pread_write.c 5.7 KB

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  1. /* vi: set sw=4 ts=4:
  2. *
  3. * Copyright (C) 2002 by Erik Andersen <andersen@uclibc.org>
  4. * Based in part on the files
  5. * ./sysdeps/unix/sysv/linux/pwrite.c,
  6. * ./sysdeps/unix/sysv/linux/pread.c,
  7. * sysdeps/posix/pread.c
  8. * sysdeps/posix/pwrite.c
  9. * from GNU libc 2.2.5, but reworked considerably...
  10. *
  11. * This program is free software; you can redistribute it and/or modify it
  12. * under the terms of the GNU Library General Public License as published by
  13. * the Free Software Foundation; either version 2 of the License, or (at your
  14. * option) any later version.
  15. *
  16. * This program is distributed in the hope that it will be useful, but WITHOUT
  17. * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18. * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License
  19. * for more details.
  20. *
  21. * You should have received a copy of the GNU Library General Public License
  22. * along with this program; if not, write to the Free Software Foundation,
  23. * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  24. */
  25. #define _GNU_SOURCE
  26. #define _LARGEFILE64_SOURCE
  27. #include <features.h>
  28. #undef __OPTIMIZE__
  29. /* We absolutely do _NOT_ want interfaces silently
  30. * * * renamed under us or very bad things will happen... */
  31. #ifdef __USE_FILE_OFFSET64
  32. # undef __USE_FILE_OFFSET64
  33. #endif
  34. #include <errno.h>
  35. #include <sys/types.h>
  36. #include <sys/syscall.h>
  37. #include <unistd.h>
  38. #include <stdint.h>
  39. #ifdef __NR_pread
  40. #define __NR___syscall_pread __NR_pread
  41. static inline _syscall5(ssize_t, __syscall_pread, int, fd, void *, buf,
  42. size_t, count, off_t, offset_hi, off_t, offset_lo);
  43. ssize_t __libc_pread(int fd, void *buf, size_t count, off_t offset)
  44. {
  45. return(__syscall_pread(fd,buf,count,__LONG_LONG_PAIR (offset >> 31, offset)));
  46. }
  47. weak_alias (__libc_pread, pread)
  48. #if defined __UCLIBC_HAS_LFS__
  49. ssize_t __libc_pread64(int fd, void *buf, size_t count, off64_t offset)
  50. {
  51. uint32_t low = offset & 0xffffffff;
  52. uint32_t high = offset >> 32;
  53. return(__syscall_pread(fd, buf, count, __LONG_LONG_PAIR (high, low)));
  54. }
  55. weak_alias (__libc_pread64, pread64)
  56. #endif /* __UCLIBC_HAS_LFS__ */
  57. #endif /* __NR_pread */
  58. #ifdef __NR_pwrite
  59. #define __NR___syscall_pwrite __NR_pwrite
  60. static inline _syscall5(ssize_t, __syscall_pwrite, int, fd, const void *, buf,
  61. size_t, count, off_t, offset_hi, off_t, offset_lo);
  62. ssize_t __libc_pwrite(int fd, const void *buf, size_t count, off_t offset)
  63. {
  64. return(__syscall_pwrite(fd,buf,count,__LONG_LONG_PAIR (offset >> 31, offset)));
  65. }
  66. weak_alias (__libc_pwrite, pwrite)
  67. #if defined __UCLIBC_HAS_LFS__
  68. ssize_t __libc_pwrite64(int fd, const void *buf, size_t count, off64_t offset)
  69. {
  70. uint32_t low = offset & 0xffffffff;
  71. uint32_t high = offset >> 32;
  72. return(__syscall_pwrite(fd, buf, count, __LONG_LONG_PAIR (high, low)));
  73. }
  74. weak_alias (__libc_pwrite64, pwrite64)
  75. #endif /* __UCLIBC_HAS_LFS__ */
  76. #endif /* __NR_pwrite */
  77. #if ! defined __NR_pread || ! defined __NR_pwrite
