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use crate::lazy::binary::raw::type_descriptor::Header;
use crate::lazy::binary::raw::v1_1::binary_buffer::AnnotationsEncoding;
use crate::lazy::binary::raw::v1_1::value::BinaryValueEncoding;
use crate::IonType;
use std::ops::Range;
pub trait EncodedHeader: Copy {
type TypeCode;
fn ion_type(&self) -> IonType;
fn type_code(&self) -> Self::TypeCode;
fn is_null(&self) -> bool;
}
impl EncodedHeader for Header {
type TypeCode = crate::binary::type_code::IonTypeCode;
fn ion_type(&self) -> IonType {
self.ion_type
}
fn type_code(&self) -> Self::TypeCode {
self.ion_type_code
}
fn is_null(&self) -> bool {
self.is_null()
}
}
/// Represents the type, offset, and length metadata of the various components of an encoded value
/// in an input stream.
///
/// Each [`LazyRawValue`](super::raw::value::LazyRawBinaryValue_1_0) contains an `EncodedValue`,
/// allowing a user to re-read (that is: parse) the body of the value as many times as necessary
/// without re-parsing its header information each time.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct EncodedBinaryValue<HeaderType: EncodedHeader> {
pub(crate) encoding: BinaryValueEncoding,
// If the compiler decides that a value is too large to be moved/copied with inline code,
// it will relocate the value using memcpy instead. This can be quite slow by comparison.
//
// Be cautious when adding new member fields or modifying the data types of existing member
// fields, as this may cause the in-memory size of `EncodedValue` instances to grow.
//
// See the Rust Performance Book section on measuring type sizes[1] for more information.
// [1] https://nnethercote.github.io/perf-book/type-sizes.html#measuring-type-sizes
// The type descriptor byte that identified this value; includes the type code, length code,
// and IonType.
pub(crate) header: HeaderType,
// Each encoded value has up to four components, appearing in the following order:
//
// [ annotations? | header (type descriptor) | header_length? | value_body ]
//
// Components shown with a `?` are optional.
//
// EncodedValue stores the offset of the type descriptor byte from the beginning of the
// data source (`header_offset`). The lengths of the other fields can be used to calculate
// their positions relative to the type descriptor byte. For example, to find the offset of the
// annotations header (if present), we can do:
// header_offset - annotations_header_length
//
// This allows us to store a single `usize` for the header offset, while other lengths can be
// packed into a `u8`. In this implementation, values are not permitted to have annotations that
// take more than 255 bytes to represent.
//
// We store the offset for the header byte because it is guaranteed to be present for all values.
// Annotations appear earlier in the stream but are optional.
// The number of bytes used to encode the header of the annotations wrapper preceding the Ion
// value. If the value has no annotations, `annotations_header_length` will be zero.
//
// In Ion 1.0, the annotations header contains several fields: an opcode, a wrapper length, and
// the length of the sequence itself. It does not include the actual sequence of annotations.
//
// In Ion 1.1, the annotations header contains an opcode and (in the case of opcode 0xE9) a
// FlexUInt length.
pub annotations_header_length: u8,
// The number of bytes used to encode the series of symbol IDs inside the annotations wrapper.
pub annotations_sequence_length: u16,
// Whether the annotations sequence is encoded as `FlexSym`s or as symbol addresses.
// In Ion 1.0, they are always encoded as symbol addresses.
pub annotations_encoding: AnnotationsEncoding,
// The offset of the type descriptor byte within the overall input stream.
pub header_offset: usize,
// The number of bytes used to encode the optional length VarUInt following the header byte.
pub length_length: u8,
// The number of bytes used to encode the value itself, not including the header byte
// or length fields.
pub value_body_length: usize,
// The sum total of:
// annotations_header_length + header_length + value_length
// While this can be derived from the above fields, storing it for reuse offers a modest
// optimization. `total_length` is needed when stepping into a value, skipping a value,
// and reading a value's data.
pub total_length: usize,
}
impl<HeaderType: EncodedHeader> EncodedBinaryValue<HeaderType> {
pub fn header(&self) -> HeaderType {
self.header
}
/// Returns the offset of the current value's type descriptor byte.
pub fn header_offset(&self) -> usize {
self.header_offset
}
/// Returns the length of this value's header, including the type descriptor byte and any
/// additional bytes used to encode the value's length.
pub fn header_length(&self) -> usize {
// The `length_length` field does not include the type descriptor byte, so add 1.
self.length_length as usize + 1
}
/// Returns an offset Range that contains this value's type descriptor byte and any additional
/// bytes used to encode the `length`.
#[allow(dead_code)]
pub fn header_range(&self) -> Range<usize> {
let start = self.header_offset;
let end = start + self.header_length();
start..end
}
/// Returns the number of bytes used to encode this value's opcode. If this value was serialized
/// using a tagless encoding, returns `0`.
pub fn opcode_length(&self) -> usize {
match self.encoding {
BinaryValueEncoding::Tagged => 1,
_ => 0,
}
}
/// Returns the number of bytes used to encode this value's data.
/// If the value can fit in the type descriptor byte (e.g. `true`, `false`, `null`, `0`),
/// this function will return 0.
#[inline(always)]
pub fn value_body_length(&self) -> usize {
self.value_body_length
}
/// The offset of the first byte following the header (including length bytes, if present).
/// If `value_length()` returns zero, this offset is actually the first byte of
/// the next encoded value and should not be read.
#[allow(dead_code)]
pub fn value_body_offset(&self) -> usize {
self.header_offset + self.header_length()
}
/// Returns an offset Range containing any bytes following the header.
