Target-Specific Arithmetic in Rust

This challenge focuses on writing Rust code that performs arithmetic operations differently based on a specified target. This is a common requirement in embedded systems or when dealing with hardware-specific optimizations, where the same code needs to behave differently depending on the underlying architecture. You'll be creating a function that performs addition, but the addition method varies based on a provided target string.

Problem Description

You are tasked with creating a function targeted_add that takes two integer arguments (a and b) and a target string as input. The function should return the sum of a and b, but the method of calculating the sum depends on the target string.

• If the target string is "x86_64", the function should perform a standard integer addition.
• If the target string is "armv7", the function should perform a bitwise XOR addition (a ^ b).
• If the target string is "riscv64", the function should perform a circular addition, where the result is the sum modulo 2^32 (i.e., (a + b) % (2u32.pow(32)) as i32).
• For any other target string, the function should return an error value of -1.

The function must handle potential overflow gracefully. For the "x86_64" target, standard Rust integer overflow behavior applies. For "armv7", overflow is handled by the nature of XOR. For "riscv64", the modulo operation inherently handles overflow.

Examples

Example 1:

Input: a = 5, b = 3, target = "x86_64"
Output: 8
Explanation: Standard integer addition: 5 + 3 = 8

Example 2:

Input: a = 5, b = 3, target = "armv7"
Output: 6
Explanation: Bitwise XOR addition: 5 ^ 3 = 6 (binary: 0101 ^ 0011 = 0110)

Example 3:

Input: a = 2147483647, b = 1, target = "riscv64"
Output: -2147483648
Explanation: Circular addition: (2147483647 + 1) % (2^32) = 2147483648 % 4294967296 = 2147483648.  Since we're returning an i32, this becomes -2147483648 due to two's complement representation.

Example 4:

Input: a = 10, b = 20, target = "invalid_target"
Output: -1
Explanation: The target is not recognized, so the error value is returned.

Constraints

• a and b will be 32-bit integers (i32).
• The target string will be a string slice (&str).
• The function must return an i32.
• The function must handle invalid target strings gracefully.
• Performance is not a primary concern for this challenge, but avoid unnecessarily complex solutions.

Notes

• Consider using a match statement for efficient target string comparison.
• Be mindful of the different behaviors of integer addition, XOR, and modulo operations.
• The "riscv64" target requires careful consideration of how the modulo operation interacts with signed integers in Rust. Use u32.pow(32) to represent 2^32.
• The function signature should be fn targeted_add(a: i32, b: i32, target: &str) -> i32.