diff --git a/lib/std/hash/sha256.c3 b/lib/std/hash/sha256.c3
index 23b0e701b..706f1d55f 100644
--- a/lib/std/hash/sha256.c3
+++ b/lib/std/hash/sha256.c3
@@ -1,177 +1,175 @@
 module std::hash::sha256;
-
-import std::hash::hmac;
+import std::bits, std::hash::hmac;
 
 const BLOCK_SIZE = 64;
 const HASH_SIZE = 32;
 
-const uint[64] K @local = {
-    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
-    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
-    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
-    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
-    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
-    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
-    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
-    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
-};
-
-// Right rotate function
-macro uint @rotr(uint x, uint n) @local => (((x) >> (n)) | ((x) << (32 - (n))));
-
-// SHA-256 functions
-macro uint @ch(uint x, uint y, uint z) @local => (x & y) ^ (~x & z);
-macro uint @maj(uint x, uint y, uint z) @local => (x & y) ^ (x & z) ^ (y & z);
-macro uint @_sigma0(uint x) @local => @rotr(x, 2) ^ @rotr(x, 13) ^ @rotr(x, 22);
-macro uint @_sigma1(uint x) @local => @rotr(x, 6) ^ @rotr(x, 11) ^ @rotr(x, 25);
-macro uint @sigma0(uint x) @local => @rotr(x, 7) ^ @rotr(x, 18) ^ (x >> 3);
-macro uint @sigma1(uint x) @local => @rotr(x, 17) ^ @rotr(x, 19) ^ (x >> 10);
-
-struct Sha256
-{
-    uint[8] state;
-    ulong bitcount;
-    char[BLOCK_SIZE] buffer;
-}
-
 alias HmacSha256 = Hmac{Sha256, HASH_SIZE, BLOCK_SIZE};
 alias hmac = hmac::hash{Sha256, HASH_SIZE, BLOCK_SIZE};
 alias pbkdf2 = hmac::pbkdf2{Sha256, HASH_SIZE, BLOCK_SIZE};
 
-fn char[HASH_SIZE] hash(char[] data)
+const uint[64] K @local = {
+	0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
+	0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
+	0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+	0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
+	0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
+	0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+	0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+	0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
+};
+
+macro uint @ch(uint x, uint y, uint z) @local => (x & y) ^ (~x & z);
+macro uint @maj(uint x, uint y, uint z) @local => (x & y) ^ (x & z) ^ (y & z);
+macro uint @_sigma0(uint x) @local => x.rotr(2) ^ x.rotr(13) ^ x.rotr(22);
+macro uint @_sigma1(uint x) @local => x.rotr(6) ^ x.rotr(11) ^ x.rotr(25);
+macro uint @sigma0(uint x) @local => x.rotr(7) ^ x.rotr(18) ^ (x >> 3);
+macro uint @sigma1(uint x) @local => x.rotr(17) ^ x.rotr(19) ^ (x >> 10);
+
+struct Sha256
 {
-    Sha256 sha256 @noinit;
-    sha256.init();
-    sha256.update(data);
-    return sha256.final();
+	uint[8] state @align(usz.sizeof);
+	char[BLOCK_SIZE] buffer @align(ulong.sizeof);   // must align along bitcount sizeof - see `final`
+	ulong bitcount;
 }
 
-fn void Sha256.init(&self)
+<*
+ Compute and return a hash value.
+
+ @param [in] data : "The input data to hash."
+*>
+fn char[HASH_SIZE] hash(char[] data)
 {
-    // Sha256 initialization constants
-    *self = {
-        .state = {
-            0x6A09E667,
-            0xBB67AE85,
-            0x3C6EF372,
-            0xA54FF53A,
-            0x510E527F,
-            0x9B05688C,
-            0x1F83D9AB,
-            0x5BE0CD19
-        }
-    };
+	Sha256 sha256 @noinit;
+	sha256.init();
+	sha256.update(data);
+	return sha256.final();
 }
 
+fn void Sha256.init(&self) => *self = {
+	.state = {
+		0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
+		0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
+	},
+};
+
 <*
  @param [in] data
  @require data.len <= uint.max
 *>
-fn void Sha256.update(&self, char[] data) {
-    uint i = 0;
-    uint len = data.len;
-    uint buffer_pos = (uint)(self.bitcount / 8) % BLOCK_SIZE;
-    self.bitcount += ((ulong)len * 8);
+fn void Sha256.update(&self, char[] data)
+{
+	uint buffer_pos = (uint)(self.bitcount >> 3) % BLOCK_SIZE;
+	self.bitcount += (ulong)data.len << 3; // always record ingested bits count immediately
 
