[libc] Rewrite string functions

Some of the C library string functions have an unknown provenance.
Reimplement all such functions to avoid potential licensing
uncertainty.

Remove the inline-assembler versions of strlen(), memswap(), and
strncmp(); these save a minimal amount of space (around 40 bytes in
total) and are not performance-critical.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 55 insertions, 7 deletions

diff --git a/src/include/strings.h b/src/include/strings.h
index 6912a1e4..8b57a40a 100644
--- a/src/include/strings.h
+++ b/src/include/strings.h
@@ -1,12 +1,23 @@
 #ifndef _STRINGS_H
 #define _STRINGS_H
 
+/** @file
+ *
+ * String functions
+ *
+ */
+
 FILE_LICENCE ( GPL2_OR_LATER );
 
-#include <limits.h>
 #include <string.h>
 #include <bits/strings.h>
 
+/**
+ * Find last (i.e. most significant) set bit
+ *
+ * @v x			Value
+ * @ret msb		Most significant bit set in value (LSB=1), or zero
+ */
 static inline __attribute__ (( always_inline )) int
 __constant_flsll ( unsigned long long x ) {
 	int r = 0;
@@ -41,6 +52,12 @@ __constant_flsll ( unsigned long long x ) {
 	return r;
 }
 
+/**
+ * Find last (i.e. most significant) set bit
+ *
+ * @v x			Value
+ * @ret msb		Most significant bit set in value (LSB=1), or zero
+ */
 static inline __attribute__ (( always_inline )) int
 __constant_flsl ( unsigned long x ) {
 	return __constant_flsll ( x );
@@ -49,24 +66,55 @@ __constant_flsl ( unsigned long x ) {
 int __flsll ( long long x );
 int __flsl ( long x );
 
+/**
+ * Find last (i.e. most significant) set bit
+ *
+ * @v x			Value
+ * @ret msb		Most significant bit set in value (LSB=1), or zero
+ */
 #define flsll( x ) \
 	( __builtin_constant_p ( x ) ? __constant_flsll ( x ) : __flsll ( x ) )
 
+/**
+ * Find last (i.e. most significant) set bit
+ *
+ * @v x			Value
+ * @ret msb		Most significant bit set in value (LSB=1), or zero
+ */
 #define flsl( x ) \
 	( __builtin_constant_p ( x ) ? __constant_flsl ( x ) : __flsl ( x ) )
 
+/**
+ * Find last (i.e. most significant) set bit
+ *
+ * @v x			Value
+ * @ret msb		Most significant bit set in value (LSB=1), or zero
+ */
 #define fls( x ) flsl ( x )
 
-extern int strcasecmp ( const char *s1, const char *s2 );
-
+/**
+ * Copy memory
+ *
+ * @v src		Source
+ * @v dest		Destination
+ * @v len		Length
+ */
 static inline __attribute__ (( always_inline )) void
-bcopy ( const void *src, void *dest, size_t n ) {
-	memmove ( dest, src, n );
+bcopy ( const void *src, void *dest, size_t len ) {
+	memmove ( dest, src, len );
 }
 
+/**
+ * Zero memory
+ *
+ * @v dest		Destination
+ * @v len		Length
+ */
 static inline __attribute__ (( always_inline )) void
-bzero ( void *s, size_t n ) {
-	memset ( s, 0, n );
+bzero ( void *dest, size_t len ) {
+	memset ( dest, 0, len );
 }
 
+int __pure strcasecmp ( const char *first, const char *second ) __nonnull;
+
 #endif /* _STRINGS_H */