pb_encode.c

/* pb_encode.c -- encode a protobuf using minimal resources
 *
 * 2011 Petteri Aimonen <jpa@kapsi.fi>
 */
 
#include "pb.h"
#include "pb_encode.h"
#include "pb_common.h"
 
/* 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
 
/**************************************
* Declarations internal to this file *
**************************************/
static bool checkreturn buf_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
static bool checkreturn encode_array(pb_ostream_t *stream, pb_field_iter_t *field);
static bool checkreturn pb_check_proto3_default_value(const pb_field_iter_t *field);
static bool checkreturn encode_basic_field(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn encode_callback_field(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn encode_field(pb_ostream_t *stream, pb_field_iter_t *field);
static bool checkreturn encode_extension_field(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn default_extension_encoder(pb_ostream_t *stream, const pb_extension_t *extension);
static bool checkreturn pb_encode_varint_32(pb_ostream_t *stream, uint32_t low, uint32_t high);
static bool checkreturn pb_enc_bool(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn pb_enc_varint(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn pb_enc_fixed(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn pb_enc_string(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn pb_enc_submessage(pb_ostream_t *stream, const pb_field_iter_t *field);
static bool checkreturn pb_enc_fixed_length_bytes(pb_ostream_t *stream, const pb_field_iter_t *field);
 
#ifdef PB_WITHOUT_64BIT
#define pb_int64_t int32_t
#define pb_uint64_t uint32_t
#else
#define pb_int64_t int64_t
#define pb_uint64_t uint64_t
#endif
 
/*******************************
* pb_ostream_t implementation *
*******************************/
static bool checkreturn buf_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count) {
  pb_byte_t *dest = (pb_byte_t *)stream->state;
 
  stream->state = dest + count;
 
  memcpy(dest, buf, count * sizeof(pb_byte_t));
 
  return true;
}
 
pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize) {
  pb_ostream_t stream;
 
#ifdef PB_BUFFER_ONLY
  /* In PB_BUFFER_ONLY configuration the callback pointer is just int*.
   * NULL pointer marks a sizing field, so put a non-NULL value to mark a buffer stream.
   */
  static const int marker = 0;
  stream.callback = &marker;
#else
  stream.callback = &buf_write;
#endif
  stream.state = buf;
  stream.max_size = bufsize;
  stream.bytes_written = 0;
#ifndef PB_NO_ERRMSG
  stream.errmsg = NULL;
#endif
  return stream;
}
 
bool checkreturn pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count) {
  if (count > 0 && stream->callback != NULL) {
    if (stream->bytes_written + count < stream->bytes_written ||
        stream->bytes_written + count > stream->max_size) {
      PB_RETURN_ERROR(stream, "stream full");
    }
 
#ifdef PB_BUFFER_ONLY
    if (!buf_write(stream, buf, count)) {
      PB_RETURN_ERROR(stream, "io error");
    }
#else
    if (!stream->callback(stream, buf, count)) {
      PB_RETURN_ERROR(stream, "io error");
    }
#endif
  }
 
  stream->bytes_written += count;
  return true;
}
 
/*************************
* Encode a single field *
*************************/
 
/* Read a bool value without causing undefined behavior even if the value
 * is invalid. See issue #434 and
 * https://stackoverflow.com/questions/27661768/weird-results-for-conditional
 */
static bool safe_read_bool(const void *pSize) {
  const char *p = (const char *)pSize;
  size_t i;
 
  for (i = 0; i < sizeof(bool); i++) {
    if (p[i] != 0) {
      return true;
    }
  }
  return false;
}
 
/* Encode a static array. Handles the size calculations and possible packing. */
static bool checkreturn encode_array(pb_ostream_t *stream, pb_field_iter_t *field) {
  pb_size_t i;
  pb_size_t count;
 
