pb_decode.h

00001 /* pb_decode.h: Functions to decode protocol buffers. Depends on pb_decode.c.
00002  * The main function is pb_decode. You also need an input stream, and the
00003  * field descriptions created by nanopb_generator.py.
00004  */
00005 
00006 #ifndef _PB_DECODE_H_
00007 #define _PB_DECODE_H_
00008 
00009 #include "pb.h"
00010 
00011 #ifdef __cplusplus
00012 extern "C" {
00013 #endif
00014 
00015 /* Structure for defining custom input streams. You will need to provide
00016  * a callback function to read the bytes from your storage, which can be
00017  * for example a file or a network socket.
00018  * 
00019  * The callback must conform to these rules:
00020  *
00021  * 1) Return false on IO errors. This will cause decoding to abort.
00022  * 2) You can use state to store your own data (e.g. buffer pointer),
00023  *    and rely on pb_read to verify that no-body reads past bytes_left.
00024  * 3) Your callback may be used with substreams, in which case bytes_left
00025  *    is different than from the main stream. Don't use bytes_left to compute
00026  *    any pointers.
00027  */
00028 struct _pb_istream_t
00029 {
00030 #ifdef PB_BUFFER_ONLY
00031     /* Callback pointer is not used in buffer-only configuration.
00032      * Having an int pointer here allows binary compatibility but
00033      * gives an error if someone tries to assign callback function.
00034      */
00035     int *callback;
00036 #else
00037     bool (*callback)(pb_istream_t *stream, uint8_t *buf, size_t count);
00038 #endif
00039 
00040     void *state; /* Free field for use by callback implementation */
00041     size_t bytes_left;
00042     
00043 #ifndef PB_NO_ERRMSG
00044     const char *errmsg;
00045 #endif
00046 };
00047 
00048 /***************************
00049  * Main decoding functions *
00050  ***************************/
00051  
00052 /* Decode a single protocol buffers message from input stream into a C structure.
00053  * Returns true on success, false on any failure.
00054  * The actual struct pointed to by dest must match the description in fields.
00055  * Callback fields of the destination structure must be initialized by caller.
00056  * All other fields will be initialized by this function.
00057  *
00058  * Example usage:
00059  *    MyMessage msg = {};
00060  *    uint8_t buffer[64];
00061  *    pb_istream_t stream;
00062  *    
00063  *    // ... read some data into buffer ...
00064  *
00065  *    stream = pb_istream_from_buffer(buffer, count);
00066  *    pb_decode(&stream, MyMessage_fields, &msg);
00067  */
00068 bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
00069 
00070 /* Same as pb_decode, except does not initialize the destination structure
00071  * to default values. This is slightly faster if you need no default values
00072  * and just do memset(struct, 0, sizeof(struct)) yourself.
00073  *
00074  * This can also be used for 'merging' two messages, i.e. update only the
00075  * fields that exist in the new message.
00076  */
00077 bool pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
00078 
00079 /* Same as pb_decode, except expects the stream to start with the message size
00080  * encoded as varint. Corresponds to parseDelimitedFrom() in Google's
00081  * protobuf API.
00082  */
00083 bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
00084 
00085 
00086 /**************************************
00087  * Functions for manipulating streams *
00088  **************************************/
00089 
00090 /* Create an input stream for reading from a memory buffer.
00091  *
00092  * Alternatively, you can use a custom stream that reads directly from e.g.
00093  * a file or a network socket.
00094  */
00095 pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize);
00096 
00097 /* Function to read from a pb_istream_t. You can use this if you need to
00098  * read some custom header data, or to read data in field callbacks.
00099  */
00100 bool pb_read(pb_istream_t *stream, uint8_t *buf, size_t count);
00101 
00102 
00103 /************************************************
00104  * Helper functions for writing field callbacks *
00105  ************************************************/
00106 
00107 /* Decode the tag for the next field in the stream. Gives the wire type and
00108  * field tag. At end of the message, returns false and sets eof to true. */
00109 bool pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof);
00110 
00111 /* Skip the field payload data, given the wire type. */
00112 bool pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type);
00113 
00114 /* Decode an integer in the varint format. This works for bool, enum, int32,
00115  * int64, uint32 and uint64 field types. */
00116 bool pb_decode_varint(pb_istream_t *stream, uint64_t *dest);
00117 
00118 /* Decode an integer in the zig-zagged svarint format. This works for sint32
00119  * and sint64. */
00120 bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest);
00121 
00122 /* Decode a fixed32, sfixed32 or float value. You need to pass a pointer to
00123  * a 4-byte wide C variable. */
00124 bool pb_decode_fixed32(pb_istream_t *stream, void *dest);
00125 
00126 /* Decode a fixed64, sfixed64 or double value. You need to pass a pointer to
00127  * a 8-byte wide C variable. */
00128 bool pb_decode_fixed64(pb_istream_t *stream, void *dest);
00129 
00130 /* Make a limited-length substream for reading a PB_WT_STRING field. */
00131 bool pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream);
00132 void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream);
00133 
00134 #ifdef __cplusplus
00135 } /* extern "C" */
00136 #endif
00137 
00138 #endif
00139