#[allow(dead_code)]
pub fn value_body_range(&self) -> Range<usize> {
let start = self.value_body_offset();
let end = start + self.value_body_length;
start..end
}
/// Returns the index of the first byte that is beyond the end of the current value's encoding.
#[allow(dead_code)]
pub fn value_end_exclusive(&self) -> usize {
self.value_body_offset() + self.value_body_length
}
/// Returns true if this encoded value has an annotations wrapper.
pub fn has_annotations(&self) -> bool {
self.annotations_header_length > 0
}
/// Returns the number of bytes used to encode this value's annotations header, if any.
///
/// In Ion 1.0, the annotations header contains several fields: an opcode, a wrapper length, and
/// the length of the sequence itself. It does not include the actual sequence of annotations.
///
/// In Ion 1.1, the annotations header contains an opcode and (in the case of opcode 0xE9) a
/// FlexUInt representing the sequence length.
#[allow(dead_code)]
pub fn annotations_header_length(&self) -> usize {
self.annotations_header_length as usize
}
/// Returns the number of bytes used to encode the series of annotation symbols, if
/// any.
///
/// See: <https://amazon-ion.github.io/ion-docs/docs/binary.html#annotations>
pub fn annotations_sequence_length(&self) -> usize {
self.annotations_sequence_length as usize
}
/// Returns the combined length of the annotations header and sequence.
pub fn annotations_total_length(&self) -> usize {
self.annotations_header_length() + self.annotations_sequence_length()
}
/// Returns the offset range of the bytes in the stream that encoded the value's annotations
/// sequence.
#[allow(dead_code)]
pub fn annotations_sequence_range(&self) -> Range<usize> {
let wrapper_offset = self
.annotations_offset()
.unwrap_or_else(|| self.header_offset());
let wrapper_exclusive_end = wrapper_offset + self.annotations_header_length as usize;
let sequence_length = self.annotations_sequence_length as usize;
let sequence_offset = wrapper_exclusive_end;
let sequence_exclusive_end = sequence_offset + sequence_length;
debug_assert!(sequence_exclusive_end == self.header_offset);
sequence_offset..sequence_exclusive_end
}
pub fn annotations_sequence_offset(&self) -> Option<usize> {
if self.annotations_header_length() == 0 {
return None;
}
Some(self.header_offset - self.annotations_sequence_length())
}
/// Returns the offset of the beginning of the annotations wrapper, if present.
pub fn annotations_offset(&self) -> Option<usize> {
if self.annotations_header_length == 0 {
return None;
}
Some(self.header_offset - self.annotations_total_length())
}
/// Returns an offset Range that includes the bytes used to encode this value's annotations
/// (including both the header and sequence), if any.
pub fn annotations_range(&self) -> Option<Range<usize>> {
if let Some(start) = self.annotations_offset() {
// The annotations sequence always ends at the value's opcode.
let end = self.header_offset();
return Some(start..end);
}
None
}
/// Returns the total number of bytes used to represent the current value, including
/// its annotations (if any), its header (type descriptor + length bytes), and the body of
/// the value.
pub fn total_length(&self) -> usize {
self.total_length
}
/// The offset Range (starting from the beginning of the stream) that contains this value's
/// complete encoding, including annotations.
pub fn annotated_value_range(&self) -> Range<usize> {
// [ annotations? | header (type descriptor) | header_length? | value ]
let start = self.header_offset - self.annotations_total_length();
let end = start + self.total_length;
start..end
}
/// The offset Range (starting from the beginning of the stream) that contains this value's
/// complete encoding, not including any annotations.
pub fn unannotated_value_range(&self) -> Range<usize> {
// [ annotations? | header (type descriptor) | header_length? | value ]
let start = self.header_offset;
let end = start + self.total_length - self.annotations_total_length();
start..end
}
pub fn ion_type(&self) -> IonType {
self.header.ion_type()
}
}
#[cfg(test)]
mod tests {
use crate::binary::IonTypeCode;
use crate::lazy::binary::encoded_value::EncodedBinaryValue;
use crate::lazy::binary::raw::type_descriptor::Header;
use crate::lazy::binary::raw::v1_1::binary_buffer::AnnotationsEncoding;
use crate::lazy::binary::raw::v1_1::value::BinaryValueEncoding;
use crate::{IonResult, IonType};
#[test]
fn accessors() -> IonResult<()> {
// 3-byte String with 1-byte annotation
let value = EncodedBinaryValue {
encoding: BinaryValueEncoding::Tagged,
header: Header {
ion_type: IonType::String,
ion_type_code: IonTypeCode::String,
length_code: 3,
},
annotations_header_length: 2,
annotations_sequence_length: 1,
annotations_encoding: AnnotationsEncoding::SymbolAddress,
header_offset: 200,
length_length: 0,
value_body_length: 3,
total_length: 7,
};
assert_eq!(value.ion_type(), IonType::String);
assert_eq!(
value.header(),
Header {
ion_type: IonType::String,
ion_type_code: IonTypeCode::String,
length_code: 3,
}
);
assert_eq!(value.header_offset(), 200);
assert_eq!(value.header_length(), 1);
assert_eq!(value.header_range(), 200..201);
assert!(value.has_annotations());
assert_eq!(value.annotations_range(), Some(197..200));
assert_eq!(value.annotations_header_length(), 2);
assert_eq!(value.annotations_sequence_offset(), Some(199));
assert_eq!(value.annotations_sequence_length(), 1);
assert_eq!(value.annotations_sequence_range(), 199..200);
assert_eq!(value.value_body_length(), 3);
assert_eq!(value.value_body_offset(), 201);
assert_eq!(value.value_body_range(), 201..204);
assert_eq!(value.value_end_exclusive(), 204);
assert_eq!(value.total_length(), 7);
Ok(())
}
}