-    while (len--) {
-        self.buffer[buffer_pos++] = data[i++];
-        if (buffer_pos == BLOCK_SIZE) {
-            sha256_transform(&self.state, &self.buffer);
-            buffer_pos = 0;  // Reset buffer position
-        }
-    }
+	// Get the buffer position back to 0 if we're midway through consuming some data.
+	if (buffer_pos > 0 && buffer_pos < BLOCK_SIZE)
+	{
+		usz len = min(BLOCK_SIZE - buffer_pos, data.len);
+		self.buffer[buffer_pos:len] = data[:len];
+		data = data[len..];
+		if (buffer_pos + len == BLOCK_SIZE) self.transform();
+	}
+
+	// When the data pointer is aligned, we can disregard unaligned loading in the `transform` macro.
+	//   We do this here from the outer call to reduce the expense of checking alignment on every single block.
+	if (0 == (usz)data.ptr % usz.sizeof)
+	{
+		for (; data.len >= BLOCK_SIZE; data = data[BLOCK_SIZE..]) self.transform((uint*)data.ptr);
+	}
+	else
+	{
+		for (; data.len >= BLOCK_SIZE; data = data[BLOCK_SIZE..]) self.transform_unaligned((uint*)data.ptr);
+	}
+
+	// Leftover data just gets stored away for the next update or final.
+	if (data.len)
+	{
+		self.buffer[..] = 0;
+		self.buffer[:data.len] = data[..];
+	}
 }
 
-fn char[HASH_SIZE] Sha256.final(&self) {
-    char[HASH_SIZE] hash;
-    ulong i = (self.bitcount / 8) % BLOCK_SIZE;
+fn char[HASH_SIZE] Sha256.final(&self)
+{
+	char[HASH_SIZE] hash @align(uint.sizeof);
+	ulong i = (self.bitcount / 8) % BLOCK_SIZE;
 
-    // Append 0x80 to the buffer
-    self.buffer[i++] = 0x80;
+	// Append 0x80 to the buffer
+	self.buffer[i++] = 0x80;
 
-    // Pad the buffer with zeros
-    if (i > BLOCK_SIZE - 8) {
-        while (i < BLOCK_SIZE) {
-            self.buffer[i++] = 0x00;
-        }
-        sha256_transform(&self.state, &self.buffer);
-        i = 0;  // Reset buffer index after transformation
-    }
-    
-    while (i < BLOCK_SIZE - 8) {
-        self.buffer[i++] = 0x00;
-    }
+	// Pad the buffer with zeros
+	if (i > BLOCK_SIZE - 8)
+	{
+		self.buffer[i..] = 0x00;
+		self.transform();
+		i = 0;  // Reset buffer index after transformation
+	}
 
-    // Append the bitcount in big-endian format
-    for (int j = 0; j < 8; ++j) {
-        self.buffer[BLOCK_SIZE - 8 + j] = (char)((self.bitcount >> (56 - j * 8)) & 0xFF);
-    }
+	self.buffer[i..(BLOCK_SIZE - 8)] = 0x00;
 
-    sha256_transform(&self.state, &self.buffer);
+	// Append the bitcount in big-endian format
+	*(ulong*)(&self.buffer[BLOCK_SIZE - 8]) = env::BIG_ENDIAN ??? self.bitcount : bswap(self.bitcount);
 
-    // Convert state to the final hash
-    for (i = 0; i < 8; ++i) {
-        hash[i * 4] = (char)((self.state[i] >> 24) & 0xFF);
-        hash[i * 4 + 1] = (char)((self.state[i] >> 16) & 0xFF);
-        hash[i * 4 + 2] = (char)((self.state[i] >> 8) & 0xFF);
-        hash[i * 4 + 3] = (char)(self.state[i] & 0xFF);
-    }
-    
-    return hash;
+	self.transform();
+
+	// Convert state to the final hash
+	foreach (x, s : self.state) *(uint*)(&hash[x * uint.sizeof]) = env::BIG_ENDIAN ??? s : bswap(s);
+	
+	return hash;
 }
 
-<*
- @param [&inout] state
- @param [&in] buffer
-*>
-fn void sha256_transform(uint* state, char* buffer) @local {
-    uint a, b, c, d, e, f, g, h, t1, t2;
-    uint[64] m;
-    int i;
+// These wrappers are necessary to significantly reduce code generation from macro expansions.
+//   Note that transformations on `self.buffer` (when incoming == null) should always be aligned.
+fn void Sha256.transform(&self, uint* incoming = null) @local @noinline => self.do_transform(incoming, true);
+fn void Sha256.transform_unaligned(&self, uint* incoming = null) @local @noinline => self.do_transform(incoming, false);
 