#ifndef PB_ENCODE_ARRAYS_UNPACKED
  size_t size;
#endif
 
  count = *(pb_size_t *)field->pSize;
 
  if (count == 0) {
    return true;
  }
 
  if (PB_ATYPE(field->type) != PB_ATYPE_POINTER && count > field->array_size) {
    PB_RETURN_ERROR(stream, "array max size exceeded");
  }
 
#ifndef PB_ENCODE_ARRAYS_UNPACKED
  /* We always pack arrays if the datatype allows it. */
  if (PB_LTYPE(field->type) <= PB_LTYPE_LAST_PACKABLE) {
    if (!pb_encode_tag(stream, PB_WT_STRING, field->tag)) {
      return false;
    }
 
    /* Determine the total size of packed array. */
    if (PB_LTYPE(field->type) == PB_LTYPE_FIXED32) {
      size = 4 * (size_t)count;
    } else if (PB_LTYPE(field->type) == PB_LTYPE_FIXED64) {
      size = 8 * (size_t)count;
    } else {
      pb_ostream_t sizestream = PB_OSTREAM_SIZING;
      void *pData_orig = field->pData;
      for (i = 0; i < count; i++) {
        if (!pb_enc_varint(&sizestream, field)) {
          PB_RETURN_ERROR(stream, PB_GET_ERROR(&sizestream));
        }
        field->pData = (char *)field->pData + field->data_size;
      }
      field->pData = pData_orig;
      size = sizestream.bytes_written;
    }
 
    if (!pb_encode_varint(stream, (pb_uint64_t)size)) {
      return false;
    }
 
    if (stream->callback == NULL) {
      return pb_write(stream, NULL, size);       /* Just sizing.. */
    }
    /* Write the data */
    for (i = 0; i < count; i++) {
      if (PB_LTYPE(field->type) == PB_LTYPE_FIXED32 || PB_LTYPE(field->type) == PB_LTYPE_FIXED64) {
        if (!pb_enc_fixed(stream, field)) {
          return false;
        }
      } else {
        if (!pb_enc_varint(stream, field)) {
          return false;
        }
      }
 
      field->pData = (char *)field->pData + field->data_size;
    }
  } else /* Unpacked fields */
#endif
  {
    for (i = 0; i < count; i++) {
      /* Normally the data is stored directly in the array entries, but
       * for pointer-type string and bytes fields, the array entries are
       * actually pointers themselves also. So we have to dereference once
       * more to get to the actual data. */
      if (PB_ATYPE(field->type) == PB_ATYPE_POINTER &&
          (PB_LTYPE(field->type) == PB_LTYPE_STRING ||
           PB_LTYPE(field->type) == PB_LTYPE_BYTES)) {
        bool status;
        void *pData_orig = field->pData;
        field->pData = *(void *const *)field->pData;
 
        if (!field->pData) {
          /* Null pointer in array is treated as empty string / bytes */
          status = pb_encode_tag_for_field(stream, field) &&
                   pb_encode_varint(stream, 0);
        } else {
          status = encode_basic_field(stream, field);
        }
 
        field->pData = pData_orig;
 
        if (!status) {
          return false;
        }
      } else {
        if (!encode_basic_field(stream, field)) {
          return false;
        }
      }
      field->pData = (char *)field->pData + field->data_size;
    }
  }
 
  return true;
}
 
/* In proto3, all fields are optional and are only encoded if their value is "non-zero".
 * This function implements the check for the zero value. */
static bool checkreturn pb_check_proto3_default_value(const pb_field_iter_t *field) {
  pb_type_t type = field->type;
 
