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dj(1): remove function pointer hijinks (fixes #66)

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This commit is contained in:
dtb 2024-02-22 19:27:14 -07:00
parent 90de1bf9a4
commit 58245c9484
Signed by: trinity
GPG Key ID: 31FF85CCB6DC7641
1 changed files with 21 additions and 21 deletions
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38
src/dj.c
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@ -203,28 +203,28 @@ Io_fdseek(struct Io *io){
if(!fdisstd(io->fd) && lseek(io->fd, io->seek, SEEK_SET) != -1)
return -1;
else if(io->fl == write_flags){
memset(io->buf, '\0', io->bs);
/* This is a dirty trick; rather than testing conditions and operating
* likewise, because the parameters to read or write are going to be
* the same either way, just use a function pointer to keep track of
* the intended operation. */
op = (int (*)(int, void *, size_t))&write;
/* Function pointer casts are risky; this works because the difference
* is in the second parameter and only that write(2) makes the buffer
* const whereas read(2) does not. To avoid even the slightest
* undefined behavior comment out the cast, just be ready for a
* -Wincompatible-function-pointer-types if your compiler notices it.
*/
}else
op = &read;
/* We're going to cheat and use bufuse as the retval for write(2), which is
* fine because it'll be zeroed as this function returns anyway. */
do{ if( (io->bufuse = (*op)(io->fd, io->buf, MIN(io->bs, io->seek))) == 0)
/* repeated code to get the condition out of the loop */
if(io->fl == write_flags){
memset(io->buf, '\0', io->bs);
/* We're going to cheat and use bufuse as the retval for write(2),
* which is fine because it'll be zeroed as this function returns
* anyway. */
do{
if((io->bufuse = write(io->fd, io->buf, MIN(io->bs, io->seek)))
== 0)
/* second chance */
io->bufuse = (*op)(io->fd, io->buf, MIN(io->bs, io->seek));
io->bufuse = write(io->fd, io->buf, MIN(io->bs, io->seek));
}while((io->seek -= io->bufuse) > 0 && io->bufuse != 0);
}else if(io->fl == read_flags){
do{
if((io->bufuse = read(io->fd, io->buf, MIN(io->bs, io->seek)))
== 0)
/* second chance */
io->bufuse = read(io->fd, io->buf, MIN(io->bs, io->seek));
}while((io->seek -= io->bufuse) > 0 && io->bufuse != 0);
}else
return EX_SOFTWARE;
io->bufuse = 0;