  78. static ssize_t __fake_pread_write(int fd, void *buf,
  79. size_t count, off_t offset, int do_pwrite)
  80. {
  81. int save_errno;
  82. ssize_t result;
  83. off_t old_offset;
  84. /* Since we must not change the file pointer preserve the
  85. * value so that we can restore it later. */
  86. if ((old_offset=lseek(fd, 0, SEEK_CUR)) == (off_t) -1)
  87. return -1;
  88. /* Set to wanted position. */
  89. if (lseek (fd, offset, SEEK_SET) == (off_t) -1)
  90. return -1;
  91. if (do_pwrite==1) {
  92. /* Write the data. */
  93. result = write(fd, buf, count);
  94. } else {
  95. /* Read the data. */
  96. result = read(fd, buf, count);
  97. }
  98. /* Now we have to restore the position. If this fails we
  99. * have to return this as an error. */
  100. save_errno = errno;
  101. if (lseek(fd, old_offset, SEEK_SET) == (off_t) -1)
  102. {
  103. if (result == -1)
  104. __set_errno(save_errno);
  105. return -1;
  106. }
  107. __set_errno(save_errno);
  108. return(result);
  109. }
  110. #if defined __UCLIBC_HAS_LFS__
  111. static ssize_t __fake_pread_write64(int fd, void *buf,
  112. size_t count, off64_t offset, int do_pwrite)
  113. {
  114. int save_errno;
  115. ssize_t result;
  116. off64_t old_offset;
  117. /* Since we must not change the file pointer preserve the
  118. * value so that we can restore it later. */
  119. if ((old_offset=lseek64(fd, 0, SEEK_CUR)) == (off64_t) -1)
  120. return -1;
  121. /* Set to wanted position. */
  122. if (lseek64(fd, offset, SEEK_SET) == (off64_t) -1)
  123. return -1;
  124. if (do_pwrite==1) {
  125. /* Write the data. */
  126. result = write(fd, buf, count);
  127. } else {
  128. /* Read the data. */
  129. result = read(fd, buf, count);
  130. }
  131. /* Now we have to restore the position. */
  132. save_errno = errno;
  133. if (lseek64 (fd, old_offset, SEEK_SET) == (off64_t) -1) {
  134. if (result == -1)
  135. __set_errno (save_errno);
  136. return -1;
  137. }
  138. __set_errno (save_errno);
  139. return result;
  140. }
  141. #endif /* __UCLIBC_HAS_LFS__ */
  142. #endif /* ! defined __NR_pread || ! defined __NR_pwrite */
  143. #ifndef __NR_pread
  144. ssize_t __libc_pread(int fd, void *buf, size_t count, off_t offset)
  145. {
  146. return(__fake_pread_write(fd, buf, count, offset, 0));
  147. }
  148. weak_alias (__libc_pread, pread)
  149. #if defined __UCLIBC_HAS_LFS__
  150. ssize_t __libc_pread64(int fd, void *buf, size_t count, off64_t offset)
  151. {
  152. return(__fake_pread_write64(fd, buf, count, offset, 0));
  153. }
  154. weak_alias (__libc_pread64, pread64)
  155. #endif /* __UCLIBC_HAS_LFS__ */
  156. #endif /* ! __NR_pread */
  157. #ifndef __NR_pwrite
  158. ssize_t __libc_pwrite(int fd, const void *buf, size_t count, off_t offset)
  159. {
  160. /* we won't actually be modifying the buffer,
  161. *just cast it to get rid of warnings */
  162. return(__fake_pread_write(fd, (void*)buf, count, offset, 1));
  163. }
  164. weak_alias (__libc_pwrite, pwrite)
  165. #if defined __UCLIBC_HAS_LFS__
  166. ssize_t __libc_pwrite64(int fd, const void *buf, size_t count, off64_t offset)
  167. {
  168. return(__fake_pread_write64(fd, (void*)buf, count, offset, 1));
  169. }
  170. weak_alias (__libc_pwrite64, pwrite64)
  171. #endif /* __UCLIBC_HAS_LFS__ */
  172. #endif /* ! __NR_pwrite */