  if (PB_ATYPE(type) == PB_ATYPE_STATIC) {
    if (PB_HTYPE(type) == PB_HTYPE_REQUIRED) {
      /* Required proto2 fields inside proto3 submessage, pretty rare case */
      return false;
    } else if (PB_HTYPE(type) == PB_HTYPE_REPEATED) {
      /* Repeated fields inside proto3 submessage: present if count != 0 */
      return *(const pb_size_t *)field->pSize == 0;
    } else if (PB_HTYPE(type) == PB_HTYPE_ONEOF) {
      /* Oneof fields */
      return *(const pb_size_t *)field->pSize == 0;
    } else if (PB_HTYPE(type) == PB_HTYPE_OPTIONAL && field->pSize != NULL) {
      /* Proto2 optional fields inside proto3 message, or proto3
       * submessage fields. */
      return safe_read_bool(field->pSize) == false;
    } else if (field->descriptor->default_value) {
      /* Proto3 messages do not have default values, but proto2 messages
       * can contain optional fields without has_fields (generator option 'proto3').
       * In this case they must always be encoded, to make sure that the
       * non-zero default value is overwritten.
       */
      return false;
    }
 
    /* Rest is proto3 singular fields */
    if (PB_LTYPE(type) <= PB_LTYPE_LAST_PACKABLE) {
      /* Simple integer / float fields */
      pb_size_t i;
      const char *p = (const char *)field->pData;
      for (i = 0; i < field->data_size; i++) {
        if (p[i] != 0) {
          return false;
        }
      }
 
      return true;
    } else if (PB_LTYPE(type) == PB_LTYPE_BYTES) {
      const pb_bytes_array_t *bytes = (const pb_bytes_array_t *)field->pData;
      return bytes->size == 0;
    } else if (PB_LTYPE(type) == PB_LTYPE_STRING) {
      return *(const char *)field->pData == '\0';
    } else if (PB_LTYPE(type) == PB_LTYPE_FIXED_LENGTH_BYTES) {
      /* Fixed length bytes is only empty if its length is fixed
       * as 0. Which would be pretty strange, but we can check
       * it anyway. */
      return field->data_size == 0;
    } else if (PB_LTYPE_IS_SUBMSG(type)) {
      /* Check all fields in the submessage to find if any of them
       * are non-zero. The comparison cannot be done byte-per-byte
       * because the C struct may contain padding bytes that must
       * be skipped. Note that usually proto3 submessages have
       * a separate has_field that is checked earlier in this if.
       */
      pb_field_iter_t iter;
      if (pb_field_iter_begin(&iter, field->submsg_desc, field->pData)) {
        do{
          if (!pb_check_proto3_default_value(&iter)) {
            return false;
          }
        } while (pb_field_iter_next(&iter));
      }
      return true;
    }
  } else if (PB_ATYPE(type) == PB_ATYPE_POINTER) {
    return field->pData == NULL;
  } else if (PB_ATYPE(type) == PB_ATYPE_CALLBACK) {
    if (PB_LTYPE(type) == PB_LTYPE_EXTENSION) {
      const pb_extension_t *extension = *(const pb_extension_t *const *)field->pData;
      return extension == NULL;
    } else if (field->descriptor->field_callback == pb_default_field_callback) {
      pb_callback_t *pCallback = (pb_callback_t *)field->pData;
      return pCallback->funcs.encode == NULL;
    } else {
      return field->descriptor->field_callback == NULL;
    }
  }
 
  return false;   /* Not typically reached, safe default for weird special cases. */
}
 
/* Encode a field with static or pointer allocation, i.e. one whose data
 * is available to the encoder directly. */
static bool checkreturn encode_basic_field(pb_ostream_t *stream, const pb_field_iter_t *field) {
  if (!field->pData) {
    /* Missing pointer field */
    return true;
  }
 
  if (!pb_encode_tag_for_field(stream, field)) {
    return false;
  }
 
  switch (PB_LTYPE(field->type)) {
  case PB_LTYPE_BOOL:
    return pb_enc_bool(stream, field);
 
  case PB_LTYPE_VARINT:
  case PB_LTYPE_UVARINT:
  case PB_LTYPE_SVARINT:
    return pb_enc_varint(stream, field);
 
