rstdlib

Commit: b91d0d8b2e95d6784ae31f9fdafffe486e5bb1b4
Parent: 0ada27c25a107564321cdb43e884b9a9e9cb1484
Author: Randy Palamar
Date:   Sun, 22 Mar 2026 10:26:57 -0600

core: add round_up/down_power_two and str8_from_c_str

Diffstat:
M
build.sh
 | 
2
+-
M
rstd_core.h
 | 
49
+++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 50 insertions(+), 1 deletion(-)
diff --git a/build.sh b/build.sh
@@ -6,4 +6,4 @@ cat \
 	rstd_intrinsics.h \
 	rstd_core.h \
 	rstd_platform.h \
->> rstdlib.h
+>| rstdlib.h
diff --git a/rstd_core.h b/rstd_core.h
@@ -67,6 +67,17 @@ ctz_u32(u32 a)
 }
 
 function force_inline u64
+clz_u64(u64 a)
+{
+	u64 result = 64, index;
+	if (a) {
+		_BitScanReverse64(&index, a);
+		result = index;
+	}
+	return result;
+}
+
+function force_inline u64
 ctz_u64(u64 a)
 {
 	u64 result = 64, index;
@@ -96,6 +107,14 @@ ctz_u32(u32 a)
 }
 
 function force_inline u64
+clz_u64(u64 a)
+{
+	u64 result = 64;
+	if (a) result = (u64)__builtin_clzll(a);
+	return result;
+}
+
+function force_inline u64
 ctz_u64(u64 a)
 {
 	u64 result = 64;
@@ -129,4 +148,34 @@ round_up_to(s64 value, s64 multiple)
 	return result;
 }
 
+// NOTE: from Hacker's Delight
+function force_inline u64
+round_down_power_of_two(u64 a)
+{
+	u64 result = 0x8000000000000000ULL >> clz_u64(a);
+	return result;
+}
+
+function force_inline u64
+round_up_power_of_two(u64 a)
+{
+	u64 result = 0x8000000000000000ULL >> (clz_u64(a - 1) - 1);
+	return result;
+}
+
+
+//////////////////////////
+// NOTE: String Functions
+
+function str8
+str8_from_c_str(char *s)
+{
+	str8 result = {.data = (u8 *)s};
+	if (s) {
+		while (*s) s++;
+		result.length = (u8 *)s - result.data;
+	}
+	return result;
+}
+
 #endif /* RSTD_CORE_H */