pb_encode.h 6.8 KB

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  1. /* pb_encode.h: Functions to encode protocol buffers. Depends on pb_encode.c.
  2. * The main function is pb_encode. You also need an output stream, and the
  3. * field descriptions created by nanopb_generator.py.
  4. */
  5. #ifndef PB_ENCODE_H_INCLUDED
  6. #define PB_ENCODE_H_INCLUDED
  7. #include "pb.h"
  8. #ifdef __cplusplus
  9. extern "C" {
  10. #endif
  11. /* Structure for defining custom output streams. You will need to provide
  12. * a callback function to write the bytes to your storage, which can be
  13. * for example a file or a network socket.
  14. *
  15. * The callback must conform to these rules:
  16. *
  17. * 1) Return false on IO errors. This will cause encoding to abort.
  18. * 2) You can use state to store your own data (e.g. buffer pointer).
  19. * 3) pb_write will update bytes_written after your callback runs.
  20. * 4) Substreams will modify max_size and bytes_written. Don't use them
  21. * to calculate any pointers.
  22. */
  23. struct pb_ostream_s
  24. {
  25. #ifdef PB_BUFFER_ONLY
  26. /* Callback pointer is not used in buffer-only configuration.
  27. * Having an int pointer here allows binary compatibility but
  28. * gives an error if someone tries to assign callback function.
  29. * Also, NULL pointer marks a 'sizing stream' that does not
  30. * write anything.
  31. */
  32. const int *callback;
  33. #else
  34. bool (*callback)(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
  35. #endif
  36. void *state; /* Free field for use by callback implementation. */
  37. size_t max_size; /* Limit number of output bytes written (or use SIZE_MAX). */
  38. size_t bytes_written; /* Number of bytes written so far. */
  39. #ifndef PB_NO_ERRMSG
  40. const char *errmsg;
  41. #endif
  42. };
  43. /***************************
  44. * Main encoding functions *
  45. ***************************/
  46. /* Encode a single protocol buffers message from C structure into a stream.
  47. * Returns true on success, false on any failure.
  48. * The actual struct pointed to by src_struct must match the description in fields.
  49. * All required fields in the struct are assumed to have been filled in.
  50. *
  51. * Example usage:
  52. * MyMessage msg = {};
  53. * uint8_t buffer[64];
  54. * pb_ostream_t stream;
  55. *
  56. * msg.field1 = 42;
  57. * stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
  58. * pb_encode(&stream, MyMessage_fields, &msg);
  59. */
  60. bool pb_encode(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct);
  61. /* Extended version of pb_encode, with several options to control the
  62. * encoding process:
  63. *
  64. * PB_ENCODE_DELIMITED: Prepend the length of message as a varint.
  65. * Corresponds to writeDelimitedTo() in Google's
  66. * protobuf API.
  67. *
  68. * PB_ENCODE_NULLTERMINATED: Append a null byte to the message for termination.
  69. * NOTE: This behaviour is not supported in most other
  70. * protobuf implementations, so PB_ENCODE_DELIMITED
  71. * is a better option for compatibility.
  72. */
  73. #define PB_ENCODE_DELIMITED 0x02U
  74. #define PB_ENCODE_NULLTERMINATED 0x04U
  75. bool pb_encode_ex(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct, unsigned int flags);
  76. /* Defines for backwards compatibility with code written before nanopb-0.4.0 */
  77. #define pb_encode_delimited(s,f,d) pb_encode_ex(s,f,d, PB_ENCODE_DELIMITED)
  78. #define pb_encode_nullterminated(s,f,d) pb_encode_ex(s,f,d, PB_ENCODE_NULLTERMINATED)
  79. /* Encode the message to get the size of the encoded data, but do not store
  80. * the data. */
  81. bool pb_get_encoded_size(size_t *size, const pb_msgdesc_t *fields, const void *src_struct);
  82. /**************************************
  83. * Functions for manipulating streams *
  84. **************************************/
  85. /* Create an output stream for writing into a memory buffer.
  86. * The number of bytes written can be found in stream.bytes_written after
  87. * encoding the message.
  88. *
  89. * Alternatively, you can use a custom stream that writes directly to e.g.
  90. * a file or a network socket.
  91. */
  92. pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize);
  93. /* Pseudo-stream for measuring the size of a message without actually storing
  94. * the encoded data.
  95. *
  96. * Example usage:
  97. * MyMessage msg = {};
  98. * pb_ostream_t stream = PB_OSTREAM_SIZING;
  99. * pb_encode(&stream, MyMessage_fields, &msg);
  100. * printf("Message size is %d\n", stream.bytes_written);
  101. */
  102. #ifndef PB_NO_ERRMSG
  103. #define PB_OSTREAM_SIZING {0,0,0,0,0}
  104. #else
  105. #define PB_OSTREAM_SIZING {0,0,0,0}
  106. #endif
  107. /* Function to write into a pb_ostream_t stream. You can use this if you need
  108. * to append or prepend some custom headers to the message.
  109. */
  110. bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
  111. /************************************************
  112. * Helper functions for writing field callbacks *
  113. ************************************************/
  114. /* Encode field header based on type and field number defined in the field
  115. * structure. Call this from the callback before writing out field contents. */
  116. bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_iter_t *field);
  117. /* Encode field header by manually specifying wire type. You need to use this
  118. * if you want to write out packed arrays from a callback field. */
  119. bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
  120. /* Encode an integer in the varint format.
  121. * This works for bool, enum, int32, int64, uint32 and uint64 field types. */
  122. #ifndef PB_WITHOUT_64BIT
  123. bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
  124. #else
  125. bool pb_encode_varint(pb_ostream_t *stream, uint32_t value);
  126. #endif
  127. /* Encode an integer in the zig-zagged svarint format.
  128. * This works for sint32 and sint64. */
  129. #ifndef PB_WITHOUT_64BIT
  130. bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
  131. #else
  132. bool pb_encode_svarint(pb_ostream_t *stream, int32_t value);
  133. #endif
  134. /* Encode a string or bytes type field. For strings, pass strlen(s) as size. */
  135. bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size);
  136. /* Encode a fixed32, sfixed32 or float value.
  137. * You need to pass a pointer to a 4-byte wide C variable. */
  138. bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
  139. #ifndef PB_WITHOUT_64BIT
  140. /* Encode a fixed64, sfixed64 or double value.
  141. * You need to pass a pointer to a 8-byte wide C variable. */
  142. bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
  143. #endif
  144. #ifdef PB_CONVERT_DOUBLE_FLOAT
  145. /* Encode a float value so that it appears like a double in the encoded
  146. * message. */
  147. bool pb_encode_float_as_double(pb_ostream_t *stream, float value);
  148. #endif
  149. /* Encode a submessage field.
  150. * You need to pass the pb_field_t array and pointer to struct, just like
  151. * with pb_encode(). This internally encodes the submessage twice, first to
  152. * calculate message size and then to actually write it out.
  153. */
  154. bool pb_encode_submessage(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct);
  155. #ifdef __cplusplus
  156. } /* extern "C" */
  157. #endif
  158. #endif