text: /* pb_decode.c -- decode a protobuf using minimal resources
   *
   * 2011 Petteri Aimonen <jpa@kapsi.fi>
   */
  
  /* Use the GCC warn_unused_result attribute to check that all return values
   * are propagated correctly. On other compilers and gcc before 3.4.0 just
   * ignore the annotation.
   */
  #if !defined(__GNUC__) || ( __GNUC__ < 3) || (__GNUC__ == 3 && __GNUC_MINOR__ < 4)
      #define checkreturn
  #else
      #define checkreturn __attribute__((warn_unused_result))
  #endif
  
  #include "pb.h"
  #include "pb_decode.h"
  #include "pb_common.h"
  
  /**************************************
   * Declarations internal to this file *
   **************************************/
  
  typedef bool (*pb_decoder_t)(pb_istream_t *stream, const pb_field_t *field, void *dest) checkreturn;
  
  static bool checkreturn buf_read(pb_istream_t *stream, uint8_t *buf, size_t count);
  static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest);
  static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size);
  static bool checkreturn decode_static_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter);
  static bool checkreturn decode_callback_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter);
  static bool checkreturn decode_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter);
  static bool checkreturn default_extension_decoder(pb_istream_t *stream, pb_extension_t *extension, uint32_t tag, pb_wire_type_t wire_type);
  static bool checkreturn decode_extension(pb_istream_t *stream, uint32_t tag, pb_wire_type_t wire_type, pb_field_iter_t *iter);
  static bool checkreturn find_extension_field(pb_field_iter_t *iter);
  static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct);
  static bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest);
  static bool checkreturn pb_dec_uvarint(pb_istream_t *stream, const pb_field_t *field, void *dest);
  static bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest);
  static bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest);
  static bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest);
  static bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest);
  static bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest);
  static bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest);
  static bool checkreturn pb_skip_varint(pb_istream_t *stream);
  static bool checkreturn pb_skip_string(pb_istream_t *stream);
  
  #ifdef PB_ENABLE_MALLOC
  static bool checkreturn allocate_field(pb_istream_t *stream, void *pData, size_t data_size, size_t array_size);
  static void pb_release_single_field(const pb_field_iter_t *iter);
  #endif
  
  /* --- Function pointers to field decoders ---
   * Order in the array must match pb_action_t LTYPE numbering.
   */
  static const pb_decoder_t PB_DECODERS[PB_LTYPES_COUNT] = {
      &pb_dec_varint,
      &pb_dec_uvarint,
      &pb_dec_svarint,
      &pb_dec_fixed32,
      &pb_dec_fixed64,
      
      &pb_dec_bytes,
      &pb_dec_string,
      &pb_dec_submessage,
      NULL /* extensions */
  };
  
  /*******************************
   * pb_istream_t implementation *
   *******************************/
  
  static bool checkreturn buf_read(pb_istream_t *stream, uint8_t *buf, size_t count)
  {
      uint8_t *source = (uint8_t*)stream->state;
      stream->state = source + count;
      
      if (buf != NULL)
      {
          while (count--)
              *buf++ = *source++;
      }
      
      return true;
  }
  
  bool checkreturn pb_read(pb_istream_t *stream, uint8_t *buf, size_t count)
  {
  #ifndef PB_BUFFER_ONLY
  	if (buf == NULL && stream->callback != buf_read)
  	{
  		/* Skip input bytes */
  		uint8_t tmp[16];
  		while (count > 16)
  		{
  			if (!pb_read(stream, tmp, 16))
  				return false;
  			
  			count -= 16;
  		}
  		
  		return pb_read(stream, tmp, count);
  	}
  #endif
  
      if (stream->bytes_left < count)
          PB_RETURN_ERROR(stream, "end-of-stream");
      
  #ifndef PB_BUFFER_ONLY
      if (!stream->callback(stream, buf, count))
          PB_RETURN_ERROR(stream, "io error");
  #else
      if (!buf_read(stream, buf, count))
          return false;
  #endif
      
      stream->bytes_left -= count;
      return true;
  }
  
  /* Read a single byte from input stream. buf may not be NULL.
   * This is an optimization for the varint decoding. */
  static bool checkreturn pb_readbyte(pb_istream_t *stream, uint8_t *buf)
  {
      if (stream->bytes_left == 0)
          PB_RETURN_ERROR(stream, "end-of-stream");
  
