from_buffer().
 * 
 * You also need structures and their corresponding pb_field_t descriptions.
 * These are usually generated from .proto-files with a script.
 */

#include <stdbool.h>
#include "pb.h"

/* Lightweight input stream.
 * You can provide a callback function for reading or use
 * pb_istream_from_buffer.
 * 
 * Rules for callback:
 * 1) Return false on IO errors. This will cause decoding to abort.
 * 
 * 2) If buf is NULL, read but don't store bytes ("skip input").
 * 
 * 3) You can use state to store your own data (e.g. buffer pointer),
 * and rely on pb_read to verify that no-body reads past bytes_left.
 * 
 * 4) Your callback may be used with substreams, in which case bytes_left
 * is different than from the main stream. Don't use bytes_left to compute
 * any pointers.
 */
struct _pb_istream_t
{
    bool (*callback)(pb_istream_t *stream, uint8_t *buf, size_t count);
    void *state; /* Free field for use by callback implementation */
    size_t bytes_left;
    
#ifndef PB_NO_ERRMSG
    const char *errmsg;
#endif
};

pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize);
bool pb_read(pb_istream_t *stream, uint8_t *buf, size_t count);

/* Decode from stream to destination struct.
 * Returns true on success, false on any failure.
 * The actual struct pointed to by dest must match the description in fields.
 */
bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);

/* Same as pb_decode, except does not initialize the destination structure
 * to default values. This is slightly faster if you need no default values
 * and just do memset(struct, 0, sizeof(struct)) yourself.
 */
bool pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);

/* --- Helper functions ---
 * You may want to use these from your caller or callbacks.
 */

/* Decode the tag for the next field in the stream. Gives the wire type and
 * field tag. At end of the message, returns false and sets eof to true. */
bool pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof);

/* Skip the field payload data, given the wire type. */
bool pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type);

/* Decode an integer in the varint format. This works for bool, enum, int32,
 * int64, uint32 and uint64 field types. */
bool pb_decode_varint(pb_istream_t *stream, uint64_t *dest);

/* Decode an integer in the zig-zagged svarint format. This works for sint32
 * and sint64. */
bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest);

/* Decode a fixed32, sfixed32 or float value. You need to pass a pointer to
 * a 4-byte wide C variable. */
bool pb_decode_fixed32(pb_istream_t *stream, void *dest);

/* Decode a fixed64, sfixed64 or double value. You need to pass a pointer to
 * a 8-byte wide C variable. */
bool pb_decode_fixed64(pb_istream_t *stream, void *dest);

/* Make a limited-length substream for reading a PB_WT_STRING field. */
bool pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream);
void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream);

/* --- 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.
 */

#ifdef NANOPB_INTERNALS
bool pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest);
bool pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest);
bool pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest);
bool pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest);

bool pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest);
bool pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest);
bool pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest);

bool pb_skip_varint(pb_istream_t *stream);
bool pb_skip_string(pb_istream_t *stream);
#endif

#endif