  case PB_LTYPE_FIXED32:
  case PB_LTYPE_FIXED64:
    return pb_enc_fixed(stream, field);
 
  case PB_LTYPE_BYTES:
    return pb_enc_bytes(stream, field);
 
  case PB_LTYPE_STRING:
    return pb_enc_string(stream, field);
 
  case PB_LTYPE_SUBMESSAGE:
  case PB_LTYPE_SUBMSG_W_CB:
    return pb_enc_submessage(stream, field);
 
  case PB_LTYPE_FIXED_LENGTH_BYTES:
    return pb_enc_fixed_length_bytes(stream, field);
 
  default:
    PB_RETURN_ERROR(stream, "invalid field type");
  }
}
 
/* Encode a field with callback semantics. This means that a user function is
 * called to provide and encode the actual data. */
static bool checkreturn encode_callback_field(pb_ostream_t *stream, const pb_field_iter_t *field) {
  if (field->descriptor->field_callback != NULL) {
    if (!field->descriptor->field_callback(NULL, stream, field)) {
      PB_RETURN_ERROR(stream, "callback error");
    }
  }
  return true;
}
 
/* Encode a single field of any callback, pointer or static type. */
static bool checkreturn encode_field(pb_ostream_t *stream, pb_field_iter_t *field) {
  /* Check field presence */
  if (PB_HTYPE(field->type) == PB_HTYPE_ONEOF) {
    if (*(const pb_size_t *)field->pSize != field->tag) {
      /* Different type oneof field */
      return true;
    }
  } else if (PB_HTYPE(field->type) == PB_HTYPE_OPTIONAL) {
    if (field->pSize) {
      if (safe_read_bool(field->pSize) == false) {
        /* Missing optional field */
        return true;
      }
    } else if (PB_ATYPE(field->type) == PB_ATYPE_STATIC) {
      /* Proto3 singular field */
      if (pb_check_proto3_default_value(field)) {
        return true;
      }
    }
  }
 
  if (!field->pData) {
    if (PB_HTYPE(field->type) == PB_HTYPE_REQUIRED) {
      PB_RETURN_ERROR(stream, "missing required field");
    }
 
    /* Pointer field set to NULL */
    return true;
  }
 
  /* Then encode field contents */
  if (PB_ATYPE(field->type) == PB_ATYPE_CALLBACK) {
    return encode_callback_field(stream, field);
  } else if (PB_HTYPE(field->type) == PB_HTYPE_REPEATED) {
    return encode_array(stream, field);
  } else {
    return encode_basic_field(stream, field);
  }
}
 
/* Default handler for extension fields. Expects to have a pb_msgdesc_t
 * pointer in the extension->type->arg field, pointing to a message with
 * only one field in it.  */
static bool checkreturn default_extension_encoder(pb_ostream_t *stream, const pb_extension_t *extension) {
  pb_field_iter_t iter;
 
  if (!pb_field_iter_begin_extension_const(&iter, extension)) {
    PB_RETURN_ERROR(stream, "invalid extension");
  }
 
  return encode_field(stream, &iter);
}
 
 
/* Walk through all the registered extensions and give them a chance
 * to encode themselves. */
static bool checkreturn encode_extension_field(pb_ostream_t *stream, const pb_field_iter_t *field) {
  const pb_extension_t *extension = *(const pb_extension_t *const *)field->pData;
 
  while (extension) {
    bool status;
    if (extension->type->encode) {
      status = extension->type->encode(stream, extension);
    } else {
      status = default_extension_encoder(stream, extension);
    }
 
    if (!status) {
      return false;
    }
 
    extension = extension->next;
  }
 
  return true;
}
 
/*********************
* Encode all fields *
*********************/
bool checkreturn pb_encode(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct) {
  pb_field_iter_t iter;
 
