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Date: 31 May 2016 16:31:22 -0400
From: "George Spelvin" <linux@...encehorizons.net>
To: andriy.shevchenko@...ux.intel.com
Cc: akpm@...ux-foundation.org, bbjorn@...k.no,
linux-kernel@...r.kernel.org, linux@...encehorizons.net,
tytso@....edu
Subject: [PATCH] lib/uuid.c: eliminate uuid_[bl]e_index arrays
>From a0d084b1225f2efcf4b5c81871c9c446155b9b13 Mon Sep 17 00:00:00 2001
From: George Spelvin <linux@...encehorizons.net>
Date: Tue, 31 May 2016 16:00:22 -0400
Subject: [PATCH] lib/uuid.c: eliminate uuid_[bl]e_index arrays
Both input and output code is simplified if we instead use a mapping
from binary UUID index to ASCII UUID position. This lets us combine
hyphen-skipping and endian-swapping into one table.
uuid_[bl]e_index were EXPORT_SYMBOLed for no obvious reason; there
are no users outside of lib/. The replacement uuid_[bl]e_pos arrays
are not exported pending finding a need.
The arrays are combined in one contiguous uuid_byte_pos[2][16]
array as a micro-optimization for uuid_string(). Choosing between
the two can be done by adding 16 rather than loading a second
full-word address.
x86-64 code size reductions:
uuid_string: was 228 bytes, now 134
__uuid_to_bin: was 119 bytes, now 85
Initialized data is also reduced by 16 bytes.
Signed-off-by: George Spelvin <linux@...izon.com>
---
Here's a patch implementing the suggestion I made earlier. This reduces
code size, data size, and run time for input and output of UUIDs.
This patch is on top of the upper/lower case hex optimization for
lib/vsprintf.c I sent earlier. If you don't have it, just ignore the
merge conflicts in uuid_string() and take the "after" version.
include/linux/uuid.h | 6 ++++--
lib/uuid.c | 24 ++++++++++--------------
lib/vsprintf.c | 32 +++++++++++++-------------------
3 files changed, 27 insertions(+), 35 deletions(-)
diff --git a/include/linux/uuid.h b/include/linux/uuid.h
index 2d095fc6..882d9ada 100644
--- a/include/linux/uuid.h
+++ b/include/linux/uuid.h
@@ -41,8 +41,10 @@ extern void uuid_be_gen(uuid_be *u);
bool __must_check uuid_is_valid(const char *uuid);
-extern const u8 uuid_le_index[16];
-extern const u8 uuid_be_index[16];
+/* For each binary byte, string offset in ASCII UUID where it appears */
+extern const u8 uuid_byte_pos[2][16];
+#define uuid_be_pos (uuid_byte_pos[0])
+#define uuid_le_pos (uuid_byte_pos[1])
int uuid_le_to_bin(const char *uuid, uuid_le *u);
int uuid_be_to_bin(const char *uuid, uuid_be *u);
diff --git a/lib/uuid.c b/lib/uuid.c
index e116ae5f..8a439caf 100644
--- a/lib/uuid.c
+++ b/lib/uuid.c
@@ -21,10 +21,10 @@
#include <linux/uuid.h>
#include <linux/random.h>
-const u8 uuid_le_index[16] = {3,2,1,0,5,4,7,6,8,9,10,11,12,13,14,15};
-EXPORT_SYMBOL(uuid_le_index);
-const u8 uuid_be_index[16] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
-EXPORT_SYMBOL(uuid_be_index);
+const u8 uuid_byte_pos[2][16] = {
+ {0,2,4,6,9,11,14,16,19,21,24,26,28,30,32,34}, /* uuid_be_pos */
+ {6,4,2,0,11,9,16,14,19,21,24,26,28,30,32,34} /* uuid_le_pos */
+};
/***************************************************************
* Random UUID interface
@@ -97,32 +97,28 @@ bool uuid_is_valid(const char *uuid)
}
EXPORT_SYMBOL(uuid_is_valid);
-static int __uuid_to_bin(const char *uuid, __u8 b[16], const u8 ei[16])
+static int __uuid_to_bin(const char uuid[36], __u8 b[16], const u8 si[16])
{
- static const u8 si[16] = {0,2,4,6,9,11,14,16,19,21,24,26,28,30,32,34};
unsigned int i;
if (!uuid_is_valid(uuid))
return -EINVAL;
- for (i = 0; i < 16; i++) {
- int hi = hex_to_bin(uuid[si[i]] + 0);
- int lo = hex_to_bin(uuid[si[i]] + 1);
-
- b[ei[i]] = (hi << 4) | lo;
- }
+ for (i = 0; i < 16; i++)
+ if (hex2bin(b + i, uuid + si[i], 1) < 0)
+ return -EINVAL;
return 0;
}
int uuid_le_to_bin(const char *uuid, uuid_le *u)
{
- return __uuid_to_bin(uuid, u->b, uuid_le_index);
+ return __uuid_to_bin(uuid, u->b, uuid_le_pos);
}
EXPORT_SYMBOL(uuid_le_to_bin);
int uuid_be_to_bin(const char *uuid, uuid_be *u)
{
- return __uuid_to_bin(uuid, u->b, uuid_be_index);
+ return __uuid_to_bin(uuid, u->b, uuid_be_pos);
}
EXPORT_SYMBOL(uuid_be_to_bin);
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 4ee07e89..44faddb1 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1313,38 +1313,32 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
struct printf_spec spec, const char *fmt)
{
char uuid[UUID_STRING_LEN + 1];
- char *p = uuid;
int i;
- const u8 *index = uuid_be_index;
+ const u8 *pos = uuid_be_pos;
const char *hex = hex_asc;
switch (fmt[1]) {
+ case 'l':
+ pos = uuid_le_pos;
+ break;
case 'L':
- hex = hex_asc_upper; /* fall-through */
- case 'l':
- index = uuid_le_index;
- break;
+ pos = uuid_le_pos; /* Fall-through */
case 'B':
hex = hex_asc_upper;
break;
}
+ /* Format each byte of the raw uuid into the buffer */
for (i = 0; i < 16; i++) {
- u8 byte = addr[index[i]];
+ u8 byte = addr[i];
+ char *p = uuid + pos[i];
- *p++ = hex[byte >> 4];
- *p++ = hex[byte & 0x0f];
- switch (i) {
- case 3:
- case 5:
- case 7:
- case 9:
- *p++ = '-';
- break;
- }
+ p[0] = hex[byte >> 4];
+ p[1] = hex[byte & 0x0f];
}
-
- *p = 0;
+ /* Insert the fixed punctuation */
+ uuid[23] = uuid[18] = uuid[13] = uuid[8] = '-';
+ uuid[UUID_STRING_LEN] = '\0';
return string(buf, end, uuid, spec);
}
--
2.8.1
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