From 84b9f3499d8d4664a943dedd7017fc70248cb605 Mon Sep 17 00:00:00 2001
From: Richard Giliam <glitch@amazon.com>
Date: Tue, 30 Apr 2024 17:01:40 -0700
Subject: [PATCH] Add 1.1 binary reader support for floats

---
 src/lazy/binary/raw/v1_1/reader.rs          | 55 +++++++++++++++++++++
 src/lazy/binary/raw/v1_1/type_descriptor.rs |  3 ++
 src/lazy/binary/raw/v1_1/value.rs           | 28 ++++++++++-
 3 files changed, 85 insertions(+), 1 deletion(-)

diff --git a/src/lazy/binary/raw/v1_1/reader.rs b/src/lazy/binary/raw/v1_1/reader.rs
index 9800c4027..e1cc08887 100644
--- a/src/lazy/binary/raw/v1_1/reader.rs
+++ b/src/lazy/binary/raw/v1_1/reader.rs
@@ -310,4 +310,59 @@ mod tests {
 
         Ok(())
     }
+
+    macro_rules! assert_closely_eq {
+        ($x:expr, $y:expr, $d:expr) => {
+            let (a, b) = ($x, $y);
+            if ((a - b).abs() >= $d) {
+                panic!(
+                    "float not close enough to expected value: left: {}, right: {}",
+                    a, b
+                );
+            }
+        };
+    }
+
+    #[test]
+    #[allow(clippy::approx_constant)]
+    fn floats() -> IonResult<()> {
+        #[rustfmt::skip]
+        let data: Vec<u8> = vec![
+            // IVM
+            0xe0, 0x01, 0x01, 0xea,
+            // 0e0
+            0x5A,
+
+            // 3.14 (half-precision)
+            // 0x5B, 0x42, 0x47,
+
+            // 3.1415927 (single-precision)
+            0x5C, 0xdb, 0x0F, 0x49, 0x40,
+
+            // 3.141592653589793 (double-precision)
+            0x5D, 0x18, 0x2D, 0x44, 0x54, 0xFB, 0x21, 0x09, 0x40,
+        ];
+
+        let mut reader = LazyRawBinaryReader_1_1::new(&data);
+        let _ivm = reader.next()?.expect_ivm()?;
+
+        assert_eq!(reader.next()?.expect_value()?.read()?.expect_float()?, 0.0);
+
+        // TODO: Implement Half-precision.
+        // assert_eq!(reader.next()?.expect_value()?.read()?.expect_float()?, 3.14);
+
+        assert_closely_eq!(
+            reader.next()?.expect_value()?.read()?.expect_float()? as f32,
+            3.1415927f32,
+            f32::EPSILON
+        );
+
+        assert_closely_eq!(
+            reader.next()?.expect_value()?.read()?.expect_float()?,
+            std::f64::consts::PI,
+            f64::EPSILON
+        );
+
+        Ok(())
+    }
 }
diff --git a/src/lazy/binary/raw/v1_1/type_descriptor.rs b/src/lazy/binary/raw/v1_1/type_descriptor.rs
index 144649f29..53d97dcc3 100644
--- a/src/lazy/binary/raw/v1_1/type_descriptor.rs
+++ b/src/lazy/binary/raw/v1_1/type_descriptor.rs
@@ -41,6 +41,7 @@ impl Opcode {
 
         let (opcode_type, length_code, ion_type) = match (high_nibble, low_nibble) {
             (0x5, 0x0..=0x8) => (Integer, low_nibble, Some(IonType::Int)),
+            (0x5, 0xA..=0xD) => (Float, low_nibble, Some(IonType::Float)),
             (0x5, 0xE..=0xF) => (Boolean, low_nibble, Some(IonType::Bool)),
             (0x8, _) => (String, low_nibble, Some(IonType::String)),
             (0xE, 0x0) => (IonVersionMarker, low_nibble, None),
@@ -109,6 +110,8 @@ impl Header {
         use LengthType::*;
         match (self.ion_type_code, self.length_code) {
             (OpcodeType::Boolean, 0xE..=0xF) => InOpcode(0),
+            (OpcodeType::Float, 0xA) => InOpcode(0),
+            (OpcodeType::Float, 0xB..=0xD) => InOpcode(1 << (self.length_code - 0xA)),
             (OpcodeType::Integer, n) => InOpcode(n),
             (OpcodeType::Nop, 0xC) => InOpcode(0),
             (OpcodeType::NullNull, 0xA) => InOpcode(0),
diff --git a/src/lazy/binary/raw/v1_1/value.rs b/src/lazy/binary/raw/v1_1/value.rs
index df0c91cb9..8b2d3c15d 100644
--- a/src/lazy/binary/raw/v1_1/value.rs
+++ b/src/lazy/binary/raw/v1_1/value.rs
@@ -236,7 +236,33 @@ impl<'top> LazyRawBinaryValue_1_1<'top> {
 
     /// Helper method called by [`Self::read`]. Reads the current value as a float.
     fn read_float(&self) -> ValueParseResult<'top, BinaryEncoding_1_1> {
-        todo!();
+        debug_assert!(self.encoded_value.ion_type() == IonType::Float);
+
+        let value = match self.encoded_value.value_length {
+            8 => {
+                let mut buffer = [0; 8];
+                let val_bytes = self.input.slice(1, 8);
+                buffer[..8].copy_from_slice(val_bytes.bytes());
+
+                f64::from_le_bytes(buffer)
+            }
+            4 => {
+                let mut buffer = [0; 4];
+                let val_bytes = self.input.slice(1, 4);
+                buffer[..4].copy_from_slice(val_bytes.bytes());
+
+                f32::from_le_bytes(buffer).into()
+            }
+            2 => todo!("implement half-precision floats"),
+            0 => 0.0f64,
+            n => {
+                return IonResult::decoding_error(format!(
+                    "found a float value with an illegal bytes size: {:?}",
+                    n
+                ));
+            }
+        };
+        Ok(RawValueRef::Float(value))
     }
 
     /// Helper method called by [`Self::read`]. Reads the current value as a decimal.