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Subject[PATCH] hex <-> int conversion routines.
Date
Hi,

When grepping through the kernel I noticed that there exists at least 27
(probably more with non-obvious names) different implementations of hex to
int conversion functions. 2/3 of them in arch and the rest in drivers and fs.
All implementations were variations of this function:

int hex_nibble (char x)
{
if (x >= '0' && x <= '9') return x - '0';
if (x >= 'a' && x <= 'f') return x - 'a' + 10;
if (x >= 'A' && x <= 'F') return x - 'A' + 10;
return -1;
}
My orignial plan was to replace some of them with this version, which (at
least on x86) compiles to roughly half the size and runs twice as fast.

int hex_nibble(char x)
{
unsigned int y; /* Unsigned for correct wrapping */
if ((y = x - '0') <= '9'-'0') return y;
if ((y = x - 'A') <= 'F'-'A') return y+10;
if ((y = x - 'a') <= 'f'-'a') return y+10;
return -1;
}
But due to the many duplicated implementations I think it would be good to
have it in a library function.

I also added three other hex-functions that can replace a lot of duplicated code.

int hexint_nibble (char x); // hex digit to int.
int hexint_byte (const char *src); // hex digit-pair to int.
char inthex_nibble (int x); // int to hex digit.
void inthex_byte (int x, char* dest); // int to hex digit pair.
I see no point in modifying any other code to use these functions until they
are approved. If it get approved, however I can feed patches to the relevant
maintainers.

Regards,
Jakob Kemi

diff -urN -X dontdiff linux-2.5.5-pre1-vanilla/include/linux/hexint.h linux-2.5.5-pre1/include/linux/hexint.h
--- linux-2.5.5-pre1-vanilla/include/linux/hexint.h Thu Jan 1 01:00:00 1970
+++ linux-2.5.5-pre1/include/linux/hexint.h Tue Feb 19 16:24:26 2002
@@ -0,0 +1,85 @@
+/*
+ * include/linux/hexint.h - hex<->int conversions.
+ *
+ * Copyleft (C) 2002, Jakob Kemi <jakob.kemi@telia.com>
+ */
+
+#ifndef _LINUX_HEXINT_H
+#define _LINUX_HEXINT_H
+
+#ifdef __KERNEL__
+
+/**
+ * hexint_byte - Convert a hex digit pair to an int.
+ * @src: Pointer to source data.
+ *
+ * Return:
+ * converted value (0-255) on success.
+ * -1 on failure.
+ */
+extern int hexint_byte(const char *src);
+
+/**
+ * _hexint_byte - Same as hexint_byte but inlined.
+ */
+static __inline__ int _hexint_byte(const char *src)
+{
+ unsigned int y; /* unsigned for correct wrapping. */
+ int h;
+
+ /* high part. */
+ if ((y = src[0] - '0') <= '9'-'0') h = y;
+ else if ((y = src[0] - 'a') <= 'f'-'a') h = y+10;
+ else if ((y = src[0] - 'A') <= 'F'-'A') h = y+10;
+ else return -1;
+ h = h << 4;
+
+ /* low part. */
+ if ((y = src[1] - '0') <= '9'-'0') return h | y;
+ if ((y = src[1] - 'a') <= 'f'-'a') return h | (y+10);
+ if ((y = src[1] - 'A') <= 'F'-'A') return h | (y+10);
+ return -1;
+}
+
+/**
+ * hexint_nibble - Convert a hex digit to an int.
+ * @x: digit to convert.
+ *
+ * Return:
+ * converted value (0-15) on success.
+ * -1 on failure.
+ */
+static __inline__ int hexint_nibble(char x)
+{
+ unsigned int y; /* unsigned for correct wrapping */
+
+ if ((y = x - '0') <= '9'-'0') return y;
+ if ((y = x - 'a') <= 'f'-'a') return y+10;
+ if ((y = x - 'A') <= 'F'-'A') return y+10;
+ return -1;
+}
+
+/**
+ * inthex_nibble - Convert an int to a hex digit.
+ */
+static __inline__ char inthex_nibble(int x)
+{
+ const char* digits = "0123456789abcdef";
+
+ return digits[x & 0x0f];
+}
+
+/**
+ * inthex_byte - Convert an int to a hex digit pair.
+ */
+static __inline__ void inthex_byte(int x, char* dest)
+{
+ const char* digits = "0123456789abcdef";
+
+ dest[0] = digits[(x & 0xf0) >> 4];
+ dest[1] = digits[x & 0x0f];
+}
+
+#endif /* __KERNEL__ */
+
+#endif
diff -urN -X dontdiff linux-2.5.5-pre1-vanilla/lib/Makefile linux-2.5.5-pre1/lib/Makefile
--- linux-2.5.5-pre1-vanilla/lib/Makefile Sun Feb 3 14:04:47 2002
+++ linux-2.5.5-pre1/lib/Makefile Tue Feb 19 15:55:37 2002
@@ -10,7 +10,7 @@

export-objs := cmdline.o dec_and_lock.o rwsem-spinlock.o rwsem.o crc32.o

-obj-y := errno.o ctype.o string.o vsprintf.o brlock.o cmdline.o bust_spinlocks.o rbtree.o
+obj-y := errno.o ctype.o string.o vsprintf.o brlock.o cmdline.o bust_spinlocks.o rbtree.o hexint.o

obj-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
obj-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
diff -urN -X dontdiff linux-2.5.5-pre1-vanilla/lib/hexint.c linux-2.5.5-pre1/lib/hexint.c
--- linux-2.5.5-pre1-vanilla/lib/hexint.c Thu Jan 1 01:00:00 1970
+++ linux-2.5.5-pre1/lib/hexint.c Tue Feb 19 16:26:00 2002
@@ -0,0 +1,33 @@
+/*
+ * linux/lib/hexint.c - hex<->int conversions.
+ *
+ * Copyleft (C) 2002, Jakob Kemi <jakob.kemi@telia.com>
+ */
+
+
+/**
+ * hexint_byte - Convert an hex digit pair to an int.
+ * @src: Pointer to source data.
+ *
+ * Return:
+ * converted value (0-255) on success.
+ * -1 on failure.
+ */
+int hexint_byte(const char *src)
+{
+ unsigned int y; /* unsigned for correct wrapping. */
+ int h;
+
+ /* high part. */
+ if ((y = src[0] - '0') <= '9'-'0') h = y;
+ else if ((y = src[0] - 'a') <= 'f'-'a') h = y+10;
+ else if ((y = src[0] - 'A') <= 'F'-'A') h = y+10;
+ else return -1;
+ h = h << 4;
+
+ /* low part. */
+ if ((y = src[1] - '0') <= '9'-'0') return h | y;
+ if ((y = src[1] - 'a') <= 'f'-'a') return h | (y+10);
+ if ((y = src[1] - 'A') <= 'F'-'A') return h | (y+10);
+ return -1;
+}
-
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