  if (!pb_field_iter_begin_const(&iter, fields, src_struct)) {
    return true;     /* Empty message type */
  }
  do {
    if (PB_LTYPE(iter.type) == PB_LTYPE_EXTENSION) {
      /* Special case for the extension field placeholder */
      if (!encode_extension_field(stream, &iter)) {
        return false;
      }
    } else {
      /* Regular field */
      if (!encode_field(stream, &iter)) {
        return false;
      }
    }
  } while (pb_field_iter_next(&iter));
 
  return true;
}
 
bool checkreturn pb_encode_ex(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct, unsigned int flags) {
  if ((flags & PB_ENCODE_DELIMITED) != 0) {
    return pb_encode_submessage(stream, fields, src_struct);
  } else if ((flags & PB_ENCODE_NULLTERMINATED) != 0) {
    const pb_byte_t zero = 0;
 
    if (!pb_encode(stream, fields, src_struct)) {
      return false;
    }
 
    return pb_write(stream, &zero, 1);
  } else {
    return pb_encode(stream, fields, src_struct);
  }
}
 
bool pb_get_encoded_size(size_t *size, const pb_msgdesc_t *fields, const void *src_struct) {
  pb_ostream_t stream = PB_OSTREAM_SIZING;
 
  if (!pb_encode(&stream, fields, src_struct)) {
    return false;
  }
 
  *size = stream.bytes_written;
  return true;
}
 
/********************
* Helper functions *
********************/
 
/* This function avoids 64-bit shifts as they are quite slow on many platforms. */
static bool checkreturn pb_encode_varint_32(pb_ostream_t *stream, uint32_t low, uint32_t high) {
  size_t i = 0;
  pb_byte_t buffer[10];
  pb_byte_t byte = (pb_byte_t)(low & 0x7F);
 
  low >>= 7;
 
  while (i < 4 && (low != 0 || high != 0)) {
    byte |= 0x80;
    buffer[i++] = byte;
    byte = (pb_byte_t)(low & 0x7F);
    low >>= 7;
  }
 
  if (high) {
    byte = (pb_byte_t)(byte | ((high & 0x07) << 4));
    high >>= 3;
 
    while (high) {
      byte |= 0x80;
      buffer[i++] = byte;
      byte = (pb_byte_t)(high & 0x7F);
      high >>= 7;
    }
  }
 
  buffer[i++] = byte;
 
  return pb_write(stream, buffer, i);
}
 
bool checkreturn pb_encode_varint(pb_ostream_t *stream, pb_uint64_t value) {
  if (value <= 0x7F) {
    /* Fast path: single byte */
    pb_byte_t byte = (pb_byte_t)value;
    return pb_write(stream, &byte, 1);
  } else {
#ifdef PB_WITHOUT_64BIT
    return pb_encode_varint_32(stream, value, 0);
#else
    return pb_encode_varint_32(stream, (uint32_t)value, (uint32_t)(value >> 32));
#endif
  }
}
 
bool checkreturn pb_encode_svarint(pb_ostream_t *stream, pb_int64_t value) {
  pb_uint64_t zigzagged;
  pb_uint64_t mask = ((pb_uint64_t)-1) >> 1;   /* Satisfy clang -fsanitize=integer */
 
  if (value < 0) {
    zigzagged = ~(((pb_uint64_t)value & mask) << 1);
  } else {
    zigzagged = (pb_uint64_t)value << 1;
  }
 
  return pb_encode_varint(stream, zigzagged);
}
 
bool checkreturn pb_encode_fixed32(pb_ostream_t *stream, const void *value) {
#if defined(PB_LITTLE_ENDIAN_8BIT) && PB_LITTLE_ENDIAN_8BIT == 1
  /* Fast path if we know that we're on little endian */
  return pb_write(stream, (const pb_byte_t *)value, 4);
#else
  uint32_t val = *(const uint32_t *)value;
  pb_byte_t bytes[4];
  bytes[0] = (pb_byte_t)(val & 0xFF);
  bytes[1] = (pb_byte_t)((val >> 8) & 0xFF);
  bytes[2] = (pb_byte_t)((val >> 16) & 0xFF);
  bytes[3] = (pb_byte_t)((val >> 24) & 0xFF);
  return pb_write(stream, bytes, 4);
#endif
}
 