  #ifndef PB_BUFFER_ONLY
      if (!stream->callback(stream, buf, 1))
          PB_RETURN_ERROR(stream, "io error");
  #else
      *buf = *(uint8_t*)stream->state;
      stream->state = (uint8_t*)stream->state + 1;
  #endif
  
      stream->bytes_left--;
      
      return true;    
  }
  
  pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
  {
      pb_istream_t stream;
  #ifdef PB_BUFFER_ONLY
      stream.callback = NULL;
  #else
      stream.callback = &buf_read;
  #endif
      stream.state = buf;
      stream.bytes_left = bufsize;
  #ifndef PB_NO_ERRMSG
      stream.errmsg = NULL;
  #endif
      return stream;
  }
  
  /********************
   * Helper functions *
   ********************/
  
  static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
  {
      uint8_t byte;
      uint32_t result;
      
      if (!pb_readbyte(stream, &byte))
          return false;
      
      if ((byte & 0x80) == 0)
      {
          /* Quick case, 1 byte value */
          result = byte;
      }
      else
      {
          /* Multibyte case */
          uint8_t bitpos = 7;
          result = byte & 0x7F;
          
          do
          {
              if (bitpos >= 32)
                  PB_RETURN_ERROR(stream, "varint overflow");
              
              if (!pb_readbyte(stream, &byte))
                  return false;
              
              result |= (uint32_t)(byte & 0x7F) << bitpos;
              bitpos = (uint8_t)(bitpos + 7);
          } while (byte & 0x80);
     }
     
     *dest = result;
     return true;
  }
  
  bool checkreturn pb_decode_varint(pb_istream_t *stream, uint64_t *dest)
  {
      uint8_t byte;
      uint8_t bitpos = 0;
      uint64_t result = 0;
      
      do
      {
          if (bitpos >= 64)
              PB_RETURN_ERROR(stream, "varint overflow");
          
          if (!pb_readbyte(stream, &byte))
              return false;
  
          result |= (uint64_t)(byte & 0x7F) << bitpos;
          bitpos = (uint8_t)(bitpos + 7);
      } while (byte & 0x80);
      
      *dest = result;
      return true;
  }
  
  bool checkreturn pb_skip_varint(pb_istream_t *stream)
  {
      uint8_t byte;
      do
      {
          if (!pb_read(stream, &byte, 1))
              return false;
      } while (byte & 0x80);
      return true;
  }
  
  bool checkreturn pb_skip_string(pb_istream_t *stream)
  {
      uint32_t length;
      if (!pb_decode_varint32(stream, &length))
          return false;
      
      return pb_read(stream, NULL, length);
  }
  
  bool checkreturn pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof)
  {
      uint32_t temp;
      *eof = false;
      *wire_type = (pb_wire_type_t) 0;
      *tag = 0;
      
      if (!pb_decode_varint32(stream, &temp))
      {
          if (stream->bytes_left == 0)
              *eof = true;
  
          return false;
      }
      
      if (temp == 0)
      {
          *eof = true; /* Special feature: allow 0-terminated messages. */
          return false;
      }
      
      *tag = temp >> 3;
      *wire_type = (pb_wire_type_t)(temp & 7);
      return true;
  }
  
  bool checkreturn pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type)
  {
      switch (wire_type)
      {
          case PB_WT_VARINT: return pb_skip_varint(stream);
          case PB_WT_64BIT: return pb_read(stream, NULL, 8);
          case PB_WT_STRING: return pb_skip_string(stream);
          case PB_WT_32BIT: return pb_read(stream, NULL, 4);
          default: PB_RETURN_ERROR(stream, "invalid wire_type");
      }
  }
  
  /* Read a raw value to buffer, for the purpose of passing it to callback as
   * a substream. Size is maximum size on call, and actual size on return.
   */
  static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size)
  {
      size_t max_size = *size;
      switch (wire_type)
      {
          case PB_WT_VARINT:
              *size = 0;
              do
              {
                  (*size)++;
                  if (*size > max_size) return false;
                  if (!pb_read(stream, buf, 1)) return false;
              } while (*buf++ & 0x80);
              return true;
              
          case PB_WT_64BIT:
              *size = 8;
              return pb_read(stream, buf, 8);
          
          case PB_WT_32BIT:
              *size = 4;
              return pb_read(stream, buf, 4);
          
          default: PB_RETURN_ERROR(stream, "invalid wire_type");
      }
  }
  
  /* Decode string length from stream and return a substream with limited length.
   * Remember to close the substream using pb_close_string_substream().
   */
  bool checkreturn pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
  {
      uint32_t size;
      if (!pb_decode_varint32(stream, &size))
          return false;
      
