暫無描述

pb_encode.h 6.1KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170
  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. 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_field_t fields[], const void *src_struct);
  61. /* Same as pb_encode, but prepends the length of the message as a varint.
  62. * Corresponds to writeDelimitedTo() in Google's protobuf API.
  63. */
  64. bool pb_encode_delimited(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
  65. /* Same as pb_encode, but appends a null byte to the message for termination.
  66. * NOTE: This behaviour is not supported in most other protobuf implementations, so pb_encode_delimited()
  67. * is a better option for compatibility.
  68. */
  69. bool pb_encode_nullterminated(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
  70. /* Encode the message to get the size of the encoded data, but do not store
  71. * the data. */
  72. bool pb_get_encoded_size(size_t *size, const pb_field_t fields[], const void *src_struct);
  73. /**************************************
  74. * Functions for manipulating streams *
  75. **************************************/
  76. /* Create an output stream for writing into a memory buffer.
  77. * The number of bytes written can be found in stream.bytes_written after
  78. * encoding the message.
  79. *
  80. * Alternatively, you can use a custom stream that writes directly to e.g.
  81. * a file or a network socket.
  82. */
  83. pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize);
  84. /* Pseudo-stream for measuring the size of a message without actually storing
  85. * the encoded data.
  86. *
  87. * Example usage:
  88. * MyMessage msg = {};
  89. * pb_ostream_t stream = PB_OSTREAM_SIZING;
  90. * pb_encode(&stream, MyMessage_fields, &msg);
  91. * printf("Message size is %d\n", stream.bytes_written);
  92. */
  93. #ifndef PB_NO_ERRMSG
  94. #define PB_OSTREAM_SIZING {0,0,0,0,0}
  95. #else
  96. #define PB_OSTREAM_SIZING {0,0,0,0}
  97. #endif
  98. /* Function to write into a pb_ostream_t stream. You can use this if you need
  99. * to append or prepend some custom headers to the message.
  100. */
  101. bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
  102. /************************************************
  103. * Helper functions for writing field callbacks *
  104. ************************************************/
  105. /* Encode field header based on type and field number defined in the field
  106. * structure. Call this from the callback before writing out field contents. */
  107. bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field);
  108. /* Encode field header by manually specifing wire type. You need to use this
  109. * if you want to write out packed arrays from a callback field. */
  110. bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
  111. /* Encode an integer in the varint format.
  112. * This works for bool, enum, int32, int64, uint32 and uint64 field types. */
  113. #ifndef PB_WITHOUT_64BIT
  114. bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
  115. #else
  116. bool pb_encode_varint(pb_ostream_t *stream, uint32_t value);
  117. #endif
  118. /* Encode an integer in the zig-zagged svarint format.
  119. * This works for sint32 and sint64. */
  120. #ifndef PB_WITHOUT_64BIT
  121. bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
  122. #else
  123. bool pb_encode_svarint(pb_ostream_t *stream, int32_t value);
  124. #endif
  125. /* Encode a string or bytes type field. For strings, pass strlen(s) as size. */
  126. bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size);
  127. /* Encode a fixed32, sfixed32 or float value.
  128. * You need to pass a pointer to a 4-byte wide C variable. */
  129. bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
  130. #ifndef PB_WITHOUT_64BIT
  131. /* Encode a fixed64, sfixed64 or double value.
  132. * You need to pass a pointer to a 8-byte wide C variable. */
  133. bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
  134. #endif
  135. /* Encode a submessage field.
  136. * You need to pass the pb_field_t array and pointer to struct, just like
  137. * with pb_encode(). This internally encodes the submessage twice, first to
  138. * calculate message size and then to actually write it out.
  139. */
  140. bool pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
  141. #ifdef __cplusplus
  142. } /* extern "C" */
  143. #endif
  144. #endif