-    // Prepare the message schedule
-    for (i = 0; i < 16; ++i) {
-     m[i] = ((uint)buffer[i * 4] << 24) | ((uint)buffer[i * 4 + 1] << 16) |
-       ((uint)buffer[i * 4 + 2] << 8) | ((uint)buffer[i * 4 + 3]);  // Ensure values are cast to uint for correct shifts
-    }
-    for (i = 16; i < 64; ++i) {
-        m[i] = @sigma1(m[i - 2]) + m[i - 7] + @sigma0(m[i - 15]) + m[i - 16];
-    }
+macro Sha256.do_transform(&self, uint* incoming = null, bool $aligned = true) @local
+{
+	uint a, b, c, d, e, f, g, h, t1, t2 @noinit;
+	uint[64] m @noinit;
+	int i @noinit;
 
-    // Initialize working variables
-    a = state[0];
-    b = state[1];
-    c = state[2];
-    d = state[3];
-    e = state[4];
-    f = state[5];
-    g = state[6];
-    h = state[7];
+	if (!incoming) incoming = (uint*)&self.buffer;
 
-    // Perform the main SHA-256 compression function
-    for (i = 0; i < 64; ++i) {
-        t1 = h + @_sigma1(e) + @ch(e, f, g) + K[i] + m[i];
-        t2 = @_sigma0(a) + @maj(a, b, c);
-        h = g;
-        g = f;
-        f = e;
-        e = d + t1;
-        d = c;
-        c = b;
-        b = a;
-        a = t1 + t2;
-    }
+	$if env::BIG_ENDIAN:
+		@as_char_view(m)[:BLOCK_SIZE] = @as_char_view(incoming)[:BLOCK_SIZE];
+	$else
+		// Unrolling this seems to make the hash slower.
+		for (i = 0; i < 16; ++i) m[i] = bswap($aligned ??? incoming[i] : @unaligned_load(incoming[i], 1));
+	$endif
 
-    // Update the state
-    state[0] += a;
-    state[1] += b;
-    state[2] += c;
-    state[3] += d;
-    state[4] += e;
-    state[5] += f;
-    state[6] += g;
-    state[7] += h;
-    a = b = c = d = e = f = g = h = t1 = t2 = i = 0;
-    m[:64] = buffer[:64] = 0;
+	for (i = 16; i < 64; i++) m[i] = @sigma1(m[i - 2]) + m[i - 7] + @sigma0(m[i - 15]) + m[i - 16];
+
+	a = self.state[0];
+	b = self.state[1];
+	c = self.state[2];
+	d = self.state[3];
+	e = self.state[4];
+	f = self.state[5];
+	g = self.state[6];
+	h = self.state[7];
+
+	$for usz $i = 0; $i < 64; $i++:
+		t1 = h + @_sigma1(e) + @ch(e, f, g) + K[$i] + m[$i];
+		t2 = @_sigma0(a) + @maj(a, b, c);
+		h = g;
+		g = f;
+		f = e;
+		e = d + t1;
+		d = c;
+		c = b;
+		b = a;
+		a = t1 + t2;
+	$endfor
+
+	self.state[0] += a;
+	self.state[1] += b;
+	self.state[2] += c;
+	self.state[3] += d;
+	self.state[4] += e;
+	self.state[5] += f;
+	self.state[6] += g;
+	self.state[7] += h;
 }
 
diff --git a/test/unit/stdlib/hash/sha256.c3 b/test/unit/stdlib/hash/sha256.c3
index 61adf853c..5efab0217 100644
--- a/test/unit/stdlib/hash/sha256.c3
+++ b/test/unit/stdlib/hash/sha256.c3
@@ -7,7 +7,7 @@ fn void test_sha256_empty()
     sha.init();
     sha.update("");
 
-    assert(sha.final() == x"E3B0C442 98FC1C14 9AFBF4C8 996FB924 27AE41E4 649B934C A495991B 7852B855");
+    test::@check(sha.final() == x"E3B0C442 98FC1C14 9AFBF4C8 996FB924 27AE41E4 649B934C A495991B 7852B855");
 }
 
 fn void test_sha256_abc()
@@ -16,7 +16,7 @@ fn void test_sha256_abc()
     sha.init();
     sha.update("abc");
 
