fix bugs in ilog2 (yoink) and add self-test+asserts.

This was SVN commit r2600.

source/lib/lib.cpp

@@ -25,11 +25,15 @@
 
 #include "sysdep/sysdep.h"
 
+#ifndef PERFORM_SELF_TEST
+#define PERFORM_SELF_TEST 0
+#endif
+
 
 // FNV1-A hash - good for strings.
 // if len = 0 (default), treat buf as a C-string;
 // otherwise, hash <len> bytes of buf.
-u32 fnv_hash(const void* buf, const size_t len)
+u32 fnv_hash(const void* buf, size_t len)
 {
 	u32 h = 0x811c9dc5u;
 		// give distinct values for different length 0 buffers.
@@ -65,7 +69,7 @@ u32 fnv_hash(const void* buf, const size_t len)
 // FNV1-A hash - good for strings.
 // if len = 0 (default), treat buf as a C-string;
 // otherwise, hash <len> bytes of buf.
-u64 fnv_hash64(const void* buf, const size_t len)
+u64 fnv_hash64(const void* buf, size_t len)
 {
 	u64 h = 0xCBF29CE484222325ull;
 		// give distinct values for different length 0 buffers.
@@ -101,7 +105,7 @@ u64 fnv_hash64(const void* buf, const size_t len)
 // special version for strings: first converts to lowercase
 // (useful for comparing mixed-case filenames).
 // note: still need <len>, e.g. to support non-0-terminated strings
-u32 fnv_lc_hash(const char* str, const size_t len)
+u32 fnv_lc_hash(const char* str, size_t len)
 {
 	u32 h = 0x811c9dc5u;
 		// give distinct values for different length 0 buffers.
@@ -135,44 +139,53 @@ u32 fnv_lc_hash(const char* str, const size_t len)
 
 
 
-bool is_pow2(const long n)
+bool is_pow2(uint n)
 {
-	return (n != 0l) && !(n & (n-1l));
+	// 0 would pass the test below but isn't a POT.
+	if(n == 0)
+		return false;
+	return (n & (n-1l)) == 0;
 }
 
 
 // return -1 if not an integral power of 2,
 // otherwise the base2 logarithm
 
-int ilog2(const int n)
+int ilog2(uint n)
 {
+	int bit_index;	// return value
+
 #if CPU_IA32
 
 	__asm
 	{
 		mov		ecx, [n]
-		or		eax, -1			// return value
+		or		eax, -1			// return value if not a POT
+		test	ecx, ecx
+		jz		not_pot
 		lea		edx, [ecx-1]
-		test	ecx, edx		// power of 2?
-		jnz		skip
+		test	ecx, edx
+		jnz		not_pot
 		bsf		eax, ecx
-	skip:
-		mov		[n], eax
+	not_pot:
+		mov		[bit_index], eax
 	}
 
-	return n;
-
 #else
 
-	if(n || n & (n-1))
+	if(!is_pow2(n))
 		return -1;
 
-	int i = 1, j = 0;
-	for(; i != n; i += i, j++)
-		;
-	return j;
+	bit_index = 0;
+	// note: compare against n directly because it is known to be a POT.
+	for(uint bit_value = 1; bit_value != n; bit_value *= 2)
+		bit_index++;
 
 #endif
+
+	debug_assert(-1 <= bit_index && bit_index < sizeof(int)*CHAR_BIT);
+	debug_assert(bit_index == -1 || n == (1u << bit_index));
+	return bit_index;
 }
 
 
@@ -193,7 +206,7 @@ uint log2(uint x)
 
 int ilog2(const float x)
 {
-	const u32 i = (u32&)x;
+	const u32 i = *(u32*)&x;
 	u32 biased_exp = (i >> 23) & 0xff;
 	return (int)biased_exp - 127;
 }
@@ -454,3 +467,35 @@ int match_wildcardw(const wchar_t* s, const wchar_t* w)
 
 	return (*w == '\0');
 }
+
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// built-in self test
+//
+//////////////////////////////////////////////////////////////////////////////
+
+#if PERFORM_SELF_TEST
+namespace test {
+
+static void test_log2()
+{
+	debug_assert(ilog2(0) == -1);
+	debug_assert(ilog2(3) == -1);
+	debug_assert(ilog2(0xffffffff) == -1);
+	debug_assert(ilog2(1) == 0);
+	debug_assert(ilog2(256) == 8);
+	debug_assert(ilog2(0x80000000) == 31);
+}
+
+static int run_tests()
+{
+	test_log2();
+	return 0;
+}
+
+static int dummy = run_tests();
+
+}	// namespace test
+#endif	// #if PERFORM_SELF_TEST

source/lib/lib.h

@@ -309,12 +309,12 @@ const size_t GiB = 1ul << 30;
 // FNV1-A hash - good for strings.
 // if len = 0 (default), treat buf as a C-string;
 // otherwise, hash <len> bytes of buf.
-extern u32 fnv_hash(const void* buf, const size_t len = 0);
-extern u64 fnv_hash64(const void* buf, const size_t len = 0);
+extern u32 fnv_hash(const void* buf, size_t len = 0);
+extern u64 fnv_hash64(const void* buf, size_t len = 0);
 
 // special version for strings: first converts to lowercase
 // (useful for comparing mixed-case filenames)
-extern u32 fnv_lc_hash(const char* str, const size_t len = 0);
+extern u32 fnv_lc_hash(const char* str, size_t len = 0);
 
 // hash (currently FNV) of a filename
 typedef u32 FnHash;
@@ -332,11 +332,11 @@ extern u64 movzx_64le(const u8* p, size_t size);
 extern i64 movsx_64le(const u8* p, size_t size);
 
 
-extern bool is_pow2(long n);
+extern bool is_pow2(uint n);
 
 // return -1 if not an integral power of 2,
 // otherwise the base2 logarithm
-extern int ilog2(const int n);
+extern int ilog2(uint n);
 
 // return log base 2, rounded up.
 extern uint log2(uint x);

source/lib/sysdep/win/wposix.cpp

@@ -535,9 +535,9 @@ int poll(struct pollfd /* fds */[], int /* nfds */, int /* timeout */)
 // used by mprotect.
 static DWORD win32_prot(int prot)
 {
-	// this covers all possible combinations of read|write|exec
+	// this covers all 8 combinations of read|write|exec
 	// (note that "none" means all flags are 0).
-	switch(prot)
+	switch(prot & (PROT_READ|PROT_WRITE|PROT_EXEC))
 	{
 	case PROT_NONE:
 		return PAGE_NOACCESS;
@@ -558,7 +558,7 @@ static DWORD win32_prot(int prot)
 	case PROT_READ|PROT_WRITE|PROT_EXEC:
 		return PAGE_EXECUTE_READWRITE;
 	default:
-		return 0;
+		UNREACHABLE;
 	}
 }
 
@@ -687,7 +687,7 @@ void* mmap(void* user_start, size_t len, int prot, int flags, int fd, off_t ofs)
 	}
 
 fail:
-	return MAP_FAILED;
+	return (void*)MAP_FAILED;
 }