#ifndef PB_WITHOUT_64BIT
bool checkreturn pb_encode_fixed64(pb_ostream_t *stream, const void *value) {
#if defined(PB_LITTLE_ENDIAN_8BIT) && PB_LITTLE_ENDIAN_8BIT == 1
  /* Fast path if we know that we're on little endian */
  return pb_write(stream, (const pb_byte_t *)value, 8);
#else
  uint64_t val = *(const uint64_t *)value;
  pb_byte_t bytes[8];
  bytes[0] = (pb_byte_t)(val & 0xFF);
  bytes[1] = (pb_byte_t)((val >> 8) & 0xFF);
  bytes[2] = (pb_byte_t)((val >> 16) & 0xFF);
  bytes[3] = (pb_byte_t)((val >> 24) & 0xFF);
  bytes[4] = (pb_byte_t)((val >> 32) & 0xFF);
  bytes[5] = (pb_byte_t)((val >> 40) & 0xFF);
  bytes[6] = (pb_byte_t)((val >> 48) & 0xFF);
  bytes[7] = (pb_byte_t)((val >> 56) & 0xFF);
  return pb_write(stream, bytes, 8);
#endif
}
#endif
 
bool checkreturn pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number) {
  pb_uint64_t tag = ((pb_uint64_t)field_number << 3) | wiretype;
 
  return pb_encode_varint(stream, tag);
}
 
bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_iter_t *field) {
  pb_wire_type_t wiretype;
 
  switch (PB_LTYPE(field->type)) {
  case PB_LTYPE_BOOL:
  case PB_LTYPE_VARINT:
  case PB_LTYPE_UVARINT:
  case PB_LTYPE_SVARINT:
    wiretype = PB_WT_VARINT;
    break;
 
  case PB_LTYPE_FIXED32:
    wiretype = PB_WT_32BIT;
    break;
 
  case PB_LTYPE_FIXED64:
    wiretype = PB_WT_64BIT;
    break;
 
  case PB_LTYPE_BYTES:
  case PB_LTYPE_STRING:
  case PB_LTYPE_SUBMESSAGE:
  case PB_LTYPE_SUBMSG_W_CB:
  case PB_LTYPE_FIXED_LENGTH_BYTES:
    wiretype = PB_WT_STRING;
    break;
 
  default:
    PB_RETURN_ERROR(stream, "invalid field type");
  }
 
  return pb_encode_tag(stream, wiretype, field->tag);
}
 
bool checkreturn pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size) {
  if (!pb_encode_varint(stream, (pb_uint64_t)size)) {
    return false;
  }
 
  return pb_write(stream, buffer, size);
}
 
bool checkreturn pb_encode_submessage(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct) {
  /* First calculate the message size using a non-writing substream. */
  pb_ostream_t substream = PB_OSTREAM_SIZING;
  size_t size;
  bool status;
 
  if (!pb_encode(&substream, fields, src_struct)) {
#ifndef PB_NO_ERRMSG
    stream->errmsg = substream.errmsg;
#endif
    return false;
  }
 
  size = substream.bytes_written;
 
  if (!pb_encode_varint(stream, (pb_uint64_t)size)) {
    return false;
  }
 
  if (stream->callback == NULL) {
    return pb_write(stream, NULL, size);     /* Just sizing */
  }
  if (stream->bytes_written + size > stream->max_size) {
    PB_RETURN_ERROR(stream, "stream full");
  }
 