-    assert(sha.final() == x"BA7816BF 8F01CFEA 414140DE 5DAE2223 B00361A3 96177A9C B410FF61 F20015AD");
+    test::@check(sha.final() == x"BA7816BF 8F01CFEA 414140DE 5DAE2223 B00361A3 96177A9C B410FF61 F20015AD");
 }
 
 fn void test_sha256_longer()
@@ -24,7 +24,21 @@ fn void test_sha256_longer()
     Sha256 sha;
     sha.init();
     sha.update("abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopqabcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq");
-    assert(sha.final() == x"59F109D9 533B2B70 E7C3B814 A2BD218F 78EA5D37 14455BC6 7987CF0D 664399CF");
+    test::@check(sha.final() == x"59F109D9 533B2B70 E7C3B814 A2BD218F 78EA5D37 14455BC6 7987CF0D 664399CF");
+}
+
+fn void test_sha256_multi_update_permute()
+{
+    char[] input = "a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string a really long string";
+    for (usz step = 1; step < input.len; step++)
+    {
+        Sha256 sha;
+        sha.init();
+        usz i = 0;
+        for (; i < input.len / step; i++) sha.update(input[i*step : step]);
+        if (i*step < input.len) sha.update(input[i*step..]);
+        test::@check(sha.final() == x"b527293dfb70dcce37e593f4c43e1b81909615722bad041b90b8df22bebd00a0", "Mismatch for step %d", step);
+    }
 }
 
 /*
@@ -37,7 +51,7 @@ fn void gigahash_sha256()
     Sha256 sha;
     sha.init();
     sha.update(c);
-    assert(sha.final() == x"053EADFD EC682CF1 6F3F8704 C7609C57 868DD757 65E08DC5 A7491F5D 06BCB74D");
+    test::@check(sha.final() == x"053EADFD EC682CF1 6F3F8704 C7609C57 868DD757 65E08DC5 A7491F5D 06BCB74D");
 }
 */
 fn void test_pbkdf2()
@@ -46,11 +60,11 @@ fn void test_pbkdf2()
     char[] s = "salt";
     char[32] out;
     sha256::pbkdf2(pw, s, 1, &out);
-    assert(out == x'120FB6CF FCF8B32C 43E72252 56C4F837 A86548C9 2CCC3548 0805987C B70BE17B');
+    test::@check(out == x'120FB6CF FCF8B32C 43E72252 56C4F837 A86548C9 2CCC3548 0805987C B70BE17B');
     sha256::pbkdf2(pw, s, 2, &out);
-    assert(out == x'AE4D0C95 AF6B46D3 2D0ADFF9 28F06DD0 2A303F8E F3C251DF D6E2D85A 95474C43');
+    test::@check(out == x'AE4D0C95 AF6B46D3 2D0ADFF9 28F06DD0 2A303F8E F3C251DF D6E2D85A 95474C43');
     sha256::pbkdf2(pw, s, 4096, &out);
-    assert(out == x'C5E478D5 9288C841 AA530DB6 845C4C8D 962893A0 01CE4E11 A4963873 AA98134A');
+    test::@check(out == x'C5E478D5 9288C841 AA530DB6 845C4C8D 962893A0 01CE4E11 A4963873 AA98134A');
 }
 
 fn void test_pbkdf2_2()
@@ -59,7 +73,7 @@ fn void test_pbkdf2_2()
     char[] s = "saltSALTsaltSALTsaltSALTsaltSALTsalt";
     char[32] out;
     sha256::pbkdf2(pw, s, 4096, &out);
-    assert(out == x'348C89DB CBD32B2F 32D814B8 116E84CF 2B17347E BC180018 1C4E2A1F B8DD53E1');
+    test::@check(out == x'348C89DB CBD32B2F 32D814B8 116E84CF 2B17347E BC180018 1C4E2A1F B8DD53E1');
 }
 
 
@@ -70,7 +84,7 @@ fn void test_pbkdf2_3()
     char[32] out;
     sha256::pbkdf2(pw, salt, 4096, &out);
 
-    assert(out == x'89B69D05 16F82989 3C696226 650A8687 8C029AC1 3EE27650 9D5AE58B 6466A724');
+    test::@check(out == x'89B69D05 16F82989 3C696226 650A8687 8C029AC1 3EE27650 9D5AE58B 6466A724');
 }
 
 fn void test_sha256_million_a()
@@ -82,7 +96,6 @@ fn void test_sha256_million_a()
     {
         sha.update("aaaaaaaaaa");
     }
-   
-    assert(sha.final() == x"CDC76E5C 9914FB92 81A1C7E2 84D73E67 F1809A48 A497200E 046D39CC C7112CD0");
+    test::@check(sha.final() == x"CDC76E5C 9914FB92 81A1C7E2 84D73E67 F1809A48 A497200E 046D39CC C7112CD0");
 }