      *substream = *stream;
      if (substream->bytes_left < size)
          PB_RETURN_ERROR(stream, "parent stream too short");
      
      substream->bytes_left = size;
      stream->bytes_left -= size;
      return true;
  }
  
  void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream)
  {
      stream->state = substream->state;
  
  #ifndef PB_NO_ERRMSG
      stream->errmsg = substream->errmsg;
  #endif
  }
  
  /*************************
   * Decode a single field *
   *************************/
  
  static bool checkreturn decode_static_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter)
  {
      pb_type_t type;
      pb_decoder_t func;
      
      type = iter->pos->type;
      func = PB_DECODERS[PB_LTYPE(type)];
  
      switch (PB_HTYPE(type))
      {
          case PB_HTYPE_REQUIRED:
              return func(stream, iter->pos, iter->pData);
              
          case PB_HTYPE_OPTIONAL:
              *(bool*)iter->pSize = true;
              return func(stream, iter->pos, iter->pData);
      
          case PB_HTYPE_REPEATED:
              if (wire_type == PB_WT_STRING
                  && PB_LTYPE(type) <= PB_LTYPE_LAST_PACKABLE)
              {
                  /* Packed array */
                  bool status = true;
                  pb_size_t *size = (pb_size_t*)iter->pSize;
                  pb_istream_t substream;
                  if (!pb_make_string_substream(stream, &substream))
                      return false;
                  
                  while (substream.bytes_left > 0 && *size < iter->pos->array_size)
                  {
                      void *pItem = (uint8_t*)iter->pData + iter->pos->data_size * (*size);
                      if (!func(&substream, iter->pos, pItem))
                      {
                          status = false;
                          break;
                      }
                      (*size)++;
                  }
                  pb_close_string_substream(stream, &substream);
                  
                  if (substream.bytes_left != 0)
                      PB_RETURN_ERROR(stream, "array overflow");
                  
                  return status;
              }
              else
              {
                  /* Repeated field */
                  pb_size_t *size = (pb_size_t*)iter->pSize;
                  void *pItem = (uint8_t*)iter->pData + iter->pos->data_size * (*size);
                  if (*size >= iter->pos->array_size)
                      PB_RETURN_ERROR(stream, "array overflow");
                  
                  (*size)++;
                  return func(stream, iter->pos, pItem);
              }
  
          default:
              PB_RETURN_ERROR(stream, "invalid field type");
      }
  }
  
  #ifdef PB_ENABLE_MALLOC
  /* Allocate storage for the field and store the pointer at iter->pData.
   * array_size is the number of entries to reserve in an array.
   * Zero size is not allowed, use pb_free() for releasing.
   */
  static bool checkreturn allocate_field(pb_istream_t *stream, void *pData, size_t data_size, size_t array_size)
  {    
      void *ptr = *(void**)pData;
      
      if (data_size == 0 || array_size == 0)
          PB_RETURN_ERROR(stream, "invalid size");
      
      /* Check for multiplication overflows.
       * This code avoids the costly division if the sizes are small enough.
       * Multiplication is safe as long as only half of bits are set
       * in either multiplicand.
       */
      {
          const size_t check_limit = (size_t)1 << (sizeof(size_t) * 4);
          if (data_size >= check_limit || array_size >= check_limit)
          {
              const size_t size_max = (size_t)-1;
              if (size_max / array_size < data_size)
              {
                  PB_RETURN_ERROR(stream, "size too large");
              }
          }
      }
      
      /* Allocate new or expand previous allocation */
      /* Note: on failure the old pointer will remain in the structure,
       * the message must be freed by caller also on error return. */
      ptr = pb_realloc(ptr, array_size * data_size);
      if (ptr == NULL)
          PB_RETURN_ERROR(stream, "realloc failed");
      
