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source: vbox/trunk/src/libs/libpng-1.6.43/contrib/arm-neon/linux-auxv.c@ 107044

Last change on this file since 107044 was 103316, checked in by vboxsync, 10 months ago

libpng-1.6.42: Applied and adjusted our libpng changes to 1.6.42. bugref:8515

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File size: 3.1 KB
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1/* contrib/arm-neon/linux-auxv.c
2 *
3 * Copyright (c) 2014 Glenn Randers-Pehrson
4 * Written by Mans Rullgard, 2011.
5 *
6 * This code is released under the libpng license.
7 * For conditions of distribution and use, see the disclaimer
8 * and license in png.h
9 *
10 * SEE contrib/arm-neon/README before reporting bugs
11 *
12 * STATUS: COMPILED, TESTED
13 * BUG REPORTS: png-mng-implement@sourceforge.net
14 *
15 * png_have_neon implemented for Linux versions which allow access to
16 * /proc/self/auxv. This is probably faster, cleaner and safer than the code to
17 * read /proc/cpuinfo in contrib/arm-neon/linux, however it is yet another piece
18 * of potentially untested code and has more complex dependencies than the code
19 * to read cpuinfo.
20 *
21 * This generic __linux__ implementation requires reading /proc/self/auxv and
22 * looking at each element for one that records NEON capabilities.
23 */
24
25#include <unistd.h> /* for POSIX 1003.1 */
26#include <errno.h> /* for EINTR */
27
28#include <sys/types.h>
29#include <sys/stat.h>
30#include <fcntl.h>
31#include <elf.h>
32#include <asm/hwcap.h>
33
34/* A read call may be interrupted, in which case it returns -1 and sets errno to
35 * EINTR if nothing was done, otherwise (if something was done) a partial read
36 * may result.
37 */
38static size_t
39safe_read(png_structp png_ptr, int fd, void *buffer_in, size_t nbytes)
40{
41 size_t ntotal = 0;
42 char *buffer = png_voidcast(char*, buffer_in);
43
44 while (nbytes > 0)
45 {
46 unsigned int nread;
47 int iread;
48
49 /* Passing nread > INT_MAX to read is implementation defined in POSIX
50 * 1003.1, therefore despite the unsigned argument portable code must
51 * limit the value to INT_MAX!
52 */
53 if (nbytes > INT_MAX)
54 nread = INT_MAX;
55
56 else
57 nread = (unsigned int)/*SAFE*/nbytes;
58
59 iread = read(fd, buffer, nread);
60
61 if (iread == -1)
62 {
63 /* This is the devil in the details, a read can terminate early with 0
64 * bytes read because of EINTR, yet it still returns -1 otherwise end
65 * of file cannot be distinguished.
66 */
67 if (errno != EINTR)
68 {
69 png_warning(png_ptr, "/proc read failed");
70 return 0; /* I.e., a permanent failure */
71 }
72 }
73
74 else if (iread < 0)
75 {
76 /* Not a valid 'read' result: */
77 png_warning(png_ptr, "OS /proc read bug");
78 return 0;
79 }
80
81 else if (iread > 0)
82 {
83 /* Continue reading until a permanent failure, or EOF */
84 buffer += iread;
85 nbytes -= (unsigned int)/*SAFE*/iread;
86 ntotal += (unsigned int)/*SAFE*/iread;
87 }
88
89 else
90 return ntotal;
91 }
92
93 return ntotal; /* nbytes == 0 */
94}
95
96static int
97png_have_neon(png_structp png_ptr)
98{
99 int fd = open("/proc/self/auxv", O_RDONLY);
100 Elf32_auxv_t aux;
101
102 /* Failsafe: failure to open means no NEON */
103 if (fd == -1)
104 {
105 png_warning(png_ptr, "/proc/self/auxv open failed");
106 return 0;
107 }
108
109 while (safe_read(png_ptr, fd, &aux, sizeof aux) == sizeof aux)
110 {
111 if (aux.a_type == AT_HWCAP && (aux.a_un.a_val & HWCAP_NEON) != 0)
112 {
113 close(fd);
114 return 1;
115 }
116 }
117
118 close(fd);
119 return 0;
120}
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