diff options
Diffstat (limited to 'mysys/my_pread.c')
| -rw-r--r-- | mysys/my_pread.c | 153 |
1 files changed, 73 insertions, 80 deletions
diff --git a/mysys/my_pread.c b/mysys/my_pread.c index f8f0fa49c10..070494e4f1d 100644 --- a/mysys/my_pread.c +++ b/mysys/my_pread.c @@ -20,61 +20,57 @@ #include <unistd.h> #endif - /* Read a chunk of bytes from a file */ - -uint my_pread(File Filedes, byte *Buffer, uint Count, my_off_t offset, - myf MyFlags) +/* + Read a chunk of bytes from a file from a given position + + SYNOPSIOS + my_pread() + Filedes File decsriptor + Buffer Buffer to read data into + Count Number of bytes to read + offset Position to read from + MyFlags Flags + + NOTES + This differs from the normal pread() call in that we don't care + to set the position in the file back to the original position + if the system doesn't support pread(). + + RETURN + (size_t) -1 Error + # Number of bytes read +*/ + +size_t my_pread(File Filedes, uchar *Buffer, size_t Count, my_off_t offset, + myf MyFlags) { - uint readbytes; + size_t readbytes; int error= 0; DBUG_ENTER("my_pread"); DBUG_PRINT("my",("Fd: %d Seek: %lu Buffer: 0x%lx Count: %u MyFlags: %d", - Filedes, (ulong) offset, (long) Buffer, Count, MyFlags)); - + Filedes, (ulong) offset, (long) Buffer, (uint) Count, + MyFlags)); for (;;) { #ifndef __WIN__ errno=0; /* Linux doesn't reset this */ #endif #ifndef HAVE_PREAD - os_off_t old_offset; - pthread_mutex_lock(&my_file_info[Filedes].mutex); - /* - As we cannot change the file pointer, we save the old position, - before seeking to the given offset - */ - - error= (old_offset= lseek(Filedes, 0L, MY_SEEK_CUR)) == -1L || - lseek(Filedes, offset, MY_SEEK_SET) == -1L; - - if (!error) /* Seek was successful */ - { - if ((readbytes = (uint) read(Filedes, Buffer, Count)) == -1L) - my_errno= errno; - - /* - We should seek back, even if read failed. If this fails, - we will return an error. If read failed as well, we will - save the errno from read, not from lseek(). - */ - if ((error= (lseek(Filedes, old_offset, MY_SEEK_SET) == -1L)) && - readbytes != -1L) - my_errno= errno; - } - + readbytes= (uint) -1; + error= (lseek(Filedes, offset, MY_SEEK_SET) == (my_off_t) -1 || + (readbytes= read(Filedes, Buffer, Count)) != Count); pthread_mutex_unlock(&my_file_info[Filedes].mutex); #else - if ((error= ((readbytes = - (uint) pread(Filedes, Buffer, Count, offset)) != Count))) + if ((error= ((readbytes= pread(Filedes, Buffer, Count, offset)) != Count))) my_errno= errno; #endif if (error || readbytes != Count) { DBUG_PRINT("warning",("Read only %d bytes off %u from %d, errno: %d", - (int) readbytes, Count,Filedes,my_errno)); + (int) readbytes, (uint) Count,Filedes,my_errno)); #ifdef THREAD - if ((readbytes == 0 || (int) readbytes == -1) && errno == EINTR) + if ((readbytes == 0 || readbytes == (size_t) -1) && errno == EINTR) { DBUG_PRINT("debug", ("my_pread() was interrupted and returned %d", (int) readbytes)); @@ -83,14 +79,14 @@ uint my_pread(File Filedes, byte *Buffer, uint Count, my_off_t offset, #endif if (MyFlags & (MY_WME | MY_FAE | MY_FNABP)) { - if ((int) readbytes == -1) + if (readbytes == (size_t) -1) my_error(EE_READ, MYF(ME_BELL+ME_WAITTANG), my_filename(Filedes),my_errno); else if (MyFlags & (MY_NABP | MY_FNABP)) my_error(EE_EOFERR, MYF(ME_BELL+ME_WAITTANG), my_filename(Filedes),my_errno); } - if ((int) readbytes == -1 || (MyFlags & (MY_FNABP | MY_NABP))) + if (readbytes == (size_t) -1 || (MyFlags & (MY_FNABP | MY_NABP))) DBUG_RETURN(MY_FILE_ERROR); /* Return with error */ } if (MyFlags & (MY_NABP | MY_FNABP)) @@ -100,65 +96,63 @@ uint my_pread(File Filedes, byte *Buffer, uint Count, my_off_t offset, } /* my_pread */ - /* Write a chunk of bytes to a file */ +/* + Write a chunk of bytes to a file at a given position + + SYNOPSIOS + my_pwrite() + Filedes File decsriptor + Buffer Buffer to write data from + Count Number of bytes to write + offset Position to write to + MyFlags Flags + + NOTES + This differs from the normal pwrite() call in that we don't care + to set the position in the file back to the original position + if the system doesn't support pwrite() -uint my_pwrite(int Filedes, const byte *Buffer, uint Count, my_off_t offset, - myf MyFlags) + RETURN + (size_t) -1 Error + # Number of bytes read + */ + +size_t my_pwrite(int Filedes, const uchar *Buffer, size_t Count, + my_off_t offset, myf MyFlags) { - uint writenbytes,errors; - ulong written; + size_t writenbytes, written; + uint errors; DBUG_ENTER("my_pwrite"); - DBUG_PRINT("my",("Fd: %d Seek: %lu Buffer: 0x%lx Count: %d MyFlags: %d", - Filedes, (ulong) offset, (long) Buffer, Count, MyFlags)); - errors=0; written=0L; + DBUG_PRINT("my",("Fd: %d Seek: %lu Buffer: 0x%lx Count: %u MyFlags: %d", + Filedes, (ulong) offset, (long) Buffer, (uint) Count, + MyFlags)); + errors= 0; + written= 0; for (;;) { #ifndef HAVE_PREAD - int error= 0; - os_off_t old_offset; - writenbytes= (uint) -1; + int error; + writenbytes= (size_t) -1; pthread_mutex_lock(&my_file_info[Filedes].mutex); - - /* - As we cannot change the file pointer, we save the old position, - before seeking to the given offset - */ - error= ((old_offset= lseek(Filedes, 0L, MY_SEEK_CUR)) == -1L || - lseek(Filedes, offset, MY_SEEK_SET) == -1L); - - if (!error) /* Seek was successful */ - { - if ((writenbytes = (uint) write(Filedes, Buffer, Count)) == -1L) - my_errno= errno; - - /* - We should seek back, even if write failed. If this fails, - we will return an error. If write failed as well, we will - save the errno from write, not from lseek(). - */ - if ((error= (lseek(Filedes, old_offset, MY_SEEK_SET) == -1L)) && - writenbytes != -1L) - my_errno= errno; - } + error= (lseek(Filedes, offset, MY_SEEK_SET) != (my_off_t) -1 && + (writenbytes = write(Filedes, Buffer, Count)) == Count); pthread_mutex_unlock(&my_file_info[Filedes].mutex); - - if (!error && writenbytes == Count) + if (error) break; #else - if ((writenbytes = (uint) pwrite(Filedes, Buffer, Count,offset)) == Count) + if ((writenbytes= pwrite(Filedes, Buffer, Count,offset)) == Count) break; - else - my_errno= errno; + my_errno= errno; #endif - if ((int) writenbytes != -1) + if (writenbytes != (size_t) -1) { /* Safegueard */ written+=writenbytes; Buffer+=writenbytes; Count-=writenbytes; offset+=writenbytes; } - DBUG_PRINT("error",("Write only %d bytes",writenbytes)); + DBUG_PRINT("error",("Write only %u bytes", (uint) writenbytes)); #ifndef NO_BACKGROUND #ifdef THREAD if (my_thread_var->abort) @@ -173,8 +167,7 @@ uint my_pwrite(int Filedes, const byte *Buffer, uint Count, my_off_t offset, VOID(sleep(MY_WAIT_FOR_USER_TO_FIX_PANIC)); continue; } - if ((writenbytes > 0 && (uint) writenbytes != (uint) -1) || - my_errno == EINTR) + if ((writenbytes && writenbytes != (size_t) -1) || my_errno == EINTR) continue; /* Retry */ #endif if (MyFlags & (MY_NABP | MY_FNABP)) |