      *(void**)pData = ptr;
      return true;
  }
  
  /* Clear a newly allocated item in case it contains a pointer, or is a submessage. */
  static void initialize_pointer_field(void *pItem, pb_field_iter_t *iter)
  {
      if (PB_LTYPE(iter->pos->type) == PB_LTYPE_STRING ||
          PB_LTYPE(iter->pos->type) == PB_LTYPE_BYTES)
      {
          *(void**)pItem = NULL;
      }
      else if (PB_LTYPE(iter->pos->type) == PB_LTYPE_SUBMESSAGE)
      {
          pb_message_set_to_defaults((const pb_field_t *) iter->pos->ptr, pItem);
      }
  }
  #endif
  
  static bool checkreturn decode_pointer_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter)
  {
  #ifndef PB_ENABLE_MALLOC
      PB_UNUSED(wire_type);
      PB_UNUSED(iter);
      PB_RETURN_ERROR(stream, "no malloc support");
  #else
      pb_type_t type;
      pb_decoder_t func;
      
      type = iter->pos->type;
      func = PB_DECODERS[PB_LTYPE(type)];
      
      switch (PB_HTYPE(type))
      {
          case PB_HTYPE_REQUIRED:
          case PB_HTYPE_OPTIONAL:
              if (PB_LTYPE(type) == PB_LTYPE_SUBMESSAGE &&
                  *(void**)iter->pData != NULL)
              {
                  /* Duplicate field, have to release the old allocation first. */
                  pb_release_single_field(iter);
              }
          
              if (PB_LTYPE(type) == PB_LTYPE_STRING ||
                  PB_LTYPE(type) == PB_LTYPE_BYTES)
              {
                  return func(stream, iter->pos, iter->pData);
              }
              else
              {
                  if (!allocate_field(stream, iter->pData, iter->pos->data_size, 1))
                      return false;
                  
                  initialize_pointer_field(*(void**)iter->pData, iter);
                  return func(stream, iter->pos, *(void**)iter->pData);
              }
      
          case PB_HTYPE_REPEATED:
              if (wire_type == PB_WT_STRING
                  && PB_LTYPE(type) <= PB_LTYPE_LAST_PACKABLE)
              {
                  /* Packed array, multiple items come in at once. */
                  bool status = true;
                  pb_size_t *size = (pb_size_t*)iter->pSize;
                  size_t allocated_size = *size;
                  void *pItem;
                  pb_istream_t substream;
                  
                  if (!pb_make_string_substream(stream, &substream))
                      return false;
                  
                  while (substream.bytes_left)
                  {
                      if ((size_t)*size + 1 > allocated_size)
                      {
                          /* Allocate more storage. This tries to guess the
                           * number of remaining entries. Round the division
                           * upwards. */
                          allocated_size += (substream.bytes_left - 1) / iter->pos->data_size + 1;
                          
                          if (!allocate_field(&substream, iter->pData, iter->pos->data_size, allocated_size))
                          {
                              status = false;
                              break;
                          }
                      }
  
                      /* Decode the array entry */
                      pItem = *(uint8_t**)iter->pData + iter->pos->data_size * (*size);
                      initialize_pointer_field(pItem, iter);
                      if (!func(&substream, iter->pos, pItem))
                      {
                          status = false;
                          break;
                      }
                      
                      if (*size == PB_SIZE_MAX)
                      {
  #ifndef PB_NO_ERRMSG
                          stream->errmsg = "too many array entries";
  #endif
                          status = false;
                          break;
                      }
                      
                      (*size)++;
                  }
                  pb_close_string_substream(stream, &substream);
                  
                  return status;
              }
              else
              {
                  /* Normal repeated field, i.e. only one item at a time. */
                  pb_size_t *size = (pb_size_t*)iter->pSize;
                  void *pItem;
                  
                  if (*size == PB_SIZE_MAX)
                      PB_RETURN_ERROR(stream, "too many array entries");
                  
                  (*size)++;
                  if (!allocate_field(stream, iter->pData, iter->pos->data_size, *size))
                      return false;
              
                  pItem = *(uint8_t**)iter->pData + iter->pos->data_size * (*size - 1);
                  initialize_pointer_field(pItem, iter);
                  return func(stream, iter->pos, pItem);
              }
              
          default:
              PB_RETURN_ERROR(stream, "invalid field type");
      }
  #endif
  }
  
  static bool checkreturn decode_callback_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter)
  {
      pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
      
