jorgecarleitao commented on a change in pull request #8640:
URL: https://github.com/apache/arrow/pull/8640#discussion_r524923532
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File path: rust/arrow/src/array/builder.rs
##########
@@ -1882,6 +1975,67 @@ impl FixedSizeBinaryBuilder {
}
}
+impl DecimalBuilder {
+ /// Creates a new `BinaryBuilder`, `capacity` is the number of bytes in
the values
+ /// array
+ pub fn new(capacity: usize, precision: usize, scale: usize) -> Self {
+ let values_builder = UInt8Builder::new(capacity);
+ let byte_width = DecimalArray::calc_fixed_byte_size(precision);
+ Self {
+ builder: FixedSizeListBuilder::new(values_builder, byte_width),
+ precision,
+ scale,
+ }
+ }
+
+ /// Appends a byte slice into the builder.
+ ///
+ /// Automatically calls the `append` method to delimit the slice appended
in as a
+ /// distinct array element.
+ pub fn append_value(&mut self, value: i128) -> Result<()> {
+ let value_as_bytes = Self::from_i128_to_fixed_size_bytes(
+ value,
+ self.builder.value_length() as usize,
+ )?;
+ if self.builder.value_length() != value_as_bytes.len() as i32 {
+ return Err(ArrowError::InvalidArgumentError(
+ "Byte slice does not have the same length as DecimalBuilder
value lengths".to_string()
+ ));
+ }
+ self.builder
+ .values()
+ .append_slice(value_as_bytes.as_slice())?;
+ self.builder.append(true)
+ }
+
+ fn from_i128_to_fixed_size_bytes(v: i128, size: usize) -> Result<Vec<u8>> {
+ if size > 16 {
+ return Err(ArrowError::InvalidArgumentError(
+ "DecimalBuilder only supports values up to 16
bytes.".to_string(),
+ ));
+ }
+ let res = v.to_be_bytes();
+ let start_byte = 16 - size;
+ Ok(res[start_byte..16].to_vec())
+ }
+
+ /// Append a null value to the array.
+ pub fn append_null(&mut self) -> Result<()> {
+ let length: usize = self.builder.value_length() as usize;
+ self.builder.values().append_slice(&vec![0u8; length][..])?;
Review comment:
you are absolutely right. xD
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