picopb.cpp

#include "picopb.h"

picopb::picopb(uint8_t *buffer,size_t length)
{
  this->buffer = buffer;
  this->length = length;
  this->offset = 0;
  this->next_size = 0;
  this->next_type = pb_type::INVALID;
}

uint64_t picopb::decode_varint(size_t *size)
{
  int index = offset + 1;
  uint64_t value = 0;
  while(index < length)
  {
    value<<=7;
    value|=(buffer[index]&0x7F);
    index++;
    if((buffer[index]&0x80)==0)
    {
      break;
    }
  }
  if(size)
  {
    *size = index - offset - 1;
  }
  return value;
}

int picopb::read_varint(uint64_t *out)
{
  if(next_type != pb_type::VARINT)
  {
    return 0;
  }
  *out = decode_varint(0);
  offset += next_size + 1;
  next_type = pb_type::INVALID;
  return 1;
}

int picopb::read_i64(uint64_t *out)
{
  if(next_type != pb_type::I64)
  {
    return 0;
  }
  memcpy(out,&buffer[offset+1],8);
  offset += 9;
  next_type = pb_type::INVALID;
  return 1;
}

int picopb::read_string(uint8_t *string,uint8_t bufsz)
{
  uint64_t string_len;
  size_t varint_len;
  if(next_type != pb_type::STRING)
  {
    return 0;
  }
  string_len = decode_varint(&varint_len);
  if(string_len > bufsz)
  {
    string_len = bufsz;
  }
  memcpy(string,&buffer[offset+varint_len+1],string_len);
  offset += next_size + 1;
  return 0;
}

int picopb::read_i32(uint32_t *out)
{
  if(next_type != pb_type::I64)
  {
    return 0;
  }
  memcpy(out,&buffer[offset+1],4);
  offset += 5;
  next_type = pb_type::INVALID;
  return 1;
}

pb_type picopb::decode_next(int *id,size_t *size)
{
  size_t string_len;
  *id = buffer[offset] >> 3;
  next_type = (pb_type)(buffer[offset] & 7);
  switch(next_type)
  {
    case pb_type::VARINT:
      decode_varint(&next_size);
      *size = next_size;
      break;
    case pb_type::I64:
      next_size = 8;
      *size = next_size;
      break;
    case pb_type::STRING:
      string_len = decode_varint(&next_size);
      next_size += string_len;
      *size = string_len;
      break;
    case pb_type::I32:
      next_size = 4;
      *size = next_size;
      break;
    default:
      next_type = pb_type::INVALID;
      next_size = 0;
      *size = next_size;
      break;
  }
  
  return next_type;
}