Adds binary eexp subfield span accessors (#850)

src/lazy/any_encoding.rs

@@ -202,6 +202,10 @@ pub enum LazyRawAnyEExpressionKind<'top> {
 }
 
 impl<'top> LazyRawAnyEExpression<'top> {
+    pub fn kind(&self) -> LazyRawAnyEExpressionKind<'top> {
+        self.encoding
+    }
+
     pub fn encoding(&self) -> IonEncoding {
         use LazyRawAnyEExpressionKind::*;
         match self.encoding {

src/lazy/binary/raw/v1_1/e_expression.rs

@@ -18,32 +18,6 @@ use crate::lazy::text::raw::v1_1::arg_group::{EExpArg, EExpArgExpr};
 use crate::lazy::text::raw::v1_1::reader::MacroIdRef;
 use crate::{try_or_some_err, v1_1, Environment, HasRange, HasSpan, IonResult, Span};
 
-#[derive(Copy, Clone)]
-pub struct BinaryEExpHeader {
-    // The number of bytes that were used to encode the e-expression's opcode and address.
-    opcode_and_address_length: u8,
-    // The number of bytes that were used to encode the e-expression's arg grouping bitmap, if any.
-    bitmap_length: u8,
-}
-
-impl BinaryEExpHeader {
-    pub fn new(opcode_length: u8, bitmap_length: u8) -> Self {
-        Self {
-            opcode_and_address_length: opcode_length,
-            bitmap_length,
-        }
-    }
-    pub fn address_and_opcode_length(&self) -> usize {
-        self.opcode_and_address_length as usize
-    }
-    pub fn bitmap_length(&self) -> usize {
-        self.bitmap_length as usize
-    }
-    pub fn header_length(&self) -> usize {
-        self.address_and_opcode_length() + self.bitmap_length()
-    }
-}
-
 /// An e-expression which has been parsed from a binary Ion 1.1 stream.
 #[derive(Copy, Clone)]
 pub struct BinaryEExpression_1_1<'top> {
@@ -64,11 +38,14 @@ pub struct BinaryEExpression_1_1<'top> {
     cache: Option<&'top [ValueExpr<'top, BinaryEncoding_1_1>]>,
     macro_ref: MacroRef<'top>,
     bitmap_bits: u64,
-    // The index of `input` at which the bitmap can be found. If there is no bitmap, this index
-    // will be the beginning of the encoded arguments.
+    // This index is the first position after the opcode and address.
+    // If the e-expression has a length prefix, it will begin at this position in `input`.
+    length_offset: u8,
+    // This index is the first position after the opcode, address, and length prefix.
+    // If the e-expression has a bitmap, it will begin at this position in `input`.
     bitmap_offset: u8,
-    // The index at which the arguments to the e-expression begin within `input`. This index is
-    // the first position after the opcode, address, length, and bitmap.
+    // This index is the first position after the opcode, address, length, and bitmap.
+    // If the e-expression has arguments, they will begin at this position in `input`.
     args_offset: u8,
 
     pub(crate) input: BinaryBuffer<'top>,
@@ -79,26 +56,66 @@ impl<'top> BinaryEExpression_1_1<'top> {
         macro_ref: MacroRef<'top>,
         bitmap_bits: u64,
         input: BinaryBuffer<'top>,
+        length_offset: u8,
         bitmap_offset: u8,
         args_offset: u8,
     ) -> Self {
         Self {
             bitmap_bits,
             input,
             macro_ref,
+            length_offset,
             bitmap_offset,
             args_offset,
             cache: None,
         }
     }
 
