Struct WritableMetadataBuilder 

pub struct WritableMetadataBuilder {
    field_names: IndexSet<String>,
    is_sorted: bool,
    metadata_buffer: Vec<u8>,
}

Builder for constructing metadata for Variant values.

This is used internally by the VariantBuilder to construct the metadata

You can use an existing Vec<u8> as the metadata buffer by using the from impl.

Fields

field_names: IndexSet<String>

is_sorted: bool

metadata_buffer: Vec<u8>

Output buffer. Metadata is written to the end of this buffer

Implementations

impl WritableMetadataBuilder

fn upsert_field_name(&mut self, field_name: &str) -> u32

Upsert field name to dictionary, return its ID

pub fn offset(&self) -> usize

The current length of the underlying metadata buffer

fn num_field_names(&self) -> usize

Returns the number of field names stored in the metadata builder. Note: this method should be the only place to call self.field_names.len()

Panics

If the number of field names exceeds the maximum allowed value for u32.

fn field_name(&self, i: usize) -> &str

fn metadata_size(&self) -> usize

pub fn finish(&mut self) -> usize

Finalizes the metadata dictionary and appends its serialized bytes to the underlying buffer, returning the resulting Self::offset. The builder state is reset and ready to start building a new metadata dictionary.

pub fn into_inner(self) -> Vec<u8>

Returns the inner buffer, consuming self without finalizing any in progress metadata.

Trait Implementations

impl Debug for WritableMetadataBuilder

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for WritableMetadataBuilder

fn default() -> WritableMetadataBuilder

Returns the “default value” for a type.

impl<S: AsRef<str>> Extend<S> for WritableMetadataBuilder

fn extend<T: IntoIterator<Item = S>>(&mut self, iter: T)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl<S: AsRef<str>> FromIterator<S> for WritableMetadataBuilder

fn from_iter<T: IntoIterator<Item = S>>(iter: T) -> Self

Creates a value from an iterator.

impl MetadataBuilder for WritableMetadataBuilder

fn try_upsert_field_name(&mut self, field_name: &str) -> Result<u32, ArrowError>

Attempts to register a field name, returning the corresponding (possibly newly-created) field id on success. Attempting to register the same field name twice will generally produce the same field id both times, but the variant spec does not actually require it.

fn field_name(&self, field_id: usize) -> &str

Retrieves the field name for a given field id, which must be less than Self::num_field_names. Panics if the field id is out of bounds.

fn num_field_names(&self) -> usize

Returns the number of field names stored in this metadata builder. Any number less than this is a valid field id. The builder can be reverted back to this size later on (discarding any newer/higher field ids) by calling Self::truncate_field_names.

fn truncate_field_names(&mut self, new_size: usize)

Reverts the field names to a previous size, discarding any newly out of bounds field ids.

fn finish(&mut self) -> usize

Finishes the current metadata dictionary, returning the new size of the underlying buffer.