  /* Use a substream to verify that a callback doesn't write more than
   * what it did the first time. */
  substream.callback = stream->callback;
  substream.state = stream->state;
  substream.max_size = size;
  substream.bytes_written = 0;
#ifndef PB_NO_ERRMSG
  substream.errmsg = NULL;
#endif
 
  status = pb_encode(&substream, fields, src_struct);
 
  stream->bytes_written += substream.bytes_written;
  stream->state = substream.state;
#ifndef PB_NO_ERRMSG
  stream->errmsg = substream.errmsg;
#endif
 
  if (substream.bytes_written != size) {
    PB_RETURN_ERROR(stream, "submsg size changed");
  }
 
  return status;
}
 
/* Field encoders */
 
static bool checkreturn pb_enc_bool(pb_ostream_t *stream, const pb_field_iter_t *field) {
  uint32_t value = safe_read_bool(field->pData) ? 1 : 0;
 
  PB_UNUSED(field);
  return pb_encode_varint(stream, value);
}
 
static bool checkreturn pb_enc_varint(pb_ostream_t *stream, const pb_field_iter_t *field) {
  if (PB_LTYPE(field->type) == PB_LTYPE_UVARINT) {
    /* Perform unsigned integer extension */
    pb_uint64_t value = 0;
 
    if (field->data_size == sizeof(uint_least8_t)) {
      value = *(const uint_least8_t *)field->pData;
    } else if (field->data_size == sizeof(uint_least16_t)) {
      value = *(const uint_least16_t *)field->pData;
    } else if (field->data_size == sizeof(uint32_t)) {
      value = *(const uint32_t *)field->pData;
    } else if (field->data_size == sizeof(pb_uint64_t)) {
      value = *(const pb_uint64_t *)field->pData;
    } else {
      PB_RETURN_ERROR(stream, "invalid data_size");
    }
 
    return pb_encode_varint(stream, value);
  } else {
    /* Perform signed integer extension */
    pb_int64_t value = 0;
 
    if (field->data_size == sizeof(int_least8_t)) {
      value = *(const int_least8_t *)field->pData;
    } else if (field->data_size == sizeof(int_least16_t)) {
      value = *(const int_least16_t *)field->pData;
    } else if (field->data_size == sizeof(int32_t)) {
      value = *(const int32_t *)field->pData;
    } else if (field->data_size == sizeof(pb_int64_t)) {
      value = *(const pb_int64_t *)field->pData;
    } else {
      PB_RETURN_ERROR(stream, "invalid data_size");
    }
 
    if (PB_LTYPE(field->type) == PB_LTYPE_SVARINT) {
      return pb_encode_svarint(stream, value);
    }
#ifdef PB_WITHOUT_64BIT
    else if (value < 0) {
      return pb_encode_varint_32(stream, (uint32_t)value, (uint32_t)-1);
    }
#endif
    else {
      return pb_encode_varint(stream, (pb_uint64_t)value);
    }
  }
}
 
static bool checkreturn pb_enc_fixed(pb_ostream_t *stream, const pb_field_iter_t *field) {
#ifdef PB_CONVERT_DOUBLE_FLOAT
  if (field->data_size == sizeof(float) && PB_LTYPE(field->type) == PB_LTYPE_FIXED64) {
    return pb_encode_float_as_double(stream, *(float *)field->pData);
  }
#endif
 
  if (field->data_size == sizeof(uint32_t)) {
    return pb_encode_fixed32(stream, field->pData);
  }
#ifndef PB_WITHOUT_64BIT
  else if (field->data_size == sizeof(uint64_t)) {
    return pb_encode_fixed64(stream, field->pData);
  }
#endif
  else {
    PB_RETURN_ERROR(stream, "invalid data_size");
  }
}
 
static bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_iter_t *field) {
  const pb_bytes_array_t *bytes = NULL;
 
  bytes = (const pb_bytes_array_t *)field->pData;
 
  if (bytes == NULL) {
    /* Treat null pointer as an empty bytes field */
    return pb_encode_string(stream, NULL, 0);
  }
 
