Added get_field_at_index and count_fields to struct values

src/values/struct_value.rs

@@ -1,3 +1,5 @@
+use llvm_sys::core::{LLVMGetNumOperands, LLVMGetOperand};
+
 use llvm_sys::prelude::LLVMValueRef;
 
 use std::ffi::CStr;
@@ -7,7 +9,7 @@ use crate::types::StructType;
 use crate::values::traits::AsValueRef;
 use crate::values::{InstructionValue, Value};
 
-use super::AnyValue;
+use super::{AnyValue, BasicValueEnum};
 
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)]
 pub struct StructValue<'ctx> {
@@ -23,6 +25,53 @@ impl<'ctx> StructValue<'ctx> {
         }
     }
 
+    /// Gets the value of a field belonging to this `StructValue`.
+    ///
+    /// ```no_run
+    /// use inkwell::context::Context;
+    ///
+    /// let context = Context::create();
+    /// let i32_type = context.i32_type();
+    /// let i8_type = context.i8_type();
+    /// let i8_val = i8_type.const_all_ones();
+    /// let i32_val = i32_type.const_all_ones();
+    /// let struct_type = context.struct_type(&[i8_type.into(), i32_type.into()], false);
+    /// let struct_val = struct_type.const_named_struct(&[i8_val.into(), i32_val.into()]);
+    ///
+    /// assert!(struct_val.get_field_at_index(0).is_some());
+    /// assert!(struct_val.get_field_at_index(1).is_some());
+    /// assert!(struct_val.get_field_at_index(3).is_none());
+    /// assert!(struct_val.get_field_at_index(0).unwrap().is_int_value());
+    /// ```
+    pub fn get_field_at_index(self, index: u32) -> Option<BasicValueEnum<'ctx>> {
+        // OoB indexing seems to be unchecked and therefore is UB
+        if index >= self.count_fields() {
+            return None;
+        }
+
+        unsafe { Some(BasicValueEnum::new(LLVMGetOperand(self.as_value_ref(), index))) }
+    }
+
+    /// Counts the number of fields.
+    ///
+    /// ```no_run
+    /// use inkwell::context::Context;
+    ///
+    /// let context = Context::create();
+    /// let i32_type = context.i32_type();
+    /// let i8_type = context.i8_type();
+    /// let i8_val = i8_type.const_all_ones();
+    /// let i32_val = i32_type.const_all_ones();
+    /// let struct_type = context.struct_type(&[i8_type.into(), i32_type.into()], false);
+    /// let struct_val = struct_type.const_named_struct(&[i8_val.into(), i32_val.into()]);
+    ///
+    /// assert_eq!(struct_val.count_fields(), 2);
+    /// assert_eq!(struct_val.count_fields(), struct_type.count_fields());
+    /// ```
+    pub fn count_fields(self) -> u32 {
+        unsafe { LLVMGetNumOperands(self.as_value_ref()) as u32 }
+    }
+
     /// Gets the name of a `StructValue`. If the value is a constant, this will
     /// return an empty string.
     pub fn get_name(&self) -> &CStr {

tests/all/test_values.rs

@@ -3,8 +3,8 @@ use inkwell::attributes::AttributeLoc;
 use inkwell::comdat::ComdatSelectionKind;
 use inkwell::context::Context;
 use inkwell::module::Linkage::*;
-use inkwell::types::{StringRadix, VectorType};
-use inkwell::values::{AnyValue, InstructionOpcode::*, FIRST_CUSTOM_METADATA_KIND_ID};
+use inkwell::types::{BasicType, StringRadix, VectorType};
+use inkwell::values::{AnyValue, BasicValue, InstructionOpcode::*, FIRST_CUSTOM_METADATA_KIND_ID};
 use inkwell::{AddressSpace, DLLStorageClass, GlobalVisibility, ThreadLocalMode};
 
 use std::convert::TryFrom;
@@ -1184,10 +1184,41 @@ fn test_consts() {
     assert_eq!(f128_val.get_constant(), Some((7.8, false)));
     assert_eq!(ppc_f128_val.get_constant(), Some((9.0, false)));
 
+    //const struct member access
+    let void_type = context.void_type();
+    let struct_type = context.struct_type(&[i8_type.into(), f32_type.into()], false);
+    let module = context.create_module("test");
+    let test_func = module.add_function("strut_test", void_type.fn_type(&[struct_type.into()], false), None);
+    let non_const_struct_val = test_func.get_nth_param(0).unwrap().into_struct_value();
+    assert_eq!(non_const_struct_val.count_fields(), 0);
+
+    let struct_val = struct_type.const_named_struct(&[i8_val.into(), f32_val.into()]);
+    assert_eq!(struct_val.count_fields(), 2);
+    assert_eq!(struct_val.count_fields(), struct_type.count_fields());
+    assert!(struct_val.get_field_at_index(0).is_some());
+    assert!(struct_val.get_field_at_index(1).is_some());
+    assert!(struct_val.get_field_at_index(3).is_none());
+    assert!(struct_val.get_field_at_index(0).unwrap().is_int_value());
+    assert!(struct_val.get_field_at_index(1).unwrap().is_float_value());
+    assert_eq!(
+        struct_val
+            .get_field_at_index(0)
+            .unwrap()
+            .into_int_value()
+            .get_sign_extended_constant(),
+        Some(-1)
+    );
+    assert_eq!(
+        struct_val
+            .get_field_at_index(1)
+            .unwrap()
+            .into_float_value()
+            .get_constant(),
+        Some((3.4000000953674316, false))
+    );
+
     // Non const test
     let builder = context.create_builder();
-    let module = context.create_module("fns");
-    let void_type = context.void_type();
     let fn_type = void_type.fn_type(&[i32_type.into(), f32_type.into()], false);
     let function = module.add_function("fn", fn_type, None);
     let basic_block = context.append_basic_block(function, "entry");