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git/*: make murmurhash portable

We can't just cast void* to u32int* and dereference it,
as this causes alignment faults on arm32 (and mips).

so do byte-loads and shift/or instead.

--- a/sys/src/cmd/git/util.c

+++ b/sys/src/cmd/git/util.c

@@ -452,24 +452,13 @@

 	u32int m = 0x5bd1e995;

 	u32int r = 24;

 	u32int h, k;

-	u32int *w, *e;

-	uchar *p;

+	uchar *w, *e;

 	h = Seed ^ n;

 	e = pp;

-	e += (n / 4);

-	for (w = pp; w != e; w++) {

-		/*

-		 * NB: this is endian dependent.

-		 * This is fine for use in git, since the

-		 * hashes computed here are only ever used

-		 * for in memory data structures.

-		 *

-		 * Pack files will differ when packed on

-		 * machines with different endianness,

-		 * but the results will still be correct.

-		 */

-		k = *w;

+	e += n & -4;

+	for (w = pp; w != e; w += 4) {

+		k = (u32int)w[0] | (u32int)w[1] << 8 | (u32int)w[2] << 16 | (u32int)w[3] << 24;

 		k *= m;

 		k ^= k >> r;

 		k *= m;

@@ -478,11 +467,10 @@

 		h ^= k;

 	}

-	p = (uchar*)w;

 	switch (n & 0x3) {

-	case 3:	h ^= p[2] << 16;

-	case 2:	h ^= p[1] << 8;

-	case 1:	h ^= p[0] << 0;

+	case 3:	h ^= w[2] << 16;

+	case 2:	h ^= w[1] << 8;

+	case 1:	h ^= w[0] << 0;

 		h *= m;

 	}

-- 

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