  if (PB_ATYPE(field->type) == PB_ATYPE_STATIC &&
      bytes->size > field->data_size - offsetof(pb_bytes_array_t, bytes)) {
    PB_RETURN_ERROR(stream, "bytes size exceeded");
  }
 
  return pb_encode_string(stream, bytes->bytes, (size_t)bytes->size);
}
 
static bool checkreturn pb_enc_string(pb_ostream_t *stream, const pb_field_iter_t *field) {
  size_t size = 0;
  size_t max_size = (size_t)field->data_size;
  const char *str = (const char *)field->pData;
 
  if (PB_ATYPE(field->type) == PB_ATYPE_POINTER) {
    max_size = (size_t)-1;
  } else {
    /* pb_dec_string() assumes string fields end with a null
     * terminator when the type isn't PB_ATYPE_POINTER, so we
     * shouldn't allow more than max-1 bytes to be written to
     * allow space for the null terminator.
     */
    if (max_size == 0) {
      PB_RETURN_ERROR(stream, "zero-length string");
    }
 
    max_size -= 1;
  }
 
 
  if (str == NULL) {
    size = 0;     /* Treat null pointer as an empty string */
  } else {
    const char *p = str;
 
    /* strnlen() is not always available, so just use a loop */
    while (size < max_size && *p != '\0') {
      size++;
      p++;
    }
 
    if (*p != '\0') {
      PB_RETURN_ERROR(stream, "unterminated string");
    }
  }
 
#ifdef PB_VALIDATE_UTF8
  if (!pb_validate_utf8(str)) {
    PB_RETURN_ERROR(stream, "invalid utf8");
  }
#endif
 
  return pb_encode_string(stream, (const pb_byte_t *)str, size);
}
 
static bool checkreturn pb_enc_submessage(pb_ostream_t *stream, const pb_field_iter_t *field) {
  if (field->submsg_desc == NULL) {
    PB_RETURN_ERROR(stream, "invalid field descriptor");
  }
 
  if (PB_LTYPE(field->type) == PB_LTYPE_SUBMSG_W_CB && field->pSize != NULL) {
    /* Message callback is stored right before pSize. */
    pb_callback_t *callback = (pb_callback_t *)field->pSize - 1;
    if (callback->funcs.encode) {
      if (!callback->funcs.encode(stream, field, &callback->arg)) {
        return false;
      }
    }
  }
 
  return pb_encode_submessage(stream, field->submsg_desc, field->pData);
}
 
static bool checkreturn pb_enc_fixed_length_bytes(pb_ostream_t *stream, const pb_field_iter_t *field) {
  return pb_encode_string(stream, (const pb_byte_t *)field->pData, (size_t)field->data_size);
}
 
#ifdef PB_CONVERT_DOUBLE_FLOAT
bool pb_encode_float_as_double(pb_ostream_t *stream, float value) {
  union { float f; uint32_t i; } in;
  uint_least8_t sign;
  int exponent;
  uint64_t mantissa;
 
  in.f = value;
 
  /* Decompose input value */
  sign = (uint_least8_t)((in.i >> 31) & 1);
  exponent = (int)((in.i >> 23) & 0xFF) - 127;
  mantissa = in.i & 0x7FFFFF;
 
  if (exponent == 128) {
    /* Special value (NaN etc.) */
    exponent = 1024;
  } else if (exponent == -127) {
    if (!mantissa) {
      /* Zero */
      exponent = -1023;
    } else {
      /* Denormalized */
      mantissa <<= 1;
      while (!(mantissa & 0x800000)) {
        mantissa <<= 1;
        exponent--;
      }
      mantissa &= 0x7FFFFF;
    }
  }
 
  /* Combine fields */
  mantissa <<= 29;
  mantissa |= (uint64_t)(exponent + 1023) << 52;
  mantissa |= (uint64_t)sign << 63;
 
  return pb_encode_fixed64(stream, &mantissa);
}
#endif