  #ifdef PB_OLD_CALLBACK_STYLE
      void *arg = pCallback->arg;
  #else
      void **arg = &(pCallback->arg);
  #endif
      
      if (pCallback->funcs.decode == NULL)
          return pb_skip_field(stream, wire_type);
      
      if (wire_type == PB_WT_STRING)
      {
          pb_istream_t substream;
          
          if (!pb_make_string_substream(stream, &substream))
              return false;
          
          do
          {
              if (!pCallback->funcs.decode(&substream, iter->pos, arg))
                  PB_RETURN_ERROR(stream, "callback failed");
          } while (substream.bytes_left);
          
          pb_close_string_substream(stream, &substream);
          return true;
      }
      else
      {
          /* Copy the single scalar value to stack.
           * This is required so that we can limit the stream length,
           * which in turn allows to use same callback for packed and
           * not-packed fields. */
          pb_istream_t substream;
          uint8_t buffer[10];
          size_t size = sizeof(buffer);
          
          if (!read_raw_value(stream, wire_type, buffer, &size))
              return false;
          substream = pb_istream_from_buffer(buffer, size);
          
          return pCallback->funcs.decode(&substream, iter->pos, arg);
      }
  }
  
  static bool checkreturn decode_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter)
  {
      switch (PB_ATYPE(iter->pos->type))
      {
          case PB_ATYPE_STATIC:
              return decode_static_field(stream, wire_type, iter);
          
          case PB_ATYPE_POINTER:
              return decode_pointer_field(stream, wire_type, iter);
          
          case PB_ATYPE_CALLBACK:
              return decode_callback_field(stream, wire_type, iter);
          
          default:
              PB_RETURN_ERROR(stream, "invalid field type");
      }
  }
  
  /* Default handler for extension fields. Expects a pb_field_t structure
   * in extension->type->arg. */
  static bool checkreturn default_extension_decoder(pb_istream_t *stream,
      pb_extension_t *extension, uint32_t tag, pb_wire_type_t wire_type)
  {
      const pb_field_t *field = (const pb_field_t*)extension->type->arg;
      pb_field_iter_t iter;
      
      if (field->tag != tag)
          return true;
      
      /* Fake a field iterator for the extension field.
       * It is not actually safe to advance this iterator, but decode_field
       * will not even try to. */
      (void)pb_field_iter_begin(&iter, field, extension->dest);
      iter.pData = extension->dest;
      iter.pSize = &extension->found;
      
      return decode_field(stream, wire_type, &iter);
  }
  
  /* Try to decode an unknown field as an extension field. Tries each extension
   * decoder in turn, until one of them handles the field or loop ends. */
  static bool checkreturn decode_extension(pb_istream_t *stream,
      uint32_t tag, pb_wire_type_t wire_type, pb_field_iter_t *iter)
  {
      pb_extension_t *extension = *(pb_extension_t* const *)iter->pData;
      size_t pos = stream->bytes_left;
      
      while (extension != NULL && pos == stream->bytes_left)
      {
          bool status;
          if (extension->type->decode)
              status = extension->type->decode(stream, extension, tag, wire_type);
          else
              status = default_extension_decoder(stream, extension, tag, wire_type);
  
          if (!status)
              return false;
          
          extension = extension->next;
      }
      
      return true;
  }
  
  /* Step through the iterator until an extension field is found or until all
   * entries have been checked. There can be only one extension field per
   * message. Returns false if no extension field is found. */
  static bool checkreturn find_extension_field(pb_field_iter_t *iter)
  {
      const pb_field_t *start = iter->pos;
      
      do {
          if (PB_LTYPE(iter->pos->type) == PB_LTYPE_EXTENSION)
              return true;
          (void)pb_field_iter_next(iter);
      } while (iter->pos != start);
      
      return false;
  }
  
  /* Initialize message fields to default values, recursively */
  static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct)
  {
      pb_field_iter_t iter;
  
      if (!pb_field_iter_begin(&iter, fields, dest_struct))
          return; /* Empty message type */
      
      do
      {
          pb_type_t type;
          type = iter.pos->type;
          
          if (PB_ATYPE(type) == PB_ATYPE_STATIC)
          {
              if (PB_HTYPE(type) == PB_HTYPE_OPTIONAL)
              {
                  /* Set has_field to false. Still initialize the optional field
                   * itself also. */
                  *(bool*)iter.pSize = false;
              }
              else if (PB_HTYPE(type) == PB_HTYPE_REPEATED)
              {
                  /* Set array count to 0, no need to initialize contents. */
                  *(pb_size_t*)iter.pSize = 0;
                  continue;
              }
              