-    pub fn with_arg_expr_cache(
+    pub(crate) fn with_arg_expr_cache(
         mut self,
         cache: &'top [ValueExpr<'top, BinaryEncoding_1_1>],
     ) -> Self {
         self.cache = Some(cache);
         self
     }
+
+    /// Returns a span of bytes representing the opcode and macro address.
+    /// Depending on the encoding, these may be distinct (for example, the span: `0xF4 0x01`,
+    /// where the `0xF4` is the opcode and the `0x01` is the `FlexUInt` address) or combined
+    /// (for example: `0x00` is both an opcode and a macro address).
+    pub fn opcode_and_address_span(&self) -> Span<'top> {
+        self.input.slice(0, self.length_offset as usize).into()
+    }
+
+    /// Returns `true` if this binary e-expression includes a length prefix.
+    pub fn has_length_prefix(&self) -> bool {
+        // If these offsets are equal, there are no bytes representing the length.
+        self.length_offset != self.bitmap_offset
+    }
+
+    /// Returns a span of bytes representing the length prefix. If there is no length prefix,
+    /// the returned span will be empty.
+    pub fn length_prefix_span(&self) -> Span<'top> {
+        let num_bytes = (self.bitmap_offset - self.length_offset) as usize;
+        self.input
+            .slice(self.length_offset as usize, num_bytes)
+            .into()
+    }
+
+    /// Returns `true` if this binary e-expression includes an argument encoding bitmap.
+    pub fn has_bitmap(&self) -> bool {
+        // If these offsets are equal, there are no bytes representing the bitmap.
+        self.bitmap_offset != self.args_offset
+    }
+
+    /// Returns a span of bytes representing the e-expression's argument encoding bitmap.
+    /// If there is no argument encoding bitmap, the returned span will be empty.
+    pub fn bitmap_span(&self) -> Span<'top> {
+        let num_bytes = (self.args_offset - self.bitmap_offset) as usize;
+        self.input
+            .slice(self.bitmap_offset as usize, num_bytes)
+            .into()
+    }
 }
 
 impl<'top> HasSpan<'top> for &'top BinaryEExpression_1_1<'top> {

src/lazy/binary/raw/v1_1/immutable_buffer.rs

@@ -963,6 +963,9 @@ impl<'a> BinaryBuffer<'a> {
                     MacroRef::new(macro_address, macro_ref),
                     bitmap_bits,
                     matched_eexp_bytes,
+                    // There is no length prefix, so we re-use the bitmap_offset as the first position
+                    // beyond the opcode and address subfields.
+                    bitmap_offset as u8,
                     bitmap_offset as u8,
                     args_offset as u8,
                 )
@@ -996,6 +999,7 @@ impl<'a> BinaryBuffer<'a> {
             })?
             .reference();
         // Offset from `self`, not offset from the beginning of the stream.
+        let length_offset = (input_after_address.offset() - self.offset()) as u8;
         let bitmap_offset = (input_after_length.offset() - self.offset()) as u8;
         let (bitmap_bits, _input_after_bitmap) =
             input_after_length.read_eexp_bitmap(macro_ref.signature().bitmap_size_in_bytes())?;
@@ -1006,6 +1010,7 @@ impl<'a> BinaryBuffer<'a> {
                 MacroRef::new(macro_address, macro_ref),
                 bitmap_bits,
                 matched_bytes,
+                length_offset,
                 bitmap_offset,
                 args_offset,
             ),

src/lazy/span.rs

@@ -1,3 +1,5 @@
+use crate::lazy::binary::raw::v1_1::immutable_buffer::BinaryBuffer;
+use crate::lazy::text::buffer::TextBuffer;
 use crate::result::IonFailure;
 use crate::{IonError, IonResult};
 use std::ops::Range;
@@ -62,3 +64,21 @@ impl<'a> Span<'a> {
         self.bytes.is_empty()
     }
 }
+
+impl<'a> From<BinaryBuffer<'a>> for Span<'a> {
+    fn from(value: BinaryBuffer<'a>) -> Self {
+        Span {
+            bytes: value.bytes(),
+            offset: value.offset(),
+        }
+    }
+}
+
+impl<'a> From<TextBuffer<'a>> for Span<'a> {
+    fn from(value: TextBuffer<'a>) -> Self {
+        Span {
+            bytes: value.bytes(),
+            offset: value.offset(),
+        }
+    }
+}