experiment: start implementing checks in wasm (client side only so far)

Signed-off-by: Xe Iaso <me@xeiaso.net>

wasm/pow/sha256/src/lib.rs

@@ -0,0 +1,139 @@
+use lazy_static::lazy_static;
+use sha2::{Digest, Sha256};
+use std::sync::Mutex;
+
+lazy_static! {
+    static ref DATA_BUFFER: Mutex<[u8; 1024]> = Mutex::new([0; 1024]);
+    static ref DATA_LENGTH: Mutex<usize> = Mutex::new(0);
+    static ref RESULT_HASH: Mutex<[u8; 32]> = Mutex::new([0; 32]);
+    static ref VERIFICATION_HASH: Mutex<[u8; 32]> = Mutex::new([0; 32]);
+}
+
+#[link(wasm_import_module = "anubis")] // Usually matches your JS namespace
+unsafe extern "C" {
+    // Declare the imported function
+    fn anubis_update_nonce(nonce: u32);
+}
+
+fn update_nonce(nonce: u32) {
+    unsafe {
+        anubis_update_nonce(nonce);
+    }
+}
+
+/// Core validation function
+fn validate(hash: &[u8], difficulty: u32) -> bool {
+    let mut remaining = difficulty;
+    for &byte in hash {
+        if remaining == 0 {
+            break;
+        }
+        if remaining >= 8 {
+            if byte != 0 {
+                return false;
+            }
+            remaining -= 8;
+        } else {
+            let mask = 0xFF << (8 - remaining);
+            if (byte & mask) != 0 {
+                return false;
+            }
+            remaining = 0;
+        }
+    }
+    true
+}
+
+/// Computes hash for given nonce
+fn compute_hash(nonce: u32) -> [u8; 32] {
+    let data = DATA_BUFFER.lock().unwrap();
+    let data_len = *DATA_LENGTH.lock().unwrap();
+    let use_le = data[data_len - 1] >= 128;
+
+    let data_slice = &data[..data_len];
+
+    let mut hasher = Sha256::new();
+    hasher.update(data_slice);
+    hasher.update(if use_le {
+        nonce.to_le_bytes()
+    } else {
+        nonce.to_be_bytes()
+    });
+    hasher.finalize().into()
+}
+
+// WebAssembly exports
+
+#[unsafe(no_mangle)]
+pub extern "C" fn anubis_work(difficulty: u32, initial_nonce: u32, iterand: u32) -> u32 {
+    let mut nonce = initial_nonce;
+
+    loop {
+        let hash = compute_hash(nonce);
+
+        if validate(&hash, difficulty) {
+            let mut challenge = RESULT_HASH.lock().unwrap();
+            challenge.copy_from_slice(&hash);
+            return nonce;
+        }
+
+        let old_nonce = nonce;
+        nonce = nonce.wrapping_add(iterand);
+
+        // send a progress update every 1024 iterations. since each thread checks
+        // separate values, one simple way to do this is by bit masking the
+        // nonce for multiples of 1024. unfortunately, if the number of threads
+        // is not prime, only some of the threads will be sending the status
+        // update and they will get behind the others. this is slightly more
+        // complicated but ensures an even distribution between threads.
+        if nonce > old_nonce | 1023 && (nonce >> 10) % iterand == initial_nonce {
+            update_nonce(nonce);
+        }
+    }
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn anubis_validate(nonce: u32, difficulty: u32) -> bool {
+    let computed = compute_hash(nonce);
+    let valid = validate(&computed, difficulty);
+
+    let verification = VERIFICATION_HASH.lock().unwrap();
+    valid && computed == *verification
+}
+
+// Memory accessors
+
+#[unsafe(no_mangle)]
+pub extern "C" fn result_hash_ptr() -> *const u8 {
+    let challenge = RESULT_HASH.lock().unwrap();
+    challenge.as_ptr()
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn result_hash_size() -> usize {
+    RESULT_HASH.lock().unwrap().len()
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn verification_hash_ptr() -> *const u8 {
+    let verification = VERIFICATION_HASH.lock().unwrap();
+    verification.as_ptr()
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn verification_hash_size() -> usize {
+    VERIFICATION_HASH.lock().unwrap().len()
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn data_ptr() -> *const u8 {
+    let challenge = DATA_BUFFER.lock().unwrap();
+    challenge.as_ptr()
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn set_data_length(len: u32) {
+    // Add missing length setter
+    let mut data_length = DATA_LENGTH.lock().unwrap();
+    *data_length = len as usize;
+}