              if (PB_LTYPE(iter.pos->type) == PB_LTYPE_SUBMESSAGE)
              {
                  /* Initialize submessage to defaults */
                  pb_message_set_to_defaults((const pb_field_t *) iter.pos->ptr, iter.pData);
              }
              else if (iter.pos->ptr != NULL)
              {
                  /* Initialize to default value */
                  memcpy(iter.pData, iter.pos->ptr, iter.pos->data_size);
              }
              else
              {
                  /* Initialize to zeros */
                  memset(iter.pData, 0, iter.pos->data_size);
              }
          }
          else if (PB_ATYPE(type) == PB_ATYPE_POINTER)
          {
              /* Initialize the pointer to NULL. */
              *(void**)iter.pData = NULL;
              
              /* Initialize array count to 0. */
              if (PB_HTYPE(type) == PB_HTYPE_REPEATED)
              {
                  *(pb_size_t*)iter.pSize = 0;
              }
          }
          else if (PB_ATYPE(type) == PB_ATYPE_CALLBACK)
          {
              /* Don't overwrite callback */
          }
      } while (pb_field_iter_next(&iter));
  }
  
  /*********************
   * Decode all fields *
   *********************/
  
  bool checkreturn pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
  {
      uint8_t fields_seen[(PB_MAX_REQUIRED_FIELDS + 7) / 8] = {0, 0, 0, 0, 0, 0, 0, 0};
      uint32_t extension_range_start = 0;
      pb_field_iter_t iter;
      
      /* Return value ignored, as empty message types will be correctly handled by
       * pb_field_iter_find() anyway. */
      (void)pb_field_iter_begin(&iter, fields, dest_struct);
      
      while (stream->bytes_left)
      {
          uint32_t tag;
          pb_wire_type_t wire_type;
          bool eof;
          
          if (!pb_decode_tag(stream, &wire_type, &tag, &eof))
          {
              if (eof)
                  break;
              else
                  return false;
          }
          
          if (!pb_field_iter_find(&iter, tag))
          {
              /* No match found, check if it matches an extension. */
              if (tag >= extension_range_start)
              {
                  if (!find_extension_field(&iter))
                      extension_range_start = (uint32_t)-1;
                  else
                      extension_range_start = iter.pos->tag;
                  
                  if (tag >= extension_range_start)
                  {
                      size_t pos = stream->bytes_left;
                  
                      if (!decode_extension(stream, tag, wire_type, &iter))
                          return false;
                      
                      if (pos != stream->bytes_left)
                      {
                          /* The field was handled */
                          continue;                    
                      }
                  }
              }
          
              /* No match found, skip data */
              if (!pb_skip_field(stream, wire_type))
                  return false;
              continue;
          }
          
          if (PB_HTYPE(iter.pos->type) == PB_HTYPE_REQUIRED
              && iter.required_field_index < PB_MAX_REQUIRED_FIELDS)
          {
              fields_seen[iter.required_field_index >> 3] |= (uint8_t)(1 << (iter.required_field_index & 7));
          }
              
          if (!decode_field(stream, wire_type, &iter))
              return false;
      }
      
      /* Check that all required fields were present. */
      {
          /* First figure out the number of required fields by
           * seeking to the end of the field array. Usually we
           * are already close to end after decoding.
           */
          unsigned req_field_count;
          pb_type_t last_type;
          unsigned i;
          do {
              req_field_count = iter.required_field_index;
              last_type = iter.pos->type;
          } while (pb_field_iter_next(&iter));
          
          /* Fixup if last field was also required. */
          if (PB_HTYPE(last_type) == PB_HTYPE_REQUIRED && iter.pos->tag != 0)
              req_field_count++;
          
          /* Check the whole bytes */
          for (i = 0; i < (req_field_count >> 3); i++)
          {
              if (fields_seen[i] != 0xFF)
                  PB_RETURN_ERROR(stream, "missing required field");
          }
          
