lib - a pwrite() implementation (Contributed by Buccapatnam Tirumala, Gautam)
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@ -147,6 +147,7 @@ _PROTOTYPE( int tcsetpgrp, (int _fd, pid_t _pgrp_id) );
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_PROTOTYPE( char *ttyname, (int _fd) );
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_PROTOTYPE( int unlink, (const char *_path) );
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_PROTOTYPE( ssize_t write, (int _fd, const void *_buf, size_t _n) );
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_PROTOTYPE( ssize_t pwrite, (int _fd, const void *_buf, size_t _n, off_t _offset));
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_PROTOTYPE( int truncate, (const char *_path, off_t _length) );
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_PROTOTYPE( int ftruncate, (int _fd, off_t _length) );
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_PROTOTYPE( int nice, (int _incr) );
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@ -107,4 +107,5 @@ SRCS+= \
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nice.c \
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priority.c \
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pread.c \
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pwrite.c \
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usleep.c
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26
lib/libc/posix/pwrite.c
Normal file
26
lib/libc/posix/pwrite.c
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@ -0,0 +1,26 @@
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#include <lib.h>
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#include <unistd.h>
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ssize_t pwrite(int fd, const void *buffer, size_t nbytes, off_t where)
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{
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off_t here;
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ssize_t w;
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if((here = lseek(fd, 0, SEEK_CUR)) < 0)
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return -1;
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if(lseek(fd, where, SEEK_SET) < 0)
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return -1;
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if((w=write(fd, buffer, nbytes)) < 0) {
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int e = errno;
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lseek(fd, here, SEEK_SET);
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errno = e;
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return -1;
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}
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if(lseek(fd, here, SEEK_SET) < 0)
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return -1;
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return w;
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}
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