pread_write.c 5.0 KB

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  1. /* vi: set sw=4 ts=4: */
  2. /*
  3. * Copyright (C) 2000-2006 Erik Andersen <andersen@uclibc.org>
  4. *
  5. * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
  6. */
  7. /*
  8. * Based in part on the files
  9. * ./sysdeps/unix/sysv/linux/pwrite.c,
  10. * ./sysdeps/unix/sysv/linux/pread.c,
  11. * sysdeps/posix/pread.c
  12. * sysdeps/posix/pwrite.c
  13. * from GNU libc 2.2.5, but reworked considerably...
  14. */
  15. #include "syscalls.h"
  16. #include <unistd.h>
  17. #include <stdint.h>
  18. extern __typeof(pread) __libc_pread;
  19. extern __typeof(pwrite) __libc_pwrite;
  20. #ifdef __UCLIBC_HAS_LFS__
  21. extern __typeof(pread64) __libc_pread64;
  22. extern __typeof(pwrite64) __libc_pwrite64;
  23. #endif
  24. #ifdef __NR_pread
  25. # define __NR___syscall_pread __NR_pread
  26. static inline _syscall5(ssize_t, __syscall_pread, int, fd, void *, buf,
  27. size_t, count, off_t, offset_hi, off_t, offset_lo);
  28. ssize_t __libc_pread(int fd, void *buf, size_t count, off_t offset)
  29. {
  30. return(__syscall_pread(fd,buf,count,__LONG_LONG_PAIR (offset >> 31, offset)));
  31. }
  32. weak_alias(__libc_pread,pread)
  33. # ifdef __UCLIBC_HAS_LFS__
  34. ssize_t __libc_pread64(int fd, void *buf, size_t count, off64_t offset)
  35. {
  36. uint32_t low = offset & 0xffffffff;
  37. uint32_t high = offset >> 32;
  38. return(__syscall_pread(fd, buf, count, __LONG_LONG_PAIR (high, low)));
  39. }
  40. weak_alias(__libc_pread64,pread64)
  41. # endif /* __UCLIBC_HAS_LFS__ */
  42. #endif /* __NR_pread */
  43. #ifdef __NR_pwrite
  44. # define __NR___syscall_pwrite __NR_pwrite
  45. static inline _syscall5(ssize_t, __syscall_pwrite, int, fd, const void *, buf,
  46. size_t, count, off_t, offset_hi, off_t, offset_lo);
  47. ssize_t __libc_pwrite(int fd, const void *buf, size_t count, off_t offset)
  48. {
  49. return(__syscall_pwrite(fd,buf,count,__LONG_LONG_PAIR (offset >> 31, offset)));
  50. }
  51. weak_alias(__libc_pwrite,pwrite)
  52. # ifdef __UCLIBC_HAS_LFS__
  53. ssize_t __libc_pwrite64(int fd, const void *buf, size_t count, off64_t offset)
  54. {
  55. uint32_t low = offset & 0xffffffff;
  56. uint32_t high = offset >> 32;
  57. return(__syscall_pwrite(fd, buf, count, __LONG_LONG_PAIR (high, low)));
  58. }
  59. weak_alias(__libc_pwrite64,pwrite64)
  60. # endif /* __UCLIBC_HAS_LFS__ */
  61. #endif /* __NR_pwrite */
  62. #if ! defined __NR_pread || ! defined __NR_pwrite
  63. libc_hidden_proto(read)
  64. libc_hidden_proto(write)
  65. libc_hidden_proto(lseek)
  66. libc_hidden_proto(lseek64)
  67. static ssize_t __fake_pread_write(int fd, void *buf,
  68. size_t count, off_t offset, int do_pwrite)
  69. {
  70. int save_errno;
  71. ssize_t result;
  72. off_t old_offset;
  73. /* Since we must not change the file pointer preserve the
  74. * value so that we can restore it later. */
  75. if ((old_offset=lseek(fd, 0, SEEK_CUR)) == (off_t) -1)
  76. return -1;
  77. /* Set to wanted position. */
  78. if (lseek (fd, offset, SEEK_SET) == (off_t) -1)
  79. return -1;
  80. if (do_pwrite==1) {
  81. /* Write the data. */
  82. result = write(fd, buf, count);
  83. } else {
  84. /* Read the data. */
  85. result = read(fd, buf, count);
  86. }
  87. /* Now we have to restore the position. If this fails we
  88. * have to return this as an error. */
  89. save_errno = errno;
  90. if (lseek(fd, old_offset, SEEK_SET) == (off_t) -1)
  91. {
  92. if (result == -1)
  93. __set_errno(save_errno);
  94. return -1;
  95. }
  96. __set_errno(save_errno);
  97. return(result);
  98. }
  99. # ifdef __UCLIBC_HAS_LFS__
  100. static ssize_t __fake_pread_write64(int fd, void *buf,
  101. size_t count, off64_t offset, int do_pwrite)
  102. {
  103. int save_errno;
  104. ssize_t result;
  105. off64_t old_offset;
  106. /* Since we must not change the file pointer preserve the
  107. * value so that we can restore it later. */
  108. if ((old_offset=lseek64(fd, 0, SEEK_CUR)) == (off64_t) -1)
  109. return -1;
  110. /* Set to wanted position. */
  111. if (lseek64(fd, offset, SEEK_SET) == (off64_t) -1)
  112. return -1;
  113. if (do_pwrite==1) {
  114. /* Write the data. */
  115. result = write(fd, buf, count);
  116. } else {
  117. /* Read the data. */
  118. result = read(fd, buf, count);
  119. }
  120. /* Now we have to restore the position. */
  121. save_errno = errno;
  122. if (lseek64 (fd, old_offset, SEEK_SET) == (off64_t) -1) {
  123. if (result == -1)
  124. __set_errno (save_errno);
  125. return -1;
  126. }
  127. __set_errno (save_errno);
  128. return result;
  129. }
  130. # endif /* __UCLIBC_HAS_LFS__ */
  131. #endif /* ! defined __NR_pread || ! defined __NR_pwrite */
  132. #ifndef __NR_pread
  133. ssize_t __libc_pread(int fd, void *buf, size_t count, off_t offset)
  134. {
  135. return(__fake_pread_write(fd, buf, count, offset, 0));
  136. }
  137. weak_alias(__libc_pread,pread)
  138. # ifdef __UCLIBC_HAS_LFS__
  139. ssize_t __libc_pread64(int fd, void *buf, size_t count, off64_t offset)
  140. {
  141. return(__fake_pread_write64(fd, buf, count, offset, 0));
  142. }
  143. weak_alias(__libc_pread64,pread64)
  144. # endif /* __UCLIBC_HAS_LFS__ */
  145. #endif /* ! __NR_pread */
  146. #ifndef __NR_pwrite
  147. ssize_t __libc_pwrite(int fd, const void *buf, size_t count, off_t offset)
  148. {
  149. /* we won't actually be modifying the buffer,
  150. *just cast it to get rid of warnings */
  151. return(__fake_pread_write(fd, (void*)buf, count, offset, 1));
  152. }
  153. weak_alias(__libc_pwrite,pwrite)
  154. # ifdef __UCLIBC_HAS_LFS__
  155. ssize_t __libc_pwrite64(int fd, const void *buf, size_t count, off64_t offset)
  156. {
  157. return(__fake_pread_write64(fd, (void*)buf, count, offset, 1));
  158. }
  159. weak_alias(__libc_pwrite64,pwrite64)
  160. # endif /* __UCLIBC_HAS_LFS__ */
  161. #endif /* ! __NR_pwrite */