          /* Check the remaining bits */
          if (fields_seen[req_field_count >> 3] != (0xFF >> (8 - (req_field_count & 7))))
              PB_RETURN_ERROR(stream, "missing required field");
      }
      
      return true;
  }
  
  bool checkreturn pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
  {
      bool status;
      pb_message_set_to_defaults(fields, dest_struct);
      status = pb_decode_noinit(stream, fields, dest_struct);
      
  #ifdef PB_ENABLE_MALLOC
      if (!status)
          pb_release(fields, dest_struct);
  #endif
      
      return status;
  }
  
  bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
  {
      pb_istream_t substream;
      bool status;
      
      if (!pb_make_string_substream(stream, &substream))
          return false;
      
      status = pb_decode(&substream, fields, dest_struct);
      pb_close_string_substream(stream, &substream);
      return status;
  }
  
  #ifdef PB_ENABLE_MALLOC
  static void pb_release_single_field(const pb_field_iter_t *iter)
  {
      pb_type_t type;
      type = iter->pos->type;
  
      if (PB_ATYPE(type) == PB_ATYPE_POINTER)
      {
          if (PB_HTYPE(type) == PB_HTYPE_REPEATED &&
              (PB_LTYPE(type) == PB_LTYPE_STRING ||
               PB_LTYPE(type) == PB_LTYPE_BYTES))
          {
              /* Release entries in repeated string or bytes array */
              void **pItem = *(void***)iter->pData;
              pb_size_t count = *(pb_size_t*)iter->pSize;
              while (count--)
              {
                  pb_free(*pItem);
                  *pItem++ = NULL;
              }
              *(pb_size_t*)iter->pSize = 0;
          }
          else if (PB_LTYPE(type) == PB_LTYPE_SUBMESSAGE)
          {
              /* Release fields in submessages */
              void *pItem = *(void**)iter->pData;
              if (pItem)
              {
                  pb_size_t count = 1;
                  
                  if (PB_HTYPE(type) == PB_HTYPE_REPEATED)
                  {
                      count = *(pb_size_t*)iter->pSize;
                      *(pb_size_t*)iter->pSize = 0;
                  }
                  
                  while (count--)
                  {
                      pb_release((const pb_field_t*)iter->pos->ptr, pItem);
                      pItem = (uint8_t*)pItem + iter->pos->data_size;
                  }
              }
          }
          
          /* Release main item */
          pb_free(*(void**)iter->pData);
          *(void**)iter->pData = NULL;
      }
  }
  
  void pb_release(const pb_field_t fields[], void *dest_struct)
  {
      pb_field_iter_t iter;
      
      if (!pb_field_iter_begin(&iter, fields, dest_struct))
          return; /* Empty message type */
      
      do
      {
          pb_release_single_field(&iter);
      } while (pb_field_iter_next(&iter));
  }
  #endif
  
  /* Field decoders */
  
  bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest)
  {
      uint64_t value;
      if (!pb_decode_varint(stream, &value))
          return false;
      
      if (value & 1)
          *dest = (int64_t)(~(value >> 1));
      else
          *dest = (int64_t)(value >> 1);
      
      return true;
  }
  
  bool pb_decode_fixed32(pb_istream_t *stream, void *dest)
  {
      #ifdef __BIG_ENDIAN__
      uint8_t *bytes = (uint8_t*)dest;
      uint8_t lebytes[4];
      
      if (!pb_read(stream, lebytes, 4))
          return false;
      
      bytes[0] = lebytes[3];
      bytes[1] = lebytes[2];
      bytes[2] = lebytes[1];
      bytes[3] = lebytes[0];
      return true;
      #else
      return pb_read(stream, (uint8_t*)dest, 4);
      #endif   
  }
  
  bool pb_decode_fixed64(pb_istream_t *stream, void *dest)
  {
      #ifdef __BIG_ENDIAN__
      uint8_t *bytes = (uint8_t*)dest;
      uint8_t lebytes[8];
      
      if (!pb_read(stream, lebytes, 8))
          return false;
      
      bytes[0] = lebytes[7];
      bytes[1] = lebytes[6];
      bytes[2] = lebytes[5];
      bytes[3] = lebytes[4];
      bytes[4] = lebytes[3];
      bytes[5] = lebytes[2];
      bytes[6] = lebytes[1];
      bytes[7] = lebytes[0];
      return true;
      #else
      return pb_read(stream, (uint8_t*)dest, 8);
      #endif   
  }
  
  static bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
  {
      uint64_t value;
      if (!pb_decode_varint(stream, &value))
          return false;
      
      switch (field->data_size)
      {
          case 1: *(int8_t*)dest = (int8_t)value; break;
          case 2: *(int16_t*)dest = (int16_t)value; break;
          case 4: *(int32_t*)dest = (int32_t)value; break;
          case 8: *(int64_t*)dest = (int64_t)value; break;
          default: PB_RETURN_ERROR(stream, "invalid data_size");
      }
      
      return true;
  }
  
  static bool checkreturn pb_dec_uvarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
  {
      uint64_t value;
      if (!pb_decode_varint(stream, &value))
          return false;
      
      switch (field->data_size)
      {
          case 4: *(uint32_t*)dest = (uint32_t)value; break;
          case 8: *(uint64_t*)dest = value; break;
          default: PB_RETURN_ERROR(stream, "invalid data_size");
      }
      
      return true;
  }
  
  static bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
  {
      int64_t value;
      if (!pb_decode_svarint(stream, &value))
          return false;
      
      switch (field->data_size)
      {
          case 4: *(int32_t*)dest = (int32_t)value; break;
          case 8: *(int64_t*)dest = value; break;
          default: PB_RETURN_ERROR(stream, "invalid data_size");
      }
      
      return true;
  }
  
  static bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest)
  {
      PB_UNUSED(field);
      return pb_decode_fixed32(stream, dest);
  }
  
  static bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest)
  {
      PB_UNUSED(field);
      return pb_decode_fixed64(stream, dest);
  }
  
  static bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
  {
      uint32_t size;
      size_t alloc_size;
      pb_bytes_array_t *bdest;
      
      if (!pb_decode_varint32(stream, &size))
          return false;
      
      if (size > PB_SIZE_MAX)
          PB_RETURN_ERROR(stream, "bytes overflow");
      
      alloc_size = PB_BYTES_ARRAY_T_ALLOCSIZE(size);
      if (size > alloc_size)
          PB_RETURN_ERROR(stream, "size too large");
      
      if (PB_ATYPE(field->type) == PB_ATYPE_POINTER)
      {
  #ifndef PB_ENABLE_MALLOC
          PB_RETURN_ERROR(stream, "no malloc support");
  #else
          if (!allocate_field(stream, dest, alloc_size, 1))
              return false;
          bdest = *(pb_bytes_array_t**)dest;
  #endif
      }
      else
      {
          if (alloc_size > field->data_size)
              PB_RETURN_ERROR(stream, "bytes overflow");
          bdest = (pb_bytes_array_t*)dest;
      }
  
      bdest->size = (pb_size_t)size;
      return pb_read(stream, bdest->bytes, size);
  }
  
  static bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
  {
      uint32_t size;
      size_t alloc_size;
      bool status;
      if (!pb_decode_varint32(stream, &size))
          return false;
      
      /* Space for null terminator */
      alloc_size = size + 1;
      
      if (alloc_size < size)
          PB_RETURN_ERROR(stream, "size too large");
      
      if (PB_ATYPE(field->type) == PB_ATYPE_POINTER)
      {
  #ifndef PB_ENABLE_MALLOC
          PB_RETURN_ERROR(stream, "no malloc support");
  #else
          if (!allocate_field(stream, dest, alloc_size, 1))
              return false;
          dest = *(void**)dest;
  #endif
      }
      else
      {
          if (alloc_size > field->data_size)
              PB_RETURN_ERROR(stream, "string overflow");
      }
      
      status = pb_read(stream, (uint8_t*)dest, size);
      *((uint8_t*)dest + size) = 0;
      return status;
  }
  
  static bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
  {
      bool status;
      pb_istream_t substream;
      const pb_field_t* submsg_fields = (const pb_field_t*)field->ptr;
      
      if (!pb_make_string_substream(stream, &substream))
          return false;
      
      if (field->ptr == NULL)
          PB_RETURN_ERROR(stream, "invalid field descriptor");
      
      /* New array entries need to be initialized, while required and optional
       * submessages have already been initialized in the top-level pb_decode. */
      if (PB_HTYPE(field->type) == PB_HTYPE_REPEATED)
          status = pb_decode(&substream, submsg_fields, dest);
      else
          status = pb_decode_noinit(&substream, submsg_fields, dest);
      
      pb_close_string_substream(stream, &substream);
      return status;
  }
  